View Full Version : Locking Shoulder Hole Size

September 05, 2001, 19:31
Has anyone measured the size of the locking shoulder hole size in their receiver?

I have measured a number of locking shoulders here and find that they come to about a .297 diameter where they enter the receiver for positioning.

The holes on the Imbels seem to be about .295.

Has anyone measured the holes on an Entre'prise or DSA for diameter?

Or, has anyone found a locking shoulder smaller than .297 on the parts fitted to the receiver?

I have never seen this figure on any post.

September 05, 2001, 23:03
Try this link

It lists O/S diameters and shoulder sizes.

September 06, 2001, 12:06
Bill, I get those same numbers, except with the oversize-shaft LS's that are turning up in some of the Australian L1A1 kits.

September 06, 2001, 13:36
Part of the problem in assembling these kits is the tiny differences in sizing.

I have not had the chance to measure the Aussie locking shoulder size so I can't speak to its size.

However, from the Imbel, G1 and STG58 the .297 seems to be the common size.

I suspect these numbers will be critical to consider in any build of any receiver. The alloy may make it a critical number.

I also believe we will be using a lot more breeching washers in the future on assemblies.

Oh, well, live and learn daily, I suppose.

September 06, 2001, 20:21
Bill , I have seen a few of the locking
shoulders from the L1A1 kits from Tapco.
They are evidently not the original locking
shoulders from the rifles themselves, because
they are new,never installed locking
shoulders. One of mine is oversized.

It is marked 10.3 and measures 0.2695 with
an outside diameter of 0.300. Others may also
have received these oversize shoulders.

These were evidently used in arsenal repairs
or rebuilds to correct loose locking
shoulders , or when the locking shoulders are
replaced a couple of times causing the hole
to become enlarged.

If you just want to find out the hole size,
check out Gunplumbers workbook. I believe
he used to send a receiver blueprint with the
printed version. It should be listed there.

September 06, 2001, 21:05
Jen has some also that are oversized G. I became interested because of the oversize holes in my Williams receiver. But it should apply to every receiver, when one considers it.

As the consumer becomes more sophisticated the solution to some of the problems in assembling these mismatched parts kits to new receivers is apparent. The next question is whether or not the locking shoulders are around and if not where we acquire them.

Every time I am around a build I become more knowlegible of the parts and their inter play. sledgehammer and I speculated that there could be a vast range of barrel shoulder and locking shoulder sizes. This is due to the large number of manufacturers. That makes any receiver have a number of problems depending on the original manufacturer. With the increased variety of kits and receivers coming on line it will become more important to know these possible dimensions.

The dark science of locking shoulders may become very important fairly soon.

September 06, 2001, 21:16
Bill check with Brad @ Gunthings he posted he has oversize shoulders.

September 07, 2001, 06:28
I saw that Sparky. I was emailing back and forth with Brad yesterday but did not get into that. He is most envious of my C2 carrying handle and I was very sympathetic to his need. Not enough to part with the handle, however.

We will have the opportunity to examine a large variety of kits and receivers at sledgehammer's on Oct. 13. So we should be able to gather a lot of ecclectic information at that time.