Over max 9mm for carbine use?

My experience with Semi auto carbines. Tells me to stick with standard loads.
You may have a longer barrel, so you would figure upping the powder charge or running a slower powder may gain you some extra fps.

Since most of them are simple blow back operated. All that really happens is the action operates before all the powder has burned. giving a nice big flash out of the ejection port. And can also get kind of dangerous.

Most 9mm carbines are unlocked blowback operated. They are not locked breech gas operated like a 5.56mm.

First they depend on the weight of the bolt and the pressure of the recoil spring to keep the breech closed until the bullet has left the barrel.

Then they depend on the momentum of the bolt and residual pressure left in the barrel pushing on the case for extraction and ejection.

Weight of bolt and strength of recoil spring are weighted to allow full cycle without the bolt battering the rear of the receiver.

Most I know of are balanced to operate with standard to +P factory ammo or with NATO issue.

If you want to go over 9mm factory/military issue pressure, one of those Spanish bolt action Destroyer carbines is a better choice than a semi-auto 9mm carbine.

A full +P load with a relatively slower powder is best in most PCC's for top velocities, but often going "over max", only gives higher pressure without much velocity gain.

I had a case of Israeli 9mm sub gun ammo. It came with a warning not to shoot it in pistols. I shot it in my UZI and it ran like a top. Wish I could get more. It was HOT and pierced primers happened on some.

Grab some Federal 9bple. Good stuff and at +p+ it gets moving mighty fast out of a carbine.

Overpressure round + blowback operation = face full of gas and brass. In the case of a Marlin Camp 9 it also means plastic fragments from the plastic trigger housing/magwell.

FYI,

Mil speck for 9mm use in MG is listed below. TM 43-0001-27


Performance:
NOTE Mid case pressures normally run 8000 to 10,000 psi higher than case mouth pressure.
Mid case pressure...................... 38,500 psi (avg), 43,000 psi (max) Velocity ..................................... 1125 + 90 fps, 15 ft from muzzle
Use:
Modified M3 Submachine Gun or commercial weapons. (The use in M9 Pistol is not authorized.) The cartridge is intended for use against personnel.
Description:
BALL Cartridge.
Propellant: Type....................................... Commercial Weight ................................... MBR Projectile weight......................... 115 gr

So mainly it is a light bullet 115gn.

Does not directly provide you with the answer for an AR max pressure, but can give you an idea of what pressures most 9mm MG are designed forl.

LeftyTSGC

My buddy had a Marlin Camp Carbine in 9mm and found some hot load data using about 9grs of Bluedot powder. The load was so hot for the 11 pound factory recoil spring that it bent a cross pin and made the hammer lock back. We had to take the gun apart and straighten the pin.

I bought that gun from him and shot it with normal loads. I sold it and missed it. I bought a second one and also bought heavier springs from wolf plus a new buffer from Blackjack Buffers. Its a nice gun. It will only do so much and thats it. You cannot turn it into a 35 remington.

If you need more power from a pistol round in a rifle buy a 357 lever action.

On the same token my Camp 45 with heavy Wolff spring does much better on 45ACP +P loads (with slow powder like Longshot that isn't all that accurate in my 1911 anyway).

A max load of Power Pistol worked great in my RRA 9mm(1500+fps) Going over max in any load is a bad idea... Play safe!

This is why I don't push extremely hot ammunition in a pistol cartridge. If you want a hot .355" diameter bullets, buy a carbine chambered for the 9 x 25 Dillon. Then (and only then) will you get the performance you seek without damaging your carbine.

It isn't complicated.

spring weight has little to do with safely delaying the action, bolt mass is more important, as energy goes up with mass staying the same the opposite and equal reaction of the cartridge firing will be a higher velocity bolt.. this could result in damage to the firearm as the bolt impacts the back of the action, a heavier spring helps this, so does a longer action but this wont be your biggest obstacle

your biggest obstacle is going to be chamber pressures.. go much higher than 9mm and youre going to have cases sticking in the chamber resulting in torn case heads which can result in damage to the rifle or to you... this is why high pressured delayed blowback rifles such as the H&K G3 have fluted chambers, something the germans discovered in WWII when they found the cases in the delayed blowback STG45 was sticking and switched to fluted chambers

so bottom line is youre not going to get much more performance out of it than what you already have without damaging the rifle or yourself unless youre able to significantly increase bolt mass, or delay the action, and flute the chambers.. neither of which youre going to be able to do on an AR-15 chambered for 9mm

A quote from the Speer Reloading Manual #10: "If magnum performance is desired, a magnum cartridge should be chosen". Truer words were never spoken, and are words to live by.

spring weight has little to do with safely delaying the action,

Click to expand...

That is totaly incorrect. The reason so many have recommended changing the 11 pound factory spring in the camp carbine is because the bolt speed is too high and cracked stocks have been a problem with this model. The recommended weight is a 21 pound Wolfe recoil spring. So yes, springs can and do make a difference.

Accurate powder has +p loads for 9mm, if you want to load hot, use that data. It maxes out at 38,500 psi.

Walkalong is right, if you have too much pressure, the case will rupture as its being extracted. Here is a link to a picture of what happens to your brass:
http://www.gunblast.com/images/EMF-JRCarbine/DSC00038.JPG
That's from shooting 9mm+P in a blowback design not rated for it.

Sweet, merciful crap! Not good! I repeat: "If magnum performance is desired, a magnum cartridge should be chosen". :banghead:

Overpressure round + blowback operation = face full of gas and brass.

Click to expand...

This.

Unless you can effectively increase bolt mass, don't push the envelope.

If you're really hell bent on doing it, I'd suggest you pick Clark's brain over in the reloading forum. I can't think of anyone else still alive who's pushed so many cartridges and weapons beyond their limits.

spring weight has little to do with safely delaying the action,

Click to expand...

That is totaly incorrect. The reason so many have recommended changing the 11 pound factory spring in the camp carbine is because the bolt speed is too high and cracked stocks have been a problem with this model. The recommended weight is a 21 pound Wolfe recoil spring. So yes, springs can and do make a difference.

Click to expand...

No, he's correct. Heavier springs will slow the bolt down more effectively, but do virtually nothing to keep the action closed during firing. It's all about Newton's 3rd law.

I am REAL sure the max pressure for any given metallic cartridge is reasonably stated on the ability of the CASE itself to withstand pressure.
Not he firearm
In any type of action.
Some cases are marked +P because the web FORWARD of the base is thicker, but that "+P" isn't that much more pressure.
Roughly guessing MAYBE 5-7% and it reduces case capacity..hmmm...
IF you reload, just use the RIFLE barrel length data for a "pistol" cartridge.
Most load manuals have data for a 9/40/10mm/45acp to be used in rifle length barrels.
The ruger 44 carbine I load for has "rifle" data for the 44mag.
If you don't reload, you most likely don't have a chrono - so you won't actually KNOW ya ain't going super fast...
But really, If you wanted or needed more power - get a more powerful chambering. I used to hunt with a 300win -hot load, but them deer die just as fast with a 6.5x55 loaded moderate...just how it really is.

I am REAL sure the max pressure for any given metallic cartridge is reasonably stated on the ability of the CASE itself to withstand pressure.

Click to expand...

Not at all. Cartridge cases can't withstand anywhere near the operating pressures, is why they need a chamber.

The firearms are designed to tolerate those chamber pressures and the resulting bolt thrust, with a decent margin. But blowback operated guns have to be tuned so that they will function with standard ammunition, meaning that increased bolt thrust will cause the bolt to open too early and blow out the case.

Case head design and web thickness does factor in, but think of it in terms of the strength of a piece of wood; a 2x4 12 inches long can support a great deal more weight than one 12 feet long. Same thing with the unsupported portion of a case, and why some chambers that aren't fully supoorted result in bulged cases, particularly with higher pressure rounds. If that lack of support were circumferential, you'd have case head separations. This is exactly the condition that occurs with OOB firing.

MachIVshooter said:

This.

Unless you can effectively increase bolt mass, don't push the envelope.

If you're really hell bent on doing it, I'd suggest you pick Clark's brain over in the reloading forum. I can't think of anyone else still alive who's pushed so many cartridges and weapons beyond their limits.



No, he's correct. Heavier springs will slow the bolt down more effectively, but do virtually nothing to keep the action closed during firing. It's all about Newton's 3rd law.

Click to expand...

exactly.. and lets use some logic here, a 9mm can operate with over 3,600lbs of thrust on the bolt, a few more pounds here or there in the recoil spring is negligible

heavier springs are all about preventing that bolt from smashing its way through the back of the receiver and embedding itself somewhere in your skull

Berettashotgun, the case just acts like a gasket. It isn't meant to single-handedly contain the pressure, it is meant to form a seal and close small gaps so the steel parts can contain the pressure.