doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 8/mm/57 Nimrod drilling [318/323?]

I am back again. To answer a guest. byDer Ami, I have done 3 chamber castings[10 days ago] to try to determ. JR orJRS. My final cast with cerrosafe meas..3605dia neck. At 1" from rim of case bore meas..314 to .322,this is a false reading as rifling is such that calipers are not totally on lands or grooves at the same time. Bore cast meas. .309 to.322 ,[ same condition with calipers] I have S &B 8/57jr and jrs factory loads. The JR load without issue however the Jrs insert 3/8" short of chambering. I can chamber it if i use some pressure. I smoked it and it is hanging up on the bullet at about 3/8" ahead of cart. rim. It did not distort in any way after having to force cart into chamber. I am totally confused as cast suggests JRS but chamber say NO. Proofmark states steel jacket bullet

Given Pilgrim's travails, is it any wonder that no 8 mm cartridge has ever achieved popularity in the USA. Until I got interested in collecting German guns, I wouldn't touch an 8mm chambered gun with a 10 foot pole. Even now I only have one drilling in 8x57JR.

I've read lots of text here and at GGCA about 8x57s and it seems the more I read the less I know. The only thing worse is the 9.3x72 of which there are several varieties.

[pilgrim
Have you shot your gun yet???
You REALLY need to come to Amarillo
Mike

Shoot the .318 in it first, and if accuracy is a bust
then look at moving up in diameter.

I just bought an 8x57JR (said to be a .318 by the seller) Simpson Jager V.drilling that has a 9/85 date code. Is it possible that the 8mm mess was standardized by 9/85 and S&B 8x57JR ammo is OK? I've ordered some S&B ammo but it's 2months backordered so I can't fire it yet.

Perhaps I am missing something, not uncommon, but you don't need a chamber casting, you need to slug the bore. Easily done by taking a cast lead ball or bullet (I last used a small fishing sinker that I tapped to about 3.3 dia.) and gently tap it into the muzzle with a brass hammer. Then poke it out with a rod from the breech and see what your diameter is with calipers.

FWIW my 1939 T&S Nimrod drilling slugged at .318 and shoots the S&B 196g JRS stuff into 3" with iron sights, or at least did 10 years ago when my eyes were better.

All that S&B stuff is steel jacketed BTW.

[pilgrim,
I believe,since the 8x57IRS won't chamber, your rifle is intended for 8x57IR.The trouble you are having with measuring the bore(groove) diameter is because the barrel has an odd number of grooves(likely 5).The precise way to measure these is with a special V anvil micrometer,or a special "V"block and normal micrometer or caliper.It is not especially uncommon for rifles to show conditions like yours.Even though the original 8x57(8x57I M88)and also 8x57IR was intended to use a .318" bullet, the barrels were larger( usually .319-.320", but some up to .322").When the bullet was changed to a spitzer (S) shape in 1903,all the rifles in the German inventory were inspected and modified as necessary to fire the new ammunition.This was accomplished in 1905 and the change to the ammunition was announced.Other than changing the sights to match the trajectory of the new ammo, the main change was in opening up the neck diameter(if needed)to fit cartridges with .323" dia.bullets.Note that this wasn't usually done by other countries that had rifles so chambered, nor for sporting rifles.All this means is that the main difference between these two chambers is the diameter of the neck.Given manufacturing tolerances, sometimes a IR chamber will accept a IRS cartridge.As you found out, sometimes you can force a IRS cartridge into the chamber.This is not a good test, however, because the neck might hold the bullet enough to increase the chamber pressure to a dangerous level.A better test is to see if a .323" bullet will easily enter the neck of a cartridge fired in that chamber.If it will,IRS ammo should be ok even if the barrel is a little smaller;conversly, if it won't,IRS ammo shouldn't be used even if the groove diameter is .323".
oldmanriver
If your drilling was made in 1985, it is likely chambered for 8x57IRS instead of IR.I suggest the same test as above.
Is everybody confused yet?
Mike