That proof thing, again

[Bruce_in_Oz]

I have excerpted notes from a January 1969 report from RSAF Enfield of a test they carried out, firing 75 x 7.62mm NATO oiled proof rounds through a No 4 barreled action 'without any serious damage to the body'.

Notes continue: "In the course of this test, two bolts were fractured, one on the 60th and the other on the 75th round, but that 'the bolt failures were such as would be unlikely to cause injury to a firer'. The military proof pressure used at the time, was 28 tsi radial, using one dry and one oiled proof cartridge per rifle. Clearly, this 'torture test' was several orders of magnitude beyond what any No 4 rifle would ever experience in routine use."

If anyone has a copy of the full report it would make an interesting addition to the technical library.

It is also worth adding that if an Enfield bolt head is cracked due to failure/overstressing, which is not that uncommon, it can simply be replaced with another, and that the main full-length locking lug on the No 4 bolt is quite massive." Not only that, but there is a hell of a lot of metal behind the locking shoulders in the receiver.

See what happens when the dainty little lugs or shoulders on "modern" rifles with no additional safety lug, unlike a Mauser, fail.

But wait, there's more!! P. O. Ackley did a bunch of tests way back when. With a SMLE action set up for .30-40 Ackley Improved, the following results were obtained:

57gn Hi-Vel#2 - 150gn ball projectile - High pressure, Primer OK
52gn 4198 - 150gn ball projectile - Leaky primer
50gn 2400 - ditto bullet - Bolt wrecked, receiver bent.

He noted:" When this action gave way, the receiver itself bent down at the rear, allowing the front end of the bolt to come up out of the receiver ring, thus allowing the bolt to be bent and to be broken. The locking lugs themselves did not give way".

Australian XP 7.62NATO No1 rifles were subjected to similar abuse to the No4 above, (and this is with receivers "modified" to accept FAL mags). The one I got to play with in the late 1970's had stretched a bit , again, more on the right than the left but had not shattered, . Not surprisingly, the project was abandoned: I suspect that factors of "logistics" and professional pride also contributed to this abandonment.

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