I bought a mould for 247 gr .308 cast bullets that were actually designed for the .300 whisper. I want to use them in .308 and .30-06 at subsonic velocity and I mainly want a reliable, very quiet cartridge. Any ideas on loads, powder, etc? Or a source for subsonic load info? Thanks in advance!
loading subsonic .308/30-06 (300 Whisper)
- Thread starter jethunter
- Start date
ummmm
the speed of sound is about 1250 fps... most 30 06 I shoot is between 2700-2900 fps
you would be better off trying to do this with a cartridge like the 300 whisper/black out/any 223 cartridge necked to .30 cal, or even a 7.72x39....
or a .45 acp is already reliable, and sub sonic,
check out loading data at http://data.hodgdon.com/cartridge_l...d speed, if not, you need to change cartridge
the speed of sound is about 1250 fps... most 30 06 I shoot is between 2700-2900 fps
you would be better off trying to do this with a cartridge like the 300 whisper/black out/any 223 cartridge necked to .30 cal, or even a 7.72x39....
or a .45 acp is already reliable, and sub sonic,
check out loading data at http://data.hodgdon.com/cartridge_l...d speed, if not, you need to change cartridge
1116.44fps at sea level. Generally it's rounded to 1100fps for simplicity. I know you are giving an estimation but it's a tad high is all.
I shoot sub sonic lead cast .32 pistol bullets out of my Lee Enfield using magnum shotgun powder. You may have to develop your own load to see what burns properly and also gives low enough velocity. Obviously it wont cycle a semi auto.
Due to the case volume difference you may have to develop different loads for both the .308 and .30-06.
Low volumes of rifle powder doesn't work as you don't reach a high enough pressure to burn it properly. I tried loading 20gr of H4895 into .303 British cases and it fired at about 800fps but loads of unburnt powder was left in the case. Load data for a smaller case at the desired velocity also wont work well since the increased case volume will mean less efficient burning.
My current load for .303 British is 5gr of Alliant Blue Dot but that is with a 90gr pistol bullet and it pushes it around 1000fps. The heavier bullet in question will produce higher pressures with the same powder loads as well as travel slower.
To develop a load I would start with a slow shotgun powder (HS-7, 2400, Blue Dot, or maybe even something like H110) at around 5 grains. First shot check for overpressure signs but chances are you will be under pressure. I get a lot of soot on my .303 cases because there isn't enough pressure to expand the brass to seal the chamber properly. Also make sure there is a new hole in the target or else check your bore to make sure the bullet actually left. Then go from there with different amounts of powder to get the velocity you want.
To clean soot out of my chamber I use a .410 bore shotgun mop and 3" cotton patches with a touch of nitro solvent. Make sure to dry your chamber really well after though.
I also load .45-70 with 500gr lead cast bullets over 16gr of Blue Dot and get around 1150fps. It just barely breaks the sound barrier and I'll be reducing it slightly to get below it in my next tests.
This site is a great help for me:
http://www.gmdr.com/lever/lowveldata.htm
It shows for a 170gr lead bullet in .30-06 and Blue Dot powder (the one I have on hand and use most often) to be 7-11 grains. So with a heavier bullet 5-6 grains would be where I start. There are enough powders listed that it shouldn't be hard to find something you either already have or can get easily. At the pressures we're talking here blowing your barrel/chamber isn't a real risk. Having a bullet not leave the barrel is a real risk though so always check for that until you find something reliable.
I have some load info for low velocity cast bullet loads for milsurp calibres, PM me your email address and I can forward it on to you.
Mark
Thanks, PM sent.
Good info, Thanks! I remember a few months back someone on here posted a bunch of data for subsonic .308 with heavy bullets but i couldn't find it or remember who it was that posted it.
My notes are not at hand, but I can say that best results in the 308/30-06 will be with fast - medium fast pistol powders IMO. I'd use loads from a Lyman Cast Bullet Handbook as a sanity check, and start my work with Red Dot. I have the same mold and have done work with it in the 7.62X39 and 303 Brit. Start at 10.0 grains over a chrony and go up or down from there. It's best to stay above 600 fps to minimize the likelihood of a bullet not exiting the bore.
I would start with 10.0 gns of trail boss, and use a magnum primer.
Stabiliity will be the problem pushing something that heavy, and that slow with a standard 1:10/11 twists.
You have to be careful with other pistol powders. They are at risk for "secondary explosive effect". You should use a filler material, magnum primer, and might want to drill out the flash hole.
GC
Stabiliity will be the problem pushing something that heavy, and that slow with a standard 1:10/11 twists.
You have to be careful with other pistol powders. They are at risk for "secondary explosive effect". You should use a filler material, magnum primer, and might want to drill out the flash hole.
GC
Very good advice.
