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Penatration & Expansion test.

 
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Old 05-22-2011, 07:43 PM
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Penatration & Expansion test.

Never did one before, but something I have wanted to try. So how's it done. I saw where Shawn put one at 25ft and with papers. Are they news paper's? Are they saturated in water? How do you load a cartridge safely enough to low pressures and speeds? Can I use the lead bullet loads for a .308 for a jacketed bullet of the same weight to accomplish a low velocity load? Fill me in guys, I need to know! Thanks.

Tank
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Old 05-22-2011, 09:30 PM
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Re: Penatration & Expansion test.

I'm curious about this also. I know how to load my 300wsm for subsonic rounds but nothing in the 1800fps at the muzzle. Trail boss works well for subsonic loads.
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Old 05-22-2011, 10:05 PM
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Re: Penatration & Expansion test.

Quote:
Originally Posted by liltank View Post
Never did one before, but something I have wanted to try. So how's it done. I saw where Shawn put one at 25ft and with papers. Are they news paper's? Are they saturated in water? How do you load a cartridge safely enough to low pressures and speeds? Can I use the lead bullet loads for a .308 for a jacketed bullet of the same weight to accomplish a low velocity load? Fill me in guys, I need to know! Thanks.

Tank
Tank.....welcome to the club! I've done quite a bit of this while testing my bullets against other manufactures. There are a lot of different medias that you can use only limited by your imagination! Some obviously work better than others. Make sure you build something substantially long because you may shoot through more than you think! With many bullets, reduced loads are apt to shoot through more than high velocity loads because of the lack of expansion. Water is a VERY good media but you need alot of it to stop the bullet. I often use a few layers of old carpet at the end of my testing media because they act somewhat like a flak jacket for catching already expanded bullets. If you build a box, make sure it is at least 6 feet long or you may not capture some of your bullets (depending on media). Another VERY common problem is finding the bullets in the media. This is more of a problem than you might imagine so think that through in your design. When I use wet paper, or cardboard, I usually slide in a "check paper" (no holes) to see where the bullet is headed. You will get a feel for this after you shoot a few as to penetration depth. A powder like IMR 4198 is good for reduced loads to duplicate long range impact velocities. Bear in mind that a bullet fired from a given twist at a muzzle velocity of say 1800' will not act exactly the same as the same bullet fired from the same barrel at 3000' and impacting at 1800'. This is because the rotational velocity of the bullet is far greater at impact which tends to aid in expanding the bullet. I don't know EXACTLY how much difference it makes, but just keep that in mind. i.e. a bullet tested in this way will likely expand a little more in the real world hunting velocity than a reduced load given the same media. Believe it or not, water will cause greater expansion than dry paper etc. Sometimes I use a layer of carpet at the beginning to simulate hide and you can use bone or ?? if you like. If you have the option, use a PORKER like Roy did! Have a ball.........Rich

Last edited by elkaholic; 05-22-2011 at 10:09 PM.
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Old 05-22-2011, 11:30 PM
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Re: Penatration & Expansion test.

When you shoot at subsonic velocities (1,040 to 1,080 fps depending on altitude), your barrel will need a little more twist to stabilize a bullet. Normally, rifle bullets are used - but this presents a problem in that most rifle bullets require a minimum of 1,600 to 1,800 fps in order to have some expansion. I own a 300 Whisper/Blackout that is designed to shoot both sub and supersonic rifle bullets. I have spoken with most major manufacturers of bullets and I have yet to encounter a normal copper-clad target or hunting bullet that will expand at subsonic velocities. They usually end up just penciling through.

My go-to subsonic round in my 300 Whisper/Blackout is a 240 gr. SMK over 7.9 gr. of Lil' Gun powder shot out of an 11 inch barrel with a one-in-eight twist. The round is devastating at close range. At 50 yards, the bullet has already begun to destabilize, with half the rounds beginning to "key-hole" on the paper target.

However, this "key-holing" can be a good thing. If you can find a long, heavy-for-caliber bullet that your rifle barrel will barely stabilize at subsonic velocities - you will find that it will begin to tumble once it penetrates the target. They saw this in Viet Nam when they first tried to shoot the longer 68-70 gr. bullet FMJ in an M-16 barrel with a one-in-nine twist. They would not stabilize much beyond a couple hundred yards. But it sure wreaked havoc on whatever it hit.

Subsonic loads do better with the faster burning powders typically associated with shotgun or pistol loads. Hodgdon 110, Trailboss, and Lil' Gun seem to work well. It can be tricky to try too much experimenting on your own as pressures vary a lot depending on how much empty space you have in the case.

You can learn a lot by reading on some of the forums dedicated to rounds primarily developed for subsonic use, such as the 300 Whisper, the 458 SOCOM, the 50 Beowolf, etc. As more people become involved with this aspect of shooting, more sources seem to surface. For example, Outlaw Bullets is a custom bullet makers that has designed a bullet that reputedly will open up at subsonic velocities. Another bullet maker (whose name currently escapes me) has a bullet with an extra large hollow point into which the reloader can insert an .17 cal varmint bullet to enhance it's expansion capabilities.

There is a lot of info on these other sites. They contain load data, and also a lot of info on expansion or bullet performance. A lot of these experiences are based on shooting into ballistic gelatin, which many believe to be most similar to human tissue.

Good luck on your quest. Be sure to post back with your findings.
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