I have an M&P 15 Sport and I would like to get either a 300 Blackout upper or barrel for it so that I can use a suppressor (one that already works with a 9mm). That said, I am new to all of this and have a question:

I believe all I need is a 300 Blackout barrel, which I believe I can afford. But what would be the advantage to getting an entire 300 Blackout upper (which I probably cannot afford *S*)?

Also, if you are up for it, do you have any recommendations for specific barrels and uppers I should be looking at? I am googling like mad, but always appreciate your experience and expertise to help me save time and have more piece of mind.

Thanks!

Well, the biggest benefit to a complete upper would be the ability to change out calibers quickly.
Also, wouldn't have to re sight in after caliber change.
As to barrels and uppers, I'd be good with CMMG, either for complete upper or just the barrel.

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Hold my beer and watch this!

There is a big difference between changing barrels and changing uppers.... You have to have the tools and knowledge to change out an AR barrel but only push out a few pins to change an upper. Also, you mentioned using a 9mm suppressor on a 300 blackout. First, the 9mm will be treaded 1/2x28 and the Blackout will be threaded 5/8x24. Then you need to consider the pressure from a rifle load going through a pistol suppressor... call the suppressor manufacturer but Im betting they say dont do it.

Just saying...

DSA ZM4 Forged 7075T6 A3 AR15 Upper Receiver; 300BLK - ZM4CBU300-D S Arms

Wow, that's another definition of "inexpensive". How do they make any money off of that? Just randomly looking around the internet I figured between $400 - $450 for parts, but that was with a $200 barrel.

Take note that it doesn't include a bcg or charging handle. That's why it's so cheap.

Thanks everyone for the replies. It will give me some reading to do tonight. As far as the suppressor compatibility is concerned, the dealer I have been working with has experience with the set up I am talking about, so I am not worrying too much about that yet (but I will verify everything later!). Mostly here I am just trying to learn more about barrels vs. uppers, before I start working more with him. I'm hoping to learn a little something, which all of you are helping me with!

Thanks!

Since your M&P Sport is 5.56, you can use your existing BCG and charging handle in the upper that doesn't have it. So you could just purchase the DSA semi-complete upper. 300 Blackout uses the firing control parts as 5.56/223. Only need a barrel change.

This is the route I'm going, but opposite. I have a 300 Blackout (for hunting) and will be picking up a 5.56 upper for it so I can go plinking at the range.

Oh really? So, to be redundant, er, clear (LOL!) I can get an upper without the BCG and charging handle and just use my existing one?

Does that require a significantly increased level of expertise to install? I think I could afford that, and I really like the idea of a (for the most part) more simple installation compared to installing a barrel.

I know even less about good retailers than I do about barrels and uppers right now, but I am finding places like Model 1 Sales and others that seem to offer the upper without all the parts. Are there retailers I should stick with and ones I should avoid with this stuff generally speaking?

Also, FWIW, I would really like to have a longer handguard on whatever I get so that I have the option of placing a light further down the barrel. Something more like this style. I am assuming that is fine and I can get whatever I want when it comes to this?

Removal and installation of a BCG and charging handle should be commonplace when dealing with an AR. After all, you should know how to disassemble your upper when cleaning.

With the .300 Blackout, you can even use your existing magazines. The cartridge is just a resized 5.56 casing to hold a 30 cal bullet.

I would go complete upper minus the BCG at minimal over just a barrel swap. With a barrel swap, you will need to make sure that the gas system is the correct length to fire the 300 Blackout cartridge. With a complete upper, it's already done for you (counting out any type of manufacturing flaws).

Sounds like that's the way to go. Thanks so much. Now I have the direction I was hoping for.


For anyone, any specific recommendations, experiences with retailers or brands, etc. would be appreciated!

CMMG is a great company that does 300 Blackout. And they are more budget than others and make a great product for the dollar. Their complete uppers start around $570.

There are other companies as well.

Noveske, Daniel Defense, Advanced Armament and a few others. But they are going to be over 1K.

Not sure what your budget is, but I follow the rule "Buy once, cry once". You get what you pay for.

$600 is about tops. Less would be great; but I too like to buy the best quality I can afford -- "afford" being the operative word right now.

That said, when you say "complete" uppers, you mean that they include the BCG and charger too, correct? If this is the case, and I can just use my existing BCG and charger, I am guessing that something int he $400 range should be possible.

I will start looking for CMMG now. Thanks!

IF you want to use the same carrier fine, but do not use the same bolt with both barrels.
Bolts wear in with one barrel over time, if you use the same bolt with both the 300 and 5.56 you may have headspacing issues.

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Hold my beer and watch this!

Interesting. Good to know. As it is, I have not even shot this Sport yet. I may not use it until I get the upper. I assume that if I hold off I won't have to be concerned about the bolt.

Thanks.

I myself would get a BCG and Charging handle for the new upper, That way everything wears in as a complete unit. Using the same BCG with both uppers is going to cause accelerated wear on the new upper and could conceivably cause bolt lock an unlock problems in the future. Where with separate "complete" uppers that problem wouldnt exist.

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Grover Oathkeeper

Poor frudoc, just now discovering that BRD (Black rifle disease) is worse than any other addiction.
Just wait till you find an extra charging handle and decide you need to build another AR around it.

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Hold my beer and watch this!

I would be very hesitant to switch a BCG back and forth between two different uppers. There are some guidelines out there as for when you can use barrels and BCGs in different stages of their life (new vs. used) and I don't recall the scenario where rotating a BCG back and forth between two uppers is a recommended practice. Actually, I wouldn't do it myself.

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Stu

It could develop headspacing issues. But that would depend on the number of rounds through the 5.56 before being used. If it's a new BCG in the Sport, then your GTG. If it has a lot of rounds, go with a new bolt, but you can use the carrier without issue.

[QUOTE=frudoc;136835332]Interesting. Good to know. As it is, I have not even shot this Sport yet. I may not use it until I get the upper. I assume that if I hold off I won't have to be concerned about the bolt.

Shoot it!!! That is why you got it. Also as mentioned earlier 9mm can will be threaded1/2 X 28 and the blackout upper will be 5/8 X 24. What kind of can were you going to get?? I would be curious which company is certifying 9mm and 300 whisper through the same can??? Be Safe,

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I BACK OUR BLUE

Im going to get the S & W 300 upper, I just got a new S & W lower for it and it seems like there are a lot of good reviews for the S &W 300 but it is a bit pricy but I like the melonite barrel .

Good review of the M&P15 Whisper here Just Enough Gun: Smith & Wesson M&P15 .300 Whisper - Guns & Ammo and an interesting article on 300 Whisper vs Blackout here NRA Mobile.

I would think it'd be fine to use the bcg in the new upper since it's new still, but I don't believe you should use it on both. You're going to have to get a new one either way in my opinion. If you use it occasionally for both, it won't wear to a specific upper and could eventually wear to the point it won't work in either. I'm not an expert though, just my thoughts on it.

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-Dik

I had a .300 for a couple of months. Other than being subsonic friendly, it does nothing as well as what I already had. I've tried different calibers, and only stayed with two in the 15 size platform. The 6.8 SPC and the 5.56/.223.

The short overall length of the .300 concerns me too. Although I haven't personally confirmed it, it appears to me that a pointed .300 could chamber in a 5.56 chamber. With the bolt and magazine being identical, if you do choose a .300 mark your magazines.

I still have a few loaded rounds, dies and such. I simply don't want to have to beat a stuck .30 caliber from one of my 5.56's to find out.

There are pics of a mangled upper at the link below. Be careful!

http://www.snipershide.com/forum/ubb...Number=3067632

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GOA
USA Shooting Supporter

This is where you must be careful. You must ALWAYS be careful. After all you are dealing with a firearm.

What about those that put .380's into a 9mm. Same type of scenario could happen. But with diligence it can be prevented.

And I think to get a .300 to fully chamber in a 5.56, you probably would have to physically jam the bolt forward, due to the larger diameter of the bullet itself.

Are you aware of just how short the .300 is? It may set some bullets back into the case a bit, but I don't think you'd have to force it to close on many pointed profile bullets.

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GOA
USA Shooting Supporter