proper rifling pitch for 9mm carbine

v35

What pitch is appropriate for 9mm bullets 115 to 147 gr ?
I got 20% keyholing at 75 yards using 124 gr plated bullets at around 1500 fps.

charliemeyer007

How hard are you driving them? I never thought plated bullets were worth the expense. Try some real bullets with your load.

Hawk Carse

Rifling pitch? I might try something like 16" which a lot of manufacturers use in pistol barrels. What have you actually got?

But your problem may be: "plated bullets at around 1500 fps".

You don't say what brand of plated bullet but Berrys says their Thick Plate is good "up to 1500 fps" but their standard grade 1250 fps.
Xtreme is similar; for 1200 to 1500 fps, use their Heavy Plate Concave Base or Hollowpoint.
I have to figure other brands are similar.

Me? I would try some real jacketed bullets before I started twisting the barrel for more or less rifling.

And I might try a different diameter. Most 9mm jacketed bullets are .355", plated .356" but a lot of barrels run large and do better with larger bullets.

tsr1965

For the most part, plated are not to be used the same as jacketed. They are solely meant to reduce leading at velocities 1000fps or under. I am suspecting that your twist is a little tight, and chewing the soft bullet up, in the first 6-8 inches of travel.

Txs

The 9" HK MP5, the 10" UZI and the 10.5" Colt SMG all use 1:10 barrels.

They're designed for the NATO standard 124gr. bullet and shoot them just fine, but the slower 147's actually give better 100yd. groups.

Faster 115gr. bullets tend to group largest out of them.

TANK78Z

I have been using Berry's Plated double struck PREMIUM 9mm bullets for several years in both my pistols and ar9 carbine . I have never had any problem with them with fit,function or needed accuracy once a proper load has been developed for each weight and firearm. taper crimping is of course the way to go and care should be taken in making a very firm but not overly tight crimp due to the thinner copper plate, more crimp then lead, less then on standard jacketed.
In my load developments I have seen a small improvement in groups when crimp is dialed in.

The carbine has a 1 in 10 twist and is 16.25 " in length ,average groups 3 " at 50 yds with 115 gr at near max loads, 124 gr with near max loads gets about 2" average groups, more then accurate enough for me and any social encounter that needs only a pistol cartridge carbine, and matching pistol. I use a red dot sight so accuracy might be better if I mounted a decent scope.
I have not been loading 147gr. so I have no info there.

I don't regularly shoot 9mm past 50 yds, I save the longer ranges for 556 or 300 blackout .

Using regular jacketed bullets I have gotten only slightly better results, not worth the cost difference.

v35

I don't see any leading so assume plating isn't stripping and lube is working.
Carbine is Keltec P2000 9mm.

charliemeyer007

I'd be trying other bullets first. 1 in 5 key holing at 75 yards, you might as well throw rocks.