Swedish Mauser accuracy woes.

[Potashminer]

A visual - a 130 grain 6.5 mm Norma "Golden Target" bullet set into a NOS Swede M94 barrel. The barrel has never had a round fired through it. One of those bullets is laying in the front. So the "straight wall" part of the bullet would be where the case neck grabs - maybe can visualize the gap that should exist between muzzle and case mouth. The "fat" part of the bullet is not close to entering the muzzle.

 

[bearhunter]

I tried a full length sized Norma brand 6.5x55 into a pre-WWI german 7x57 sporter. Won't quite let the bolt close. I think is hanging up at rear end of the case. At very rear end, 6.5x55 chamber is .4815" as per SAAMI; 7x57 chamber is .4777" A 6.5x55 cartridge calls out by SAAMI at .4803" diameter on rear end. So a 6.5x55 case is a smidgeon too fat on very rear, to fit into a SAAMI 7x57 chamber. But if chamber had first been 6.5x55, then reamed out for 7x57 without shortening the barrel, I think a 6.5x55 would fit into that re-done chamber. Most military do not reload cases - so fire new round, extract and on to next new round - would never know the difference how chamber was done?

I also tried with a made-in-1955 Husqvarna Model 4100 in 7x57 - same story - quite certain I am seeing rub marks on extreme rear end of the case, where it would have been trying to enter chamber. Bolt was all the way forward, but would not turn down.

I have no new factory 6.5x55 brass to try - all here has been previously fired at least once.

I tried a 6.5x55 case in a Brazilian Mauser 7x57 chamber an hour ago. It entered the chamber without any issue or hang up.

Sporting chambers tend to be on the minimum/median side of spec, while military chambers tend towards the maximum side. For obvious reasons

 

[Potashminer]

It had never occurred to me to try putting a 6.5x55 case into a 7x57 chamber - obviously will go, in some cases. Length to shoulder / neck is so close, would think it would fire without issue if the bolt was able to close. Other similar "rimless" case combinations exist, that will chamber and fire - 308 Win onto a 30-06 chamber, for example. The major "clue", in this instance, short of a chamber cast, will be what OP discovers for groove and land sizes in that barrel.

 

[The_Shmoo]

Rudimentary slugging of the bore has been completed, grooves mic to ~.286". Next step is to acquire some snap caps and ammo for function testing. Thank you everyone for your assistance in this matter.

 

[Potashminer]

So that groove dimension is constant with a 7mm bore. Next is to ID what it is actually chambered for. You already know that Swede 6.5x55 cartridges fit and fire - could be a 7x57 Mauser chamber. Could be a wildcat based on 6.5x55 altered to use 7mm (.284") bullets. If you can not do an actual chamber cast, might be able to borrow a Full length sized or new 7x57 case and see if that chambers? Is more than checking "headspace" - normal gauges are only checking a distance from bolt face to a reference point within the chamber - you are now also concerned about neck diameter and length, case diameter, etc. Likely gets to throat size and length, once you insert bullets into an empty case that fits properly.

 

[Rob]

Why not just do a chamber cast and measure it?

 

[cosmic]

Well - North American 6.5 brass is smaller at the base and rim than Euro brass, as it is made from 308/30-06 stock. Since you already shot 6.5 in the gun without blowing out the shoulder, I would see no issue in trying 7x57, as there are:
- no other 7 mm cartridges of that (short) length that I'm aware of, except 7-08 with is a relatively new offering.
- it is known that many m94's were converted to 7 x 57.

 

[Potashminer]

Well - North American 6.5 brass is smaller at the base and rim than Euro brass, as it is made from 308/30-06 stock. Since you already shot 6.5 in the gun without blowing out the shoulder, I would see no issue in trying 7x57, as there are:
- no other 7 mm cartridges of that (short) length that I'm aware of, except 7-08 with is a relatively new offering.
- it is known that many m94's were converted to 7 x 57.

I guess I should not be surprised if North American ammo makers use 308/30-06 stock to make 6.5x55 - but North America's SAAMI says otherwise on their chamber and cartridge drawings. Home hand loaders can no doubt "make it work", but I would have thought there was some reason for NA ammo and firearms makers to follow SAAMI standards - but is not a "law" over here - no "penalties" for non-compliance, like there is for C.I.P. standards in many Euro countries.

I looked at the 2015 SAAMI cartridge drawings - I see the note says body diameters are -.008. So drawing is showing a maximum diameter. SAAMI calls out the Swede 6.5x55 at the case body just ahead of the extraction groove at .4803" to .4723". For 30-06, same place on the brass - calls out diameter at .4698" to .4618" So, smallest SAAMI compliant 6.5x55 should still be larger diameter than largest SAAMI compliant 30-06.