Below are some posts from this thread: http://www.silencertalk.com/forum/viewt ... highlight=
It should probably be here in a 308 thread instead of a 30-06 thread.
I just finished loading 50 rounds after getting my last data results. I am going to order soem more Trail Boss powder. It seems to oput perform my other pistol powders. I used to use Unique for this... No more. Trail boss has it beat hands down.
Hopefully some of this is helpful to others who are trying to work up loads for the 308. Notice how the ES (Extreme Spread) gets lower as the load density goes up.
From the other thread:
The 30-06 would probably have a 1:10 twist so a 170-180 gr flat base round nose bullet would stabilize OK. The issue is the case is huge! If you have a 308 I would use that as the case if you have a 1:10 twist in a 308 hat is even better.
A 30-06 holds 70.6 gr of H2O and a 308 holds 58.9 gr of H2O Figure you will only be using 40% or less of the space in a 30-06. Compare that to 0ver 45% usage in the 308.
Trail boss has a density of .328 g/cc so a load of 9 gr in a 30-06 case would only fill 39% of the case.
8.8 gr of trail boss in a 308 with a 150 gr bullet (flat base round nose) will fill 46% of the case. It will be stable in a 1:12 and 1:10. and is subsonic.
Even that load density will cause less than stellar performance with a fairly wide range in velocity
In Winchester brass using Winchester primers 8.8 gr of Trail boss with the 150 gr Hornady 30-30 bullet gave me average vel of 961 Extreme spread of 77 fps and a SD of 30 in a 1:11.25 twist in a 22" barrel.
Next step is to go up to a 170 gr 30-30 bullet and seat it deeper to take up more case space. I suspect it will give me a better pressure curve and better more consistent velocity.
For the 30-06 I would start by using 170-180 gr 30-30 bullets (flat base round nose) Use Trail boss powder... and try 10-11 grains to start. It will probably be super sonic. Cut back .5 gr at a time till you get close then change .2 gr at a time. Target 1025-1050 FPS.
Once you get close to that... Shoot 2 or 3 5 shot strings over your chronograph and see what your #'s are. While doing that set the target up at 25 feet. check to see if your holes are nice and even. If you are sure the load is stable then use your silencer.
1100 fps is the most unstable velocity.
The 150 gr bullet out of a 1:12 has a Stability factor of 2 at 1100 fps. 1.25 is all you need.
A 168 gr SMK at 1750 fps just gets to the 1.26 stability factor. At 1100 fps it is only .68 and is very unstable. While at 800 fps it is at a stability factor of 1.04 and is considered "Marginal"
While a 180 gr flat base round nose bullet at 1100 fps in a 1:12 twist has a stability factor of 1.64 so it more than stable at sub sonic speeds in a 1:10 and 1:12 twists.
Getting a stable bullet is not the problem it's the large case capacity and the problems that causes. Trail Boss powder is light and fluffy so it will fill more of the case but STILL it is really not enough for a good burn.
I would consider the 308 case the largest I would try and use for subsonic loads. I am sure the 30-06 can work but getting it to be accurate it the problem.
OK .. You guys got me started.
I went out and got some 170 gr RN FB bullets.
I upped my charge to 8.9 gr Trail boss.
150 gr & 170 gr bullet
941 fps --- 866 fps
964 --- 875
923 --- 844
1008 --- 919
998 --- 902
AV=967 --- av= 881
ES= 84 --- es=75
SD=36 --- Sd= 29
The heavier bullet looks promising...
I ran back and loaded some new rounds
150gr -- 170 gr Bullets
9.2 gr -- 9.5 gr Trail Boss
1042 FPS - NA (leads backwards)
988 -- NA
1002 -- 965
1000 -- 957
886 ERR 930
SD 58 ES=35
es= 156 sd= NA
The 170 gr bullet looks good... I will bump it to 10 gr Trail Boss next time I load some more.
The 150 I will bump to 9.3 gr but I may get Super/Trans sonic "flyers." so the max may be 9.3 gr.
The 170 gr bullet is getting better/consistent pressures.
At a load of 9.5 gr we are at 50% full
At 10 gr trail boss we are at 53% full.
I don't have enough time to do another trip to my press and range before I loose light.
Maybe tomorrow I will have the best loads for the 308 using trail boss and the 170 gr and 150 gr bullets.
I suspect the 170 will be my keeper sub-sonic round till I get my whisper built.
I finally got good results with the 308
22" 5R Mike Rock GAP M700 1:11.25 twist
Winchester brass, Winchester primer
Trail Boss powder
150 gr Hornady RN Flat base and 170 Hornady RN Flat Base
I went up to 9.4 gr in the 150 bullet
Average= 1011 FPS, ES = 34, SD= 13
I will settle in at 9.5 gr and call it quits.
I shoots very well. All sounded consistent.
My goal was 1000 fps - 1050 fps.
The 170 gr bullet
10.5 gr Trail Boss
Average 1014, ES= 69, SD=26
I am going to go up to 10.7 and call it quits there.
The exterior ballistics for the 170 and 150 are very close at up to 150 yards.
Sighted in at 100 yards scope height at 1.9"... bullet path is about 3.5" high at 40-70 yards... 1.5" high at 90 yards... then 1.9" low at 110 yards. 4" low at 120 yards..
The 170 gr bullet has 325 ft lbs at 100 yards, and 299 ft lbs at 150 yards.
The 150 gr bullet has 286 ft lbs at 100 yards, and 263 ft lbs at 150 yards.
The 150 is a much softer point and will expand easily. I think the 170 is made for more rugged conditions.
For most of my applications the 150 will do. The 170 for larger critters or where I need more penetration or to knock over steel..
Rodents and raccoon size game the 150 Hornady would be a good mix.
The sound of the bullet hitting the hemlock stump was by far louder than the "report" M700 GAP AAC short Cyclone