Why aren’t .45acp carbines more popular?

[mavracer]

If I ever get around to getting a stamp I'll do a short .300 Blackout. Should be a good house gun and a fun range piece.

i wish I hadn't held off on stamp collecting.
The ballistics comparison between subsonic 300 and 45 ACP are pretty close. Available SD ammo cost definitely favors the 45 but the 300 definitely suppresses better and IMHO there's no comparison ballistically if you switch the 300 to supers.

 

[Mosin77]

i wish I hadn't held off on stamp collecting.
The ballistics comparison between subsonic 300 and 45 ACP are pretty close. Available SD ammo cost definitely favors the 45 but the 300 definitely suppresses better and IMHO there's no comparison ballistically if you switch the 300 to supers.

Tangential but I’ve never looked into the matter: a .30 is easier to suppress, or suppresses quieter than a .45 caliber?

 

[someguy2800]

For me I wouldn't consider 45 acp for a home defense carbine simply because 5.56, 7.62x39, and 300 blackout exist. They are way way way more terminally effective, and an appropriate carbine chambered in one of them (AR or AK) will be more reliable and have a higher capacity in a shorter mag. They will also have a lower recoil impulse unless you get a gas operated or delayed PCC. Outside the home, PCC's get left in the dust in terms of range.

For a fun range plinker, 45 acp is simply too expensive for me to have any interest. 9mm is the way to go for that.

 

[someguy2800]

Tangential but I’ve never looked into the matter: a .30 is easier to suppress, or suppresses quieter than a .45 caliber?

If they were both in locked breach guns they would be pretty similar. In general smaller calibers suppress a little better, but 45 acp would have lower muzzle pressure and less gas volume, so it would probably be a tossup based on suppressor design and the specific load used.

If the 45 acp is a blowback operated gun like many 45 pcc's are, then there is absolutely no question that 300 blackout will be quieter.

 

[Nuclear]

I have a 45ACP radially delayed CMMG that started out as a pistol and now is a 16” rifle (until I get the SBR stamp). I ran it with a silencer when a pistol and it is almost as quiet now with the rifle barrel only. Yes, the bullets don‘t really come out any faster, but they stay subsonic (quieter) that way. I’ve lit off a 5.56 indoors, and it is loud, even with hearing protection. Recoil is about like a 30 Carbine, not bad at all. I’ve got it sighted in at 20 yards, the longest shot in my house and a good distance for PCC competition. The gun’s price is comparable to an equivalent 9mm. It weighs about the same as a 9mm PCC, empty. About the only downsides are the weight of the ammo and the cost of the ammo, which is still half the cost of 300 BO.

 

[mavracer]

Tangential but I’ve never looked into the matter: a .30 is easier to suppress, or suppresses quieter than a .45 caliber?

It's easier to suppress with a smaller exit bore.

If they were both in locked breach guns they would be pretty similar. In general smaller calibers suppress a little better, but 45 acp would have lower muzzle pressure and less gas volume

Umm while the psi would be lower the volume is more than double.
I really don't have enough personal experience with a suppressed 45 nor do I have a meter so I'm mostly going off the many reviews I've seen and posts here by experts like MachIVshooter of Ecco Machine.
I will add that if a person reloads and has a locked breach 300 Blackout, like my Ruger American Ranch, that doesn't require X psi at the gas port to cycle, you can use pistol powder like Unique and hit 1050 FPS with 200-220gr bullets and it's ridiculously quiet suppressed.

 

[someguy2800]

It's easier to suppress with a smaller exit bore.

Umm while the psi would be lower the volume is more than double.
I really don't have enough personal experience with a suppressed 45 nor do I have a meter so I'm mostly going off the many reviews I've seen and posts here by experts like MachIVshooter of Ecco Machine.
I will add that if a person reloads and has a locked breach 300 Blackout, like my Ruger American Ranch, that doesn't require X psi at the gas port to cycle, you can use pistol powder like Unique and hit 1050 FPS with 200-220gr bullets and it's ridiculously quiet suppressed.

I don’t know where you are getting double from. Typical 45 acp load is like 4-8 grains of powder. A typical 300 blackout load that will have enough gas to cycle will be like 10-13 grains of powder. Are you talking about the expansion ratio of the bore? I was referring to the total volume of gas being ejected.

You can go even faster than unique if you don’t need to cycle. I have a 300 blk straight pull upper with no gas port. My favorite 300 blackout suppressed load is 4.5 grains of 700x with a 190 grain coated cast bullet. That is as close to silent as I’ve ever seen from suppressed firearm.

 

[mavracer]

I don’t know where you are getting double from. Typical 45 acp load is like 4-8 grains of powder. A typical 300 blackout load that will have enough gas to cycle will be like 10-13 grains of powder. Are you talking about the expansion ratio of the bore? I was referring to the total volume of gas being ejected.

Pounds per square inch
A 16"X.308 tube is 1.19 cubic inches
A 16"X.452 tube is 2.56 cubic inches
The volume of gas is greater in the bigger tube.

 

[Nasty Canasta]

I have a Thompson semi auto & it certainly wouldn’t be the first gun I’d be looking to get it my hands on in a home defense scenario but I could make it work if it was all that was available. With a 5lb drum in your arms will get tired before you run out of ammo. Fun range toy with a classic profile other than the 16” barrel. This one was rough as a cob out of the box & took a lot of work to smooth out & get 100% reliable & even with the crude Lyman open sights will easily break clays at 50 yards one after another.

 

[someguy2800]

Pounds per square inch
A 16"X.308 tube is 1.19 square inches
A 16"X.452 tube is 2.56 square inches
The volume of gas is greater in the bigger tube.

I’m talking about the volume of propellant gas, not the volume of the bore.

 

[mavracer]

I’m talking about the volume of propellant gas, not the volume of the bore.

Neither one is burning powder in the can.
The gas that the can has to deal with is what's in the barrel when the bullet uncorks from the barrel.

 

[someguy2800]

Neither one is burning powder in the can.
The gas that the can has to deal with is what's in the barrel when the bullet uncorks from the barrel.

Even in a 16" barrel, a 300 blackout loaded to cycle a semi auto will be burning gas in the can. That's why I already noted a 45 acp will have a much lower muzzle pressure.

 

[someguy2800]

Some of the other common powders that will cycle.

 

[someguy2800]

compared to some 45 acp loads. Note the muzzle pressure. Will be an even bigger difference in a shorter barrel.

 

[mavracer]

I’m talking about the volume of propellant gas, not the volume of the bore.

Look I'm just going off what I've been told by the guys who build and test suppressors and a pretty good understanding of the laws of physics.
Bottom line for X psi there is more gas in a .452 tube than in a .308 tube.

There's a reason that a 45 ACP can has to have a larger volume to be as quiet as a 9mm when the 9mm is higher pressure.

 

[someguy2800]

Look I'm just going off what I've been told by the guys who build and test suppressors and a pretty good understanding of the laws of physics.
Bottom line for X psi there is more gas in a .452 tube than in a .308 tube.

I'm not trying to attack you, we are just have a discussion. I'm one of those guys that build and test suppressors, though not nearly as many as some.

The pressure is not a fixed value so you can't say "X psi" for both because the pressure curves are not going to be the same. The bullet is accelerating down the tube so the volume in that tube is expanding as the burn is also petering out and the gasses cool. The .452" bore has a much larger expansion ratio so the pressure tapers off faster and it takes less pressure to get the same velocity because the sectional density of the bullet is much smaller as well. You've already seen how this pressure curve affect the muzzle pressure and sound signature with your unique 300 blk load. Its not really fair to compare a load that will cycle a semi auto in one caliber to a load that will not cycle a semi auto in another caliber.

Its definitely true that a smaller diameter bullet is quieter. Even shooting through the same suppressor with the same baffle hole size, my single shot 300 blackout load is quieter than my 44 mag with similar powder loads in both. With twice as much propellant mass in a semi auto 300 blackout load compared to a 45 acp and much higher muzzle pressure its going to negate some of that bullet diameter affect though. Its been my experience opening up the baffle hole size doesn't make that much of a difference within reasonable limits. I think what happens is the larger bullet creates a larger wake behind it that carries more un disturbed gas out the end with it. For example if I take a 9mm suppressor and open up the baffles from like 7/16" to 1/2" I can't really tell any difference. To get my 44 mag down to the sound levels of a 9mm through that same suppressor I have to drop the charge weight way way down to the point I'll start sticking bullets. That's why I would bet that 45 acp and 300 blackout will be kind of a tossup in term of noise. Will depend a lot on the load and barrel length. I have never tried suppressing a 45 acp so I'm guessing based on experience. And like I mentioned before if the 45 acp gun is blowback then it will be pretty much certain to loose. I know there are some gas operated 45 acp AR's and the CMMG radial, but I think 95% of the 45 acp carbines out there are blowback.

 

[v8stang289]

45acp is one of my favorite calibers, so I put together this 8" barreled SBR that takes Glock mags.
Being blowback, the recoil impulse is more than you'd expect, but not sharp at all.
Runs like a top with 13rd glock mags, but it's been a challenge finding 26 rounders that feed reliably.

 

[mavracer]

The pressure is not a fixed value so you can't say "X psi" for both because the pressure curves are not going to be the same.

X would be a variable, so it's not a fixed value. for any value you make X there is more volume in the larger tube.

The .452" bore has a much larger expansion ratio so the pressure tapers off faster

Because the volume is larger or smaller?

and it takes less pressure to get the same velocity because the sectional density of the bullet is much smaller as well.

Yes the .452 bullet has a lower sectional density, because it as a larger cross section IE there's more SI for the P to be applied to.

 

[someguy2800]

X would be a variable, so it's not a fixed value. for any value you make X there is more volume in the larger tube.

Because the volume is larger or smaller?

Yes the .452 bullet has a lower sectional density, because it as a larger cross section IE there's more SI for the P to be applied to.

So how do you apply a single variable for two curves that only cross at one point? I can explain it to you but I can’t understand it for you. All the data you need to understand it is above.

 

[mavracer]

So how do you apply a single variable for two curves that only cross at one point?

It doesn't matter for any value of X the volume of the tube is larger.
Volume is the space that the gas occupies.
It doesn't matter if a 1 gallon tank has 10 psi or 10,000 psi it's volume is 1 gallon.

 

[someguy2800]

It doesn't matter for any value of X the volume of the tube is larger.
Volume is the space that the gas occupies.
It doesn't matter if a 1 gallon tank has 10 psi or 10,000 psi it's volume is 1 gallon.

And how much volume does the gas that was in those two tanks occupy when they are released and allowed to expand to atmospheric pressure?

 

[mavracer]

And how much volume does the gas that was in those two tanks occupy when they are released and allowed to expand to atmospheric pressure?

Sigh yes if the volume is equal the one with the higher pressure will.
Now answer this if you have a 1 gallon tank with 500 psl and a 2 gallon tank with 500 psi which one has a greater amount of volume when released?

 

[Crosshair]

So what am I missing? Why are .45acp carbines not the go-to for PCC/home defense?

Because 9mm is seen as being "Good enough". In the 1980s, 90s, and 2000s, 9mm was seen as being somewhat inadequate. Which is why the market for 9mm PCCs then was so lethargic and everyone was using .223. The public perception has changed to 9mm now being perfectly adequate for an autoloader carbine. It's not a matter of 9mm vs 45. It's a matter of "adequate" vs "adequate". Except one of those "adequate" options was more expensive.

That perception though, can change.

Look at things like the Savage 340 in 30-30. For YEARS they languished as an "inadequate" gun. Everyone wanted 308, 270, 30-06, 7mm and 300 magnums. It was not hard to find half a dozen 340s gathering dust at any decent sized gunshop. Around the 2010s, at the same time everyone and their dog was still buying ARs, the public perception changed. People realized that shooting a deer 75 yards away with a 300 Magnum was stupid and these "old" bolt action 30-30s were actually perfectly adequate for the job AND easier on both the shoulder and wallet. The once plentiful supply dried up as they became desirable again.

The 1986 Miami shootout led to a ~25 year move to 40 S&W and, to a lesser extent, 45 ACP. Another high profile incident could easily cause another move back to heavier calibers. Suddenly that "adequate" vs "adequate" scenario turns to an "inadequate/marginal" vs "adequate". Shelves will fill with used 9mm PCCs like they used to be full of Savage 340s as people make the switch. Or be relegated to a closet or "spare" gun.

Will such an event happen? Who knows. For all I know the NFA will be declared unconstitutional and submachineguns in 32 ACP and 30 Super Carry will become hugely popular. (Recoil sensitive elderly will absolutely love them.) Leaving 9mm to go hang out with 45 ACP.

Blowback 9mm PCCs already suffer from sharp recoil impulse thanks to the heavy bolt slamming around. Some of the .40s are downright uncomfortable. A .45 would be even worse.

I disagree that this is an inherent problem of 9mm blowback PCCs. I instead see it as a problem with specific designs. The Hi-Point 995 and Kel-Tec Sub2000 are two guns that are a bit "slappy" with the recoil. The Sub2000 due to using a really lightweight bolt and the 995 due to the stock flexing upwards when the bolt reaches the rear of travel. By contrast, the PC-9 stock, both old and new, do not flex like the 995 and have enough bolt mass to avoid the problems that the Sub2000 has. When I take new women shooters out, they tended to like my PC-9 more than my Mini-14. From their perspective, the muzzle blast seems to be more of an issue than the actual recoil. Men like the Mini because "Big Boom". Recoil of either is irrelevant.

I think the pistol caliber guns pretty much fell out of favor when the AR's got smaller and offered more in the way of performance. Other than something like a special-use type gun, like the above, I really dont see much point in them anymore.

This was true a decade or so ago, but the popularity of PCCs has exploded in the last 5-10 years. There are many reasons for this. (In addition to what I have mentioned above.)
1. Short ARs suck. The muzzle blast is dreadful and just not fun to live with for regular shooting. People put up with them for awhile, but nowadays fireworks are cheaper if you want to feel concussive blast a few feet from your face. It is my observation that this tends to be a large issue for women. They don't like huge muzzle blast, don't want to put up with it, and I can't say that they're wrong.
2. Logistics. We've been through enough ammo shortages in living memory that this is a big deal for a lot of people. Most of us here are in the top 1% of shooters, so have large stockpiles to get us through these. The other 99% don't have 10,000 rounds in their basement. These people will have perhaps a few hundred rounds of centerfire ammo on hand. Instead of having to figure out what the optimal mix of pistol and rifle ammo to have is, they can just stockpile a few hundred rounds of the same ammo. Or they pick up a PCC in addition to their AR so they have a rifle that can make use of their pistol ammo and/or have a gun for their wife/girlfriend/kids.
3. More realistic expectations. You're not going to be making 400 yard shots when the range goes two-way. Kevlar isn't a magic forcefield and doesn't cover your face anyways.
4. Backstops and impact area. PCCs are typically okay to use at pistol-only indoor ranges. Outdoors, the impact area for shooting a PCC is much smaller than a .223. Same reason 22 Hornet or 22 Magnum gets used for pest control rather than a .223.
5. Tactical Cowboy guns. This trend has been going under the radar. Henry has been selling lever action guns as fast as they can build them for many years. In ban-states, your option ted to be a gimped AR, Clinton Clips, or other abominations. Rather than put up with that, many people just go for a lever 357 Magnum, slap a red-dot on it, and call it good. Then buy a 38 Special revolver.

That's enough commenting from me for now. Hope someone finds this insightful.

 

[shafter]

People are adopting 9mm in large numbers and want a carbine with compatible magazines and ammo. 45 is still going strong but it's hardly going through a resurgence.

 

[someguy2800]

Sigh yes if the volume is equal the one with the higher pressure will.
Now answer this if you have a 1 gallon tank with 500 psl and a 2 gallon tank with 500 psi which one has a greater amount of volume when released?

I'll reformulate that question into something that is actually relevant to the conversation. How about if we have .74 grams of gas in a 1.2674 cu in tank at 2208 psi in tank 1, and 3.5 grams of gas in a 2.6648 cu in tank at 675 psi in tank 2. Are you getting it now? I was never talking about the volume of the barrel. I was always talking about the volume of gas that needs to be suppressed after it has exited the bore.