Keyhole issues

[Astocks2622]

I wrote a while ago about the great success I had with my first casting session making some 200gr 10mm hardcast. They have proven accurate and reliable; I'm completely satisfied with them.
However, I have had major issues with 2 other molds.
One is a Lyman 457124 I was hoping to use in my 458 socom as a heavy plinker. It's sized .4595". Good news is it feeds super slick, and had very consistent velocities. However, it was keyholing in all the loads I tried, from 1300-1500 fps. One hit so perfectly sideways I could have just about reverse engineered the mold from the hole in the target.
The other is an Accurate Molds 35-147C, sized .356. Running about the same velocity as my plated target load, about 850-900fps. Same deal. With my 6" target barrel, it keyholes at 10-15 yards about 30% of the time. With a 4" conventional rifled barrel, I didn't notice keyholing.
Both bullets were cast with 3:1 pure:lino with 1% tin added, which should give me 3% antimony, 2% tin, 95% lead. Estimated hardness from the alloy calculator I found here gives me 12bhn. As tested with the lee system, it's casting about 13bhn, so the calculator seems pretty close. I used BAC lube on both.
Were these bullets too hard for the low pressures they saw? All I can figure is that they didn't obturate enough? I would have thought my sizes wind have given plenty of rifling engagement, so I'm trying to figure out why they're keyholing. Any help would be appreciated.

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[dondiego]

Sound like they may be too small.

[farmbif]

I dont know anything about socom but what cartridge are you putting the 35-147's sized to ,356 in?
as a general rule I size cast bullets .002 or more oversize. as big as I can make them so they will still chamber.
for example I lube size bullets for 357 mag and 38 spl at .360

[Astocks2622]

The 35-147c is being used in a 9mm, so .355, nominally.
The socom is 458, supposedly. I'll cast some pure PB of each to slug the barrels.

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[Sig556r]

Check your 458 socom muzzle attachment (brake or flash hider), may not be concentric, thus, keyholing. If you're sizing .4595" they should've fine unless you have an oddly sized or over sized barrel. Also, your velocities seem to be on the lower end, try warming them up. What twist is your barrel?
For your 35-147C sized .356", slug your barrel (for 38/357 that's undersized, for 9mm it depends on barrel which ranges from .355 to .357) & size 0.001"-0.0015" over.
For both cases, ensure you're not swaging the boolits when seating as they'll be further undersized. In such case, you may wanna use M-dies.

[farmbif]

I'm no expert but sometimes heavy bullets for a caliber end up tumbling which can be caused by twist rate and or low speed. famous heavy for caliber bullet that keyholes is the 200 grain round nose Lyman shot in 38 spl.
like I say I'm no expert but just thinking out loud here

[Astocks2622]

Check your 458 socom muzzle attachment (brake or flash hider), may not be concentric, thus, keyholing. If you're sizing .4595" they should've fine unless you have an oddly sized or over sized barrel. Also, your velocities seem to be on the lower end, try warming them up. What twist is your barrel?
For your 35-147C sized .356", slug your barrel (for 38/357 that's undersized, for 9mm it depends on barrel which ranges from .355 to .357) & size 0.001"-0.0015" over.
For both cases, ensure you're not swaging the boolits when seating as they'll be further undersized. In such case, you may wanna use M-dies.

Thanks. I've not had accuracy issues with any other bullet in the 458 socom, so wouldn't think I have an alignment issue with the brake? Barrel is a Tromix 1:14 16.25". 1600fps is about the top end for 400gr jacketed bullet in multiple data sources, I was running a load ladder up to get around those speeds, as I couldn't find cast specific data. I could open up the sizer die to .461 if my barrel slugs large.

I don't think I'm swaging them as I seat. There's not much resistance, and I expand the mouth a bit extra with cast. However, I do run them through a Lee FCD, though I'm pretty minimal on the crimp. I'll try pulling a couple loaded rounds and see what the bullets measure.
Thanks.


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[45DUDE]

^^^^^^^^^^^ I agree farmbif. I have a 9 mm I am trying to use 158's in and no mater what I size them to they go perfect sideways @25 yards. 124's do plenty good. I am thinking the twist to bullet weight is doing it. I haven't given up. I have some other molds to try. Just something to play with. I had to get a faster twist barrel in 38 special to make 200 gr boolits work correctly.

[Astocks2622]

I've been shooting 147gr out of my 9's for 10 years with no problems. This mold is actually slightly shorter than the plated bullets I've been using. I don't think that's the issue with the 9. It's possible that's part of the problem with the 458, but it's designed for heavy subsonic bullets?

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[Plate plinker]

I size my 9mm to .3575 and that solved my keyhole issue. It’s a 127 gr boolit.

[Astocks2622]

Well, shoulda slugged my barrels a while ago.
458 slugged at .459-.4595. so it looks like I need .4605
And my problem 9mm slugged at .3565-.357. actual bullets after sizing were .357, so maybe I can just use my .359 I have for my 357mag bullets...
Anyway, it'll be a bit before I can cast again and get to the range. I'll keep this updated when that happens.

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