Link-down timing

[Blakenzy]

Is it posible for short linkdown timing to be responsible for high hits on target? In other words can a barrel begin pivoting down before the bullet has exited the barrel? or, will a gun out of spec in this regard be unable to cycle correctly? Oh, and what is the best way to measure link down timing?

Thanks

[Candiru]

Is it posible for short linkdown timing to be responsible for high hits on target? In other words can a barrel begin pivoting down before the bullet has exited the barrel? or, will a gun out of spec in this regard be unable to cycle correctly? Oh, and what is the best way to measure link down timing?

Thanks

As I understand it, if link-down starts happening while there's still pressure in the barrel, you'll see evidence of it in rounded or flanged barrel lugs. Are you seeing any of those in your gun?

For timing test instructions, visit the Technical Issues (http://m1911.org/full_technic.htm) section of this site and look for the entry titled "Test the timing of your M1911A1...".

If your gun is shooting high, I'd look at the shooter before the gun (no offense meant to you). Are you also seeing weak ejection?

[Blakenzy]

There is a little wear on the upper barrel lugs but then again it could be due to normal wear and tear since this a very old Colt, mfg 1946 I believe. According to the article you mentioned if there is a problem with timing the gun should self destruct within 5000 rounds or so. I am sure that this gun has fired much more than that during its life time.

The high hits are probably due to shooter error. However, even though it doesn't seem that this gun has been tinkered with in any important fashion I can't be sure. I would love to have a qualified gunsmith look it over but I just can't reach any. I do believe it has been refinshed, because it has a deep blued mirror like polish that doesn't look original and the markings on the slide are faded toward the tip. The bore is a little pitted and the lands are somewhat worn. The trigger is really heavy at 7-7.5 lbs as far as I can tell. Also, I had to replace the extractor because it had broken hook with a Wilson BP. The ejection is erratic with brass flying every which way, but the are no jams or FTF, FTE. Now I have to get an oversized FP stop. So, with all these details in mind I just thought that the timing could be out of whack as well.

Do you know of any gunsmith (qualified) that would accept to take a look at the internal assembly, hammer and sear?, because I think that is where the heavy trigger pull problem lays. Ideally I would send the whole gun over however that would be very very hard if not imposible. I could mail the hammer and sear separately though, if some one would take the job.

[1911Tuner]

According to the article you mentioned if there is a problem with timing the gun should self destruct within 5000 rounds or so. I am sure that this gun has fired much more than that during its life time.



The heavy damage would occur if there was a timing issue related to the vertical impact surface, or other cause in which the barrel couldn't completely disengage from the slide...causing an impact on the lugs...upper and lower. A simple early linkdown that starts before the bullet has exited wouldn't shear the lugs, but would cause them to become radiused or rounded on the front corners, possibly accompanied by light flanging on the tops...but not necessarily.

Such early linkdown problems can also be fingered by "tadpole tail" primer indents, though that can also be caused by other issues not related to barrel linkdown and drop timing. You may also notice brass shavings in or around the firing pin port.

And the answer to your original question is...yes. If the barrel starts to drop at the rear during bullet transit, it can raise the point of impact on target, but it won't be consistently in the same place, with an elongated vertical string instead of a group.

Normal wear and tear in a correctly timed gun doesn't roll the corners of the upper lugs. Wear deformation is straight-line. I've seen many old pistols with advanced lug deformation and wear with corners still fairly sharp and true...barrel and slide.

Point the gun straight down and rack the slide briskly. Does it hit a light snag about a quarter-inch out of battery?

[Blakenzy]

I gave a close look at the barrel upper lugs, and as far as I can tell they appear to have well defined corners. They do not seem rounded. I do however notice a few points on the top of the lugs towards the right side that seem more polished or worn than the surrounding metal. If it were a true early linkdown problem the wear would have to be the same across all of the lug, right? Also I do not notice "tadpole tail" primer indents on spent cases. As far as racking the slide while pointing the gun straight down goes, I cannot perceive any snag (what does this tell?).

Probably noting wrong with the timing then, or is there? I will have to find a more skilled marksman to test fire this pistol and see what's what.

1911Tuner: Thank you for your enlightening input. BTW, what would be the correct lug depth/height for a commercial Colt mfg 1946? Also, how long are these pistols expected to last on average, assuming that standard pressure, quality ammuntion is used (no +p stuff)? And while I'm at it, can a heavy trigger be caused by simple wear or is it more likely that someone was messing around with what they shouldn't have?

[1911Tuner]

do however notice a few points on the top of the lugs towards the right side that seem more polished or worn than the surrounding metal. If it were a true early linkdown problem the wear would have to be the same across all of the lug, right? Also I do not notice "tadpole tail" primer indents on spent cases. As far as racking the slide while pointing the gun straight down goes, I cannot perceive any snag (what does this tell?).

The more polished tops are probably nothing more than burnishing from the lockup under pressure...or seating. Most of the time, you'll only see it at the top of the radial lugs.

No tadpole tails and no battered/rounded lugs is a good sign that the gun is timing correctly.

No snag when pointed down means that the link is getting the lugs completely clear of the slide...another good sign.

The high point of impact...if it's grouping consistently...is a matter of adjusting the sights. Lowering the rear lowers the POI. Lowering the front sight raises the POI.

If the gun is verttically stringing the shots, with some hitting close to the POA, and other s climbing higher, or even one high/one low/one on target means that the barrel isn't returning to battery consistently to the same place. That's a vertical engagement issue caused by incorrect fitting of the lower lug to the slidestop pin.

Let the gun snap to battery from the halfway point. Push down firmly on the barrel hood. If it moves down...there's your bug. .005 inch of movement changes the POI about 3/4ths inch at 25 yards.

[Hobbes]

So where can one get the test kit? I asked Schuemann and they said they don't supply them anymore...

[1911Tuner]

So where can one get the test kit? I asked Schuemann and they said they don't supply them anymore...


Basically, the only thing the kit does is take the slack out of the link by using a spring to force the barrel upward when it's in linkdown. You can accomplish the same thing by using a 7/16ths wooden dowel in the barrel that goes into the chamber, and levering the rear of the barrel upward. A little awkward to use without a vise to clamp the gun into...but doable.

This also tests the link to see if it's the correct length for the pistol's specs. If the clearance isn't sufficient with all the slack taken out of the link, you need a shorter link. Then, if the barrel lugs don't disengage and provide clearance...you've probably got an issue with the vertical impact surface or the location of the lowr lug.


A simpler test for the link is just to flip the pistol upside down and rack the slide briskly. If it hits a snag about a quarter-inch out of battery, but cycles smoothly when right-side up...the link is too long. This can also be an expedient field test for VIS mislocation...just to see if there's an obvious problem...but not as definitive or as reliable as a true timing test. A too-short link *usually* causes the snag when the pistol is right-side up, or with the muzzle tilted toward the floor at about 45 degrees.

[Hobbes]

Thanks Tuner, you always got the answers :)
I ask because I'm going to use a Kart EZ fit bbl in a RRA slide and am sweating getting the timing right, especially since the Kart supposedly comes with the correct link already installed (not sure how they manage to do that).