FYI!! Shooting the 22LR to 223 projectiles through a can may damage them!!

[Lizard333]

The can was used with hundreds of rounds before trying it with bullets mentioned above. A reputable builder I believe AAC built the can.

[mckenziedrums]

Not sure I'd consider AAC a reputable can builder anymore but I doubt that's the problem. Most of the time I've seen a slight increase in velocity with a suppressor mounted. You could be right on the edge of the bullets holding together without it. Use a slower twist barrel and try backing off a bit speed wise.

[jmorris]

He tried it with his can and had some come apart in the can, causing damage to it. I have hear about the Barnes Varmint Grenades doing the same and I believe it may be because of the thinner jackets not holding up to pressures

The only time I had problems with bullets coming apart it was due to centrifugal force not pressure or velocity. Back before "black" rifles outnumbered bolt guns, .223 twist rates were much slower and thin jacketed bullets were more common. Fire a 50 grain bullet out of a 1-12 twist barrel at 3300 fps and they do just fine, take the same round and fire it from a 1-7 twist barrel and only tiny particles make it to a target that's only 25 yards away.

In any case a suppressor owner should always test loads without the can on, to make sure they are stable and in doing so he would have found out they were not staying together in the first place.

[tiger762]

Hmmm, I have never had a jacket separate in flight but looking at the numbers (just thinking out loud) we have:

1. 3000 feet per second
2. 7" twist
3. rotational velocity is then 3000 * 12 / 7 or 5143 times per second
4. Bullet circumference is 0.224 * 3.14159265 or 0.704"
5. circumferential velocity is then 5143 * 0.704" / 12 or 301.6 feet per second
6. For every inch the bullet moves forward, the jacket rotates about a tenth of an inch
7. If the rifle silencer is 8" long and the jacket separated at the muzzle, it would fling off a fragment that indeed would hit baffles.

I just have never experienced it myself.

[runfiverun]

your rotation or rpm would be more like 252,000 rpm

[jmorris]

From Tigers example that would be 308,571 RPM with 1:7 twist and 180,000 RPM with 1:12 twist or around 42% reduction, just with a different twist rate.

Might take a look at "maximum spin velocity" here.

http://www.varmintal.com/aengr.htm

I have done a 2D Finite Element calculation of the spin velocity necessary to fail a .224" 40 gr. bullet with a 0.012" gilding metal jacket wall and a pure lead core. The yield stress used for the gilding metal (G21000 95Cu/5Zn) was 15 KSI. At a spin velocity of 307,500 rpm a condition of plastic instability occurs. (It comes apart)

[clodhopper]

Some interesting tidbits in the text there. Thanks for linking jmorris.

[seppos]

Maybe a harder alloy and bonding would strenghten the structure enough to withstand higher velocity?

S

[clodhopper]

I think bonding may help. When you look at the area with the highest stresses it is the cylindrical body of the bullet.
A little crease from the rifleing would make you want some glue.

[Valornor]

It doesn't solve the problem....if the bullets were being overspun then they would come apart with out without the suppressor. Any velocity increase due to be use of a suppressor wouldn't increase the rotational speed of the bullet since it's free spinning the moment it leaves the barrel. In fact the moment it leaves the barrel the spin begins to decay due to drag.

[Lizard333]

What if the jackets were bonded to the core? I've recovered other slugs on 40's and 45's that had almost 97% weight retention. That would be the glue.......

[jmorris]

It really depends on the jacket. We know bullets can withstand more than 3000 fps out of 1:7 twist barrels, just not all of them.

The important part of this to know is that bullets can come apart due to too fast rotational speed or become unstable due insufficient rotation to stabilize, either way you should know what they are going to do before you fire them through a suppressor.

[M.A.D]

With the 0.012 x 1.4 copper cups i make for sub sonic 30 cal ... I tell everyone, if your running 1-7 or 1-8 twist.. No faster then 1200 fps

[seppos]

If one looks closely the pics in vamint als page, one notices that the deformation of the core and jacket is different. As I said earlier, the bonding might help as it transform the twin layer projectile more like a solid one. Also from the lead alloy side, it would be beneficial to choose a alloy that would withstand higher rotational forces, such as copper or zink enriched alloys.
Good info in lead and lead alloys forum.
Those alloys are harder to swage, but might still work.

Check out about copper alloys with heat treatment:
http://castboolits.gunloads.com/show...=1#post3334464

With bullets it is also possible as separate procedure after bonding and pointing.

S

[ofreen]

I won't fire RF jacketed bullets through my cans. I have been making RF .224 bullets since the 80's and have fired who knows how many thousands through mostly .223's. I first started using them in my old SP1 with its 1:12 twist and a Ruger No. 1 (1:14 if I remember right) with excellent accuracy. However, even when using FED brass for jackets (they are thicker than most) I would get an occasional bullet that would fail to make it to the target. Later AR's with 1:9 twists would aggravate this, and I won't bother with 1:7 any more since I don't want to cut the velocity that much to keep them together. Kind of a drag not being able to use RF jacketed bullets with the cans, but even one baffle strike is too many.

[mozeppa]

everytime i shoot cans ....it damages them!

unless....i miss!