The recoil and reciprocating buffering action

[Joe H]

Peter,

Thanks for the discussion on the buffer. Some of the Semi Bren builds eliminate this buffer and use the space for a striker spring. Maybe ok for a semi since I've never heard of one failing but I hate to remove any buffers even on a semi build.

Joe

[Lee Enfield]

Ahhhhhh. Thank you.

I had always understood the "buffer assembly" to be merely the spring and piston buffer plate.

Now seeing the "piston buffer Nut" and "friction Collar" it becomes clearer.

How much wear would the "Collar, friction" actually experience? Does it actually expand and grip anything, or is it another "blish block" ie) great theory, little to no practical value (now that Thompsons have been brought up) concept?

[Peter Laidler]

GOOD question L-E. The friction collar - or as I prefer to call it, the brake ring - does actually work. It does spread and does grip the side walls of the buffer housing. If you were so minded and had a class of students to set a series of tasks for you could set up a small trial with a cut-open, cut down butt slide buffer housing and measure the poundage WITH and withOUT the nut and collar. Interestingly, when you visually inspect a well worn buffer housing you can actually see the witness marking made by the collar.

Another good part of your Q is that it has prompted me to re-read the student notes again. It mentions that the 3 small recesses in the rear end of the friction collar are there to ensure that the ring opens up equally around its circumference so as to friction equally around its circumference. I found it interesting precising (?-is that a word?) the old Shrivenham course notes for this. Makes you think...... Just ONE small part of the gun can be so mechanically interesting and important. Or just nerdy for the engineers amongst us!

[Joe H]

GOOD question L-E. The friction collar - or as I prefer to call it, the brake ring - does actually work. It does spread and does grip the side walls of the buffer housing. If you were so minded and had a class of students to set a series of tasks for you could set up a small trial with a cut-open, cut down butt slide buffer housing and measure the poundage WITH and withOUT the nut and collar. Interestingly, when you visually inspect a well worn buffer housing you can actually see the witness marking made by the collar.

Peter,

I'm currently working on a semi BAR. I just got a copy of "Rock in a Hard Place" about the BAR. They give a detailed description of how the BAR buffer works. Same design as the Bren and same description as noted above.

Just as you said a small mechanically interesting part to us nerdy engineers

Joe

[TactAdv]

.....Just as an aside to this.......I've had the "pleasure" of repairing a few fullauto M1918A2 BAR's over the years and one of the more common issues is that the steel portions of the "cups-and-cones" buffer (all FOUR) inside the buffer stack are VERY hard to keep free of rust, the buffer tubes being inside the stock more often than you'd want to think get heavy accumulations of not just dust and lube, but also a lot of moisture gets trapped in there and that is one area that is invariably overlooked when cleaning the guns. Many guns start to have trouble, especially when set to "semi-auto" setting as the sliding actuator plug stops moving freely as required, and the buffer stack can get either very sluggish or possibly even just jam solid from years of rusting inside the tube. That buffer assembly is almost never completely cleaned, except when the gun stops working and the whole thing is torn down to find out why. Usually, it appears people just try and keep dumping more applications of some kind of spray lube in there which quite happily accumulates and combines with whatever amount of dust and grit that finds its' way inside too.

Same would hold true with the Bren.......therein laying a measure of advice. ;-)))

-TomH

[Joe H]

.....Just as an aside to this.......I've had the "pleasure" of repairing a few fullauto M1918A2 BAR's over the years and one of the more common issues is that the steel portions of the "cups-and-cones" buffer (all FOUR) inside the buffer stack are VERY hard to keep free of rust, the buffer tubes being inside the stock more often than you'd want to think get heavy accumulations of not just dust and lube, but also a lot of moisture gets trapped in there and that is one area that is invariably overlooked when cleaning the guns.

Thanks Tom for the insight.

The fire control on the semi will be hammer fired so the actuator will serve no purpose but I still want that buffer to work. I guess I'd better pull it apart and give it a good cleaning. I think the gun was in WWII rebuilt after the war with a new barrel, put in storage and then de-milled.

Joe

[Peter Laidler]

The gun crews weren't permitted to strip the buffer although we did teach them how to take the butts off and grease the return spring tube. That's why the Armourers would almost automatically, out of habit I suppose, just test the buffer every time he encountered a Bren coming in. You could just feel the graunchy ones that needed stripping down.

Almost forgot to say that you'd occasionally get a buffer plate that had cracked right around the centre hole. Stripped a few of them in your time Tankie and Skippy?

[tankhunter]

Just a 'Few' Pete!...........

I never encountered any completely seized buffer units in Service. I guess it was due to the fact that all units had either six monthly or Quarterly inspections by Us Armourers!

Had a few buffer 'Anvil' plates with cracks in them. But when you consider the battering some of them get. It's not suprising!

Back to the 'Bellvue Washer's' mentioned by another Poster.

These are used in the L7A2 /M240/ MAG 58 Buffer units. They are VERY hard, but do have a certain amount of Elasticity. I used to test a unit when it was out of the Butt stock. For whatever reason. By putting the Buffer unit under a Flypress. And compressing against the round buffer anvil, & the rear of the buffer housing nut (For the screw, stock, bolt)
You CAN see the anvil compress under load. Thus Proving the buffering action was working OK inside it.
The L7 Buffer units ALSO had a cone & cup set up internally. That worked the same as the Bren/ LMG. The only difference was, the cone was steel. & the 'Cup' was neoprene.
You HAD to grease everything inside the housing upon reassembling. You would think this might reduce the buffering action. By reducing frictional forces with the Lubrication introduced. But it didn't do anything to affect the intended buffering action!

Upon ANY GPMG series of guns. Coming to me for whatever reason. Upon stripping down to inspect/ repair, or whatever was needed. It was a VERY Simple matter. To shake the butt assembly, & listen for the possibility of rattling. This indicated immediately, that one or more of the washers had failed. & fractured. Of course, when you stripped the assembly down. You inspected every component. & rebuilt the unit to in service standards.

[tr63]

Peter,

Thanks for the discussion on the buffer. Some of the Semi Bren builds eliminate this buffer and use the space for a striker spring. Maybe ok for a semi since I've never heard of one failing but I hate to remove any buffers even on a semi build.

Joe

So if you have semi auto Bren that the Buffer has been removed is this going to be problem ?

[AmEngRifles]

Thank you for resurrecting this thread. I needed it.