Considering a given load's ability to reliably function a recoil or blowback operated firearm: how to choose?
In factoring the energy and/or momentum of alternate loads which will deliver a surer "push" of the slide or breech block?
I suspect momentum might be the deciding number but I took the easy physics course at school...
My apologies to weasels.
You can math it out, or you can buy a few boxes of various ammo and see what happens in the real world. I know what I prefer to do.
IMHO the closer you stay to "original weight, original velocity" in a given caliber, the more likely it is that a wide variety of guns will function with a given load. The same applies to guns themselves and the calibers they were originally designed for.
Now, in 9mm, I'm going against my own advice to a small degree, and my preference is 147gr bullets/loads. That said, I think bullets that are heavier are more likely to function a gun as intended, vs "light for caliber" stuff. Velocity and barrel length, being intertwined, also play a factor. The type of gun also is a factor, smaller autos are often more sensitive to ammo type. "Hotter" ammo is often more reliable... but that's not universal, sometimes you can have too much of a good thing.
Failure to feed is probably the most common stoppage attributed to ammunition, due to bullet contour.
The other types of stoppages (failure to fire, failure to extract, and failure to eject) are the result of a defective cartridge, defective gun, or shooter error.
The main thing I'm concerned with is a blowback 9mm PCC that seems to eject in a less than stellar manner.
A well maintained, clean, and lubricated sample. It runs pretty well but I would like to see a little more fling in the brass. Last round locks the bolt to the rear fine. Feed reliability has not been a factor with frankly anything I've put through it.
I mostly shoot 147s at a standard velocity and desired a quantifiable choice to build in a functional margin.
I probably could have phrased this as 147, 124, or 124 +P while keeping felt recoil as low as feasible. However, I do like to know the numbers behind what I'm doing.
My apologies to weasels.
May I ask what specific 9MM PCC, and barrel length ? The various ejection designs used , in PCC's could be a factor in your ejection pattern.Originally Posted by 314159
Extra power magazine springs add pressure (friction) on the slide too as the slide moves back and forth. It's probably not a big deal but just adding this as a possible thing to consider. Too weak magazine springs may not push the next round into position fast enough for the pistol to feed reliably. I use to load my pistols with a full magazine, chamber a round, and then top off the magazine. Now, I chamber a round and drive on with the magazine with one less round in it.
The PCC in question is a Beretta CX4. It actually runs really well.
The core question is really: "What factor is most applicable to driving the bolt to the rear with alacrity? Energy or momentum?"
I know I just need to go to an outdoor range and measure how far the brass is flung (is that a word?). I like to know the theory behind this stuff.
My apologies to weasels.
I have a Beretta CX4 in 9mm. It's odd in appearance for sure. I like the idea of magazine compatibility between the CX4 and the 92 series. It wasn't on my radar until a friend bought one.
I wouldn't get hung up on the energy versus the momentum thing. What you do want is enough energy to successfully drive the bolt rearward to facilitate ejection and rechambering the next round. What you don't want is short stroking of the bolt. In the CX4, you have the weight of the bolt and the recoil spring at play. I came down on the side of energy because energy from the fired cartridge moves the bolt rearward and the energy from the recoil spring pushes the bolt forward.
This is just my opinion, take it for what's worth. As has been said, I would pick several flavors of ammo and see which one gives you the desired results. Keep us updated on what you settle on.
I chased this a bit with my 9mm AR back when I first got it, and had trouble with it, and once I figured out the extractor position relative to the bolt was the problem, it has run at pretty much 100% on anything and everything, including some weak sauce 115gn reloads that probably shouldn't have worked. If it is working I wouldn't worry too much about the ammo, IMO.
If the only concern is the gusto of ejection, maybe consider what it is being compared to. And if ( I am ASSuming...) you are comparing it to a DI AR, those cases are being flung out by a pretty strong ejector spring, while the blowback gun nudges them when they collide with the ejector as it passes under the bolt. And since it is a blowback gun the bolt is heavy and slow out of necessity. So maybe they are coming out just fine, but just being compared to a dissimilar system?
I've done some informal testing. Within my humble and unscientific experience; momentum.
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