Minimum Driving Band Width

[Morgan Astorbilt]

Hi, I'm considering lightening the boolets thrown by my 4-cavity NEI mold by milling the top of the mold blocks. It's a # 284A .451-180 in Meehanite. By removing material from the base of a boolet, I determined that I could reduce the weight from 182gr. (In WW) to 163gr., by removing .040"
This is a single grease groove boolet with a crimping groove. The driving band is
.090" wide, and this would reduce it to .050". I'm wondering if this will cause the driving band to melt or be driven forward into the grease groove when fired.

The loads are very light, 4.25gr. Bullseye, and the reason for lightening is to reduce recoil for use in Cowboy Action Shooting. I dislike aluminum molds, which is why I didn't order a Lee #90570, which a group of fellow shooters are ordering in six cavity. (Our commercial boolet supplier can't get lead).
Thanks for any input,
Morgan

[leftiye]

Could do, thicker is stronger. There are lots of boolit designs out there with narrow base bands, but I doubt that they are for high power (pressure) loads. Even with hard lead, the seal would be better with the wider band, and you'd get more gas cutting. You might not like that boolit if it were any lighter too (I'd guess).

[Blammer]

I see the bullet your looking at doing that to, and personally I would not.

You may be better off selling it outright and then looking to order another the way you want it, and I bet you may find enough interest to warrent running a GB with that design...

here is another thought, run a different alloy, that may be lighter, it may be harder but that shouldn't matter much.

have you looked at NEI's 282a? 451-170-GC, but you can ask them to make it a plain base instead

[Bass Ackward]

It ain't just the band width that's at issue, but also the balance point of the bullet.

I'd rather see you put some bubble gum or something in the noses if you need to lighten them than full with the base myself. :grin:

[Morgan Astorbilt]

Guys, I just received the mold a week ago. I spoke to them at NEI about a 160gr., but they wanted $200 to cut a cherry, so I ordered the 180gr.. The bullet is blunt enough so that removing forty thou won't affect the balance. With this cut off the bottom, it resembles the Lee 160gr. 90570, except the grease groove on the Lee would be farther forward about 15 thou. These aren't schuetzen bullets, they're being fired out of SAA's at steel targets from about twenty feet, using just enough powder to get the bullet out the barrel, with reliable ignition. The pressure is so low, that the cases don't even obturate, powder residue blowing back into the chambers. Lack of recoil is more important than accuracy. I've cast about 7,000, and will test them to see if they can be loaded to the same recoil level as the 160's.

If I decide to cut the blocks, I'm not so sure I want to do it on my Bridgeport, for fear the edges of the cavities might chip. I'll probably bring it to a shop with a surface grinder, and let them do it.

Thanks for the input,
Morgan

[Morgan Astorbilt]

Well boys, After a brief phone call to Joel at NEI, I went down to the shop and whacked .040" off the top of the mold. I did it in four .010" cuts with a 2-1/2" indexable cutter at 300RPM, after filling the cavities with Cerrosafe to prevent possible burrs in the cavity edges. Everything looks OK, the two screw holes in the top didn't burr up either, so maybe the Cerrosafe wasn't necessary.
The furnace is heating up as I type this, wondering how close to my target weight of 160gr. I'll come. Thanks again for all the input.
Morgan

[Hardcast]

Well boys, After a brief phone call to Joel at NEI, I went down to the shop and whacked .040" off the top of the mold. I did it in four .010" cuts with a 2-1/2" indexable cutter at 300RPM, after filling the cavities with Cerrosafe to prevent possible burrs in the cavity edges. Everything looks OK, the two screw holes in the top didn't burr up either, so maybe the Cerrosafe wasn't necessary.
The furnace is heating up as I type this, wondering how close to my target weight of 160gr. I'll come. Thanks again for all the input.
Morgan


Please post the results when you are done casting. I am curious how this works out for you. Thanks

[Morgan Astorbilt]

Hardcast-
Cast about 300 boolets, weighed a half dozen, four were exactly 160.4gr., one was 160.8, and one was 161. I made sure they were all filled out fully, but didn't take note of which cavity they came out of. They're surely good enough for cowboy action shooting! Funny, how when you don't need that consistency, you get it. Got to hand it to Joel, he sure make a good mold!

The Midway heater under my Lyman 450 is heating up as I type this. BTW, it's adjustable, someone mentioned they're not, on another thread. They're even "Guaranteed for Life" a detail that was touted in Midway's catalog when I bought it, but have no proof thereof. I asked the order taker at Midway about the guarantee a while back, and what they would replace it with, since they're no longer selling them. She had no idea, didn't even know they ever sold them under their brand. Guess when it gives out, I'm out of luck.
Morgan

[Dave Berryhill]

So, milling .040 from the .451 diameter mold lightened it up by about 20 grains when using WW. Was that a plain base, beveled or gas check mold?

[Morgan Astorbilt]

Dave, It's a plain base. It originally threw 182gr. bullets. The thin base band is making it harder to adjust the stop screw on the sizer to keep the lube from going under the bullets, while not putting any in the crimp groove. For cowboy action, I don't cull a bullet if the base isn't completely filled, I just consider it a bevel base. With these bullets, the lube will flow under them if I have any pressure on the lube feed screw handle. With only one lube groove, I only have to crank it every four bullets or so, so I just keep an eye out for the "bevel base" bullets, and every thing's alright. Something I didn't foresee as a consequence of thinning the base band. Everything's a learning experience.
Morgan

[ktw]

There was "a lube on the base of the bullet while resizing" thread here recently. Someone else offered the (brilliant) suggestion that a styrofoam spacer on top of the punch would solve that problem. He punched them out of 'meat tray" material with the sizer.

A spacer like that might be enough to raise the bullet far enough in the sizer die to reduce your lube problem.

-ktw

[Morgan Astorbilt]

Don't understand. Raising the bullet will bring the lube holes even further below the bullet. I've got to bring the bullet down without the holes lining up with the crimp groove. Maybe the foam conforms to the bevel edges of the bullet base to seal it off from the lube. I'll give it a try, and maybe use a piece of soft leather, like buckskin. I only get the "bevel base" bullets as the mold is heating up. I was in a hurry to see what the bullets weighed, and started casting before it reached proper temperature.
Thanks, Morgan