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SwampYankee · January 22, 2010, 12:34 PM

I now have two MAS 49/36 .308 conversions. After a little cleaning, the first one runs perfectly and I can feed it any ammo I like. The second one would fail to extract on almost every round and inspection of the chamber and brass showed that the front 1/3 of the chamber (that had been cut by Century) was a mess of gouges and scratches.

I took a fired case, screwed it to steel rod as a drill attachment, applied some Flitz and polished the heck out of it. The extraction is now up to about 75%.

My question is, how much is too much polishing? I would like to go at it a little more but do not want to overdo it. I bought some LC brass that I assume was fired from an M60 and it will not chamber easily in this rifle (and is a bear to resize), which makes me think that by military standards, I still have a couple thousandths of leeway to make the chamber bigger?

I'm in the process of building a new gas valve and I suspect that will help a lot too.

January 22, 2010, 12:34 PM	#1
SwampYankee Registration in progress Join Date: November 1, 2008 Location: I can be found on a number of other forums. Posts: 1,333	Too much chamber polishing a .308? I now have two MAS 49/36 .308 conversions. After a little cleaning, the first one runs perfectly and I can feed it any ammo I like. The second one would fail to extract on almost every round and inspection of the chamber and brass showed that the front 1/3 of the chamber (that had been cut by Century) was a mess of gouges and scratches. I took a fired case, screwed it to steel rod as a drill attachment, applied some Flitz and polished the heck out of it. The extraction is now up to about 75%. My question is, how much is too much polishing? I would like to go at it a little more but do not want to overdo it. I bought some LC brass that I assume was fired from an M60 and it will not chamber easily in this rifle (and is a bear to resize), which makes me think that by military standards, I still have a couple thousandths of leeway to make the chamber bigger? I'm in the process of building a new gas valve and I suspect that will help a lot too.