Yet another 9x19mm ammo question - bullet weights vis a vis barrel length

[GunGoBoom]

OK, folks, I've pretty much decided on going with a 147 gr. loading (probably Double-Tap) for defensive use in my F.S. CZ (4.7" bbl), and in my CZ PCR (3.9" bbl).

But what about my backup, the Kahr MK9 with a 3.0 barrel? Would I lose enough performance/velocity from a 147 grain loading by losing that last inch of barrel length that I'd be getting more bang for my barrel-length buck, by using say, a 124/127 gr loading for the backup piece? IOW, which loading(s) work most efficiently with which bbl length? And what of reliability in choosing between the 124 and 147 loadings (for the MK 9 Kahr being my specific question)? Equally good or better with one vs. the other?

Please post what bullet weight (and other specs of your defensive loading of choice - brand, bullet type, etc.), and specify whether this is for your:

1. Full-sized 9mm (4.5 to 5" bbl)
2. Compact 9mm (3.7 to 4.4" bbl)
3. Sub-compact 9mm (2.5 to 3.6" bbl)

Thanks.

 

[hartzpad]

I was under the impression that with most calibers it is better to use heavier bullets in shorter barrels than lighter bullets, using the heavier bullets gives a short barrel pistol similar penetration to a longer barrel pistol using lighter bullets. I plan to use 147gr. DT 9mm in my Kahr PM9. I read somewhere that at least with 10mm, there is less velocity loss with heavier bullets comparing long and short barrel lenghts than with lighter bullets out of the same barrel lengths.

 

[GunGoBoom]

ok, thanks Hartz, that's good to know - think I'll use 147 DTs in ALL of them.

 

[Ken Rainey]

They say that using a lighter bullet and/or a plus P loading in a short barrel will do more to keep up the velocity to help with expansion. The deal is that some people think expansion is the key when actually, it's adequate penetration...which, since the velocity is less it will have less chance of expansion and more chance for penetration. I use Ranger 147 in all my 9mm pistols - G26 to G17. It's a standard pressure and is easier to control, especially in smaller pistols. It's designed to expand in a wide window of velocity and has the weight to get deep enough. Expansion is nice but should be considered an "extra" thats good to get - not a requirement, since it doesn't always happen. Remember, it's where the bullet goes more than it is if the bullet expands.

 

[wally]

The key factor in penetration is Sectional Density of the bullet times Velocity. The 147 gr 9mm round has a slightly higher SD than a .45 230gr round so if you get 800-850 fps you'll have in theory the same penetration as a .45ACP round.

The fly in the ointmnet is expansion -- any expansion greatly reduces sectional density reducing penetration and at a faster rate with lighter bullets. Expansion and therefore bigger holes is nice but penetration adaquate to get to the vitals is essential because expansion can't make up for poor placement but poor penetration can negate proper placement.

I carry 180 gr .40 S&W in my Kahr PM40 and use 147gr in 9mm if reliable.

--wally.