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Thoughts on the M&P15 barrels

This is a discussion on Thoughts on the M&P15 barrels within the M16 AR15 forums, part of the Rifle Forum category; I have a M&P15 MOE (the first one not the new one with the 1:8 4150 cmv barrel) Anyways i bought it back in the ...


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Old August 15th, 2012, 07:36 AM   #1
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Thoughts on the M&P15 barrels

I have a M&P15 MOE (the first one not the new one with the 1:8 4150 cmv barrel) Anyways i bought it back in the summer of 2011. Its been a great gun for me, have shot lots of LC 855 and 193 ammo through it. Pretty good accuracy with the 55gr m193 at 100 yds. Anyways it has the 4140 chrome lined barrel in 1:9 twist. Now I have been looking at getting another upper for it, thinking of a piston upper. What are your thoughts on the S&W uppers? Thoughts on 4140 steel for barrels? I know 4140 isnt (mil-spec) but i dont really give a darn because i probaly only shoot 1-2K rounds a summer. So thats about 20,000 or less in 10 years and by then ill have something new anyways. And what does a mil-spec barrel give you that the 4140 wont other then life? I dont throw the gun in the mud, im not a navy seal swimming in the ocean getting salt all over the gun either. The reason for a piston upper is because i hate cleaning the rifle... and i love my M1A because it has a piston and doesnt get crap all in the rifle like the AR does

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Old August 15th, 2012, 08:24 AM   #2
 
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To sum it up, 4150 can be treated to a higher hardness/strength than 4140. If you harden either one too much, it becomes too brittle.

What this means is that the 4150 barrel can be used at a higher rate of fire for a longer period time than the 4140 barrel. The 4140 will sag and become unusable sooner.

How much sooner I cannot answer because no one to my knowledge has really done the kind of destructive tests on a 4140 AR-15 barrel as they have done to a mil-spec M4/M16 with a 4150 barrel. Suffice to say if you are firing no more than 50 rounds per minute you will probably not notice the difference. If you are firing much more than that (more than 500 rounds over 10 minutes or so?) you will probably begin to notice the difference (just a guess on my part).

I have also read that 4150 has more desirable properties in cold weather as well, and that may in fact be the primary reason that it is used. 4150 is less resistant to cracking when exposed to rapid and large temperature variations (a lot of firing followed by cool down in arctic conditions).

Edited to add: The M1 Garand and I believe M14 barrels use 4140 steel if that tells you anything. Personally I buy 4150 if I can get it, otherwise 4140 works okay too. The general consensus is that if you don't shoot full auto, you won't notice.

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Old August 15th, 2012, 08:54 AM   #3
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alright thank you for the information. Yea no rapid firing here.. i might dump a 30 round mag in a few seconds while runnin and gunnin but I dont like to blow away my ammo as its expensive. Hmm the cold intrigues me however as Ill be living in PA in about a year, from maine stationed in nj.... and i will ocassionally shoot outside in the winter, but usually never when its 20 degrees or lower, thats just too cold for me to enjoy shooting haha. I was shooting my little .22 when it was about 30 out and my hands were freezin on the gun.

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Old August 15th, 2012, 07:37 PM   #4
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As long as the upper/barrel come from a reputable manufacturer, I don't think it will matter what the material is made out of for your uses.

I'm not a piston guy, but I'm not against them either. I've just never seen the point for my uses. Then again, I'm pretty "neglectful" of my ARs.

What is wrong with the upper you have now that is making you want to look elsewhere?

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Old August 16th, 2012, 03:57 AM   #5
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nothing, its a good upper i was just considering a switch to the piston upper. And S&W has a piston upper for sale, mostly because last time i cleand my rifle it took forever i had shot 400 rounds through it and carbon build up was everywhere. I know piston systems run cleaner, thought about selling my upper and buyin the piston upper.

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Old August 16th, 2012, 09:24 AM   #6
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Why not get a conversion kit for the one you have? It will be cheaper than buying a whole new upper. I would look at something like the Adams Arms kit, personally.

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Old August 16th, 2012, 12:28 PM   #7
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was unaware that there was a conversion kit... ill check it out

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Old August 16th, 2012, 06:56 PM   #8
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Hamstrocity's right that converting would be cheaper and it's how Adams started out and how many builds have been done and still are. If you do decide on a new upper though consider an Adams also. Their barrels are very nice, use 4150 CM steel and are melonite treated. Their system is one of the best around in my opinion. It's also the one used by more companies than anyone else. Smith, Sabre, Huldra, Core, Spikes for example.

The complete Adams uppers are pinned in place and offer a good selection of lengths and handguards. Conversion is cheaper though and works a 100% as long as you assemble it right. It's not hard and you'll be able to change it out with new barrels down the road as easy.

http://adamsarms.net/products.asp?category=100023

http://www.rainierarms.com/?page=sho...nufacturer=103

http://www.riflegear.com/c-74-gas-piston-uppers.aspx


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