Inquiring minds want to know.  It seems it would be more logical at lower speeds to just go with the heavier round.  

Is it just hype?  Are there really more benefits to the .300BLK in an AR15 pistol?

ever try to shoot a 45 at 100 yd?

.45acp yet I got out to 75 yards with decent group Tried 100 yards nope and this was an HK UPS Tactical 45 that was dead on at 25 yards. Yet for the round I know it isn't the reach you at long ranges. Yet my .357 mag Cold King Cobra with 6" barrel yet that would reach out and touch you at 100 yards with 3-5" group from a rest. Yet that bitch bucked like hell worse that .44 mags with 6" barrels. Shot plenty of both and that Colt was just hurting after about 10 rounds. Although it was early 90's model and is a bitch to find now. The one that I got rid of that I wish I haven't. I blame the Clinton ban cause traded it for preban AR at the time in mid 90's.

Easy to build. Reliable. Standard parts other than barrel. 223 based brass. .308 bullets. Super sonic capability. Etc etc.

What he said. Even if we're talking subsonic only.

I've been going back and forth for the last month between a tactical .45acp and a 8-10" .300 pistol as my primary bedside mate.

Still havent decided.

300 blk is cheaper and easier to gather parts for.  Ammo is more expensive.

45acp options are fewer, but you can go shorter.  Macon armory has a 5" option.  Cheaper to shoot,  but more expensive upfront build costs.

You're never going to accidentally shoot a 45apc round in your 5.56 uppers...

.300 Blk 220gr at 1000 fps is pretty close to .45 ACP.

120 gr at 2200 fps is way past .45 ACP.

300 Blackout is also going to retain more velocity and energy at longer ranges.

I'm with you.  I'm not looking for a 100 yd gun.  I have plenty of those.  If I had 100 yds to make a move, it sure wouldn't be with a barrel shorter than 10".  I just can't envision a pistol length weapon worth anything more than a way to fight my way back to my primary weapon.

In energy, yes.  In expansion,  probably not even close.

I love the 300blk, but it doesn't necessarily out perform any particular round, but it does a lot of things pretty well, including run with supers and subs.  Tough to do that in the AR platform in a rifle round.

why this or that?
get both, they are different tools, an 8 round plus in small pistol package.
and a 30 round 300 blk, that can run sub, and supers, from a short barrel well past the 45acp effective range, the package is however larger.
together both are small enough to not draw unwanted attention, easy to hide,....ect  

pistol #1 lets me fight my way back to the car, to get bigger pistol #2.  and lord I pray I never have to do such, but having the tools to do so is a good thing.

just a thought.

       




 

I avoided the issue by building a 10.5" 5.56. Not only was the build cheaper but I can buy cheap ammo 7.50 a box at the local sporting goods store, much less even cheaper surplus in bulk.

The OP mentioned a slower moving bullet that was heavier but the reality is that a small high speed bullet like 5.56 is still carrying over 1,000 foot pounds of force at 80m when bullet drop for the .45 is becoming problematic to guess at. A longer barrel simply doesn't fix it;

For a .45 I'm shopping older S&W .45 cal third gen guns all stainless and seeing them on gunbroker used for under $400. For the AR pistol, which barely cost over $500 to build, I can take it hunting and have more effective and ethical killing power at longer ranges, which makes it a better gun hunting, and for HD, 30 round mags for more firepower.

I just don't see the rationale behind making a pistol caliber carbine when I can have a rifle caliber pistol with much higher power and capacity. Handgun calibers are never more powerful than rifle calibers - as we say, you use the pistol to fight to the rifle. Well, when I carry the pistol, I can fight to the next level, an AR pistol in a rifle caliber, which should more than sort out the intermediate situation. When I need a rifle then frankly the enemy is far enough out what we have to do is manuever to get close enough to see each other - under 125m - and we are right back to AR pistol ranges. With no hold over, either, or significant need for a scope. It's all iron sights that close.

I know there are a lot of pistol caliber carbine fans out there but the concept relates to a very old tradition. The modern ballistic application of using a rifle cartridge in a pistol dates back to the early sixties, and for our purposes, when the Army adopted the XM177 - an AR pistol with a stock used for CQB. That was 1965, and that trend has continued to advance as we get more familiar with the superior ballistics and firepower.

I'll take 30 5.56 rounds out of a 10.5" barrel over "x" teen rounds of .45 - almost double the power and capacity right out of the box. The .45 works as a 21 foot gun for CCW but for HD it's barely qualified to help me fight to the other.

Yes.  100 yards is no problem for a 45 ACP.

As one who owns a few pistol caliber carbines in .45acp I can say that out of a 16" barrel it's very effective out to 100 yards. Maybe not as much out of a shorter barrel but very useable.

I'm new to the AR pistols but I can say for sure there's not nearly as many options for a .45acp AR, rifle or pistol. Glock mags seem to be the most common but requires a dedicated lower.

RWI has the best setup IMHO with their DI45 & modified grease gun mags. And there's Olympic's setup, mags are expensive & proprietary but will run on a std. lower. I think either of these setups are around $800.

.300 BO has gotten a lot cheaper over past few years, not as cheap as 7.62x39 but it's comparable in cost to 30-30 in quite a few brands and available as cheap as 50 cents/round from Magtec and S&B. Hornady in either caliber is a buck a round.

I've got both.  if I had to grab one to kill something, it would be the 8" suppressed .300blk with 110gr Barnes supers, because I've seen first hand what it will do to deer and hogs inside 200yd.
If I'm plinking 'cheap' then I grab the .45.  It's a blast to shoot and will be more fun once my Form1 is approved for the QD can.  It's nowhere near as accurate as the .300blk at 100yd.

.300blk


.45 on the right

Why would you choose a lighter subsonic round?  Seems that if speed is limited, weight is king for energy delivered to the target.  I admit to being extremely ignorant about the 300blk.  

I think he misspoke, as I'm not aware of any 110gr subsonic loads, though I could be completely wrong

Who's talking about lighter subsonic rounds?  In most "normal" AR setups, any .300blk shy of ~170gr is going to have to be supersonic to cycle.
I'm talking about the factory loaded 110g TAC-TX load, which is supersonic, over 2000fps out of an 8" barrel, and will expand fully down to ~1300fps.

Barnes 110gr .300blk out of a 10" barrel has the same energy at the muzzle as M193 5.56 out of a 16" barrel.  It has more than double the energy of 230gr .45 for any given barrel length.

ETA: sorry, I caught my typo, meant to say 'supers' not 'subs', though I have killed some hogs with subs, though not nearly as effective.

Okay.  Thanks.  I was a bit confused.



 

also

300 BLK is easier to convert, barrel swap only.
Also more flexible.

45 ACP is awesome in an AR, but the edge goes to 300 BLK.

Pretty hard to find inexpensive to moderately expensive 45 ACP AR15 platform rifles.

.300 BLK AR15 rifles are common and relatively inexpensive, you can do a PSA build for under $600 if you catch the sales.

That was my reason.

If your going to do a 45, you may want to consider the Roland 460 as it picks up a bit more speed and will shoot 45's though the same barrel.

If you're going with blowback, .460 is starting to push it on available carrier mass.
And shooting ACP through a Rowland barrel would be iffy depending on the gun, since the round indexes on the case mouth.
You can get away with it in some handguns since the lip feeds under the extractor, which will hold it against the breech to be struck by the firing pin, as opposed to a gas AR where the extractor has to snap over the rim and may push it away from the bolt face.

In other words, a pistol caliber AR isn't an AR. It just looks like one, for our extents and purposes it's a modified action blowback gun.

And since we are talking pistols, 16" barrels aren't the common denominator in expressing ballistics. If anything, the original 10.5" barrel of the XM177 is the standard. Looking at the pressure curve and amount of gain in speed per inch of barrel, there's not much to add to the .45, conversely, the 5.56 doesn't lose as much as some think. 5.56 ouf of a 10.5" barrel is still going over 2500 fps.

A .45 doesn't even approach that. It does make things up in mass for the larger bullet - but again, 5.56 retains 1,000 foot pounds at 80m, where the .45 does not. Not even.

The Army had it's time with .45 SBR's - the tanker submachine gun for one - and it was resolved that there simply wasn't enough power despite the larger magazines compared to the 1911.

The point being that we should be selecting the cartridge that delivers sufficient power for the intended range and target - enough to carry at least 1,000 foot pounds if game hunting to that distance we might shoot to hit one. .45 is can get that job done at limited ranges (I'm shopping for a handgun in that cartridge) but when you extend the range it loses too much power (large frontal area and inefficient aerodynamics) compared to a 5.56 or .300. For the limited range and effort of carrying it, a full on stainless .45 weighing three pounds loaded is smaller and just as effective as the larger AR pistol in .45 and arguably a much better choice.

Some like to disparage AR pistols as being range toys useless for anything else, and in a pistol cartridge some argument could be make that it's more justified - but it's still a firearm and in it's operating envelope it will still be lethal. We just need to define it and use it there, no expecting it can perform miracles beyond the limits of physics.

It's about range and target, pick the best cartridge to do the job, and you will be more right than wrong.

All things equal the .45 parts and market support are just less.

I would go .300 BLK birst easily.

Depends really.  If I knew I was going to get into a gunfight, more is better.  My .45 SBR holds 30 rounds, has a red dot, and a stock.   It's much more accurate with much quicker followups than a handgun.
No, it's not a rifle caliber, but it's got the handling and (relative) accuracy of a rifle.

 

I'd like to actually shoot a 5.56 carbine with 18", then 11.5, then 300 with 6.5 or so inch barrel indoors with the same hearing protection and see what the blast is like.
A friend says he would never fire his 416 with 11.3 barrel without a can though he didn't say with or without ear pro, inside or outside.
I suspect muzzle blast being no problem the 5.56 in 10.3 with any softpoint would be pretty effective out to over 100 yards.
That .300 under  $300 with 8.5 barrel without bolt carrier assembly is tempting but so is the 10.3 5.5.6 at around the same price from PSA.