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foudufoot
Gunboards.Com Gold Star Member

USA
1030 Posts
Posted - 11/20/2005 : 9:38:43 PM
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I took my MAS 49 to the range with FNM ammo and noticed that every 3-4 shots, it fires 2 or 3 shots per trigger pull. Scared the $#!7 out of me so I put it away. Not to mention that the range doesn't allow automatic weapons.

Has anyone run into the same problem and know how to fix the problem?

Thanks and Regards, Dan.

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ThePitbullofLove
Gunboards.Com Gold Star Member

USA
2012 Posts
Posted - 11/20/2005 : 10:32:29 PM
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It's a fairly common occurance. Most of the problem is ammo related. Commercial ammo uses a softer primer than the military ammo this rifle was designed for.

I'll assume the rifle was broken down, and the bolt and firing pin & channel cleaned throughly?

Was your FNM ammo labeled 7.5 MAS or 7.5 MASS?

The 49/56 has a heavy free floating firing pin, and inertia can cause it to prodtrude slightly from the bolt face on the bolt's closing. Using military ammo or ammo with hard military style primers and the problem is diminished.

Some say that using a "lightened" firing pin helps considerably, and they turn their pins down somewhat to reduce their mass. There was an outfit that produced titanium firing pins, but I'm not sure if they're still available.

I "solved" my slamfire problems (thusfar anyway), by "springing" the firing pin. That is, I took the spring from a ball point pen, and trimmed it down to fit over the nose of the firing pin. Through a bit of experimentation and trimming, I was able to find a length that allowed reliable firing and has yet (knock wood) to slamfire since the mod.

Good luck!

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marysdad
Gunboards.Com Silver Star Member

USA
808 Posts
Posted - 11/21/2005 : 01:35:23 AM
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I had the same experience that you relate and put my M1949 away for a number of years, before I started reading up on this and other boards. There are a number of solutions that include: the ball point pen spring, rubber o-ring on firing pin, lightened firing pin, and flatten tip of firing pin.

I could never figure out how to get the ball point pen thing to work, but others obviously have. I didn't like the o-ring trick because it could eventually fail without warning.

Titanium firing pin is great, but expensive. Some folks have turned an original firing pin on a lathe to remove excess metal, lightening it in the process (be advised, MAS firing pins are hardened/tempered to a fairly high Rockwell value). I made a model lightened firing pin out of mild steel, just to see how much lighter it would be. I was able to reduce the weight by about 25 percent. I never fired the rifle with this pin, being concerned that it would quickly begin to deform.

On my rifle, the firing pin protrusion was 1.5mm (.060), about in the middle of the allowable range of 1.3mm - 1.8mm (.051 - .071). I took a fine file and carefully removed .010 from the tip of the firing pin, leaving a flattened tip. Some posters say to remove 1.0mm (.040), which would have been grossly excessive in my case.

I ran a 40 round range test and had no slam fires: 10 single-loaded rounds (stripped from magazine); 5 two-round loadings; 5 three-round loadings; and, 1 five-round loading.

Apparently, slam fires can also be caused by an out-of-spec mating of the trigger group and stock (esp. when dealing with a mismatched or a replacement triggergroup and/or stock). With the bolt & carrier removed, hold the trigger all of the way back and manually cock the hammer until it engages. Use a caliper or depth mic to measure how high the hammer protrudes above the bottom of the receiver well. If it measures between 0.8mm and 1.0mm (.032 and .040), you're fine (mine was .040 on a matching receiver/triggergroup/stock). If not, you may want to try shimming the triggergroup to bring things into spec. You must do this all with the trigger held back or you will get a fautly measurement. Don't ask why the French do it this way, they just do.

The following thread has more detail on most of the above: http://www.gunboards.com/forums/topic.asp?TOPIC_ID=75537&SearchTerms=49-56,slam,fire

The problem is curable and the cure isn't too painful. These rifles are tremendously good shooters. Your patience and persistence will be handsomely rewarded.

Ralph




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Gunboards.Com Gold Star Member

USA
1030 Posts
Posted - 11/21/2005 : 07:26:25 AM
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Thanks guys! The FNM FMJ ammo reads FNM and 7,5x54 at 12 and 6 o'clock on the casing. It has the usual FNM green wax around the primer. The box is labelled 7,5 French MAS in large font and 7,5 x 54 mm in small font underneath. Fired casings have a deep indent in the primer with a circle around it. The casing itself also appears to have a slight circular depression on one side. I'll send pictures when I can locate my camera.

Any suggestions for other commercial or milsurp ammo that wouldn't require modifying the MAS? Thanks again. Dan

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foudufoot
Gunboards.Com Gold Star Member

USA
1030 Posts
Posted - 11/21/2005 : 8:07:02 PM
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Correction. The box is labeled 7,5 French Mass. What's the origin?

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ThePitbullofLove
Gunboards.Com Gold Star Member

USA
2012 Posts
Posted - 11/21/2005 : 10:21:17 PM
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Portugal. Cole's is the ammo's importer.

You'd need to either modify/correct the rifle as discussed above or handload your own ammo with military style primers (harder primers) to solve the slamfire problems.

I did the spring of the firing pin trick, and I've had no issues of late with FNM ammo slamfiring.


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foudufoot
Gunboards.Com Gold Star Member

USA
1030 Posts
Posted - 11/21/2005 : 10:47:02 PM
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Thanks PBOL! Just bought some original MAS ammo to get the feel of the real thing. Where can I get the o-ring? I don't want to file down the original pin. I think I'd rather pay $75 for a titanium pin. Thanks again. Dan

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DeanSchmidt
Gunboards Premium Member

USA
131 Posts
Posted - 12/04/2005 : 6:20:01 PM
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Who has these titanium pins? I loaded some ammo special with CCI#34 primers and am still having trouble with slam fires.


Edmond
Gunboards.Com Silver Star Member

France
635 Posts
Posted - 12/09/2005 : 04:11:59 AM
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Strange, it may be hammer following the bolt instead of real slam fires. Never had any slam fire with CCI 34.

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DeanSchmidt
Gunboards Premium Member

USA
131 Posts
Posted - 12/11/2005 : 7:31:39 PM
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I took about five thousands off the end of the firing pin and the problem seems to be cured. I have run about 60 rds through the gun since of commercial FNM and handloads with CCI #34 primers without a slam fire.


jonk
Gunboards.Com Gold Star Member

1743 Posts
Posted - 12/11/2005 : 11:47:15 PM
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I also get slam fires even with the CCI 34 primers. But instead of one per clip on average, perhaps 1 per outing.

I might look into the spring idea.

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mp510
Gunboards.Com Gold Star Member

USA
1064 Posts
Posted - 12/12/2005 : 3:01:43 PM
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With my CAI century 7.62mm coversion, which has other reliability problems that gunsmith is currently fixing, I had a slam fire in the first few shots that I took. Luckily it went into the target and safely into the backstop! The ammo was south african surplus. the gunsmith said that it might be due to excessive protrusion and he would guage the firing pin and reduce it if necesary.

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alton1911
Gunboards Super Premium Member

USA
256 Posts
Posted - 12/18/2005 : 07:57:47 AM
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Problem...I see no problem, I think of it as a bonus...but I have noticed that the FNM portugese ammo does the same thing in mine..I am guessing it is manufactured with softer primers. I field stripped the bolt from the action. Then cleaned what looked like a perfectly clean firing pin and coated it with Hopps gun oil. Have not been able to make it slam fire since then. Hope this helps. The bolt comes out easily enough with no tools all the work can be done on sight at the range. Thanks,
alton1911
 
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