This quote from HA got me to thinking out loud so if this is a dumb question, please bear with me.....

Quote:

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Pre 64's don't have a gas block and if something goes wrong that could get you blind.. If you want a win mod 70 then look for a current classic that was made in CT..

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So if the gas block of the M70 Classics is truly a worth while improvement has anyone come up with a retro fit for a true Pre-64 action? Since the gas block is a small piece of steel attached to the extractor collar, opposite the extractor and free to rotate around the bolt like the extractor does ---- is it feasable that a similar piece of steel, contoured to fit the Pre-64's left raceway be fashioned and attached to a new collar? Would it have any benefit or is it really a non-issue?

Thanks for the indugence

I was the guy who tried to explain to Swamp how it was done. I'm no gunsmith but was smart enough to listen to a real one when he did this to one of my rifles.

Bill Leeper retro-fitted the new gas block to my old bolt, he considered it a worthwhile modification.

Dennis, you take a really stupid person from Maine and line him up where the gas would escape. BIG problem is you have to put up with him tagging along and asking stupid questions and making stupid statements until it did happen (and it won't). I know, there are no stupid questions (although "he" is the case that proves that statement false) but as my son says, "there are no stupid questions, only stupid people." Now you have to test it out first, lol.

First off, it's not a gas block, rather a bolt stop extension that can be changed depending on calibers used in the same length of action. If excessive gas comes down the raceway, it's not going to stop gas any better than the claw extractor, both of which will be flying into the air.
The design of the bolt stop was originally designed as a cost-savings, but luck would have it, it also proved to be valuable in stopping the distortion of the left bolt lug caused by pulling the bolt back to quickly and smacking the bolt stop. With this in place, it virtually eliminates that problem while letting the control of the bolt be dictated by a small, easy part to manufacture.
This is in no way an added safety feature, but IMO a better method of manufacturing an action that must use varying lengths of cartridges, plus stopping the distortion of the bolt lug.

Strangely enough Winchester, perhaps not knowing any better, calls it a gas block. Go figure! On the pre-64 rifles they did indeed use a similar system to limit bolt travel for short cartridges. Later they simply stamped out shorter bolt stops.
I recognized the lug protection feature of this (apparently mis-named) gas block right away and retro-fitted it to my own M70s. The intent behind the block was to block the left locking lug raceway in the event of a ruptured case. It would work in conjuntion with the bolt stop to restrict the flow of gas into the shooter's eye. A laudable intention. Whether or not the block is real effective in doing this I can't say since I've not overloaded the old M70 to test it out. I don't plan on doing so!

I can let you know how things play out when things get a little overloaded in a PF model 70. Things are a little fuzzy for a minute, your eyes sting like crazy, and you become fairly angry. Then you make a mental note to never group someone elses handloads with someone elses rifle, and always wear your safety glasses . It didn't help, I'm sure, that I'm a lefty and was shooting a right handed rifle. No permanent damage and I now consider myself oh so much more wise.

Another story, involving another left handed shooter and a model 70 classic. This young gentleman loaded his rifle, a 300 win mag, from a nice new box of factory ammunition. I guess he failed to notice that the last cartridge he dropped into the magazine didn't wear a belt (it was an 30-06) and when he chambered and fired the cartridge at a mule deer strange things happened to the floorplate (it blew off and got bent). Sadly the blast damaged his vision in his left eye and even more tragic was the fact that he had been blind since birth in his right eye. Fortunately, as I understand it, he has since made a full recovery.

Accidents happen, but as Bill said I don't plan on blowing myself up with my model 70's. Don't be stupid and use common sense, and above all make sure the guy your helping develop a load for has common sense as well . Come to think of it maybe there was a reason he asked my to group that load?

Chuck

It would be even be more effective to vent gas if it had a hole or two on the left hand side of the action. The right side gas venting hole really does not do much since the whole right hand wall of the action is open. Thanks.

Thanks for the replies! While I'm NOT a gunsmith or mechanical engineer I often wondered how well that little piece of metal would fair with the pierced primer or a case head seperation. Apparently it's just a placebo. Also it seems it does have merit after all but not for reason I thought it would.



Chic, All I can is ROTFLOL



Chuck, I think very shortly after that happend to me the handloading "friend" would get butt stroked with his own rifle.



Bill, did you have to shorten the bolt stop the corresponding thickness the gasblock/lugbuffer (??) added? IF it's not too much trouble could you post a picture of your conversion?



Thanks again,

Dennis

It's not really possible for me to post a picture just because I'm such a slow learner. It has taken me this long to learn how to fake literacy!
Not much to show anyway. The new extractor collar fits fine and it is necessary to cut the bolt stop back a bit.
I have to get on this picture business. Regards, Bill.

Matt,
I didn't speak with anyone at Winchester regarding their nomenclature for this part simply because it didn't seem necessary to do so. What I did was look at their parts list in which they list it as a gas block. I also noted that when I ordered a couple of gas blocks, I got the parts I expected to get. In other words, I got gas blocks!
The bolt stop extension you refer to was the part for the Pre-64 M70s in 308, 243, 22 Hornet etc. It looked remarkably similar to the gas block and was, no doubt, the inpiration for same.
There is no question the bolt shroud should have been designed differently. There was in fact an article describing an improvement to the M70 bolt shroud to better block the raceway in The American Rifleman years ago. Regards, Bill

Matt, Bill or anyone else,

Please correct me if I am wrong here, as I believe that the Mauser 98 bolt flange seems to act as a secondary gas block protection since the majority of hot gas must vent thru the thumb cut notch first. Without any venting on the left hand wall, I believe that hot gas (depending on the cartridge) streaming down the raceway can overcome the bolt flange so it would seem that the best way to obtain maximum protection from hot gas in the event of a cartridge failure is to have some sort of venting first and then blocking it as secondary source of protection. Regardless, some protection is better than no protection, right? Just an observation while we are on the subject! Thanks

Few years ago J.K. Cloward put a flange on the bolt sleeve of an M70 pre-64 for me, style of the 98 Mauser.

In my opinion, calling this part a gas block is a misnomer. It is attached to the bolt by the extractor ring, which is sheet steel less than .040 thick, and by a very narrow strap of that. In effect, this part is like a "piston", and the left rail the "cylinder" along which the gas block shall be propelled violently backward in the event of case head rupture.

MRC names this part the "bolt stop", which properly describes its function. There are two sizes - magnum and standard length. They engage the bolt release tang, which is an extension of a lever-shaped part that intrudes into the raceway. The bolt release is machined out of 4140 or .416 steel, properly hardened and robust enough to fragment and slow the "gas/block/bolt/stop/piston" when it comes rushing down the raceway. The gas flange on the bolt sleeve stops the solid material and diverts any remaining gas 90 degrees to the left and away from the shooter's face.

In the event of a pierced primer, case head separation, or reasonable overload (blown primer) this part suffers no, or seems to suffer, no ill effect. It sits there, acting like a bolt stop should. It is a very inexpensive way to handle bolt travel for various cartridges. The M1999 venting is quite good and pierced primers, even blown primers, do not release enough gas. To this, I can speak with authority, having instituted and conducted the proof-testing procedure currently used by MRC. When the slave barrels get dirty and they do after 20-30 rounds of proof loads, the pressures go up. Almost every load blows the primer. Nary a bolt stop suffers. In fact, nothing suffers. The bolt has HUGE vents into the magazine box and all the gase goes there.

But proof testing is (only) about 85,000-88,000 psi. In excess of 110,000psi brass flows. If the case head ruptures, a huge volume of gas is released into the action, usually through the extractor gap in the c-ring. The extractor claw usually shatters. Gas begins to vent through the receiver ring holes and the excess drives down the ejector slot into the left raceway, flame cutting that extractor ring and propelling the boltstop rearward.

This area is of concern for pre-64 owners. It is a major design weakness, and that weakness is entirely in the area of the bolt sleeve, which should have a Mauser style gas flange. That is the real cure.

Preventitive is "Don't load hot".

Rod thank you for that very thorough description. Just what I was lokking for in refence to my very first post in this thread. That filler piece is not much for blocking gas, works great as a bolt stop!

Rod and I are most definitely in agreement on this one. If you think that "gas block", or bolt stop is going to block gases, you've got another thing coming. It would be like hiding behind a garbage can when Harry Callahan was shooting his 29 at you. If it makes you feel better, stay put, but more protection is in order.