Bolt Carrier / Barrel Questions S.O.S

[adambecker1]

I am looking to buy a new model MP 15 sport tomorrow. I can not for the life of me find out 2 things.
1. Does the barrel stay the same width under the hand guard or does it turn into a "pencil" barrel?
2. Does the extractor spring have a rubber O-Ring around it from the factory? ( people say putting an 0 ring around this spring is a must)
Any comments would be appreciated, I am looking to purchase tomorrow and I am on the fence yet. NEWBIE Jitters of spending
$700

 

[turbo38gn]

I am looking to buy a new model MP 15 sport tomorrow. I can not for the life of me find out 2 things.
1. Does the barrel stay the same width under the hand guard or does it turn into a "pencil" barrel?
2. Does the extractor spring have a rubber O-Ring around it from the factory? ( people say putting an 0 ring around this spring is a must)
Any comments would be appreciated, I am looking to purchase tomorrow and I am on the fence yet. NEWBIE Jitters of spending
$700

Have you been frequenting M4Carbine.......

1. I can't say if it's a pencil barrel under the handguard, but I can say it shouldn't make a hill of beans difference..

2. Same goes for the o-ring, makes absolutely no difference

 

[MasterTech1960]

Mine is .750 at the gas block and under the guard it is .743 , not much of a difference. Do not know any thing about the o-ring you speak of. Some guy put a o-ring on the front pin post to tighten up the lower to upper movement. My 15 does not have that issue.

 

[JaPes]

1. No. It is not a pencil barrel underneath. It's a bull barrel. No grenade launcher mount cut.

2. Yes. The extractor spring has an O-ring.

Most importantly, $700 is a bit steep to pay for a 15-Sport right now. I've seen deals and sales anywhere between $550 and $600. If you're going to pony up $700, might as well get an AR with the prancing pony roll mark on the lower (Colt LE-series).

If you have any other questions, just ask. Welcome to the sub-forum.

 

[JaPes]

Mine is .750 at the gas block and under the guard it is .743 , not much of a difference. Do not know any thing about the o-ring you speak of. Some guy put a o-ring on the front pin post to tighten up the lower to upper movement. My 15 does not have that issue.

Field strip your BCG. Push out the extractor retaining pin from the bolt. Keep your thumb on the extractor because there is a little spring tension there. Remove the extractor. There's a little spring and O-ring there. The O-ring adds additional extractor tension to ensure that the extractor doesn't slip off the rim of the spent casing.

I've run an AR-15 with and without the O-ring and observed no difference. If your AR-15's bolt had an O-Ring from the factory, leave it there. If yours didn't come with an O-ring, only install one if you have extracting issues.

 

[wjs81866]

Yes there is a o ring and spring under extractor

 

[Mydogmax]

Welcome to the forum. Lots of good advice (and humor) here. Take some time and research the prices before you shell out $700 for the M&P Sport. Gunbuyer.com sells them for $529 w/free shipping & no other fees. That's where I got mine.Smith & Wesson M&P15 Sport No Forward Assist sw 811036
They're out of stock right now but they replenish their supply quite often. Buds Guns has them for $617 (in stock now) They also ship free but will charge you a 3% fee if you use a credit card. It's your money of course. Just trying to help.