Largest locking shoulder?

[kpj53]

Just wondering, I have seen .834 measured flat to tip listed as the 'X3' shoulder. I know the markings dont always go along with a certain measurement but I'm wondering if there any factory made longer than .834 out there.

Information

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[Peter Laidler]

Unless anyone has taken the time to measure a box full of them, I doubt whether anyone will be able to tell you. That's because, as you say, the actual number on the locking shoulder or barrel nut or flash eliminator washer or bolt head etc etc was just a very inaccurate guide.......... When we took one size out we put it back in a big tray full of them and selected another, As a matter of interest, we had a small block fitted with a dial test indicator that we'd use to ascertain a slightly longer (or shorter) shoulder so the actual size marked never really came into the equation

[kpj53]

Thanks for the reply,

Was thinking maybe someone had measured some. BRP shows .834 as X3 (but maybe thats just the longest they have), but I really need more like a .845 to get headspace correct on a semi auto reweld with the bolt and barrels I have. Was just wondering if that size was even a possibility or the difference between marked ones was like .001-.002.

Unless anyone has taken the time to measure a box full of them, I doubt whether anyone will be able to tell you. That's because, as you say, the actual number on the locking shoulder or barrel nut or flash eliminator washer or bolt head etc etc was just a very inaccurate guide.......... When we took one size out we put it back in a big tray full of them and selected another, As a matter of interest, we had a small block fitted with a dial test indicator that we'd use to ascertain a slightly longer (or shorter) shoulder so the actual size marked never really came into the equation

[ActionYobbo]

Set the barrel back to headspace and get the correct barrel nut or shim the barrel nut you have

[kpj53]

Set the barrel back to headspace and get the correct barrel nut or shim the barrel nut you have

Thats most likely the only thing that can be done (other than cut the receiver in half again and shorten it lol), I have three barrels and they all headspace within .002 of each other and lock in tight. Unfortunately thats not something I can do here at home.

It actually functions 95% with .020 over max headspace with new PPU ammo, had a few broken shoulders left behind in the chamber out of 120 rounds. But HXP and some other 50s surplus i have will split the case a little above the rim every time, thats when I checked the headspace and found it so far off. If I can get .013-.014 closer with an .834 shoulder it sure wont hurt. I wont be putting thousands of rounds through it so if I can just get not to lock with an .074 HS gauge I'd be happy.

Will most likely have to send it out to get the barrels set back and new locking nut fitted in the future.

[Joe H]

kpj53,

It's been a while since I had to work with the locking shoulder. I think the "normal" size was about .812 -.814". "Normal" being used very loosely. So I doubt there were any made significantly larger than .834" given what they were made for (adjusting for machining tolerances and wear in the barrel & receiver).

I had a similar problem with a MGS build. I made a new locking shoulder long enough to get the headspace right. If you make one be sure the LS bears on the receiver recess and not the screw. LS should be hardened. Sketch below.

Another option I used was to TIG 4140 rod on to the LS face and then grind back to size, see sketch for grinding angle. The 4140 will provide a hard face.

Joe

[kpj53]

kpj53,

It's been a while since I had to work with the locking shoulder. I think the "normal" size was about .812 -.814". "Normal" being used very loosely. So I doubt there were any made significantly larger than .834" given what they were made for (adjusting for machining tolerances and wear in the barrel & receiver).

I had a similar problem with a MGS build. I made a new locking shoulder long enough to get the headspace right. If you make one be sure the LS bears on the receiver recess and not the screw. LS should be hardened. Sketch below.

Another option I used was to TIG 4140 rod on to the LS face and then grind back to size, see sketch for grinding angle. The 4140 will provide a hard face.

Joe

Thanks for the reply,

I may just weld one, barrels fit real nice on this one and it shoots straight. Even with the huge headspace it will still do 2-3 moa at 200 yards easily. If the largest X3 I can find knocks .013-.014 off from the .820 that was in there it will probably be fine with new brass ammo. An .834 shoulder will keep the bolt from closing all the way on a .074 CHS gauge, but will not keep the carrier from locking under its own weight. It takes about another .010 to stop the carrier from locking the bolt. Not sure how much it will tighten (or loosen) up when it warms up.

I'll see what happens when I actually get an X3 shoulder here in a couple days. Its an absolutely gorgeous rifle and it will not be fired all that much or used for home defense But I'd like to be able to use surplus ammo, FMJ PPU dried up and who knows when more will come in.

[stencollector]

The weather was decent tonight so I went out and grabbed my little box of locking shoulders. I measured them up and was getting some that were substantially smaller than yours, and some that were substantially larger. So I pulled out my old Canadian Army Catalogue of Ordnance Stores for the Bren gun. It lists 11 sizes of locking shoulder, beginning with 0, 00, 1, 1x, 2, 2x, 3, 3x, 4, 5, and 6. My largest one measured a whopping 8790 and went down to 8530. Most are Inglis, but one of the largest ones is marked 3X and is Enfield marked, which is unusual for the guns I work with. Most are pretty pure Canadian.

There are some various manufacturers part numbers on some of them that don't tie in with my parts catalogue. Mind you the parts catalogue only lists 2 part numbers, MGD1352 and D5(E)3720/30. The smallest and the largest are all the 1352 number while the X sizes have the 3720/30 number. There are seperate Canadian Nato Stock Numbers for each of the 11 sizes mind you.

Photo shows the spread. I have more of them hiding somewhere....will have to look further unless one of these would do the trick.

I must say that I am jealous of the American semi-auto guns. Here in Canada, even as re-welds, they are considered prohibited converted autos since they use the original receivers, even though they were cut up. Hopefully someday someone makes up brand new upper semi auto only receivers.....I would happily drop 10K on such a gun if it was legal.

[kpj53]

The weather was decent tonight so I went out and grabbed my little box of locking shoulders. I measured them up and was getting some that were substantially smaller than yours, and some that were substantially larger. So I pulled out my old Canadian Army Catalogue of Ordnance Stores for the Bren gun. It lists 11 sizes of locking shoulder, beginning with 0, 00, 1, 1x, 2, 2x, 3, 3x, 4, 5, and 6. My largest one measured a whopping 8790 and went down to 8530. Most are Inglis, but one of the largest ones is marked 3X and is Enfield marked, which is unusual for the guns I work with. Most are pretty pure Canadian.

There are some various manufacturers part numbers on some of them that don't tie in with my parts catalogue. Mind you the parts catalogue only lists 2 part numbers, MGD1352 and D5(E)3720/30. The smallest and the largest are all the 1352 number while the X sizes have the 3720/30 number. There are seperate Canadian Nato Stock Numbers for each of the 11 sizes mind you.

Photo shows the spread. I have more of them hiding somewhere....will have to look further unless one of these would do the trick.

I must say that I am jealous of the American semi-auto guns. Here in Canada, even as re-welds, they are considered prohibited converted autos since they use the original receivers, even though they were cut up. Hopefully someday someone makes up brand new upper semi auto only receivers.....I would happily drop 10K on such a gun if it was legal.

I would trade the semi bren for a few SVT 40s lol, at least you guys get the SVTs fairly cheap.

Appreciate the time you put in, but you must be measuring them differently than me. This is what I am using for measurements:

30: Bren Locking Shoulder - BRP CORP Store

I have an X3 here that measures .832 and another unmarked that measures .820. I measured them by putting them on the corner of a steel block and pushing down in the caliper jaws so they sit flat.

Couple pics:

[stencollector]

So realizing that my numbers are substantially different from the others, I tried again measuring a different way. I put the flat of the shoulder against the caliper, and measured to the small edge. The 3X measured the largest again, and a bunch of the others ended up grouped together. Is this the method you guys used?

In the first method, I measured from the bottom of the small edge to the highest lip. When I checked the overall heights of the locking edge, I realized this method really didn't measure the distance.

Photo attached with the new measurements.