Barrel Nuts / Headspace and such

[DOD 7.62]

Apologies in advanced if this has all been covered before, first thing, barrel nuts, is selecting the right size a simple matter of changing sizes till ones too tight to lock up then moving back one size? If not what's the correct procedure? Next, locking shoulders, I understand there are eight or so sizes but was there a more common size, if you don't readily have access to a full set where is the best place to start? Is there a way to measure what size is required (like with the L1A1) or is it all trial and error. Lastly locking shoulders weren't calibre specific were they? Same part .303 to L4? Any info appreciated.

Daniel

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Peter Laidler]

Sooooooooooo many questions and all you asked are interrelated - a bit like the No4 bolthead.

Like No4 boltheads, while barrel nuts might have a number on them, it should only be taken as a bit of a very, very loose guide. We would start with a big box of them and if it was just one barrel, as in the L4 gun, then yout keep trying until you gtet a barrel nut that locks down hard on the barrel. Once locked down, you shouldn't be able to move the barrel in the body. It MUST be tight. Don't even attempt to alter a barrel locking nut at the ring part because they are diamond hard. If you don't believe me, just try to centre punch a dot on the front or rear face.

Locking shoulders................ The samer. Treat any numbers on them as a general guide to the size. I say this because like barrel nuts, because they have been used in another gun and replaced, doesn't mean that they're worn out. They might be slightly used IN THAT GUN, but they are perfectly serviceable so that go back in the tray/box to be used again.

L4 locking shoulders are NOT the same as .303" Bren locking shoulders. L4 locking shoulders are the same sizes as 7.92mm Bren locking shoulders so it makes locating them doubly difficult.

I forget the CHS limits of the L4 guns without looking it all up again, any ideas Tankie?

But on that subject, I used to let the block go forwards by running it in the piston extension against the CHS gauges with my fingers and check the gap between the shoulder and the locking face of the breech block.

But believe me, there's a LOT more to it with a Bren/L4. There's breech block stop and barrel face clearance and running clearance and...............

[tankhunter]

Pete, no, off hand, neither can I! I DO know however, they are different to the L7 & L1A1 Rifle.
As an aside, the Navy L3 Gun CHS sizes were different also! I dont know why? but there was a tighter size for the L4A3. Also base workshops CHS limits were tighter to allow for in Service wear later in usage.

I also have the info, but is is all upstairs in my attic on Microfische. Getting it all down & ploughing through it would be a pain!

However, IF you get stuck & Pete dosent come up with the goods. Let me know, & I will dig it all out.

[Kev G]

CHS -

ATB Kevin

[DOD 7.62]

Thanks everyone, all great information. Peter, you mentioned there is a lot more to the L4 with headspace, "breech block stop, barrel face clearance, running clearance", etc, if you have the time could you expand on this please?

Daniel

[Peter Laidler]

I just knew that I'd answered this earlier...... Just remembered, I did it under the Australian Brens thread! Anyway, maestro KG has it above for unit but Field and Base workshops, 1.634" NO-GO.

[Peter Laidler]

Re your ask in q 5 DOD. To be honest, we were taught the technical stuff on Brens, L4's and the bit Browning M1919 in the third year of our apprenticeship under the not so pleasant 'Harry' Weeks........, known to us as 'sir' but pronounced 'cur'! It took 3 months to learn this stuff and that was after we'd done 2 years of other technical stuff. There was a lot of classroom theory and much practical work on the bench before we became remotely proficient.

What I'd suggest is this. What about putting a small ad in one of the RAEME newsletters/comrades journals or in one of the local RSL's for a 70's era ex RAEMEArmourer to come and assist/teach you. It's not just a case of quoting the EMER either as this is really just a bible for gauging limits. Most of the stuff is done from pure experience and learning.

I'm sure Tankie and Skippy will come in and agree here............

[DOD 7.62]

Thanks Peter, but you can relax, I wasn't after an online armourers course, it's not a job I'd remotely think to tackle myself in the back yard. Sorry if I've miss phrased my question, I guess what I was more interested in was why? Your statement was that "There's a lot more to it with the Bren/L4" Is it because it's a rimmed case? The higher pressure of the 7.62Nato Cartridge? An advent of the modifications applied in the conversion process? All of the above? If it's all to technical and can't really be summarised fair enough. I was just interested?

Daniel

---------- Post added at 08:51 AM ---------- Previous post was at 08:47 AM ----------

Oops! Re my last post. Before I get my nuckles whacked, I did of course mean "Rimless case", (7.62) my bad.

Daniel