A colleague of mine at a university I work at is conducting research for protective structures. They currently have a .308 rifle and reloading equipment to test armor materials, but they are looking to conduct tests with a projectile traveling in the 50 - 100 feet per second range. Knowing that I'm a shooter and reloader they asked me if I thought that this was possible. I don't know, so I'm turning to you all for advice. My guess is that it would be a very fine line between getting a projectile with those types of velocities and getting a bullet stuck in the bore. I'm thinking that they might be better off with a cross bow or something. They've got some budget, but probably not enough to do things properly and build a gas gun. Any ideas or suggestions?
REALLY low velocity reloads for laboratory tests?
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Clark
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I would do it with soft lead, and not a jacketed bullet.
I could do it, and so could a lot of others.
I could do it, and so could a lot of others.
A college kid could throw a projectile 100 feet per second.
It wouldn't take much to set up a rig using compressed air, a valve, and a piece of pipe. Don't know how fast you could go.
A short-barreled 38 revolver with lead bullets should be able to get down to 500 fps or so, and up over 700. Then a 357 to 1400. Then the 308 with Unique or Trailboss.
It wouldn't take much to set up a rig using compressed air, a valve, and a piece of pipe. Don't know how fast you could go.
A short-barreled 38 revolver with lead bullets should be able to get down to 500 fps or so, and up over 700. Then a 357 to 1400. Then the 308 with Unique or Trailboss.
that line would be RAZOR THIN! i have no idea why they would want to have a bullet go that slow, except to study the rifling grooves left in a bullet. and really, they do not need to go anywhere near that slow in order to do that. i am presuming that they want to be able to stop the bullet with a minimal amount of equipment or room inside of a room. they make a bullet testing tube for studying bullet performance, i think they call it test tube, but i can not guaranteee that. one of those would work very well for "catching a bullet.
RugerBob
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Might want to try some rubber or wax bullets with mag primer and no powder at all. They make them set ups for 38s so you might have to make your own.
The pressure required to get a bullet to clear the bore will result in a higher velocity than that. Try a spitball from a straw, that's about the only way you're getting a velocity that low.
Somewhat more seriously, a compressed air setup with a regulator is going to be their best bet. Think along the lines of the stuff Mythbusters rigs up all the time. Nice thing about the regulator is that with no powder burn to introduce irregularities, the velocity should be very repeatable. In addition it will be much easier to fine tune to the exact velocity that they want.
Somewhat more seriously, a compressed air setup with a regulator is going to be their best bet. Think along the lines of the stuff Mythbusters rigs up all the time. Nice thing about the regulator is that with no powder burn to introduce irregularities, the velocity should be very repeatable. In addition it will be much easier to fine tune to the exact velocity that they want.
Air tank, regulator and some copper pipe. Dial in any velocity you want.
Yep - see it on Mythbusters often. Looks like it works great.
A slingshot can beat 50fps. Even most airsoft guns and paintball guns are in the 200-300 fps range out of a smoothbore tube?
Yep - see it on Mythbusters often. Looks like it works great.
A slingshot can beat 50fps. Even most airsoft guns and paintball guns are in the 200-300 fps range out of a smoothbore tube?
yeah, you'd have trouble staying that low with just a bullet and a sling shot.
Maybe get a paint ball gun off craigslist, some heavy .308 heads, and sabot it in some foam. You might be able to get it down in that range. Maybe. But it has nothing to do with how a bullet actually behaves at that point.
Maybe get a paint ball gun off craigslist, some heavy .308 heads, and sabot it in some foam. You might be able to get it down in that range. Maybe. But it has nothing to do with how a bullet actually behaves at that point.
Funshooter45
Member
As mentioned, it will be difficult or impossible to not stick the bullet in the barrel going that slow. So, don't use a .308 caliber bullet at all. Go down to a 7mm bullet. That .284" bullet will not engage the rifling so it won't get stuck. Accuracy won't be very good, but I don't think that's an issue. Get some 7mm-08 brass or just use a 7mm-08 die and neck the .308 brass down to accept the 7mm bullet. Try using a regular large rifle primer only at first and see what happens.
Clark
Member
When I was in Jr. high math, the teacher could do mph to fps conversion calculations faster than we students could.
He explained that he remembered one ratio 88 fps = 60 mph = 1 mile/minute
Now, 47 years later, it still works.
rodregier
Member
Sabotted painball gun setup looks the most viable to me. The compressed air tank setup would be my second choice.
Keep in mind if your test setup is a stand-in for .308 projectiles launched from long range,
your simulation won't have the same rate of spin as the real-world projectiles at say 1200+ yards. So it will not exactly replicate the ballistic challenges of the real world problem.
Same mistake the producers of CSI: (LV) made in an episode. They were dealing with pistol bullets, spin differece probably not as important for that scenario. (They used reduced loads to demonstrate penetration at long range of a pistol bullet.)
Clark is "the man", always worth listening to on the topic of interior ballistics.
Keep in mind if your test setup is a stand-in for .308 projectiles launched from long range,
your simulation won't have the same rate of spin as the real-world projectiles at say 1200+ yards. So it will not exactly replicate the ballistic challenges of the real world problem.
Same mistake the producers of CSI: (LV) made in an episode. They were dealing with pistol bullets, spin differece probably not as important for that scenario. (They used reduced loads to demonstrate penetration at long range of a pistol bullet.)
Clark is "the man", always worth listening to on the topic of interior ballistics.
Clark
Member
Ever watch any of the couple hundred Jörg Sprave sling shot videos?
http://www.youtube.com/watch?v=Bm5YOYrRejY&feature=related
It depends on the point of the test.
If it must be a firearm launching the projectile I would prefer a smooth bore like a .410 w/a undersized slug in a cloth jacket. If it be the .308 chamber I would look at a .243 bullet & you may be able to use a paper jacket. Use a fast powder.
If it must be a firearm launching the projectile I would prefer a smooth bore like a .410 w/a undersized slug in a cloth jacket. If it be the .308 chamber I would look at a .243 bullet & you may be able to use a paper jacket. Use a fast powder.
I don't know what science they are trying, but i would try a bullet in a gravity drop, from a rail or swinging arm, with a frictional brake to control speed. I don't think any bullet SHOT would stabilize at that speed. Might have to add a ratchet or catch device to prevent multiple strikes (bounce).
gamestalker
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They could easily do it with a sling shot. That weapon will allow them to work with various velocities with much less preparation time, and far less expense too. I suggest a Wrist Rocket or simular type sling shot.
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