Safety Breeching

[Ron J]

This practice is described in Harold McFarlands book, as turning a small hub on the breech end of a barrel so it goes into the I.D. of the C-ring on a Mauser. Then the front of the bolt is modified, slot cut into the back of the barrel (like a 24/47) and the end of the cartridge is almost completely enclosed. He champions this due to higher chamber pressures of some newer cartridges. My brothers doing a Brazilian 98 - the cartridge will be .338-06. I'm wondering if it's a common practice, worth it, necessary?

[BobVZ]

I don't believe the .338-06 generates any more pressure than the '06 or 8x57 which this action is well suited to. Certainly if your brother intends to roll hot handloads it might be an added measure of insurance. Even with the enclosed feature, gas from a casehead rupture will still travel out the boltface undercut and the extractor relief channel. It does give some added protection though for ruptures at 12 or 6 o'clock. I don't hear of too many people doing it. Ruger uses the old '93 style breeching in the M77 chambered in some hot numbers. I've heard of no problems there. The best protection against casehead separations is to have a tight chamber with proper headspace combined with sanely loaded quality brass. I had one done several years ago and it cost me an extra $75 on the re-barrel.

[z1r]

The Yugo intermediates are all safety breeched. They were the only ones except for a few FN's. That should tell you something.

 

It's very easy to do the conversion but requires you to remove the cartridge guide nibs on either side of the extractor slot in the lug. Feeding may suffer.

[bilurey]

The original purpose of safety breeching was to handle excessive pressure occuring when the deterent coating on smokeless powder flakes did not adhear properly. Cartridge brass hardening technology was fairly new when dealing with smokeless powder pressures, leading to significant type S (case head separation) failures in the M1888 Commission rifles causing deaths and serious injuries, which led to user loss of confidence in these arms, which led to safety breeching.

 

Improvments in brass hardening technology and the developement of Centralite as a deterent coating for powder flakes eliminated the expensive extra machining required for safety breeching. It also allowed for the extension of the left lug head beyond the rim of the boltface which acts as a support for extracted cartridges, keeping them from dropping off the boltface prior to reaching the ejector blade for proper ejection.

 

The expense of safety breeching was considerable in mass production. The barrel is fitted then reamed and polished to final headspace. Safety breeching required additional breech extension machining and headspacing, then after being fitted to the receiver, scribing lines indicating the position of the head of the extractor in the face of the safety extension which blocked forward movement of that portion of the ejector head which extends beyond the face of the bolt rim. The fitted barrel is removed and a ramp bevel is milled between the scribed lines on the breech extension to allow room for the head of the extractor which protrudes beyond the bolt face. This is a precise cut as it also cuts into the chamber and minimal tolerances would be required. Next the barrel is reinstalled into the action, insuring proper alignment of the bevel cut and proper clearence for the bolt head. Bevel cut too shallow and the bolt won't close, too deep and a corresponding gap appears in the chamber wall. Finally the head of the left lug must be ground down flush with the rim of the boltface permitting the bolt to close against the face of the rear extension of the barrel. As the vast majority of 98 bolts were not safety breeched, it would have been simpler to turn out normal 98 standard or intermediate bolts and then grind down the left bolt lug extension as opposed to setting up special tooling for a bolt body without this feature. Paul Mauser went with what worked until modifications became necessary, or improvments proved economically adventagious. Bilurey

 

 

 

 

 

 

 

 

 

 

[Ron J]

Thanks all. Learn something new with every square inch of these Mausers.

[Guest Guest_Uncle Jaque_*]

Thanks all. Learn something new with every square inch of these Mausers.