I have a 2 year old Sport. Rifle is running great no problems at all.

I have about 2000 rounds through it and I was wanting to get some spare parts for it, like a firing pin, bolt, extractor etc.

I was thinking about getting a whole BCG from BCM and taking my whole BCG out, cleaning it really...really good and using it as a spare. That way I have all of the parts in that area if I need a replacement.

Does anyone know if the BCM BCG will have any issues in a M&P 15 Sport?

Its a full auto BCG so there will be some additional weight which on the Sport might be a good thing in terms of making is slightly softer shooting(possibly). (I have not changed the buffer or spring on this AR, its all stock)

Any input would be great thanks!

Is there a reason why you are putting a full auto BCG on? BCM makes good stuff so i doubt you'll have nay issues. There are many good BCG's out there. I personally just picked up an IceArms NIB group. Shoots really smooth. I also am running a Rainer Arms one in my other gun. Switching your buffer will help quite a bit if you want a softer feel.

No reason other than BCM makes really good products. Their BCG's have been used quite a bit and get great reviews. If they made a semi-auto I would get it.

With the M&P Sport (and probably other models in the line) being over-gased (16 inch on a carbine gas system) I am pretty sure the extra weight won't negatively impact the gas system. I could probably add a H buffer as well and still be ok.

I am fine with the smoothness of the rifle now, I am just looking to stock up on some parts that are possibly prone to breaking at some point. Getting a full BCG seems like a good idea since you get all of the parts that could break in that area. The added weight and possible reduction in recoil is just a side benefit.

I guess I am looking for reasons not to do it......like they don't fit or rub or something weird like that.

The fit should be just fine, assuming the rifle and BCG are made to spec. (And they most likely are.) The big negative to having a spare BCG laying around is it is tough to avoid the temptation to build another rifle around it. Especially now that quality parts are plentiful and cheap. But maybe you have more willpower than I do and will be OK.

Yep. You'll be fine with that. I run Spike's FA BCGs in my other ARs. One was a spare for my M&P but it just turned into a full M4 clone.

aphelion, BillyJack2012, thanks for the input.

Trust me, I am very tempted to get a BCM 16inch Mid-Lenght upper with my BCG order

Put my Eotech on it, then turn my Sport upper with its 1/8 5R barrel and its Centurion Arms Carbine Cutout, free float rail into a dedicated long range upper (Scope).

Then the next step would be to get a stripped lower and build it up, and put it on the BCM Middy. I really would not want to keep that Sport upper and lower from being apart for too long that would be just cruel

A friend of mine runs a 15-Sport with a full auto BCG, the stock buffer, and stock buffer spring. He's had no issues. I've run my Sport with a H, H2, and H3 buffer. Of those three, I prefer the H2 buffer.

The advantage to buying an entire spare BCG (tested for headspace) is to have an immediate drop in replacement should anything break. If your carrier's gas key is properly staked and in good condition, just buy an entire spare bolt.

I own two AR-15's. I keep in my toolbox all the parts required to rebuild a bolt:

1. Extractor
2. Extractor Spring
3. Extractor pin
4. Extractor "O" ring
5. Ejector
6. Ejector Spring
7. Ejector Roll Pin
8. Firing Pin
9. Firing Pin Retaining Pin
10. Cam Pin
11. Gas Rings
12. Ejector removal/installation jig (pictured below)

The fun part of AR-15 ownership is customization. Have you considered non-traditional parts?





Fail Zero EXO (Nickel Boron) coated BCG. Comes in semi-auto and full auto carriers. If you're running a stock combat trigger, you can install the coated trigger. The bolt doesn't need to be lubed. Clean the bolt with a solvent moistened rag, no scraping required.





AR-restor hydraulic buffer. You want a smoother action and lower perceived recoil? This one does the trick every time. I get back on target quicker using this buffer.

Keep your stock OEM parts in the spare parts bin.

__________________
-John

JaPes thanks for all of the information.

My goal is really to stock some spares. I love shooting my sport out on our family ranch for fun and I hunt with it. I am thinking about a taking a carbine class in 2014 as well.

Last summer I installed a Centurion Arms C4 Carbine cutout FF rail. I had to remove the Delta Ring at the time so I had to pull my gas tube. When I ordered the rail I ordered an extra carbine gas tube and a few gas tube retention pins.

At the time I thought I should get some spare parts and my thought was that if something was going to break it would be the somewhere in the BCG, Firing pin, extractor/spring, ejector spring, lug on the bolt or a bad gas ring.

To your point a fully assembled BCG can just be dropped in and whatever part that is broken fixed later.

I will pickup a H buffer as well, but replace just the BCG first for a while then try the H buffer out next. I really don't want to mess with the gas system too much. It works and works well now.

I have one around "just in case". However that is probably overkill as the only component there that is ever likely to let go is the bolt itself. The cam pin hole side sections are a bit thin and subject to a lot of stress over time. The bolt's locking lugs can chip or even shear in our lifetimes although I've never seen it.

I did replace the bolt only on an AR when I replaced the barrel to let the locking lugs wear in to each other. Probably unnecessary but the bolt was fairly inexpensive and had about 3K rounds on it. (I also checked the headspace, which is usually on the money anyway, but a good thing to do.)

Beyond that the only real issue I've ever had was to beef up the extractor on a carbine. I use the "D-Fender" grommet but there are other similar devices.

BTW I run "H" buffers.

More deponent saith not.

If you want softer get an H2 buffer. Botach had Fail Zero BCG's in stock for $169, and you get 10% off with "tenoff" code.

BCM BCG is very good quality and will work just fine. The slightly heavier carrier will work just fine.