1911 barrel lug link-down interference

[bullseyeboy]

Here's one for Mr. Tuner: I'm wondering if this could be contributing to my somewhat frequent nose down FTF with LSWC heads.

I tried the link down test to check for link binding (recoil spring removed, slide back, barrel pushed down & to rear, slide stop inserted with arm hanging vertical).

The slide stop is binding...doesn't swing freely. But, on my 1911, it's not the link it's the barrel lugs that are binding the slide stop pin and making it teeter-totter on and off the frame. I can see 0.010" - 0.015" of the lugs when looking straight through the slide stop pin hole with the barrel in the furthest down and back position.

The lugs on this barrel had been welded up and recut. It is accurate, but it doesn't seem right. Am I worrying about nothing here, or does this need some kind of attention?

bulleseyeboy

 

[1911Tuner]

Stuck

Howdy Bullseyeboy,

From the sounds of it...the lower lug wasn't cut right after it was welded up.
hard to say without an eyeball peek. Seems like it would be tough to get the slidestop pin through the frame with that much of the lug in the way. Is the lug visible through the top of the hole or the rear?

Use a dial caliper to measure the thickness of the lower lug feet...right down at the tips and report back. .110 to .115 inch is about the range you're lookin' for.

Any way you can post a clear picture? With a lighted background...

Anyway, I wouldn't think that it would cause your failures to feed...but that's just a WAG at this point. Most nose-dives are magazine issues.

 

[bullseyeboy]

Howdy Tuner! I'll try to describe it a little better sir...

When looking through the slidestop hole from the left side of the frame with the barrel pushed down and back all the way...about 0.010" to 0.015" of the front radius of the barrel lug is visible extending into the hole at ~1-2 O'Clock.

When the slidestop pin is installed it contacts the lug and prevents the barrel from bedding down onto the frame in this link-down position. The air gap between the barrel and frame nearest the frame feedramp is a good thumbnail thickness when the slide is installed.

There is no clear cartridge position pattern to my FTF. It seems to happen randomly on any cartridge position. All magazines are steel Metalform 7-rounders. (It is worse with a couple of these magazines than the others.) The nose of the LSWC bullet buries itself into, and slightly under, the bottom of the barrel ramp.

bullseyeboy

 

[1911Tuner]

Bad Lug

Howdy Bullseyeboy,

Yep...Now that'll cause a feed problem. I've got a better visual on it now and can see what's happenin'.

I don't think I'd take it back to the smith who welded and recut the lower lug.
Anybody in your area who does any custom work or match-tuning/building on 1911s?

With the barrel standing that far off the bed in linkdown, there also may be problem with getting the barrel unlocked from the slide as it recoils. Check the front corners of your locking lugs for flanging or radiusing too.

Standin'by...

 

[bullseyeboy]

Thanks for the assistance Tuner

The locking lugs are nice and sharp...no flanging or battering...must be clearing the slide OK.

I don't have the name of anyone in my area who does this kind of work. I'll try touching it up with a flat file...just enough...to let the barrel bed down to the frame and eliminate that air gap.

Let ya know how it goes.

bullseyeboy

 

[1911Tuner]

File?

Whoa Hoss! I don't advise wadin' in with a file. The lower lug and the slidestop pin lock the barrel into the slide...and if it's cut wrong, it could cause some real problems.

First...make SURE that's where the real problem is. lay the barrel in the frame and use a strong light to see if the lower lug feet are holding the barrel that far off the bed.

Hopin' ya get this before ya stark hackin' away at it.

Standin' by...with bated breath

 

[bullseyeboy]

wouldn't a file work better'n my bench grinder?

From what I can see the perpetrator is a poorly shaped front radius on the lower lugs...the end of the radius that's furthest from the lock- up flat. It doesn't blend into the front flat smoothly like other lugs I've seen. It looks like it's gotten a little pounded from hitt'n the slidestop pin on link-down or link-up.

Possible explanations: 1. An apprentice smith hit quittin' time on Friday and forgot to finish this job on Monday, or 2. He thought that if a tight barrel lock-up was good, then a tight lock-down might be good too! It does catch a little on the beginning of the front stroke when cycling the slide by hand.

bullseyeboy

 

[1911Tuner]

Lumpy Lug

Hmmmmmm He said as he wrinkled his already furrowed brow.

Sounds like the link is too short...at least for the lug reweld. Also a real possibility
that the lower lug's feet are too long and holdin' the barrel off the bed. Without
the slidestop pin...does the barrel lay in the bed?

Standin' by...

 

[bullseyeboy]

barrel lays in bed, check

"Without the slidestop pin...does the barrel lay in the bed?"

Yes sir, it does...no perceptible rocking with the slidestop removed.

bullseyeboy

 

[1911Tuner]

Bed Check

Good deal...Sounds like maybe just a bad cut/fit on the lower lug...We'll wait to see what turns up when ya get an eyeball on it.

 

[1911Tuner]

Cross Post

Howdy Bullseyeboy,

I posted this reply on another thread and had to go pull it and transfer. I know that right about now, a new guy named Tinkerer is wonderin' if I'm nuts or somethin'...

Here's the reply:
_____________________

Ya wanna be real careful when swappin' links. If you do go with a shorter one, be sure to run a quick check. Turn the gun upside down and rack the slide. Slowly once, and briskly once. If there's any hard spot in the cycle...don't shoot the gun with that link. It should cycle as smoothly as it does when the gun is held normally.

Determine as closely as you can what the center-to-center distance is between holes in the link. The only way to get it exactly is to measure across pins that precisely fit the holes...but you can get close with a dial caliper.

Measure both hole diameters...divide each one by two...and add the two measurements. Then, measure carefully the space between the holes..subtract .001 inch..and add that figure to the first. That'll be close enough for gub'mint work. Generally, you're limited to plus/minus .003 inch difference in links...assuming that somebody didn't long link your gun before you got it.

MOST...standard factory links are .278 inch center to center....plus/minus .001 inch.
if yours is out of that range by .002 inch or more... it's probably too long. Try to stay as close to .278 as you can and still have function. Slide unlocking smoothly...Slidestop pin not getting into a bind with the lower lug as the link swings to vertical with the pin through it. If the barrel is riding or standing(locking) on the link slightly, it's better than the barrel NOT unlocking when the slide recoils. That'll clean the lugs off the top of the barrel in short order, and could crack the slide or frame in some cases.

Luck!

Tuner

 

[Dave Sample]

I do not care for welding up barrels, but I have one in my Carry Commander that I ruined for a 5" gun for a client. I did another one right and could not bear to throw away a Kart NM barrel so I had it welded up for my own use. I agree with Tuner, except for this. If it works, use it till it doesn't and then have it fixed right. It may have been badly done and they may have reduced the barrel bed which is an area that should never be touched. It is hard to put back. I have seen some welded and brazed barrels that are criminal and I use new Kart Barrels for my guns. I don't like to put heat on any part of a 1911, but that is just me. All of the big boys are welding stuff all over the place so I know I am wrong about that. I aways hate to hear about this kind of work being done. It makes us all look bad, and we aren't.

 

[bullseyeboy]

link size

Hi there Tuner!

Measured the link and found that the center to center dimension is about 0.290". It has the number 13 stamped on it. I assume this means 0.013" over the spec. .278"? The slidestop pin hole is 0.206" diameter along the line between the two holes and about 0.203" at 90 degrees to that dimension.

The slidestop pin has a 0.200" diameter.

The lockup flat on the lower barrel lug covers a tiny bit of the slidestop pin hole on the link when the link is in the lockup position (maybe 0.003"-0.005"), so the barrel is not riding the link at lockup. Lockup is tight.

When the slidestop pin is put in the barrel link and swung around the lug, it drags a little on the (battered) area at the front of the lug. Any risk in just smoothing that area down a couple thou?

bullseyeboy

 

[1911Tuner]

Dimensions

Howdy Bullseyeboy,

Wow! .290? That's a long link!

Sounds like somebody welded the lower lug to get better lockup in the slide with the lug and crosspin...which is the right way to do it...and he had to long-link it to set the pin far enough from the centerline to allow it to swing around the corner. The locking lugs or the slots may have been welded too. The pin should make very light contact right at the tangent of that forward radius...Light contact...and it should cam the barrel upward as it moves farther into the battery position.

I think the guy understood what he was doing, but may not have finished it up or checked for link interference in linkdown. As long as the return to battery is reliable and the pin doesn't bind between lug and link...and the locking lugs aren't gettin' beat up by the slide...it's probably okay.

If the barrel is going to bed with the slidestop pin through the link, it's probably okay too.

If you want to create a little more clearance between the lug and pin, I'd use the edge of a good pocketknife to scrape it in rather than using a file. If you can find a length of .195 drill rod and some fine lapping compound...about 5 micron...you can finish lap the lug. Put a light smear of the compound in the
lug feet radius. Assemble the gun as usual, but substitute the drill rod for the
slidestop pin...Recoil spring in place and slide in battery to put pressure on the contact area. Chuck the drill rod up in a hand drill and goose the trigger 2 or 3 times. Easy does it. Just enough to seat the pin into the radius and knock off the high spots. Put just a little downward pressure on the barrel hood too...maybe 2 or 3 pounds.

Remember that the flat area on the lug isn't truly flat. It's cut on a very small angle that rakes forward toward the front radius of the lug. Try to follow that angle with your knife blade or scrape.

Luck to ya, m'fren!

Tuner

 

[1911Tuner]

Almost forgot

The .003 inch difference between the measurements on the large hole in the link is probably due to the armorer relieving the bottom of the hole a little to address the binding problem while preserving his tight vertical lockup and keeping the linkdown timing within spec. He had what he wanted in lockup, but had a bit of bind on the pin. .003 inch is about the limit, so he evidently understood this. My feelings are that the vertical lock may be just a bit too
tight for best reliability, but good for accuracy, assuming that he tended to everything else.

 

[bullseyeboy]

Thanks Tuner!

Your comments have been extremely helpful.

This 1911 is a 1962 Colt accurized for target work, and that's all I plan to use it for. It only has to be reliable when clean and well-oiled!

Happy Thanksgiv'n to you and yours.

bullseyeboy

 

[1911Tuner]

Target Pistol

Mighty welcome Bullseyeboy, and happy Turkey Day right back atcha.

Just go slow on the scraping and try to keep the lug standin' square on the pin. You can check it by usin' a black or blue magic marker to see if there's one side bearin' more of the load than the other. Be careful not to overdo the final lap with the drill rod. You can do it by hand if you need to...It'll just
be slower.

Luck!

Tuner