how does a BCM bolt carrier group compare to a M&P sport?


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wolverine_173
December 30, 2012, 04:09 PM
? Is there any real advantage?

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hardluk1
December 30, 2012, 05:42 PM
No advantage in the civilian world. Chrome to melonite, m elonites harder!! Time will tell. I certainly would not upgrade anything on a sport except a trigger.

wolverine_173
December 30, 2012, 09:22 PM
I hear such good things about bcm. i was told if building an ar the bcm bolt carrier group is the best for the money

COLOSHOOTR
December 30, 2012, 09:28 PM
I'm not really getting whst your asking but assume you're asking if the BCM is worth upgrading too...

The BCM BCG is magnetic particle inspected (MPI), will be property staked and has proper mil spec springs/insert. If you are running the gun hard it may be a good upgrade. If it is just a plinker/range gun no need to go buy a BCG if you have an M&P as the S&W offerings have been pretty good.

If you were building from scratch the BCM parts are definitely the best for the money.

wolverine_173
December 30, 2012, 10:01 PM
If you had both and was selling the bcm upper would you swap the bgc and keep the one from bcm?

wriggly
December 30, 2012, 10:29 PM
If you had both and was selling the bcm upper would you swap the bgc and keep the one from bcm?
If it were me, I would leave the BCM BCG in the upper. I am sure the person buying it may have a problem if you did not disclose that before completing the sale. Plus it would be "The High Road" way of doing business.
The BCM BCG is probably full auto, the Smith "sport" BCG is definitely semi auto. Now, the Smith BCG's are made well, and are very good BCG's, but you take the chance of alienating a buyer.......your call. I know that if I bought a BCM upper from someone, and that someone represented it as including the BCG and CH, I would expect them to be BCM as well as the rest of the upper.

wriggly
December 30, 2012, 10:36 PM
One other thing.....did you check the headspace of the BCM BCG in your "Sport" with a "Go Gauge" and a "Field Gauge"? How about the "Sport BCG in the BCM upper? They are headspaced accordingly for the uppers they were matched to. You could be setting up the buyer for a Kaboom, or yourself for that matter. Not likely because they are both reputable manufacturers but a possibility nevertheless.

wolverine_173
December 31, 2012, 01:25 PM
I would obviously tell the person that it had a smith and wesson bcg instead of a bcm bcg

1911 guy
December 31, 2012, 02:29 PM
If I were selling a BCM upper, I'd leave the bcg in with the sale. While not a really common problem, there can be headspace issues with swapping back and forth. I'd say just leave it alone. If I were building from the ground up, I'd opt for a BCM bcg. But an already existing upper from S&W? I'd probably be content to just stick with the bcg from the sport with the sport upper.

wriggly
December 31, 2012, 02:45 PM
I would obviously tell the person that it had a smith and wesson bcg instead of a bcm bcg
Good to hear. Headspace still could be an issue. Why chance it? Remotely possible but it is possible.

As for Smith & Wesson AR components, they are top notch. I don't want to open a can of worms about the Full auto vs Semi auto BCG argument, but in reality, 11 grams difference doesn't really matter. I have no problems with the BCG Smith puts in the Sport. The whole darn gun is quality, and I should have grabbed 3 or 4 of them when they were on sale for $600 back in October. They are making their own parts, and their quality is up there with the big boys.

ugaarguy
December 31, 2012, 02:57 PM
The sport has an HPT/MPI bolt, the extractor spring has both the black rubber insert and the black o-ring surround, the carrier is internally chromed, and the carrier key screws are properly staked. It's the same bolt carrier group that's in all the M&P15 rifles. There's no need to replace it with a BCM BCG that's exactly the same.

Quentin
December 31, 2012, 03:36 PM
Fair is fair, I wouldn't swap them around now. But if putting together an AR over buying something off the rack I would buy BCGs as good as BCM. I have two BCMs, one in a BCM upper and the other in a PSA. The slight extra cost buys piece of mind.

I also have a Daniel Defense BCG first used to upgrade an ArmaLite upper but later I sold the ArmaLite upper with its BCG and bought a DD upper for the DD BCG (which had a low round count in the ArmaLite and headspaced fine in the DD).

WinThePennant
December 31, 2012, 06:13 PM
Is headspacing really an issue with ARs any more? I know that it can be, but today's machining is so good that I never hear of this being a problem any more.

hentown
December 31, 2012, 06:23 PM
IF the headspacing were not correct, how, exactly, would you go about correcting it? All barrels that are bought with the extensions attached are already headspaced.

I have one AR with the BCM bcg. It ejects @ 1:00 o'clock. All the semi-auto BCGs that I'm using eject properly @ around 4-4:30.

Quentin
January 1, 2013, 02:02 AM
IF the headspacing were not correct, how, exactly, would you go about correcting it? All barrels that are bought with the extensions attached are already headspaced.

I have one AR with the BCM bcg. It ejects @ 1:00 o'clock. All the semi-auto BCGs that I'm using eject properly @ around 4-4:30.


If the headspacing fell very slightly out of spec, then possibly another bolt might bring it back in. Really there's not much else you can do but get another barrel.

What buffer weight do you have? My rifles with FA BCGs with H buffers or H2 buffers eject at about 4 o'clock.

Infidel4life11
January 1, 2013, 02:39 AM
I have no issues with my Sport what so ever. I took a BCM BCG with me to Iraq and Afgan if that tells you anything. I got my sport used and cheap I love it for what it is. BCM wil always be my top pick.

henschman
January 1, 2013, 05:00 PM
FYI, I've opened up several Sports, and they all had MP marked bolts.

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