New M&P15, a few questions.

[ecrist]

I have a brand-new Smith & Wesson M&P15. Two guys at the shop where I purchased it gave me conflicting information on how to use it to start. First, the guy said to just shoot it and have fun. No special new-gun treatment. Another guy came up, said that was wrong, and I should clean the rifle after each shot for the first 20 shots. What gives?

Another question, all my magazines are marked 5.56x45. Call me silly, but I assume this is referring to the diameter of the casing, and not the grain of the projectile. Am I correct?

Any other advice? Been a long time since I cleaned one of these for Uncle Sam, any new tricks, things I should/shouldn't do?

[DefensiveCarry.com]

[atctimmy]

The second guy was a tool. Just shoot it and have fun.

The 5.56 is the diameter of the bullet in millimeters and the 45 is the length of the case in mm as well. So it reads "five point five six by forty five".

[tommyp]

Cleaning it after every shot for the first 20? No, that's crazy talk. Shoot the crap outta it. 2 schools of thought - clean after every outing, clean after every couple hundred shots. I don't think i disassembled mine till after the first 300 shots, and I still haven't touched the gas tube.

5.56 is size - not sure about diameter or what, but it's size related. There is typically a bit more powder in the 5.56 casing though. Someone I'm sure will chime in with a bit more. There's thought on how much powder you should run based upon your rate of twist, but I forgot what the deal is. Some say it affects accuracy. Basically, with it stamped 5.56 it can take 5.56 or .223. 5.56 i know has a bit more powder in it, and can rip apart a barrel stamped for .223, but they're interchangeable in a barrel marked 5.56. I shoot the .223's simply because at my lgs they're cheaper. Hope that at least helped some.

[RKM]

I didn't clean my M&P15 until I shot a few hundred rounds though it.

Most M&P15's (maybe all of them) are 5.56 chambers. Shoot 5.56 NATO (5.56x45) or .223 through it. .223 is cheaper.

tommyp... you're referring to the grain of the bullet, not the powder. The grain of the bullet is the weight. Typically, the heavier the bullet needs a faster twist. Most M&P15's are 1:9 or 1:7. Either barrel can shoot upto 75 grain bullets without issue. I've shot 75gr rounds out to 100 yards without key holing, which basically means the rounds because some unstable it starts to flip end over end. You shouldn't have this problem. The 1:12 barrel in the old M16's will have trouble with heavier rounds.

[ecrist]

My M&P15 is stamped for 5.56 and has a 1:9 twist. Casing length makes sense. This clears a lot up for me.

[ecrist]

I forgot to ask, where can I get decent, reliable, bulk ammunition? I'd like 5.56.

[RKM]

Look on ammunitiontogo.com They usually have good options. And it's always changing.

[gasmitty]

Try ammoman.com and ammotogo.com for starters, to get an idea of bulk pricing. Ammoman's prices include shipping, ATG's don't. If you have local gun shows, check prices there, too - the tradeoff being sales tax vs. shipping cost. The smart thing to do is to compare price per round delivered.

Small point, but your gun with a 1:9 twist will shoot 55 gr ammo a little more accurately than the 62 gr and heavier, but betwen 55 & 62 that's really splitting hairs. General rule is that the heavier (longer) bullets stabilize better with a faster rifling twist rate.

There is an on-going debate about the use of steel-cased ammo (such as Wolf) vs brass-cased. It comes down to what you are willing to do. I personally don't use steel-cased ammo in my ARs, because the only stuck cases I've ever seen were steel, not brass, but that's just MY experience and prejudice.

Oops, almost forgot. Shoot he HECK outta your carbine, and enjoy it!!!

Oops, almost forgot. Shoot the HECK out of your carbine, and enjoy it!

Beyond that - get yourself a stack of magazines, and recognize that you're not married to them. Mags don't last forever. Don't go nuts with cleaning; ARs don't need (or want) to be white-glove clean, and keep the bolt lubed. ARs will run when they're dirty but they won't run when they're dry.

[atctimmy]

There is typically a bit more powder in the 5.56 casing though. Someone I'm sure will chime in with a bit more. There's thought on how much powder you should run based upon your rate of twist, but I forgot what the deal is. Some say it affects accuracy. Basically, with it stamped 5.56 it can take 5.56 or .223. 5.56 i know has a bit more powder in it, and can rip apart a barrel stamped for .223, but they're interchangeable in a barrel marked 5.56. I shoot the .223's simply because at my lgs they're cheaper. Hope that at least helped some.

Tommy grains are a unit of weight. They measure bullet weight and powder weight in grains. 1 oz = 437 grains. So a 55 grain bullet is describing the weight of the projectile, not the powder charge. The reason the weight of the bullet affects accuracy is that heavier bullets are longer and they need a faster twist rate for them to stabilize. So it's the length of the bullet and how it reacts to the rifling that determines accuracy. Or at least it's one of many factors involved in accuracy.

Individual "pieces" of powder are not called grains (like sand) they are called kernels (like popcorn). So a loaded 5.56X45 cartridge containing 25 grains of powder will have 350 (<- made up number *) kernels of powder.

* I had to make up a number because I don't know what a realistic number would be. It is always measured by weight or volume.

[atctimmy]

OP: For decent mags on the cheap look here:

http://www.cdnninvestments.com/

The Fusil mags are only $9.99 a piece and are pretty nice.

[ecrist]

I ended up going with Bulk Ammo. They have 900 round cases for 5.56x45 FMJBT for $305 until tomorrow, which is the cheapest price I was able to find. You can check it out for yourself here; I bought two cases. :)

@atctimmy, I purchased a couple extra magpul magazines at the same shop. I paid $14.95 each for them.

[ecrist]

Just wanted to follow up. My new rifle shoots great. Got a couple relatively new shooters involved, as well. Once has never really held a rifle and the other is new to the AR-15. We fired 300 rounds, without a single misfire. We also put about 180 rounds through my Glock 22. A good couple hours shooting for all.

[atctimmy]

Nice! I recently bought the M&P 15 as well. I have bee very pleased with it. 100% since day one.

[C hawk Glock]

Next should be the M&P 15-22! I love it and it saves a ton of dough!

[kudzu]

Next should be the M&P 15-22! I love it and it saves a ton of dough!

Yeah, it's hard to explain what a hoot the "baby AR" is to shoot!