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Designing a 300 Blackout bullet - not subsonic heavyweight - Mountain Molds

Designing a 300 Blackout bullet - not subsonic heavyweight

Elkins45
Posts: 9
Joined: Wed Apr 11, 2012 6:13 am

Designing a 300 Blackout bullet - not subsonic heavyweight

Postby Elkins45 » Wed Apr 11, 2012 6:28 am

First post, so excuse me if it's stupid.

I'm trying to work out a bullet to shoot in 300 Blackout in a 1/8 twist barrel, but I don't want one of those mammoth 250 grainers that people are casting to shoot in subsonic or suppressed guns. I just want a plain base bullet that can be shot accurately out of a 1/8 twist barrel but is light/short enough to fit in the brass block. I don't know if I would be better served by a bore riding design more like the Lee bullets or a relatively full length bearing bullet with a lot of grooves so I can experiment with how many grooves to fill.

Here are two drawings I have messed around with. Both are 200 grain bullets.

Image

Image

Which probably has the best chance of performing well in my 1/8 barrel, or do I need to go a different direction entirely?

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mtngun
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Re: Designing a 300 Blackout bullet - not subsonic heavyweight

Postby mtngun » Wed Apr 11, 2012 5:22 pm

The twist has no bearing on your design decisions. It is what it is, no point worrying about it.

The loverin tends to be superior at high velocities. At low velocities I couldn't tell you but would guess it is a toss up.

Elkins45
Posts: 9
Joined: Wed Apr 11, 2012 6:13 am

Re: Designing a 300 Blackout bullet - not subsonic heavyweight

Postby Elkins45 » Wed Apr 11, 2012 6:49 pm


Elkins45
Posts: 9
Joined: Wed Apr 11, 2012 6:13 am

Re: Designing a 300 Blackout bullet - not subsonic heavyweight

Postby Elkins45 » Thu Apr 12, 2012 4:55 am

Unless you tell me there's a reason you can't or won't make one of these, I've narrowed down my bullet to one of these. All are 200 grain tangential ogive with a .120 base, .280 nose and .100 front band with .7 groove to band ratio and 55 degree grooves. The only difference is the number of grooves. My thinking is that the smaller number of wider bands might be a better choice to resist deformation over the 'normal' higher number of narrower bands.

Any reason to prefer one of these over the others?

Image Image Image

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mtngun
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Re: Designing a 300 Blackout bullet - not subsonic heavyweight

Postby mtngun » Thu Apr 12, 2012 9:56 am

I have had better luck with small bands and a larger GtoB (1 to 1.5). Your mileage may vary.

Small bands deform less than large bands, because the displaced metal is pushed into the groove rather than forcing the entire bullet to deform. That is why some solid copper bullets have grooves.

The smaller bands are more difficult to cast, though.

The problem with a fast twist is not skidding in the rifling, it is the high RPM's causing an out-of-balance bullet to wobble once it leaves the barrel. As long as you seat the bullet to kiss the rifling, I doubt if you'll see problems with the bullet skidding on the rifling.

That is all armchair theory, the only way to know for sure is to try it.

Thanks for posting the bullet pics, that helps a lot.

Elkins45
Posts: 9
Joined: Wed Apr 11, 2012 6:13 am

Re: Designing a 300 Blackout bullet - not subsonic heavyweight

Postby Elkins45 » Mon May 28, 2012 5:25 pm

I wish I had specified a bit of nose taper because I'm having to seat it really deep into the powder space in order for it to chamber. I haven't had a chance to shoot them yet but I have several loaded up and ready to go. I think the full diameter design is going to limit my powder choices quite a bit because of the seating depth.


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