Very light pellets at very high speed?

following

It gets harder and harder as air resistance increases (especially with something carrying less inertia). Seems you got the rig to try it, give it a go and let us know?

slight highjack, any word on the allot GTO slugs, thanks.

Aside, recently I have read/seen a couple of gun reviews* that showed good results with alloys in and around the "speed of sound".

also watching.

* if I remember I will post links.

During the transonic zone, the pressure on the tail of a bullet/pellet changes as the vapor cone collapses, and the projectile may become unstable (similar to a toy top losing speed). 

Because pellets use their skirt for stability, the vapor cone is detrimental to their flight stability and can cause considerable turbulence and or loss of stability from the beginning.

To test a pellet's stability, try firing at a sheet of paper supported with cardboard and see if they keyhole or produce a slightly oval hole.

Atmospheric density will be the main determining factor.

It would take a lot of fps to work. Reason is, a pellet slows down quickly. It has its own drogue chute in the rear. If the target is close enough to be able to get the pellet to it before the pellet falls back into the trans sonic region, it may work. Issue, is that won't be far at all. long range is out as you can't push a pellet fast enough to still be at super sonic at longer distances. 

As it falls thru ss again, it will be a rough ride upsetting any accuracy that it had. Usually tumbling.



knife

The short answer is yes, that's true. As long as a projectile remains above or below the speed of sound, it avoids the turbulence of the sound barrier. But, that is unrelated to the optimum speed for a given pellet or slug. When you consider that diablo shaped pellets were designed for speeds closer to half the speed of sound, it is doubtful that one is going to shoot well at super sonic speeds. And, it's not really practical. In order to maintain supersonic speed at 50 yards, using a 16 grain, .22 pellet, you would have to have a muzzle velocity of over 1400 fps. That calculation is from a chart that probably does not consider the shape of a pellet, so I'm sure it is not absolutely accurate, but maybe sufficient for a rough idea of what would be required. You would also have horrendous bore leading with pure lead pellets. 

Also don't forget that shooting a 16gr pellet at the same tune as a 60gr slug your pellet will be out the bore way faster being much lower in fpe compared to the slug. So it might not shoot as fast as you hope.

The short answer is yes, that's true. As long as a projectile remains above or below the speed of sound, it avoids the turbulence of the sound barrier. But, that is unrelated to the optimum speed for a given pellet or slug. When you consider that diablo shaped pellets were designed for speeds closer to half the speed of sound, it is doubtful that one is going to shoot well at super sonic speeds. And, it's not really practical. In order to maintain supersonic speed at 50 yards, using a 16 grain, .22 pellet, you would have to have a muzzle velocity of over 1400 fps. That calculation is from a chart that probably does not consider the shape of a pellet, so I'm sure it is not absolutely accurate, but maybe sufficient for a rough idea of what would be required. You would also have horrendous bore leading with pure lead pellets.

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Imho, all the responses state parts of the problem, and elh does a great job putting the pieces together. However, his statement about leading is absolutely correct and often overlooked. Years ago I had a FT rifle built that shot 7.9 CPs (the original "good" ones) at 1025 fps. It shot laser flat and would consistently produce the smallest groups I have ever shot. The first time out, my card looked like "the chicken walk" dropping only a couple for my best ever score. But during the afternoon relay it all fell apart. Fellow shooter, Brit Harrision,advised me that the problem was leading - and he was right. In fewer than 100 shots, the barrel leaded up giving shotgun patterns. Thoroughly cleaning the bore dialed the accuracy back. Cannot imagine the amount of fouling that would occur in a rifled barrel at the velocities contemplated here.

Interestingly, I just found 3 old, unopened boxes of those brown box 7.9 CP pellets, as well as some10 g. I've long since parted with the rifle for which I bought them. Think I'll wash and lube a few and see how they shoot. My only gripe with those pellets, they were very dirty.

Interestingly, I just found 3 old, unopened boxes of those brown box 7.9 CP pellets, as well as some10 g. I've long since parted with the rifle for which I bought them. Think I'll wash and lube a few and see how they shoot. My only gripe with those pellets, they were very dirty.

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Heard yesterday Crosman has discontinued the 7.9 pellet.

Pointless.. Even if you would fire really light pellet at 1600FPS it only gets bit over 10yds before it drops to below speed of sound. There simply is zero reason to even try to pass sound barrier with pellet shape projectile no matter how fast you shoot it even at 3000FPS it just dosent get past 40yds with supersonic speeds.. Its dragg stabilized projectile that is only suitable for subsonic speeds and dragg just get too huge above it. 

Here's a stupid question: can I cast slugs out of pure tin in the same molds as I make lead slugs? Or mostly tin? Avoid the "drag chute" effect of a diablo but still get up to those higher velocities maybe. That would be interesting to try. 


The comment about pellets losing speed quickly (and so a high speed pellet would be a short range solution only) had crossed my mind - and maybe that could be good for some? Very flat high speed for short range with the confidence that you aren't going to damage things beyond 75m or whatever.


i think a very light aerodynamic slug could be interesting to mess with.

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Iv considered that too but you need different twistrate for high speeds.. When you go supersonic your twistrate required to balance projectiles actually slows and you need faster twistrate for subsonic speeds. Would be interesting to try tho.. As long as you remember your BC number drops as well when your mass (SD) drops. 

Thanks. This would be for shorter range only due to low mass and low density / BC for sure. Thinking of casting a round nose boat tail slug in tin that is 48 grains in pure lead. Maybe this type of projectile will be ok spinning faster after a hyper-speed trip down the barrel. 


ok to cast in pure tin?

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Yep I dont see no issue except price is significantly higher than lead like 20x more. 

VLP * VHS= VBA

Where:

VLP= Very light pellet

VHS= Very high speed

VBA= Very bad accuracy.

Maybe a Jacketed Arrow type projectile like the M1 Abram's tank shoots, would handle supersonic much better with better accuracy if it can be done, 

Okay to cast in tin, but tin does cost like 10X what lead cost.

What you gain in speed, will quickly be lost to lower BC valve for the lighter weight.

There is no free lunch, as the saying goes.

Tin is too hard, will not sufficiently obturate to fill the grooves.