20 Ga full bore HB discussion thread

[338RemUltraMag]

Here is where we are going to hammer out the details of the 20 GA A.C.E. slug. Give me a few numbers to work with like diameter and target weight.

[jason f]

I would think 450-500 grain.

[jason f]

Some 20 ga slug guns have a slower twist than the 12's so length is an issue. I would think about. .700 on length and 628-630 on diameter. My full bore slugs drop at 629. Shoot great from h&r ush.

[jason f]

http://www.accuratemolds.com/bullet_...=62-450S-D.png

Here is the slug I am using now.
Maybe a little wider and flatter metplat.
increase length a little to make up for weight loss of hollow base.

[338RemUltraMag]

Here is a preliminary design for the 20 GA slug:

[jason f]

Jbm ballistic calculator shows would be stable at 1000fps and up in a 1-35 twist slug gun. I know most would shoot it a lot fast than that. At 500 grains shouldn't be to hard to get it up to 1600fps in a 24" barrel.

[338RemUltraMag]

Here is the .629 diameter mold:

[jason f]

That's perfect. Let's see what others have to say. I posted in the casting for shot guns thread to this link for some input.

[338RemUltraMag]

Good to hear, I will let this ride and see where it goes.

[jason f]

I would definitely take one.

[jason f]

Different pin designs would be a nice option.

[turbo1889]

I asked about the details on the block design you guys are going to cut these in on the other 12ga. buy that is in the active buy section.

In this thread I'll post my thoughts on the actual design of the slug itself:

~ It's obvious that this is a "thumper" slug designed to hit hard at short range with no thought given to trying to streamline for longer range. So long as that be what you are after then its nose is perfect for that. No complaints on that point from my view point, just lets be clear about what it is and what it is not.

~ The curve on the nose should take a roll crimp okay, can't say for sure of course but its no worse and looks slightly better then roll crimping up against a round nose slug profile which has been done successfully for generations. Curves don't seem to cause trouble with overrunning of the roll crimp, its shallow straight angles that seem to do that.

~ That is a long heavy full diameter front band on the nose supported underneath by a solid core in the nose sections of the slug. I wouldn't suggest anything harder then 30:1 alloy if firing through a full choke smooth bore gun. Stick to soft lead with maybe a touch of tin if firing this one through smooth bores with anything more then a skeet or IC choke tube boys.

~ Hollow base is about the same depth as I would make it but not exactly the profile I would use, I tend to use more of a squared off plug shape with hardly any rounding to the tip just a little on the edges and only a slight angle on the sides just barely enough to release the slug and keep the skirt walls a little thicker and end up the same weight and balance point as a result. Your more rounded and tapered profile will probably cast a little easier and will a little less heat or tin but the skirt won't be as strong.

~ If I buy this slug as drawn (12ga. or 20ga.) I'll probably build my loads "Fed. True-Ball" style using bulk bag jaw-breaker candy balls of appropriate size (something I already do with Lyman foster slug molds that have been modified by cutting bands on their sides out to full bore diameter and shortening the HB pin to make the front half nose part solid all the way through), the HB profile as you have it drawn with a rounded tip and tapering out strongly to make thinner skirt walls at the base would probably be best suited to loading that way using the ball to support the skirt from the inside just like I currently do with my modified Lyman RN foster molds.

[turbo1889]

As to hollow base pin shape, how about a flat top bell shaped pin along these lines:




For this 20ga. slug the exact dimensions of of such a bell shape I would choose would be 0.44" diameter of the pin at the base of the slug. Going down to 0.40" diameter at the top of the bells lip where the angle changes 0.12" up from the base of the slug and then continue straight up from there on a shallow 3-to-5 degree angle to a pin depth of 0.40" with the fillet curves on the top edges of the bell being approximately 0.07" radius or so. Would make for a stronger skirt on this slug, remember the highest structural stress loads on a hollow base shotgun slug skirt trying to colapse the skirt lengthwise under the acceleration forces are at the very base of the skirt so you don't want weak thin skirt and adding thickness to the skirt above the base does not make it stronger since the base is the weakest link anyway.

[jason f]

Are you gonna put this in the group buy? Or after the 12 gauge ones are done.

[turbo1889]

. . . after the 12 gauge ones are done.

I would ASSume that is the plan.

[338RemUltraMag]

This will go up after the 12 ga, I want to make sure the first one runs smooth w/o worry of another GB

[bikerbeans]

Gb = ?

[jmort]

Group Buy

[turbo1889]

He is basically saying, "One at a time boys, I don't want to try to run multiple groups buys at once, at least until I get this down to a system for me."

[338RemUltraMag]

He is basically saying, "One at a time boys, I don't want to try to run multiple groups buys at once, at least until I get this down to a system for me."

Yes, this is exactly what I meant at first I want to start slow to ensure perfection than send out a mass of shatty work, thank you Turbo!