Converting S&W M&P15A to a top tier gun?

AR/M4 AR Technical Discussion
1

Hi everyone.
I have some questions and ideas to throw out there and I am looking for some good informed opinions. Any help you can offer me is appreciated, and I apologise if my thoughts seem to come across as “scattered out”, as I am in the planning stage of aquiring a weapon built with top shelf parts.

I have a complete Smith and Wesson M&P15A. I would ideally like to sell this rifle and build a new one using BCM components, but I am having trouble with selling it without taking a huge hit. What got my gears turning was my desire to have a rifle with a 13.8" Troy MRF. Then I decided that if I was going to go through the trouble of installing a FF rail, then I may as well adress the barrel as well and replace the 1/9 twist one with a BCM 1/7 twist. Then, obviously upgrade to a BCM auto bolt carrier group. Long story short, While on G&R Tactical’s website, I started looking at the complete BCM 16" midlength gun, as well as their seperate BCM lower receiver groups and uppers.

So here is what I want to know. If I swapped the barrel and BCG that are currently on my gun with their BCM counterparts (meaning BCM auto carrier group and 1/7 16" M4 profile bbl) and then installed my Troy rail, would I be anywhere close to having a good, reliable and durable weapon? And would I be able to do this and still use a pinned FSB?

Another way to ask this question: Is there anything wrong with my carbine length gas system, S&W upper receiver housing, and lower receiver group (other than staking of the RE nut) that BCM does so much better that would justify me buying a new BCM lower group and then a new midlength upper?

I also considered converting to a midlength system using my S&W upper, but would this even be practical/feasable? Another question that comes to mind when considering this is whether or not I would be able to use a pinned FSB if I switched (I read somewhere that the barrel and FSB are drilled at the same time and that it is not possible to swap one pinned FSB to a different barrel).

And yet another thing to consider would be to simply buy a new BCM 16" midlength upper, shave the FSB, install my rail, find a folding front sight and call it a day.

There are so may different ways I could do this, but with my limited knowledge and experience I am having trouple finding the best balance between cost, practicality, labor-intensity and quality.

Please let me know what you think my best bet would be!

All opinions are appreciated, and I thank all of you.

Mark

2

The S&W is very very close to a top tier weapon. Many hold the 1/9 twist against it, but this is only a issue if you are gonna shoot ammo with weights higher than 62 gr. IMHO. They are great tough weapons! I actually buy S&W bolts and carriers as an alternative to BCM, lots of folks get caught in the kool aid, and sell them off real cheap. They are damn good. I would vote keep the M&P, shave the front sight, put your rail on and be done. You wont notice the gas system change looks wise with that long of a rail. Mid-length does ease stuff up a bit, but you can do that with a heavier buffer and achieve the same thing. It is one of those things though if it is gonna bug you now, its gonna bug you later. Take the loss if it does and get what you want as opposed to trying to make something you don’t really want into something else.

3

Have you factored in the cost of all the tools you’re going to need for this, as well?

You can get a Daniel Defense 16" carbine barrel with a 1/7 twist from Brownells right now for $157, so you may want to consider that over the BCM, especially if you’re lacking on cash. But if you’re going to go ahead and pull the barrel off, then you might as well go ahead and buy a mid-length barrel and gas tube, especially since you’re going to have the Troy free-float tube on it. Don’t ditch the FSB - just shave it down.

Also remember you’re going to need a front BUIS to replace your FSB.

As for the bolt carrier group, I would keep the one you have and just swap out the buffer for an H-buffer. Make sure it’s staked well and press forward.

As for the lower receiver and upper receiver, you’re G2G. No need to swap them out.

4

How does it shoot for you now?

5

First of all there is nothing wrong with S&W carbines. I think they offer a solid product for the money. If it were mine I would keep it and buy a complete BCM upper in your choice of rail and sights and be happy. Later on buy a stripped lower, learn to assemble it with a good quality LPK and you have 2 complete weapons. The lower is a good way to start the build process and you do not need nearly as many weapon specific tools. Go slow, learn, and add to the arsenal.

6

Well it runs just fine now, but I know there are “heavier duty” components available. I appreciate everyone’s opinions. Especially because I am slowly being convinced to spend LESS money. In all actuality, I just want to have a quality weapon, but as you guys have said, its not a bottom of the barell gun to begin with. I guess that I could hang on to my current bbl and bcg until money better allows for an upgrade.

And just for my knowlege, I would still like to know about pinning FSBs to different bbls. What all would that entail?

7

I’d just make sure everything that is supposed to be staked is staked and shoot the rifle to verify reliable function before I did anything else.
gotm4,Rob_s and C4IGrant,just to name a few,have threads covering everything from functional reliability to accessories.
As for rails,research all the flavors before you buy that way you do not end up buying a bunch of gear you do not like.
I personally try to keep my weapons under the KISS theory,so I focus on functional details within the weapon.If it runs it runs,if not correct the issue and roll on…so live fire testing would be the first step.
I’d buy a H and H2 buffer and do some testing there to see what status your system is running in and tune.
The 1/9 twist to me is not that big of an issue as long as the chamber is correct. I have a couple uppers with that twist which shoot just fine with ammo from 50gr. to 69gr…Same goes for the barrel steel.
If the rifle is paid for and runs I see absolutely no reason to take a loss on it.I’d do as the others pointed out and add the components you want as you go,or buy a upper that will meet the eye candy requirements and specs,then drop it on your M&P lower.Save the original upper as a backup,or buy a lower and build it into another weapon…two is one as they say.

8

I have a MP15 and it is a solid weapon. It serves as my KISS carbine. Never had a malfunction after more than 2,000 rounds. My only complaint is the gritty stock trigger.

I choose to upgrade the bolt with a BCM upgrade kit, replaced the trigger with G&R lpk trigger, and replaced the buffer to H-buffer.

9

Keep it as is and if you want something else just buy another one. The M&P will suit you fine as is for most appliications.

10

Look for Rob’s “Oh no, I bought a…before I knew better” thread, or something like that, in the stickies.

11

This is the thread I print out and give to my family and friends when this discussion comes up.
https://www.m4carbine.net/showthread.php?t=24397
Lots of help there from several points of view.

12

I agree with this, keep the S&W or sell it and get what you want. I bought a neutered BM before the AW ban sunset and it has gotten a new barrel with bayo lug, two sets of stock upgrades, railed h-guards etc, etc. It is now my most expensive AR compared to my Noveske’s and LMT’s and still not any better than when I bought it.

13

Ok so I had a hard time following what was going on in the first post. So Ill give it a shot, so to speak…

I have 2 smiths that I built from lowers so I cant speak for the internal parts that are factory, but I know that the DPMS parts kit that i used in mine, was easy enough to make run a little smoother. I did some kinda custom stuff, the simplest being to run JP trigger springs and cut the tail of off the stock hammer, and placing a little grease on the sear. I also polish the bearing surfaces on the bolt carrier groups to make things a little smoother in the uppers, but this ones a little more advanced.

For the 1 in 9 I prefer it honestly. I MOSTLY run 55grn so its perfect for me. I do however have a 1 in 8 that I am trying out right now. It seems cool but I havent run anything heavier through it yet.

14

In the current issue of Combat Tactics I have an article that is essentially a cleaned up version of that thread and I believe is a bit easier to follow as it’s broken down into stages based on importance and cost.

15

that was a REALLY good article!!!

16

ditto on that!!:slight_smile:

17

Thanks guys. :smiley:

18

Its funny I totally missed the “I have an article”!!! Ether way good read. I dig this forum it seems like half the authors of the articles I read are here.

19

How about just putting a DD 12.0 or 9.5 FSP rail on it, and rollin.

Maybe I missed something lately, but I was under the impression that the Smiths were pretty well sorted out, with the only issue being the 1/9 barrel, which for many, may not be an issue at all.

Shoot it with DD rail on it, and as money becomes available, upgrade it according to the various threads already mentioned.

Bob

20

That’s pretty sound Advice… :slight_smile:

Ty Hoeffer
Palmyra, VA