Largest locking shoulder?

[kpj53]

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.

Thats a little better

Looks like I have one of the larger ones already at .832. I appreciate the time you put in. Most likely I'll have to have one welded up.

[stencollector]

I'll try and get back into the shed tomorrow or Saturday. I'm pretty sure I have a bunch more.

Since the "large" ones are marked 3x, I suspect there are larger with the sizes 4, 5 and 6. Mind you, the measurements from BRP seem to be contrary to that theory.

[kpj53]

I'll try and get back into the shed tomorrow or Saturday. I'm pretty sure I have a bunch more.

Since the "large" ones are marked 3x, I suspect there are larger with the sizes 4, 5 and 6. Mind you, the measurements from BRP seem to be contrary to that theory.

I'm pretty sure .834 is about as long as they get from the factory. From what I have read so far X3 is the largest but who knows. If you have the time take a look, even an .837 would help

[TactAdv]

This brings up the obvious question, is there an original manufacturing drawing that specifies the "baseline" or "blank" dimensions for the locking shoulder to be used to grind all the registered sizes specified?

They had to start with some form of blank that would have to have been long enough to grind to at least the longest registered size specified?

That is the original information I'd like to see.
-TomH

[kpj53]

This brings up the obvious question, is there an original manufacturing drawing that specifies the "baseline" or "blank" dimensions for the locking shoulder to be used to grind all the registered sizes specified?

They had to start with some form of blank that would have to have been long enough to grind to at least the longest registered size specified?

That is the original information I'd like to see.
-TomH

Would be good to know the info but it seems the only way to know for sure is to measure, I have three X3 marked shoulders here now, they are all within .002 of each other one is new and two are used.

I dont think the spread is that far, I would think whoever was doing the marking could be a bit off, thats why it was best to pick and choose between many.

[Kev G]

For reference -

[Peter Laidler]

Have you just got these drawings KG - or had them some time. They seem to raise a couple of interesting but puzzling queries

[nzl1a1collector]

ohh goodie those images will help id the 100 odd locking shoulders I found under a rock

[Kev G]

Have you just got these drawings KG - or had them some time.

Had them a few years now Pete ?

ATB KG

[kpj53]

Those drawings are interesting thanks for posting them.

FWIW, after a welded locking shoulder wearing heavily after only 20 rounds I ended up cutting an .015 shim to put behind a new X3 shoulder, opened the screw hole .015 bit with a tiny bit of taper on the shoulder so it tightens snug against the shim. Put a small notch on the top of the shoulder and a small bend at the top of the shim to keep it from dropping out if it loosens, plus a little bit of loctite bearing mount between the shim and shoulder - I dont think it will ever go anywhere..

200 rounds later all is fine and nothing has moved, shoulder screw is staying tight with some red loctite. Something I'll have to keep an eye on but I thought it was a better alternative than cutting down 3 barrels and custom making a barrel nut or trying to have a custom shoulder made.

Was a little cold today (20 degrees F) but it was a good day to put 100 rounds through it to sight in all three barrels at 200 yards. My kid was freezing but the Bren worked 100%