The Last Old Mauser Part II

My wife’s birthday is this Friday and she said she would like to go out to dinner at a local Mexican restaurant. Unfortunately, the restaurant does not take reservations, the place is mobbed with turistas who are in search of… authentic Maine Mexican food, and the summer help service is terrible. I realize my wife does not really want to go, but if she can get me to say, “No”, I will owe her one and she will wield the power of guilt. If I say “Yes”, she will feign elation and then hide both of my good t-shirts, causing me to cancel dinner, and I will still owe her one and she will still wield the power of guilt… which is what she really wanted for a birthday gift. Life does not always move in a straight line.

Before firing a rifle, and as part of a periodic inspection, headspace should be checked. If it is good, a cartridge will be properly supported and its case will not stretch significantly when fired. If headspace is below minimum spec, there is no assurance a round will chamber. This could be a big deal if you’re hunting brown bear, you shoot and miss, he takes exception to your overture, and you can’t chamber a second round. Too much headspace and chamber pressure will stretch out a cartridge case until it fails in the form of case head separation, or fractured neck or shoulder, and your face and/or hands get a dose of hot brass and powder residue, propelled by 50k+ psi pressure.

The chamber specs for the 8x57mm Mauser chamber specs have changed over the years, particularly in regard to shoulder angle. CIP’s current junction cone spec, the angle of both shoulders, is  38°12’06” for the cartridge and 38°19’59” for the chamber. The SAAMI spec is associated with a single shoulder angle, rather than junction cone, and is approximately half of the CIP equivalent method; 20º48′ cartridge with a headspace dimension of 1.8786″ – 0.007″ and 19º chamber with a headspace dimension of 1.8843″ – 0.010″. The current CIP Pmax 3900 BAR (56,551 PSI) – For 0.323″ Groove Rifles Only. The current SAAMI MAP pressure spec for the 8mmx57mm is 35,000 PSI.

Prior to 1947, the Winchester Spec for the 8mm Mauser set the shoulder angle for both cartridge and chamber as 20º48′. The handloaders handbook of cartridge conversions sets the cartridge shoulder angle at 22º. Forster Products makes two different sets of headspace gauges, one for the old spec 20º48′ and one for the more recent 19º, suggesting that a chamber cast be made to determine which is correct. They further caution that using the newer spec gauge in the older chamber will result in the nose of the gauge hitting the rifle’s bore before the gauge seats at the correct location on the shoulder, causing the gauge to falsely check long… which is what happened with this M24/47.

The pressure disparity between CIP and SAAMI is related to the 8mm Mauser originally being produced with a 0.318″ rifling groove diameter 8×57 J and later changed to 0.323″ diameter 8×57 JS. Out of concern for the 0.323″ bullet being forced through a 0.319″ bore, SAAMI and almost all U.S. manufacturers curb pressure to the SAAMI spec and caution handloaders ad nauseam. The result is a wheezing, anemic 8x57mm that is destined to be a substandard performer. Really unfortunate as the 8x57mm should be a relatively heavy hitter.

Military Mausers stopped even the infrequent use of 0.318″ groove barrels in 1903 and few M98 versions were produced with the smaller bullet diameter. Unfortunately, many factory and custom civilian firearms rifles and customs through the 1950’s were produced with the 0.318″ bore so it is always good to check groove diameter before loading up cases with buckets full of powder and attempting to drive a big peg down a small hole.

The subject rifle has an 0.323″ groove diameter. Having built, seen and shot sporterized military Mauser actions modified and rebarreled for just about any 30-06 Springfield length cartridge, I’ve not seen one have a problem as long as inspection showed the receiver to be in good shape, headspace was correct and handloads were kept to SAAMI spec pressure levels. In fact, one of my favorites was an M98 military action barreled for the 25-06 Remington, a cartridge with a 65,000 PSI MAP. The handloads presented top at 56,000 PSI in this rifle and that is the ceiling I use for the 8×57 Mauser.

Lots of good bullets… These are but four

These are all good bullets. The lighter weight for hogs and deer, the heavier for larger game like elk, moose and bear. They are all single core construction with the exception of the Partition which is of A Frame construction.

If these are not to your liking, there are thirty two bullet types/weights currently in production, spread over ten manufacturers, in weights from 150 to 250 grains.

With a once fired, neck sized case, Re17 and the 150 grain bullet, the assembly was routine. With a fresh full length sized case, careful assembly is required and the load is notably compressed. It is still the highest velocity, normal pressure combination I have encountered. The 8x57mm seems to like Re17 across the bullet weight spectrum and accuracy came with increasing bullet weight.

 

 

And as we ride off into the sunset…

 

Good rifle, good accuracy, good reliability. It is also a fun rifle to take out and blast away with every now and then. So what is it that makes this my last military surplus Mauser? While it is good for its age, it could easily be replaced with any new $400 rifle chambered for the 308 Winchester. The new rifle would be made with better materials, more accurate and supported with a warranty. Nostalgia and a sense of history only goes so far.

 

 

 

The Last Old Mauser Part I
The Last Old Mauser Part 2