Double "Rat's Tail Springs"

[Flying10uk]

The thing that I don't like about having 2 springs working closely together is that if one spring fails/breaks then the broken parts are liable to foul on the other spring. With press tools where compression springs are commonly used as part of the tool to strip metal off punches and to keep metal flat I don't recall ever fitting an inner spring to increase spring pressure. I did sometimes fit an extra spring on another part of the tool and also increase the size of the spring.

[Sentryduty]

I can understand that, however the main take away in a firearms application, breaking one spring of any sort generally puts a gun out of operation, if it knocks another out along the way the net change is still a spring assembly replacement.

With the field tool roll for the C6 (FN MAG 58, L7, M240B pick your name) we would carry a spare recoil spring and guide rod assembly for repairs. The change would take less than 30 seconds, and breakages were rare. I can't recall if they were a single or double spring, but my point is, for field repair we would just change assemblies. With the "school guns" provided at training centers for Machine Gun courses we would generally see failures relating to wear and tear of extremely high round counts with guns approaching the end of their service life. With one of these such guns I had the cocking handle tear off in my hand while clearing a stoppage on my gun in the Sustained Fire Role. From there it was a matter of opening the feed cover and hooking a length of cord on the feed roller like a garrote and clearing the gun.

Our first line and deployment guns were in much better condition, and seldom had any major issues. Having a junky MG for training is better anyway, gives a gun team lots of practice on IA's and stoppage drills. LOL.

[Vincent]

My guess is a sufficiently stronger spring would not work in the tube assembly. That’s because it would be made from thicker wire. Thicker wire would increase the solid length and change the working length of the spring.

Adding the inner spring maintains the same solid length and working length of the spring. So there’s no need to redesign the whole assembly.

[Peter Laidler]

The application of the double return springs in the Bren was for a slightly different reason. For the Bren it was to cushion the violently recoiling portions so that by the time the heavy piston, piston extension, piston post etc AND breech block reached the buffer most of the kinetic energy had been removed and the working parts hit the buffer at a reduced rate. Previously to this they were slamming into the buffer and causing a radial fracture to the buffer plate. There WAS a slight increase in the double return spring weight over the single return spring weight but if my memory serves me right, it increased from 13.5 lbs to 16 lbs from the cocked position. Feel free to correct me if the figures are slightly incorrect. But it was a small price to pay and although piston/body buffers did fracture it was a rare occurrence. And while we always polished the face of the buffer they were well hammered and by polishing them we could see the start of any trouble

Previous to this double return springs episode, it was the piston post, spring and plunger that got a hammering as the piston, piston extension piston post etc struck and unlocked the breech block due to the much increased gas caused by the enlarging of the gas ports, The plunger bottomed out in the piston post causing it to mushroom out deep in the hole, jambing the spring onto the post (rendering it totally redundant thereafter) so that any buffering of the piston post as it unlocked the breech block was non existant.

Is anyone interested in this guff.........? Anyway it was PARTIALLY cured by the new Mk2 piston post and plunger that couldn't bottom out and jamb up together but in doing so, broke the piston post springs at approx 70,000 rounds. That's the reason why your Bren gun spare parts wallet contains a spare piston post spring. There, a small bit of Bren Gun History

So mote it be!

[Vincent]

Is anyone interested in this guff.........?

Yes. I am very interested and appreciate you taking time to share it.

I am also looking forward to the book.