Thread: Subsonic 308

Originally Posted by veitnamcam

Something hard but with very low density will have no momentum and stop suddenly while the projectile expands around it.
But if soft enough should not need anything ?

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In theory
1/2 of this is still theory until we send finished lead ------> that way
Helping the expansion is the key and there is a number of options avail in the tooling that's done.

The logic of using the big 240gr SMK's (that the original 300Wispers were shooting) is that the high BC of those bullets allowed it to retain about 90% of it velocity and energy all the way out to about 300m. It's like a giant freight-train...once it reaches top speed, it takes a long time to slow down again.

Energy is Ke=1/2m.v2 (2 is ment to be squared, but I can't figure out how to insert the correct symbol)

So velocity (v) is the most important part of this equation as it squared. But since we want to limit the velocity to subsonic, then to get some of the killing power back we need to up the weight as much as possible. If you could find a heavy (240gr ish) bullet that will expand at subsonic velocities, then you'll have a very good killer of game.

My 30Apache is average at best at killing using the 240gr SMK's. The results would be the same no matter what was driving it (.308, 300Wisper, 300blackout...doesn't really matter) as the exit velocity is going to be the same. Its the projectile that's the limiting factor and no matter what I've tried they all suck when compared to high velocity rounds.

Keep us posted VC if you do find a good killer, as I'd love to make my rifle more effective than it is now.

kj

Yep dead right velocity is fixed so more weight= more energy, however unless you have built something with a fast twist with subs in mind you aint going to stabilise a 240 at sub velocity in your average 1 in 12-1 in 10 twist factory 308.

Dunno what weights Spanners has in mind but no doubt will find out shortly

Who wants to lend me some NV? just sorted some private access

Surely something along the lines of an upscaled .22lr hollow point projectile would be as effective as anything else!
At subsonic impact speeds, fragmentation of bullets is unlikely and certainly unpredictable, even if bone is hit.
A cast lead projectile, with a hollow point, designed to expand at low speeds in .30 cal is going to make a big wound and with enough weight, will still get good penetration.
I've recovered .22lr bullets that have expanded to around .45 diameter so a .30 cal of the same design is going to be pretty effective!

I hope to be able to go up to 260gr lead tip hollow point but it may top out at 240
260 would be a push to stabilize anyway depending on the nose profile.
Have got 1.5 and 6S IIRC

The options I have avail are:
-jacketed lead tip hollow point
- jacketed hollow point
- jacketed plastic ball tip
- jacketed steel ball tip
- jacketed round nose

All nose lead sections split internally
Options for:
Serrated jackets
Bonded cores
Rebated boat tail

Also have 44 cal in the above less the split core and serrated jackets

Penitration is not the issue, the issue is using all or almost all the avalable energy inside the vital zone of the animal.
Best way to do that is fragmentation and sharp edges to cut and cause damage.
Its not an easy ask of a subsonic projectile but Im sure it can be done.

Not that I would but Im sure I could put a round tip on a bit of 12mm round bar and drive it threw a deer in a crush, let it out and watch it trot round untill it staggered and fell over.

For me its not enough to poke a hole threw something,it has to cause damage.

Hmmm just thinking out loud, but how about a massive dia 1/4" hollow point that is then re-packed with some lead shotgun shot?

That could work.............maybe

See the plastic and steel tipped options

I just made a prototype (rough as guts) but the light is too shit to get a pic. Will post pic tomorrow..
But basically i just used a mini cutoff wheel in my die grinder to cut 4 slits on the front 1/3 (but not the very tip) through the jacket of a 240smk so it will peel back like a banana?

Originally Posted by kimjon

I just made a prototype (rough as guts) but the light is too shit to get a pic. Will post pic tomorrow..
But basically i just used a mini cutoff wheel in my die grinder to cut 4 slits on the front 1/3 (but not the very tip) through the jacket of a 240smk so it will peel back like a banana?

I've got a jacket serrater die for that purpose
6 serrations IIRC. Not at home at the mo to check

Rubbish pic, but you get the idea. Kim's sub-smasher V1.1



Four slits cut lengthwise, starting a few mm from the hollow point nose. The idea is that the nose should tear off or expand on impact...then the jacket should rip apart along the four cut ''slits''. The rear section should remain fairly intact and would weigh about 160gr on its own, so hopefully this will smash its way right through both shoulders tearing a large hole along the way????

Well that's the idea anyway, only one way to find out? Will take it out for a hunt next week and see if the theory matches reality?

kj

Post up results :thumbup:

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Originally Posted by hanse

Wee bit out of my league here but, when the 5.56x45 was designed and tested before the "Nam" they were relying on the tumbling effect to cause massive wounding, now im pretty certain that the projectile was a 55gr pill called M193, Changed when the 556x45 became a Nato round in 77 because It was apparently inhumane due to the massive wounds it caused in comparasion to its small size. It tumbled and yawed I believe because of its centre of gravity was close to the base of the pill. Its tendancy to yaw and tumble "could" well be recreated by using a 7.62 pill with a similar profile/scale to the M193. Unsure what the lower velocity will do but a naturally unstable projectile is just that so maybe worth a go. 110gr barnes hehehe

The cannelure on the M193 causes it to break apart when it tips over, if speed is sufficient. The change over I believe was due to concerns about defeating body armor - M855 has a steel penetrator.

Back on topic, what about a 110gr V max? Yay/nay?

Don't think the vmax would work being designed to be launched at well over 3k. The pistol pills do work just need to be heavyer .

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