Keyhoing boolits

[edctexas]

I am shooting an H&K P30L in 9mm. My H&K P30L in 40S&W works fine with cast boolits. The 9mm seems to shoot reasonably straight at 10 yds, but the rounds all keyholed, that is the hole in the target is elliptic not round.

The boolit is a NOE 358-121RN. The rounds tried were unsized running 357 as I figured it would like a larger boolit as does the 40S&W. The p30L's use a polygonal bbl. The brass was Winchester with CCI Small pistol primers igniting 3.4 grn of Grn Dot.

Is the boolit too big? What sort of things causes keyholing. I have loaded 1000s of 45ACP and never had a problem.

Ed C

[petroid]

What does the barrel slug? What is your alloy?

[243winxb]

polygonal bbl.not for cast?? Maybe?? http://www.brianenos.com/forums/index.php?showtopic=44400

[dubber123]

I've seen plenty of poly barrels work just fine with cast. I too would like to know what it slugs at. I'm not sure what your velocity is, but 3.5 grains of Green Dot shoves a 155 gr. boolit to 910+ fps. from my 3.7" 9mm

[Shiloh]

Fired thousands of rounds in polygonal barrels. No issues. I di however KaBoom two .40's with polygynal barrels.
I attribute that to the unsupported rear of the cartridge. It isn't near the issue with the 9mm.

I have ONE 9mm mold, the LEE 125 RN that drops large enough for the 9mm. The other go to mold is a LEE
.358 125 gr. RF. The boolits are set deeper with 4 grains of Unique. I have taken to 4.4 grains of Unique but backed down.

SHiloh

[runfiverun]

you either ain't pushing them fast enough, or they ain't big enough.
357 seems large until you actually measure the barrel.
the only other thing that could cause your issue is starting the boolit crooked into the barrel.

[tazman]

I don't have a 9mm with a polygonal barrel. I did use that boolit in my 9mm with Green dot but I was loading 4.1 grains. I ran through nearly a pound of grn dot at that loading.
The Lyman Cast Bullet Handbook calls for 3.5-4.4 grains of Green Dot with that boolit.

[edctexas]

The alloy used is straight air cooled WW. The boolits as cast run 0.359 to 0.360 measured with a Starrett mike. The barrel slugged a max diameter of 0.3555. The chamber accepts the 0.360 boolits. I tried making a test rd (not power/primer with the OAL at the Lyman Cast manual OAL. The case does not seem to squeeze the boolit down in diameter. The primers show slightly more flattening than I would like to see on the fired rds. That is probably due to the larger boolit size. There was a very small amount of leading at the muzzle. Six or so very small flakes came out on the patch following a pass with a bronze brush. There was a star of lube on the muzzle crown.

Should I try a 0.356 or 0.357 dia? What about trying a GC? With a sized boolit I should be able to go faster.

Ed C

[MtGun44]

Bigger is better, as a general rule. If it will chamber, shoot it. Try .357 and then .358 and then
.359. Only Mr. Target knows the answers to this particular puzzle.

Bill

[44man]

Sideways boolits are not spun to match twist or the boolit is skidding to reduce spin.
Even too slow will take you out of the spin needed for a boolit. Polygon barrels need to deform the entire boolit to fit and turn. Might take a larger boolit. I have no experience there.

[runfiverun]

the holes could be a bit out of round because the paper isn't tight to the backer board too.

the little bit of lead flakes at the muzzle and the slight tipping are your clues here.
you just need to ferret out what is happening at the muzzle.
not enough pressure there, are you seeing smoke [what color] etc,,, and put the pieces together.

you are losing contact [sealing] with the barrel somehow it could be simple like you need a little more powder in the case.
or slightly more complicated like you need a little more oil in your lube to make it past the point the gasses quit pushing the boolit.
or the crown is a tick off and the gasses are enough to tip the base of the boolit on exit, or it's got a burr grabbing at the boolit stripping a little lead.