Insufficient frame/barrel ramp gap

[Candiru]

I think I've found the cause of the three-point jams in my project gun, jams that even Colt hybrid mags don't seem to totally eliminate: There isn't enough gap between the frame ramp and the barrel ramp.

Here's a photo I took of the barrel at total link-down (click for larger):


http://how-i-did-it.org/img/misc/tn_ramp.jpg
(http://how-i-did-it.org/img/misc/ramp.jpg)

My understanding is this gap should be 1/32", or 0.03125"; as far as I can tell, it's just a little over half that, and the difference is causing the bullet to hit the barrel ramp too low after passing over the frame ramp, forcing premature cam-up and another visit from our mutual friend, Mr. Stem Bind.

My questions are these: Am I correct in seeing the undersized ramp gap as a problem, and if so, what are my options for fixing it?

The only fix that occurs to me is to sand the barrel's ramp in slightly, but not so much as to compromise case support. Here's what I have to work with:


http://how-i-did-it.org/img/misc/tn_support.jpg
(http://how-i-did-it.org/img/misc/support.jpg)

This is a stock, unreamed Kart EZ-Fit barrel, so I don't have any spare headspace to play with. If you're wondering, I'm using an Essex frame.

What are your thoughts as to possible solutions? Of course, if you think I've misdiagnosed things from the start, please let me know!

[1911Tuner]

Looks like ample gap from here....but my eyes may deceive me. They've done that a lot lately. You also have a little wiggle room on the barrel ramp should you have to move it. The case is fully supported where it matters...which is ahead of the web. It's when you lose support farther forward...where the powder charge lies...that you have a problem.

Altering the barrel ramp's position may cure your 3-Point Jam, and it may not. It depends on the frame ramp's specs...and possibly the frame bed's vertical dimensions. Have you tried one of the tapered-lip magazines in it?

[Jerry Keefer]

[QUOTE=Candiru]
Just one thing I might add...Some polished radii on those razor sharp corners/edges might do wonders...

unreamed Kart EZ-Fit barrel, so I don't have any spare headspace....... <<<<<<<<<This won't help a three point, but, every chamber should be finish reamed...which can be done with out changing the head space.

Good Luck

Jerry

[1911Tuner]

This won't help a three point, but, every chamber should be finish reamed...which can be done with out changing the head space.

+1, Jerry...and if you do have to go a little deeper into the chamber with the reamer, it won't affect headspace in the ka-boom direction.

[gbw]

Looks like ample gap from here....but my eyes may deceive me. They've done that a lot lately. You also have a little wiggle room on the barrel ramp should you have to move it. The case is fully supported where it matters...which is ahead of the web. It's when you lose support farther forward...where the powder charge lies...that you have a problem.

Altering the barrel ramp's position may cure your 3-Point Jam, and it may not. It depends on the frame ramp's specs...and possibly the frame bed's vertical dimensions. Have you tried one of the tapered-lip magazines in it?

How so? Especially the frame bed's vertical dimensions.

Reason I'm asking is that, despite every trick I've read of or can think of, I still have the same problem as well (see the "Stem Bind" thread from a couple of weeks ago.) As best I can tell, frame ramp is 31 degrees. Tried Colt factory magazine, also.

I had about the same frame barrel 'shelf', or perhaps a little less, than Candiru's photo shows. I did move the barrel ramp forward (knowing I was risking the barrel), and consequently it probably is now too step. It didn'tseem to hurt anything, but it really hasn't helped much either. Still very rough feeding on the early rounds, especially with LWC.

So I'm very interested in Candiru's solution if one is found.

BTW Candiru, the stock Caspian frames I've used give even less ramp / barrel shelf than Essex. So I don't think you made a bad choice there.

I've done a good bit of looking / reading / researching on this problem lately and there is a LOT of it out there. How much is mag related and how much something other I don't know, probably Tuner does.

But this excessive stem bind / 3-point jam seems to be by far the most pervasive problem in the 1911 world.

[Candiru]

Looks like ample gap from here....but my eyes may deceive me. They've done that a lot lately. You also have a little wiggle room on the barrel ramp should you have to move it. The case is fully supported where it matters...which is ahead of the web. It's when you lose support farther forward...where the powder charge lies...that you have a problem.

Altering the barrel ramp's position may cure your 3-Point Jam, and it may not. It depends on the frame ramp's specs...and possibly the frame bed's vertical dimensions. Have you tried one of the tapered-lip magazines in it?

I may be the one whose eyes are being fooled; here's what I did to figure the distance: I took a caliper and set it to 0.03", then compared that gap with the frame gap. I should probably grab my Mil-Spec to compare and make sure I'm not being a gun hypochondriac.

I haven't had a chance to try the tapered-lip magazine at the firing range yet, but it hasn't totally eliminated jams when hand-feeding rounds. I suspect it'll drop the incidence of jams with ball ammo at the range below the perceptible point, since I was only averaging one jam per fifty rounds with wadcutter mags. Still, it bothers me that I can hand cycle all day with the Mil-Spec and not see a problem. Hmmm, it just occurred to me that dropping Wolff springs into the tapered-lip mags may keep the front of the follower up better and help this issue.

It's funny you should mention the frame bed; I just took a good look at it and it shows evidence of hard contact. It looks like the barrel and link are set up so that the legs hit the VIS at the same time as the barrel reaches the bed, but the slight angle of the barrel causes the frame ramp to hit first. Take a look:


http://how-i-did-it.org/img/misc/bed.jpg
(http://how-i-did-it.org/img/misc/bed.jpg)

That would support the idea that the frame bed is too high.

Finally, I was afraid I'd have to end up getting the chamber finished. The last guy who finish-reamed a chamber for me butchered the ramp, chattered up the rifling, and charged me $40 for the honor. As someone who doesn't have a lathe and has never done before, do I have any chance of doing better or should I just find another 'smith?

[CJR]

Candiru,

It appears to me that your barrel ramp-to-chamber edge looks sharp. It should have a .020"R (Kuhnhausen Vol2, 109,110,111). Likewise, your barrel appears to be impacting the horizontal frame bed as well as the frame's vertical impact surface(VIS). It should only hit the VIS and not the horizontal frame bed. Looks like you need to clearance the horizontal frame bed to eliminate barrel contact there. Likewise, running a chamber reamer into your barrel would eliminate any undersized areas or ovality and help reliable functioning.

Best regards,

CJR

[robot1911]

I agree with this...get a little bevel on that barrel rollover edge as Jerry Keefer said. And, since that's a Kart barrel, it would be wise to ream it because many of them do have a little hump in there that needs to be removed.
If you don't trust your 'smith, send the barrel to me and I'll ream it and radius the rollover point for you. All it'll cost you is U.S. Mail.

Bob

[alpha19]

I have a Springfield Hi-cap thats doing the same thing. My gun seems to have a little more gap than yours just from looking at the pics. In my case i'm going to take it to a gunsmith in a couple of weeks.

[Candiru]

Have you tried one of the tapered-lip magazines in it?

Actually got out to the range to try out the mags. Even using Colt mags with Wolff springs, feeding is still a little ka-chunky and I get occasional jams.

[1911Tuner]

Actually got out to the range to try out the mags. Even using Colt mags with Wolff springs, feeding is still a little ka-chunky and I get occasional jams.

Check the breechface guide block width. Should be .484-.488 inch. Look to see if the lower edge of the extractor's tensioning wall protrudes beyond its side of the wall. Bevel as necessary to blend it with the wall. One surefire test is to remove the extractor and see how it feels. If the feed is smooth, it's the extractor.

If it's unchanged...

Does the rough feed still happen with only 3 rounds in the magazine? If it does, either the frame ramp is too shallow...The barrel ramp is too steep...or both.

[gbw]

Just to nail this down a bit, so we're all using the same references:

"shallow" means angled too much toward the horizontal
"steep" means angled too much toward the vertical

have I got it right?

Like Candiru and many others, I'm still baffled by rough feeding, especially in the early rounds, more pronounced with shorter or sharper nosed, SWC lead bullets. So far, no mag I've used has helped much.

Thanks, as always

[Lazarus]

Candiru,

Your photo does not show a particular problem with the frame ramp/barrel ramp relationship, (other than a sharp edge at the top of the barrel ramp). The important relationship now, is the vertical location of the frame bed in relation to the top round in the magazine. Your frame bed appears similar to my Vermont project, a bit shallow. While it is possible to relieve the slide and barrel to achieve enough barrel drop, if the frame bed is sitting too high vs the magazine, there will still be feed jams.

I'd like to see a picture of a full mag locked into the frame and a mark where the round strikes the feed ramp.

-Lazarus

[1911Tuner]

Just to nail this down a bit, so we're all using the same references:

"shallow" means angled too much toward the horizontal
"steep" means angled too much toward the vertical

have I got it right?

Correct. Too close to horizontal means that the rounds don't deflect high enough to glide across the top corner of the barrel ramp.

Too close to vertical means that the rounds stop on the frame ramp...and mimic a nose-dive failure to feed.

In either example, jacketed ball is more forgiving...which has lead in great part to the myth that the 1911s are only reliable with hardball unless they've been extensively and skillfully modified/tweaked/tuned/ramped/throated/polished/lemon-scented by a
pistolsmith...a blanket statement that only applies to a small percentage...usually based on one man's experience with one or two guns.

However..."More Forgiving" doesn't mean completely forgiving. If the specs on either ramp is too far out, even ball can lead to hair-pullin', cussin', cryin', and prayin'...which can sometimes be remedied by adjusting the bullet seating depth and cartridge OAL...which has given rise to yet another myth, that the 1911 pistol is ammo-sensitive...or rather cartridge length sensitive. Neither could be farther from the truth if...IF...the specs and tolerances are closely held.

While it's true that the shorter OAL presented by some of the SWC bullet profiles are best fed by "wadcutter" magazines, and longer cartridge OAL or ball-like bullet profiles generally do better with tapered, gradual-release magazine designs...if the gun is right, either one should do. Of course, that also depends on whether the magazine itself is "right."

Good magazines...A good extractor, correctly adjusted...Good ammo. See to these three things, and don't overspring the gun...and most of'em will run without too much fanfare. If this weren't the case, the thousasnds upon hundreds of thousands of
USGI and earlier commercial Colts would have earned a reputation akin to the French Chau-Chaut LMG instead of the dead reliable
livesaver and widowmaker rep that it earned in the dozens of awful places that it served..."The Yankee Fist" is a good pistol, but it has to be well-made.

[gbw]

One more note, somewhat OT.

After Tuner and Keefer mentioned it above, I finished reamed the Kart barrel on one of my projects. Using a Manson Precision .45 Finish reamer, it took a fair amount of steel from the forward part of the chamber as they thought, and also cut a freebore (looks to be .100 or so), and re-cut the leade (beginning of the rifling).

Finished as per Lubaloy with paper on a stick. (I jsut love this guy's 'handle').

The point is, that while this may be a fluke or coincidence, 25 yd. accuracy went from 2" - very good - to < 1", spectacular. Also now the gun is not nearly as sensitive to ammo OAL with lead bullets.

[1911Tuner]

The point is, that while this may be a fluke or coincidence, 25 yd. accuracy went from 2" - very good - to < 1", spectacular. Also now the gun is not nearly as sensitive to ammo OAL with lead bullets.

Yep, yep...and yep.

In case you haven't picked up on it...Lub is a "ringer." A Pro from Dover, who doesn't want his true identity known here. As noted in another thread, the experienced hands can get away with things that sound suspect, but are usually born of trial-and-error or from sitting at the knee of an old master. Sometimes I take an unorthodox approach
to solving a problem, often doing something that many of the pros say never to do...or I neglect to do something that they say to always do, whichever the case may be...but if it works, it works. There are several ways to relieve the kitty from his furry coat. The trick is in knowin' where to start, and how much hair to pluck.

[Candiru]

Check the breechface guide block width. Should be .484-.488 inch. Look to see if the lower edge of the extractor's tensioning wall protrudes beyond its side of the wall. Bevel as necessary to blend it with the wall. One surefire test is to remove the extractor and see how it feels. If the feed is smooth, it's the extractor.

If it's unchanged...

Does the rough feed still happen with only 3 rounds in the magazine? If it does, either the frame ramp is too shallow...The barrel ramp is too steep...or both.

Already had to open up the breech face to get rounds to feed, so it's sitting at a smidgen under .488". The extractor has been radiused at the bottom, so it's pretty well blended with the wall. Also, I've learned from reading this forum: Pulling the extractor was the first thing I did when I started seeing three-point jams, but they continued with or without the extractor present.

However, I haven't tried the three-round test. I'll get back with the results of that.

[Lubaloy]

"In case you haven't picked up on it...Lub is a "ringer." A Pro from Dover, who doesn't want his true identity known here."

Tuner,
Well.....it is true that I support my family with my 1911 work. And I do feel that I'm quite good at it.
But there is no 'hidden agenda' behind my desire for anonymity.
I just like to be able to help and share without the weight of my reputation complicating things.
If my advice sounds wrong...well don't take it. If my advice sounds right...well give it a shot.
I'd rather be 'just one of the guys'.
And this is your sandbox, Tuner. You work VERY hard to help and teach these guys the finer points of the 1911. And it works well the way it is now. I have ZERO need to disagree with you on the finer points.
I'm definitely not trolling for work, fame or fortune. I just like helping where and when I can.
Hopefully everyone here is OK with that.
:)

[1911Tuner]

But there is no 'hidden agenda' behind my desire for anonymity.

Didn't figure there was, Lub. A man trollin' for work or fame uses his real name and website, complete with pricing and such...and unless I miss my guess, you've probably got more than you can do anyway. :cool:

If Jerry Keefer would go public, he wouldn't have time to scratch his...ummm...FOOT!