Bren Barrel nut question

[Vincent]

I would like have a spare barrel for my semi-auto Bren III and be able to change barrels as quickly as possible. I really don’t want to change the locking shoulder every time I change barrels.

Does the barrel nut have an effect on the CHS?

I checked the barrels I have and didn’t have any luck finding one that would headspace with the nut that’s on the gun. Now I am wondering if I might get lucky and find a barrel and nut combination that would headspace without having to change the locking shoulder or does it not work that way?

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.

[WallyG.]

Your on the right track... its possible if you have a good many to choose from... but trading barrels might also get you the same... all depends on what spares you can work with. Barrel, nut, locking shoulder are the three input variables. If you need more space BRP has shims that will hold the barrel further out by several thousanths.

[Peter Laidler]

Mmmmmmmm....... We fitted zillions of barrels to Brens and two of the conditions (there were many, believe me....) were that the barrel nut was to remain the same, as was the locking shoulder. Fitting barrels was a looooong learned process at Carlisle under an ogre called Harry Weeks, otherwise known as '.....Sir, spelled CUR...'. If you have a Mk3 Bren. If you have one barrel that fits perfectly, locks up tight and is in CHS then others should also be close. The barrel nut simply tightens up the barrel by pushing the barrel shoulder rearwards against the barrel facing shoulder of the gun. You can get away with increasing the CHS by fitting barrel washers that come in 2 sizes of .002" and .003", up to a maximum of .006" and in any case, only 2 can be fitted.

As you can see, this COULD add .006" to your CHS but it could alsoover- tighten up the barrel you want to fit too. Then you have to try to find a barrel nut that will tighten BOTH barrels. Barrel fitting really is a classroom discussion, observation, discussion, practice, and on and on and on. Our school Brens were all well worn so barrel fitting was a true trial for us......

Additionally, we had Brens cut completely in half longitudinally down at the centre section so that we got to understand the theory and the actual dynamics of what was happening.

[Vincent]

….. The barrel nut simply tightens up the barrel by pushing the barrel shoulder rearwards against the barrel facing shoulder of the gun…..

Thanks Peter. That’s what I really needed to know.

I am guessing the two shim maximum of .006" is to prevent part of the breech block from contacting the body?

[Joe H]

Vincent,

Have you actually measured the head-space with the different barrels? As long as you are within "Field" you should be good to go. I'm assuming we are just talking about .303 British. In my experience the 303 is very tolerant of loose head-space, I expect because of the long solid base of the cartridge. Most of what I know about the .303 indicates you have to be way out to start having problems. On the other end of the scale 7.62 x 54R requires very tight head-space.

If I'm going to use a 7.62x54r barrel I set it up for tight head-space. So far other .303, .308, 8mm all fit with no head-space adjustment. So far I haven't had to mess with other barrel nuts or shims.

Just my experience

Joe

[Vincent]

Yes, .303. I checked them with .074” and .064” gages. The bolt locks up on the .074” NO-GO gage.

[tr63]

to read /find