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how do u blow out a case to hold more powder

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Unread 11-29-2004, 09:28 AM
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Join Date: Oct 2004
Posts: 175
how do u blow out a case to hold more powder

just trying to learn more about it
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Unread 11-29-2004, 10:11 AM
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Join Date: Jun 2004
Location: Fort Shaw, Montana
Posts: 6,848
Re: how do u blow out a case to hold more powder

Well, the comment blowing out a case has to do with wildcatting an existing case to increase the powder volume.

All cases have some taper to their body sections. This is needed so that the case will easily pop loose from the chamber after firing. The less taper you have the more difficult extraction can be so there is a certain point where we have to stop.

Most modern case designs, at least the ones in the last 30 years are minimal in taper, there are exceptions.

The rounds with the most taper such as the 22-250, 257 Roberts and for the big guns the 338 Lapua gain the most volume when their body taper is reduced and the shoulder diameter increased.

Rounds such as the 308 family and WSM rounds do not gain as much percentage wise.

TO do this a chambering reamer need to be built to the specs you want and your chamber then needs to be recut to these new dimensions.

Then, in most cases a standard parent case can be fired in this new fatter chamber and the pressure of the round will blow the parent case out to fit the larger dimensions of the new chamber.

Care should be taken though as some case modifications require special steps to insure safe headspace gas seals if the shoulder is set back any amount.

Good Shooting!!

Kirby Allen(50)
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

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Unread 11-29-2004, 10:39 PM
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Join Date: Sep 2002
Posts: 453
Re: how do u blow out a case to hold more powder

do a search on P.O. Ackely and see what comes up. Blowing out means taking out the body taper and usually adding an increased angle on the shoulder (30-45degree)
You try to get closer to the target,..and I keep trying to get further away.
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Unread 11-30-2004, 12:51 AM
Gold Member
Join Date: Sep 2004
Location: Nevada
Posts: 836
Re: how do u blow out a case to hold more powder

My two target guns require fire forming exsisting shells. For non standard wildcat rounds you can then send in a shot case and RCBS will make you the dies.

270 ackley improved actually only gained about 4-5 grains of powder over the standard 270 winchester.

Fire form - You just insert an off the store shelf round and pull the trigger. The pressure expands the case to fit the barrel dimensions. The improved round has a steeper shoulder and a longer body

I had a 223-7mm Tompsen Contender pistol. I bought cases of .223 rifle rounds and you pull the trigger. The .223 just bounces down the barrel. but the case opens up to the 7mm size. Really a nice gun with 130 gr. rounds
.270 Ackley improved 29 inch 1.250 dia. target barrel 7mm STW 28 inch 1.250 target barrel. I also love my .458 mag for varmints and the biggest game in the world.
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