Slide to frame fit

[aphco]

I have always heard and read that a tight slide to frame fit is required for accuracy and a looser fit is more reliable. And I read where custom packages, even for carry purposes, tighten the fit.

The question is what happens if the fit is too tight?
Does the slide fail to operate under firing conditions or is it just more subject to jamming and failing to return to battery? Or will the slide fail to move rearward after firing? I would imagine these conditions would be worse under higher operating temperatures.

Obviously the slide cannot be so tight that it cannot load the first round, but what determines the difference between "too tight and just right"?

Also, what is the pupose of polishing the breech face? Even if it has tool marks, how does that effect anything?

[Hunter]

Slide to frame fit has little to do with accuracy. Barrel to bushing to slide fit is much (much) more important. Too tight slide to frame fit may jeapordize reliability. When tolerances are cut down there is less room for fouling so as fouling builds up that can render parts out of spec.
Tool marks on the breech face are not a good idea. As the case head is riding up the breech face while the slide is going to battery with a fresh round and resistance from the breech face to the case head can also jeapordize reliability similar to an extractor being too tight.

[Captain Eagle]

I disagree. We have also proven that theory wrong by using a 1911 with a very nice slide to lower end fit and a Kart Barrel in a Colt. I have the targets. There is no such thing as too tight. It will not cycle if it is too tight.

[Hunter]

Jerry Kuhnhausen lists 15% of accuracy is derived from slide to frame fit. A few gunsmiths I know say that may be on the high side. Kuhnhausen also says that a tight frame to slide fit may cause slide drag. If the slide rails became galled because of fit that too could cause drag and need to be redressed adding clearance.
Tight slide to frame is not as beneficial as trigger and barrel to bushing fit.

[Captain Eagle]

How did he arrive at the number? If you think that loose guns are more accurate than tight guns, then I have to surrender to your train of thought and wander off into the sunset.

[Hunter]

That is a question for Mr. Kuhnhausen but I tend to believe him.
I did not say loose guns were more accurate than tight guns.
I said there is much more benefit with a good trigger, and barrel to bushing to slide fit then slide to frame.
Consistent lock up is where mechanical accuracy is achieved. That occurs at the barrel bushing and consistent barrel lock up.
I see where a bullseye gun will benefit from a tight slide to frame fit as it will play a part in accuracy but I do not believe this thread is about a bullseye gun.
Do you disagree generally speaking a tighter built pistol may have more reliability issues than one built to specs?

[Joni Lynn]

A good number of years ago I was discussing slide to frame fit with the late Jim Clark. He told me it was in his opinion at best 2% to 5% of the 'final' accuracy achieved when building an accurized 1911. He was a nice knowledgeable gentleman to talk with.
He went on to mention that if you are using a frame mounted optic then the accuracy will be more greatly affected by slide to frame fit. Consistency of everything returning to the same exact place is needed.
Les Baer has sort of a trademark in his tighter than tight slide/frame fit and mine seems to run & run even when getting dirty.
I'd guess there's a difference between being manufactured that tight/snug and being made that way after the fact.
Also when someone just pinches the slide rails in I would think it also changes the angle of the rails a bit so lapping would be needed since slide/frame rails wouldn't be well aligned afterwards.

[BTF/PTM]

I've heard the opinion Hunter gave, too, minus the actual percentage. Slide/barrel fit is much more important than slide/frame fit. The biggest reason for that is the simple fact that, by the time the slide begins its rearward recoil motion, the bullet has left the barrel and is a couple hundred feet away from the gun. Thus, as long as the battery position of the gun is solid (tight barrel/slide fit and slide racked fully forward), the gun will be plenty accurate to hit its target. I heard this from a gunsmith here in San Diego who is a die-hard 1911 fanatic.

[Ten_Ring]

Alot of 1911 "Ol' timers" have told me "if it don't rattle, it ain't right". Not to go off topic, but that's the reason the AKs are so reliable, they are lose, they rattle, they work!

[Joni Lynn]

The first places to go for accuracy would be barrel to bushing fit, bushing to slide fit and the fit of the rear of the barrel. A good trigger is also needed if you're going to shoot the gun to it's potential.

[Hunter]

Here is an x-ray picture of a Government Model just before the bullet exits the muzzle.
http://i66.photobucket.com/albums/h264/Hunter1911/Gun20Fired.jpg

[aphco]

Here is an x-ray picture of a Government Model just before the bullet exits the muzzle.


Cool picture.
Thank you all for answers to the original question, but...if slide/frame fit is of relatively little importance why is it always part of an accuracy package. I completely understand "looser is more reliable" but is tighter more accurate? Apparently there is some disagreement.

Subscribing to Tuner's philosophy of "functional reliability" a carry gun should be quite loose, but does that give up any accuracy?

Hunter- in reference to the breechface- are you saying that a rough breechface can grab the casing enough to cause a jam, much like a rough ramp??

[Hunter]

You can have an accurate pistol that is reliable keeping in mind accuracy is a relative term.
Slide to frame fit will have a bearing on accuracy but not as much as other factors. I imagine that part of the accuracy package is to snug up a loose slide to improve fit but not tighten it up to the point of excess.
The case head of the round being loaded will slide up a smooth breech face much easier than one that is rough.
There is a degree of improvement but there is a such thing as too much of a good thing, I believe.
It is no secret that I am not a gunsmith or even close but I have a vague idea on how a Government Model works and a great gunsmith to inquire to when I get in over my head.

[BigJon]

A 1911 isn't an AK. Also, even a tighter-built AK can be as reliable as a looser one, and more accurate too boot. I think Hunter's right that accuracy and reliability are relative. A pistol can be made much more accurate than a rattle trap and still not lose practical reliability.

Best,
Jon

[OD*]

but...if slide/frame fit is of relatively little importance why is it always part of an accuracy package.
Because people who don't know any better have come to expect it, they mistake "tight" for quality. Most custom gunsmiths give slide to frame fit about 5% of an accuracy job.

[BTF/PTM]

That x-ray picture is awesome!

Another argument that's actually against a "precision fit" slide and frame that's tight to extreme standards for the sake of accuracy is that, especially in the case of stainless steel, if the gun gets good n' hot during the course of firing and everything is expanded and things are gritty and not as oiled as they should be, stainless steel is known to gall. In other words, the two stainless steel parts will swap material with each other and can slow the motion of the slide. That would be one case where a precision fit could actually reduce reliability.

[Frank]

I have several 1911s that have absolutely no discernible side-to-side or up-and-down play in the slide to frame fit. Yet the racking of the slide is as smooth as silk (or as slick as a hot knife through butter, or -- well you get the idea). These are also guns that have seen hard use in training, practice and competition, have not been pampered and have been absolutely reliable. So I know that a gun doesn’t need to rattle to be reliable.

I don't think it's a matter of increasing tolerances to allow for fouling. When you detail strip a 1911 that's been shot a good deal, you find all manner of nooks and crannies in which fouling has collected. The fouling has collected in those places away from operating parts and bearing surfaces. I really don't think that you want the fouling to collect between bearing surfaces, like the slide/frame rails. If the tolerances are too large, gunk could indeed collect there and impair the smooth reciprocation of the slide along the frame. So tolerances need to be close enough to prevent fouling buildup in those areas.

Consider also your car's engine. You wouldn't want there to be a lot of play in the fit of the connecting rods to the crank shaft. Play translates to vibration, wear and breakage.

DVC

[Jammer Six]

Looser is gooder. Joni Lynn has it right.

[auto45]

I'd bet that most of the "tight-fitting" issues are the barrel dimensions and fit, not a tight fitting slide/frame.

Chambers too tight, hood fit to "bullseye" specs, little clearance in other areas and perhaps, tight bushings.

I don't see how a loose slide/frame fit enhances reliability if the slide is moving both vertically and horizontally inconsistently on the frame. The design works either way, but for how many rounds?
Of course, you have to define "loose".

If I recall, Tuner mentioned the pre WWII 1911's slide/frame fit were more towards the Kimber fit, than the current loose Colt fit. The "loose" WWII guns were spec'd "loose" to speed up production and allow easy interchangeability between manufacturers, not to increase reliability.

[1911Tuner]

Topic: Fitting slide to frame

Category: IMHO

Cold-fitting is something that I did a couple times and abandoned it. It's pretty much fits into the "Quick'n'Dirty method of getting a tight fit...which is another matter of personal tastes.

I much prefer to use file and stone to bring the frame to the point that I can move it onto the slide...full travel...and back off by hand...using a very small amount of a fine lap for one pass...and finish fitting using oil and elbow grease.

At that point, if there's not a bit of play...I like to create a little with J&B and oil. I like about .003 inch side-to-side and up/down...dry. Oiling the rails then provides zero, and the slide is riding on oil when there's oil present...and leaves enough clearance so that if the rails are dry, the parts won't gall if they heat up.

And no, Cap'n. Peening steel doesn't soften it. You have to anneal it...or draw it carefully if you're looking to hit within a certain range on the Rockwell "C" scale.

Cheers

[ColtAllure]

I'm coming to this thread a bit late, but I'm very interested in the X-ray picture. Where did you get it? Are there more? Or any other visible-light high-speed pics?

Hard data are sooooo rare in the study of our beloved 1911.

CA

[BigJon]

Topic: Fitting slide to frame

Category: IMHO

Cold-fitting is something that I did a couple times and abandoned it. It's pretty much fits into the "Quick'n'Dirty method of getting a tight fit...which is another matter of personal tastes.


Johnny, this is one of the very few areas that I may have to disagree with you. I say "may," because I'm not sure what you're referring to when you say "cold fitting." If by that you mean just stoning and lapping things down, then I'm with ya. However, if it's cold swaging, I'd have to differ - iIt's definitely NOT "quick" - definitely longer than milling - it takes me hours to do it.

While we may disagree on the "quick" part, though, I'm 100% in agreement on the "dirty part!" Very messy task to be sure! What I'm referring to is not filing or stoning things down and then lapping. It's also not just slamming the raw receiver and slide together until they give up. It's something in between - getting tolerances closer than they come (referring to oversized stuff like Caspian receivers/slides here) with files, stones and paper, and then swaging the rest of the way with lubricated abbrasives.

In the end, though, it is a matter of personal tastes, as you mentioned. To each his own!

Best,
Jon

[BigJon]

I'm coming to this thread a bit late, but I'm very interested in the X-ray picture. Where did you get it? Are there more? Or any other visible-light high-speed pics? Hard data are sooooo rare in the study of our beloved 1911. PG

Ain't it a cool photo?!?? Sorta puts to bed all those discussions about whether the slide stays locked, or substantially still locked, until the bullet leaves. (Not that I cared much anyway - as long as the bullet does in fact leave! lol!)

Best,
Jon

[1911Tuner]

I'm not sure what you're referring to when you say "cold fitting."

Starting with oversized frame rails or undersized slide rails and forcing them together with a hammer or an arbor press is known as "Cold Fitting." I much prefer bringing the dimensions in to a light interference fit and lapping/seating as a final fit.

[BigJon]

Understand. Thanks for clarifying things for my aging brain.

Best,
Jon

[ColtAllure]

When discussing the impact of close fits on reliability, it seems important to distinguish between a pistol contaminated with fouling (firing residue), and one contaminated with foreign debris.
Fouling appears to be fine grained and the softer of the two. I don't think fouling (within reason) presents much of a reliabiity problem with the more closely fitted slides in the .002-.005 range.
But sand, dust and mud are another matter. These are usually made of harder minerals, sometimes with large grain sizes. Ordinary beach sand, for example, has grain sizes from .001-.050 in. Grains in the lower end of this range can enter into closely fitted pistols and cause interference or friction.
Everyone tests pistol reliability by seeing how well the pistol functions when fouled. But few are willing to test with foreign debris.

CA

[gans]

Please explain. It seems that a slide/frame fit with less than .001" would have less room for debris to enter. And one with more room could have more debris enter.

[1911Tuner]

WHen discussing clearances related to reliability, one thing to bear in mind is that too far in either direction can cause reliability to suffer. Sloppy loose clearances can allow larger particles in...which makes things much worse than being a little too tight. There's a happy medium...a compromise...that doesn't work perfectly under all conditions, but which works well enough to bet your life on in all but the worst of circumstances.

Now...Everybody go look at the X-Ray picture and study on it carefully...and describe what you see.

[Frank]

... sand, dust and mud are another matter. These are usually made of harder minerals, sometimes with large grain sizes. Ordinary beach sand, for example, has grain sizes from .001-.050 in. Grains in the lower end of this range can enter into closely fitted pistols and cause interference or friction....
I have to disagree. Patrick Sweeney did a series of mud, sand, dust, etc. torture tests with several makes of 1911, including a Kimber Warrior and a Wilson CQB. The results were published in The Gun Digest Book of the 1911, Volume 2. Bottom line is that even the Wilson, probably the finest fitted of the bunch, wasn't fazed.

DVC

[emilio]

http://i66.photobucket.com/albums/h264/Hunter1911/Gun20Fired.jpg

i see a lot of things, but most interestingly i see the barrel pushing forward in its locking lug recesses.

- emilio

p.s. get my pm, 'Tuner?

[Frank]

WHen discussing clearances related to reliability, one thing to bear in mind is that too far in either direction can cause reliability to suffer. Sloppy loose clearances can allow larger particles in...which makes things much worse than being a little too tight. There's a happy medium...a compromise...that doesn't work perfectly under all conditions, but which works well enough to bet your life on in all but the worst of circumstances....
Exactly. Again consider the fit of the connecting rods to the crankshaft in your engine. Too tight and it will seize. But too loose and it will shimmy, bind, rattle and shake things to pieces.

DVC

[RickB]

I see photographic evidence disproving the theory that the standard recoil system allows the recoil spring to "snake" around in the frame and slide; clearly, there's no way it could happen, unless the head of the guide didn't fit squarely to the frame.
My "take" on the slide/frame fit is that if you have a tight fit when the barrel is fitted, and the slide/frame fit subsequently loosens, your accuracy goes to heck. I have a Colt M1991A1 that had the frame swaged to tightly fit the slide, and then I installed a Kart EZ fit barrel. The gun would shoot cloverleaf groups at fifteen yards (with me pulling the trigger!). About 2000-3000 rounds later the slide was rattling on the frame, and the goups are now twice what they were. Reliability remained the same, as the fits loosened. I never performed any sort of torture tests, but I'm more interested in a gun shooting once in a row, 5000 times, than shooting 5000 times in a row.

[1911Tuner]

i see a lot of things, but most interestingly i see the barrel pushing forward in its locking lug recesses.

Close. The barrel can't be pushed forward any further than its mechanical limit at the lower lug and slidestop pin. Study it a little closer...and remember that action and reaction occur at the same instant.

Yep. Got your PM, emilio. Lotta irons in the fire right now, but I'll get back to ya...and thanks.

[1911Tuner]

My "take" on the slide/frame fit is that if you have a tight fit when the barrel is fitted, and the slide/frame fit subsequently loosens, your accuracy goes to heck.


Exactly why you don't want to use the barrel fit to take the vertical slack out of the slide to frame fit...at least if you don't want to rebuild the gun every 5-6,000 rounds. Jamming the barrel firmly into the slide places upward pressure on the slide. Get the excess slack out first...then fit the barrel so that it doesn't fall when you press down on it while allowing the slide to go to battery without actually wedging the barrel upward tightly.

One is purely for accuracy with durability as a secondary consideration. The other is for reliability and durability first...with accuracy in second place...even though it will be enhanced with a good barrel fit.

[Captain Eagle]

Round up the usual suspects.....................
I consider Tuner a very good pal of mine and even though we have different opinons on these things, it should not affect our friendship.
That is all they are. Opinions.
I have heard all the various Internet Experts talk about this stuff and so far, not one of them has offered any proof. Opinions are just that and nothing more.
I like the things that Patrick Sweeny does because he proves his points. I have never had the time or desire to do what he does and so I think it's neat to drop guns for high up with a loaded round in the chamber and find out what I have said for years is true. They do NOT go BANG! Extractors go for 300,000 rounds without a burp and so on.
We put one of our 1911's out at Gunsite for six months and had everyone there shoot it a lot. We kept track of the milage and that gun is at 40,000+ rounds now and we have continued the hard use test for over a year. So far, so good. It is a very tight gun and still is 100 % reliable. So much for that stuff.
Keep up the good work, Tuner , because you are still one of my heros!

[Dave Berryhill]

Exactly why you don't want to use the barrel fit to take the vertical slack out of the slide to frame fit...at least if you don't want to rebuild the gun every 5-6,000 rounds. Jamming the barrel firmly into the slide places upward pressure on the slide....

Ok, I'll bite. What difference does it make if the slide and frame have no vertical play and the barrel is fit so that the lugs in the slide are making contact with the lug recesses in the barrel and having a slide and frame with a loose fit and the slide and barrel making the same contact, thus taking up the vertical slack?

[Jammer Six]

Exactly. Again consider the fit of the connecting rods to the crankshaft in your engine. Too tight and it will seize. But too loose and it will shimmy, bind, rattle and shake things to pieces.

DVC
The crankshaft lives in a sealed environment, and is in no danger of being dropped in the mud, picked up, and turned over.

Not to mention the environment is a constant bath of filtered lubricant...

The environment a 1911 fights in and a crankshaft operates in just don't compare.

If you don't believe me, drain your crankcase, run you crankshaft dry, and let us know what happens. A crankshaft is WAY touchier than a 1911.

Davey, it's nice to hear you like Tuner. :D

[Mylhouse]

I'm the furthest thing from an expert on this board, but what I see when I look at the X-Ray pic is that the slide stop pin isn't making solid contact with the lower barrel lugs. It would seem the pistol is riding the link instead of the feet. Or however the terminology goes.

[1911Tuner]

Ok, I'll bite. What difference does it make if the slide and frame have no vertical play and the barrel is fit so that the lugs in the slide are making contact with the lug recesses in the barrel and having a slide and frame with a loose fit and the slide and barrel making the same contact, thus taking up the vertical slack?

Sorry I wasn't clearer, Dave.

I meant that barrels that are fitted to take yp the vertical slack don't really tighten it up...They just push it up and give the impression of a well-fitted slide. I like to get the slack out, leaving just a tiny bit...maybe .003 inch. Then fit the barrel so that it doesn't actually push up on the slide...but won't drop if I press on the hood. Maybe a little odd way of approaching it, but it's worked well for me.

m the furthest thing from an expert on this board, but what I see when I look at the X-Ray pic is that the slide stop pin isn't making solid contact with the lower barrel lugs. It would seem the pistol is riding the link instead of the feet. Or however the terminology goes.

The lower lug isn't in contact with the pin because the slide has already begun its rearward trip and is hauling the barrel back with it. The barrel is undergoing a forward drag from the passage of the bullet, and is resisting the slide. Here...the forced horizontal engagement keeping the breech locked...which doesn't really occur until the gun is fired. "Locks up like a vault" when static/in-battery is a popular term that doesn't happen. Simply in battery isn't locked. It's held by spring tension and...in a tightly-fitted gun...a sort of wedging action...friction. But locked? Nope.

So...The 1911 is almost a delayed or retarded blowback pistol. The only thing that keeps it from being in that category is the fact that the slide doesn't move independently of the barrel. There are 6 things that are delaying the slide.

They are:

Slide mass...Barrel mass...Recoil spring load...Mainspring load...Hammer mass...Bullet drag. Of the six, the last one is the big one.

[Frank]

Well Jammer, there are other difference between the crankshaft and slide/frame assembly. The stresses are a whole lot higher on the crankshaft. It's going a whole lot faster for longer, and it's running a whole lot hotter for longer. It's also not in a particularly sterile environment. There's all kinds of debris in the crankcase and all sorts of ash, microscopic metal particles, sludge and varnish in there. And a lot of stuff gets by the filter.

The point is that metal parts that move against each other work best when they are fit together properly. There of course must be some gap or the parts won't fit together at all. But if there's too much of a gap, the parts don't move against each other smoothly. They twist, crash, clash and bang against each other.

DVC

[ColtAllure]

Wow, quite a post rate on this thread. To go back several messages, Sweeny's sand tests seem dubious to me, since he used talcum powder to simulate fine sand. Talc is extremely soft and has *lubricating* properties :)
His mud test was better, but mud may not penetrate well, and he did rinse the gun before attempting to fire.

I don't believe that bullet drag retards the slide at all, for a given muzzle velocity. There are two ways to see this. First, we can consider a conservation of momentum argument. The bullet exits with some velocity, the slide/barrel must recoil with the velocity which conserves momentum (minus a really small amount due to the recoil spring, hammer mass, and mainspring - I'm only talking about the point where the bullet exits the muzzle). So only muzzle velocity is important, not bullet drag.

Another way to analyse it is by consider the forces. If the barrel bore is slightly undersize, and rough, this will increase bullet drag. Then more pressure will be required for the same muzzle velocity. This increased pressure will push backwards on the slide, and compensate for the increased drag. Thus, high or low bullet drag does not affect slide travel, if muzzle velocity is held constant.

CA

[1911Tuner]

I don't believe that bullet drag retards the slide at all, for a given muzzle velocity.

And here we go! :D

Bullete drag on the barrel doesn't have anything to do with momentum. It's a completely different set of numbers. Bullet drag on the barrel is related to the coefficient of friction...the resistance that the barrel offers to bullet passage...and the force driving the bullet.

Since the slide pulls the barrel backward with it...and the drag exerted on the barrel is
trying to hold the barrel forward...how can it NOT delay the slide?

Stick a cork in a pipe with a rope attached to the cork. Pull the pipe in one direction and the cork in the other. Whatever resistance is offered to the cork BY the pipe...the cork also offers TO the pipe. As you pull...when the cork starts to slip through the pipe...the pipe will start to slip off the cork at the same time. Hence...whatever force is resisting one is also resisting the other. Part of Newton 3 dictates that force forward equals force backward. That works in reverse too. Whatever force is resisting in one direction...is resisting equally in both directions. If it takes X units of force to push the bullet through the barrel...it takes X units to pull the barrel backward off the bullet.

[Mylhouse]

Thanks, Tuner, for the excellent explanation. I now have a new understanding of how it all works.

[ColtAllure]

As I said, there are two ways to analyse these kinds of systems. One uses forces, one uses conservation of momentum. Both *must* give the same answer. I have used both in my post, and they do give the same answer. The momentum argument is often clearer, as is becoming obvious.

Consider the thought experiment where there is zero bullet drag, yet muzzle velocity is the standard 850 ft/sec. The slide must still recoil with the velocity necessary to conserve momentum (with the caveats given in the first post). This must satisfy the equation Bullet mass x 850 = slide/barrel mass x slide velocity (again neglecting the small effects). Surely the principle of conservation of momentum is not in question here.

To restate my force analysis even more clearly, let's go back to the high school level. If the bullet drags on the slide/barrel, the slide/barrel must drag on the bullet (Newton's First). So the bullet must be pushed harder to overcome the drag, if muzzle velocity is kept up. The only way to push the bullet harder is with more pressure, and this also pushes the slide back harder, giving the same slide velocity as if there was no drag.

The two analyses agree, bullet drag does not retard the slide if muzzle velocity is constant.

<I have deleted a paragraph here, as I had a misconception about the corks and strings. It is replaced with:>

The cork and string example is different, because the tension on the two strings does not have to be equal, whereas the internal pressure in the bullet example must push forwards and backwards equally.



The mathematics of the momentum argument is much easier. The force argument really requires vector diagrams.

CA

[1911Tuner]

So the bullet must be pushed harder to overcome the drag, if muzzle velocity is kept up. The only way to push the bullet harder is with more pressure, and this also pushes the slide back harder, giving the same slide velocity as if there was no drag.

Better go back and work'em again...and this time remember Newton 1B...and remember to plug in the differences between static friction and kinetic friction. The moving object requires less force to keep it moving than it did to get it started. So, as the bullet accelerates ever faster, it requires less and less force to accelerate it ever faster.

Most...but not all...of the delay occurs at the outset of the action/reaction event...when resistance is highest and pressure is at a peak. Coincidentally, it also occurs where it does the most good...before a lot of momentum is established in the slide. This resistance that is offered to the slide is what deforms barrel lugs and cracks slides at the breechface guide/ejection port junction on the top left side.
It also cracks barrel lugs. It also stretches revolver topstraps and creates a little problem known as "Excessive Endshake" because the topstrap is being stretched as the barrel is being forced in one direction, and the recoil shield in the other.

Oh...It's real, all right...and I've got the busted slides to prove it.

[ColtAllure]

Oh yes, bullet drag does cause internal tension in the slide, but it is the same force forwards and backwards, so it does not affect slide motion.

Conservation of momentum is derived using Newton's laws. This is why the answers must match.

There's really not much more I can say. Maybe we'll discuss it over dinner, sometime, and I'll demonstrate my point on the traditional medium of all great physics and engineering, the cocktail napkin :)

CA

[Jammer Six]

Well, I posted the sum of my knowledge of engines.

I have a 2002 Chevy pickup, and I just paid more for a 30,000 mile checkup than I did to put a new 350 in my '69!

I'm not even sure my '02 HAS a crankshaft-- to hear the dealer tell it, it's ALL a big series of computers, and the wheels are just programmed to go round and round...

One the 69, I could do just about everything-- head gasket, crank shims, whatever. Not sure I can even get the oil changed on the '02.

[1911Tuner]

Oh yes, bullet drag does cause internal tension in the slide, but it is the same force forwards and backwards, so it does not affect slide motion.

Keep cipherin'. Ned Christiansen proved that the bullet drag in the barrel delays the slide about 5 years ago when he repeatedly fired one without a recoil spring...making the only delay on the slide (besides its own mass) the barrel's mass and the hammer and mainspring. There was no change in the timing of the event...and very little added impact between slide and frame.

It might help to understand that the two action/reaction sides...bullet and slide...are being forced in opposite directions. The barrel is just along for the ride...but it also acts as a vector by resisting in both directions. Whatever drag is placed on the bullet by the barrel...the barrel also has the same drag imposed on it by the bullet. The barrel is moving away from the bullet's direction of travel, while the bullet is moving away from the barrel's direction of travel.

Put the cork in the pipe and pull. There's movement...so there's momentum and the conservation of same...and there's also resistance in both directions. Whatever resistance that the pipe offers to the cork...the cork also offers to the pipe.

[ColtAllure]

Yes, Ned's experiment was a good one. I posted quite clearly that the recoil spring was a very minor factor (at the time of bullet exit). Ned changed the recoil spring, not the bullet drag (while keeping the muzzle velocity constant).

Show me an experiment where the variable in question, bullet drag, is the only thing changed. If *that* changes the timing signifcantly, then you've made your case, and there must be a momentum leak somewhere.

Seriously, I think you would find the momentum approach much more clear in this case. All it requires is one multiplication and one division, and you have the slide velocity, independent of the bullet drag (neglecting small effects, yada yada yada).

CA

[Frank]

...I have a 2002 Chevy pickup, and I just paid more for a 30,000 mile checkup than I did to put a new 350 in my '69!

I'm not even sure my '02 HAS a crankshaft-- to hear the dealer tell it, it's ALL a big series of computers, and the wheels are just programmed to go round and round...

One the 69, I could do just about everything-- head gasket, crank shims, whatever. Not sure I can even get the oil changed on the '02.
Tell me about it. I remember when I used to work on my cars. Now, I pop the hood and don't recognize anything.

DVC

[ColtAllure]

I think some our fellow members feel that there's been enough physics in this thread. Or at least enough thermodynamics (heat) :) I'm happy to take the hint :)

CA

[1911Tuner]

Show me an experiment where the variable in question, bullet drag, is the only thing changed. If *that* changes the timing signifcantly, then you've made your case, and there must be a momentum leak somewhere.

As it happens, Bill Caldwell has come up from Louisiana to work on one with me that'll do just that....and according to him...Jim Clark agreed wholeheartedly...but since he's dead now, I can't call on him to post his twist on it. So...We'll just have to wait and see how the testing goes.

One point. Don't confuse "time" with "timing." Time is a function of distance, while timing is mechanically fixed. They're related...but they're not the same.

[ColtAllure]

I look forward to hearing the results of your experiments. Please remember to control muzzle velocity.

I promise to keep my notions of time and timing straight. But Tuner, I'd like your promise not to misuse high school kinematics in ways that violate the conservation of momentum. Deal? :)

CA

Like Homer Simpson said when Lisa invented a perpetual motion machine - "Young lady, in this house we obey the Laws of Thermodynamics!"

[1911Tuner]

Deal?

Deal...but you're still not workin' the right equation.

Control muzzle velocity? Not sure what you mean...

[gans]

If I am mistaken, ColtAllure can correct me.

The barrel slowing down the slide is not an issue.

The muzzle velocity is a constant. Yes the barrel will push forwards because of the bullet friction, but so what. It does it in all firearms.
Now if you increase the bullet friction (say with a barrel with a tighter bore or more or deeper rifling), you will increase the forward force that the barrel will exert on slowing down the slide. However, you will reduce the muzzle velocity. Now you have to add more powder to the cartridge to get back the velocity that you loss so that you control the muzzle velocity. Thus you have increased the pressure. That pressure increase will push the slide rearwards more. That will now void the increased forward force of the barrel.

[1911Tuner]

Gans...Very good. Since we're essentially hijacking the thread, it might be better to start over with a new one. The mistake here is that it's being studied for the bullet's whole trip...and the delay that actually means something only occurs at the outset. Like the small radius on the firing pin stop...its delaying effect is over almost as soon as the hammer moves, even though it doesn't end there. For all practical purposes...it's over.

Before the new thread emerges, I'll leave you with this thought. If you tie two trucks together with a chain and pull in opposite directions...you have a balanced force..or an equilibrium...until the force becones unbalanced, and one or the other starts to win. As one truck moves forward, dragging the other...it builds momentum, and requires less power to keep going. BUT! As long as the losing truck is still attached, it's slowing the winner down, no matter how fast it's pulled backward. If the speed continues to increase, a point is reached that the losing truck's resistance is pretty much meaningless...though never completely...for all practical purposes, the winner's momentum cancels it out. The reason that it's so hard to see in the ballistic event is that it's over so quickly, and delays it for such a short distance.

We'll do more later. CA! I'm lookin' forward to a lively debate.

[ColtAllure]

I look forward to the discussion too, as always.

CA