An idea on how to get better performance from sub-sonic bullets

[320pf]

An idea on how to get better performance from sub-sonic bullets...

I was thinking of a way to get sub-sonic bullets to perform better. So here it is...

Take a Sierra 200, 210, or 240 gr. bullet and score the shank approximately 2/3 of the way to the ogive with a tube cutter. It you score the bullet almost all the way through the jacket material, I suspect the the bullet will break up when/if it tumbles inside the target. This should significantly increase the preminant wound channel thereby incapacitating the target more effectively.

This will deform the bullets shank a bit by making it a bit larger than 0.308 in. immediately near the cut but sub-sonic loads are low pressure and firing the bullet down the bore will just swage the bullet back to the correct diameter. One drawback from this that I can think of is that you might quicken/increase the fouling of the barrel. I think that regular barrels cleaning should be able to remove this though?

All comments welcome.

320pf

[justshoot]

If you make or have a HP (hollow point) and then do any any jacket cuts Vert. in length. It will expand for sure.
You need a Larger HP though than the factory gives.
Factory HP is designed for Hyper Vel. expansion not subsonic. You need to open-up the HP larger and the jacket scores will take over from there. much like your, HP personal defence Pistol ammo. Like the hydrashock or sabers.
.

[rumlover]

SMKs perform quite well. The hollow tip collapses on impact causing the bullet to yaw and tumble. I've pulled several out of the soft mud over the past two weeks and the jackets were all torn with deformed, exposed lead with a total diameter around 5/8" (these were .30 240's) and about 1 1/8" long.

Unless you are shooting a very heavy bullet, you're not likely to dump a lot of energy into the target by expanding the bullet and still get an exit wound at sub velocities when shooting large game animals. You can blend your own lead alloy bullets to a very soft compound, cut swags into the side, a large hollow point, lube them and throw 'em a a sub velocity. It may deform enough to do what you are looking for but you've lost the high BC and probably decreased accuracy. With fast twist rates you also begin to risk deforming the bullet in flight as the centripital forces try to tear/deform the lead. I haven't done any research on where that limit resides, but I'm sure it could be calculated with shearing tests on whatever compound you came up with. If you define performance as taking large game and finding your kill, the SMKs will do fine. If you have an issue with your existing twist rate and the bullets you want to shoot, you'll either have to change barrels or shoot shorter pills. The Hornady 220 RNSPs are very stable in a 1/10 barrel and will take a deer (I've taken 8 over the years). None have gone more than 100 yards (just like a well placed bow kill) and all rounds exited the body cavity

Hunting with sub loads should be looked at like long range bow hunting, not traditional gun hunting until such time that the bullet technology comes around to the subsonic market.

[GREYGHOSTt]

How's about these 240 grn spitzers 9.8 grns 2400
8"ssk 300 whisper fired into dry magizines
click on pic o enlarge.

[GREYGHOSTt]

Another pic!!click on pic to enlarge

[rumlover]

Those results are very similar to what I pulled out of soft mud at 100y with my 308/240 SMK load.

[Pitt300]

GREYGHOSTt
Whose 240s are those?
I'm VERY impressed!

[GREYGHOSTt]

those were made by bulletts bullets..
aka me:grin:

[320pf]

Dry magazines and mud does not simulate "meat" very well. You need to shoot them into ballistic gelatin or another simulant to see how they will preform.

320pf

[rumlover]

Well, after 12 for 12 deer total being shot with subs (8/Hornady 220s and 4/SMKs of various weight) I'm confident their performance has been proven and results left buy the bullets match the results of those I've shot in to other media.

[320pf]

Well, after 12 for 12 deer total being shot with subs (8/Hornady 220s and 4/SMKs of various weight) I'm confident their performance has been proven and results left buy the bullets match the results of those I've shot in to other media.

No argument from me. I am also quite happy with the Sierra 200 and 240 MK performance. I just made my original suggestion because this subject is brought up frequently on this site. You are correct, vertical cuts will likely have a negative impact on accuracy. But I did not suggest this! I suggested using a tube cutting tool to thin the jacket. The idea being that when the bullet tumbled in the target, the bullet would break at the score... increasing the permanent wound channel

After my original post I came across a cannelure tool by corbin. Using this tool to put a cannelure would not have a negative effect on accuracy, providing that one does not make the cannelure too deep.

A cannelure would do two things. Primarly, it would secure the bullet placement in the case. This could be desirable in an auto. Secondly, in would also increase the possibility that the bullet would fragment aften impact.

http://www.corbins.com/hct-1.htm

320pf

[rumlover]

I put up a post on a new bullet design. My thoughts were to create a high BC, stable bullet that would allow shooters with factory twist rated barrels to shoot sub loads all the while providing effective (not necessarily efficient) killing potential--AND safely be shot in the varying barrels found on the market. While I've passed the point of no return by spending booko cash on specialized barrels, I'd like to take what we've all learned and try to put it to good use for the masses.

My thoughts were a design with the following:
-BC over .5
-Reduced friction for safety reasons (a need I see when using factory guns to prevent the likelyhood of a barrel stoppage)
-hollow cavity up front (not necessarily a hollow point like the SMK, but that would be a good starting point)
-high sectional density looking for the heaviest alloys to pack into the shortest pill
-No exposed lead to vaporize and fill up the cans (problem found in sealed 22 cans)


What would you guys add?

[Night Shooter]

I'm having some serious issues shooting new 300 Whisper with 220 Gr. SMK HPBT in a 1 in 8 twist 16" barrel/upper from Model "1" Sales loaded with 9.2 grains of H-110...I think I can throw rock more accurate...they are even hitting the edge of my supressor and keyholing at 75 yards. They aren't shooting well without the supressor at the same distance...starting to keyhole but not as bad...4-6" groups ! Doesn't appear to be stablizing...comming out the barrel.
Any suggestions ?

[pug]

I believe I would check the twist just as a precaution. I usually use a 2 1/2 to 3" square patch in the cleaning rod loop. Insert the patch down the bore just a little and then put a piece of masking tape with a tail sticking up 8" down the rod from the muzzle. Start pushing the tight patch down the bore and the rod should start to rotate and make one full turn by the time the marker gets to the muzzle. Take a couple of readings to make sure. If it doesn't make one full turn then put the marker 10" from the muzzle and see if its a 1:10.

[rumlover]

I concur, wrong twist rate is probably the culprit. What powder/charge are you using? Have you cronyed the rounds? Also, there is the possibility of the threading for the suppressor being off center of the bore (as opposed to the barrel centerline). If your twist rate is the 1/8 advertised, take the can off and see if your prefered load still keyholes at 75+. If it doesn't, send the barrel to a more reputable smith, I'd suggest Noveske for AR work, and have the barrel threading re-done for the suppressor. If that's not the issue, find someone with a bore scope and look for burs in the rifling or throat (pay special attention to the gas port area and muzzle). If that isn't the issue, try some shorter pills and get the velocity up close to 1050--if you're not already there.

Outside of that, I'm not aware of anything else that could affect stability.