How ya doin guys, Im a newbie to the AR world and shooting for that matter and was wondering what was the difference between bullet grains i read about 55,62,64 and so forth. I just purchased a M&P 15 sport and pick it up this Thursday. SORRY for being such a noob and please bear with me on my journey.

Welcome to the club...I started out shooting 55 gr and for the most part still am, they are the most economical and seem to shoot really well in my Sport. I have read about using other weights and I have actually loaded 100 68 grain but I still go back to shooting the 55 grain

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Grover Oathkeeper

I have reloaded some Sierra 65 gr Gameking and 69 gr HP's using TAC and got some pretty good groups. I have a Vortex Strikefire mounted on my M&P 15 and shot this group some time back.

I'm not sure what the twist ratio is on the Sport model but if you're like me and just shoot paper 55gr work great.

If your just starting out, buy whatever is cheapest in the 50 to 70 grain range and bang away. The sport, with a 1 in 8 twist, will handle 'em just fine.

I'm having some 75 gr Hornady match and 77 gr sierra match king loads cooked up I cant wait..... The heavier the bullet the better for sheer accuracy. 55 gr works great as an everyday shooter, I run 62 gr or 64 gr soft points or 75 gr tap for defensive loads.

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CLEAR!

Keep in mind that a projectile's weight (grains) is only 1/2 of the equation. The projectile shape is the other 1/2.

"(From left to right) Hornady 40-gr. V-Max; Nosler 50-gr. Ballistic Tip; Nosler 55-gr. Ballistic Tip; Nosler 60-gr. Partition; Sierra 69-gr. MatchKing; Berger 73-gr. Match; Swift 75-gr. Scirocco; Hornady 80-gr. A-Max; Sierra 80-gr. MatchKing; Berger 90-gr. VLD."

Source: Handloading The .223 Remington For The AR15

(Good Article)

Keeping it simple...

The longer boat tail projectile is more aerodynamic than the shorter stubbier projectile, and has the potential to cover longer distances with better accuracy.

Given that there is a finite amount of propellant that can be safely loaded in any cartridge, there is a point of diminishing performance because it takes more energy to propel a heavier projectile than a lighter one.

The heavier grain projectiles aren't more accurate because of the weight alone, they weigh more because there is more projectile: the boat tail.

I always stumble on this part, so someone please please please correct me:

The lighter projectiles require less rifle twist rate (1:9) because anything faster and the projectile's break apart due to centripetal force (a.k.a. spin themselves apart)

The heavier projectiles can handle more rifle twist rate (1:7) because the additional mass can resist the centripetal force.

The 15-Sport has a 1:8 5R progressive gain rifled barrel, so it's like the Goldilocks of the AR15 twist rates. Not too fast. Not too slow. Good for a wide range of projectile weights. The 1:8 5R progressive gain rifling deforms the projectile less as it travels through the barrel, contributing to a higher potential for accuracy.

So which grain projectile should you use? It all depends on what type off shooting plan to do. For practice rounds, I buy whatever is on sale. I love shooting the super affordable Russian steel case ammo.

I have some expensive Hornady VMax & ZMax ammo I have yet to shoot.

I know I'm over simplifying a bit. The hand loaders here will fill in the blanks for me.

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-John

Forgot to add, welcome aboard! Don't be afraid to ask questions. No one starts out knowing everything.

The more I learn, the more I realize I have even more to learn.

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-John

Thank you sir, In honored to be part of this community. True g entlemen and scholars. That answered my question. Man am l stroke can't wait to pick up my rifle and get to the range.

I tell/ask every new sport owner to run a few hundred rounds through your gun stock before you start to mod it out. I regret not doing it myself.

I have been doing a lot of reading, according to my reloading manuals once you get above 77grs then you have to start loading the bullets one at a time (supposedly) But I dont know.

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Grover Oathkeeper

Unless you reload, your best bet is the Lake City 55gr or 62gr as loaded by Federal if you can find it. Good brass to load if you ever get started or to trade off. The brass used in Federal American Eagle with the same weight bullets is usually Federal brass and most reloaders find it too soft.

Other than that, the bullet weight will depend on what you are using your AR for. The heavier weights only come into their own past 200 yards.

And to go along with this the 55 grain will do excellent to 300, the Marine Corp says that you need heavier to go beyond that accurately. I myself havent tried yet but I know people who are shooting 55gr to 400 accurately. I regularly shoot 250 to 300 on very small targets and to watch the hits with rarely a follow up shot is pretty cool.

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Grover Oathkeeper

I load 75 and 80gr Amax's and they don't stabilize until after 100yds. I do have to feed them 1 at a time as a previous poster said. The OP, being a new shooter, probably just wants to get some trigger time, could or could not have an optic, more than likely has no idea about reloading and should, IMO, buy some cheap bulk stuff in the 50 to 70 gr range and have at it. For those of us that do reload I just started a new thread on handloading for the AR.
Pet loads for AR-15

Welcome.

Normally the the faster the rifle twist the longer(heavier) bullet you can shot out of it. The Sport I believe is 1 in 8 as another poster stated. It should be able to stabilize most of the bullets available for .223. If you shoot paper and start seeing a keyhole or out of round hole, that is a good indication the bullet is starting to tumble and needs more twist.

Jim F

As some of the other people have said and I wholeheartedly agree get some 55gr fmj, inexpensive stuff and go out and have fun. As most of us have discovered the Sport will eat anything you feed it and like it. If you buy the Tulammo or Wolf or any of the steel cased ammo you may want to clean it a little more thoroughly because they dont expand as much as the brass and will get your chamber dirtier. The rifles love that stuff and shoot it as well as anything. You can generally buy it for $4 to $6 a box of 20 and that will last about "that" long LOL. After you have shot it a while and want to start either working on accuracy or "combat" effectiveness you may want to switch up to a better (being a subjective word) ammo. I dont remember how many 100's of the steel cased ammo before I bought my first 1000 round case of Federal 5.56x45 (it says american eagle in the fine print) but I also started reloading with the used brass at the same time. All 55 grain, I am now buying from freedom munitions, mostly their reloads because of the saved expense but also some of their blaster training ammo (even cheaper) and will save the brass to reload with my Hornady V-Max and Z-Max (zombie bullets) because I can load these cheaper than I can buy them and they are great on prairie dogs and coyotes. FMJ tend to blow right through whatever you shoot, not necessarily a clean kill. All of this has been my experience and opinion.

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Grover Oathkeeper

I generally shoot American Eagle (Federal) 55gr FMJ - it's relatively inexpensive and I can make 1" groups at 50 yards with an unmagnified optic (and could probably do a bit better if I put a magnifier on it). 55 and 62 gr bullets are just fine out to 300 yards, and my personal opinion is that if you're shooting at anything over 300 yards away, you should be using a bigger caliber anyway. Even with heavier loads, the .223/5.56 just doesn't carry enough energy beyond that point for my preference. YMMV, of course.

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Slow is smooth, smooth is fast