difference in 7.5 French and 308 mags for the MAS 49/56

S

saands

New member
Anyone know the difference between the original 7.5mm French mags for the MAS 49/56 and the ones out there for the 308 conversions? Did they have to bend the lips some for the SLIGHTLY smaller diameter 308 case?

Thanks,

Saands
 
Saands, a lot of them will work unaltered. But I do sometimes have to 'open' the feed lips a little to allow the .308 to sit a little higher. On the ones that require this the bolt will just pass right over the cartridge until you alter them. George
 
Thanks George ... Have you done the 7.5x54 to 7.62x51 conversions? I'm thinking that this would be a good winter project to keep me off the street and out of the puddles ;) ... from what I've read, the typical process is to shorten the chamber end of the barrel, rethread it and then re-chamber it with a 308 reamer, shortening the gas tube to match. Sounds pretty straight forward (I wouldn't have said that before rebarreling the Turks with Rem700 bbls, but now my perspective has changed quite a bit). What I have not seen much detail on is the regulation of the gas into the gas tube ... do people typically try to do an adjustable system or just add a fixed restriction (or maybe the preference is a "waste-gate" like on a turbocharger).

Also ... can the front sights be moved after rechambering or do you need to index them by setting the shoulder back? While, in theory, indexing the barrel shouldn't be so difficult, perfect results have thusfar evaded me :( so that would be a small concern.

Am I nuts for pondering this one?

Thanks again,
Saands
 
Saands, yes I've done a bunch of them. The bbl threads are metric so you'll need a lathe with that capability to pick up and extend the threads. Everything is shortened by .531" (9 complete threads). You need to do that exactly so that everything idexes correctly. It isn't the sights you have to worry about so much as the gas port/block. I add adjustments to the gas system. The surplus ammo that folks buy has too much variance in pressure from make to make for the rifles to function well for all of them. Most of the rifles, once the gas is adjusted correctly for the load will function just great. But occasionally I run across stubborn ones that no matter what you do just don't seem to want to function. I have one in the shop right now that is totally eluding me. It will work great with commercial ammo but refuses to cooperate with milsurp. It's the last one that I'll be converting by rechambering. I've rebarreled several keeping the gas system the original length and never had a problem. They generally function 100% "right out of the box". So from now on anyone who want's me to convert one will have to go with rebarreling. George
 
George: Thanks for the info ... the knowledge and experience here still amaze me!

My lathe has a set of (as of yet unused/untested) metric threading gears, so that part should be OK.

You mentioned rebarreling ... that is actually good news becasue it implies that a replacement is available if something doesn't work out :D If it isn't a trade secret, would you mind telling me where you get them? Are they pre-threaded and pre-ported

Adjustable gas system: Do you favor adding a restriction or bleeding some of the pressure off by adding an additional exhaust. Is there a part sold for this or do we just get creative here?

Just for grins ... what's a professional rebarrel run? You've been so much help with the projects that one of these days I'm gonna HAVE to send you a job! It wouldn't keep me off the street for the winter this way, so I'd have to invent another excuse ... but I'm pretty a pretty creative guy :D

Thanks again,
Saands
 
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