Low & Slow: reduced loads
Since Forrestdweller brought this up, I will show you what I have on this project. I have not tested much of these loadings but they seem reasonable and a place to start. Comments?
Low & Slow: reduced loads
1. .308 Winchester
a. 26 inch barrel with a 220 grain NEI .308 cast bullet over 3 grains of Clays is almost silent
b. 24 inch barrel with a 150 grain RCBS bullet, 3 and ˝ grains was needed and it was like a loud cap gun.
c. 150gr cast bullet* load 13 grs. of Red Dot in .308 or .30-06 at about 1600 fps
d. 170gr, cast bullet* 13 grs. of Red Dot in .308 or .30-06, about 1500 fps
e. 200gr. cast bullet* 13 grs. of Red Dot in .308 or .30-06, about 1450 fps
f. play with powder levels of Bullseye or Clays for silent loads...but you are not going to get there with 180 grain cast slugs and under.
g. 170 thru 190 grain cast slugs
i. 5 grains of WW231 or HP38 will go around 1000 fps
ii. 8 grains of Unique goes 1250 fps.
iii. 20 grains of 2400 or 18 grains of SR 4759 goes 1800 fps.
iv. * Note: Lubricated Jacketed bullet velocities are about 120-150fps less than a lubricated lead bullet of the same weight.
2. 3006 Springfield
a. 150gr cast bullet* load 13 grs. of Red Dot in .308 or .30-06 at about 1600 fps
b. 170gr, cast bullet* 13 grs. of Red Dot in .308 or .30-06, about 1500 fps
c. 200gr. cast bullet* 13 grs. of Red Dot in .308 or .30-06, about 1450 fps
d. 210 grains cast bullet
i. with 10 grains of Red Dot or Green Dot 12 grains will go 1200 fps (without recoil & very quiet @ about 700 ft-lbs of muzzle energy) good to 100 to 125 yards for training or small game hunting.
ii. 13 grains of Unique will go 1500
iii. 28 grains of 4759 will give 2000 fps with over 1800 ft-lbs of muzzle energy
iv. * Note: Lubricated jacketed bullet velocities are about 120-150fps less than a lubricated lead bullet of the same weight
3. The Buckshot Option
a. 30-caliber rifles loaded with a single 0-Buckshot, .32-inch diameter, 48 gr., round lead ball.
b. 3.0 grains of Bullseye powder with Dacron of Kapok fiber and then the lead ball.
c. called "the ideal cellar and small-game load," and is suitable for most of the major .30-caliber rifles (including the .30-’06 Springfield, .308 Winchester, .30-30 Winchester, .300 Savage, and .30-40 Krag).
4. Rules for subsonic loads:
a. As you lower the bullet weight in any caliber with cast bullets for quiet loads, you actually need more powder.
i. Bullet weight determines the efficiency of the powder burn.
ii. Barrel length determines the loudness of the report.
b. Drill Flashole* to 3.5mm (9/64") to allow all the primer flash to enter the case and ignite the powder completely.
c. Use Magnum Primers for maximum primer flash and better powder ignition.
d. Lube all bullets. Moly is good but animal fat is better.
e. Lubricate the bore regularly while shooting.
f. Never crimp bullets into cases. Never seat bullets "into the lands."
g. Try not to use powder charges of less than 40% load density.
h. If load density is less than 40%, use tamping or fillers to keep the powder at the bottom of the case.
i. a portion of tissue paper (big enough to crumple against the case walls for a grip) over the powder to hold it back against the primer.
i. Make sure the bullet exits the bore after each shot.
j. Use only the fastest burning pistol powders - N310, N312, Bullseye, Clays, Titewad, HP38, Red Dot.
k. Any sort of slow ignition or hang fire is a warning of imminent Secondary Explosive Effect (SEE).
l. *Note: safety issue! These cases must marked and never used with full power loads!
5. To prevent jacketed bullets from sticking
a. In a dirty bore, all conventional jacketed bullets used for subsonic loads must be lubricated.
a. The traditional method: dip the bullets in melted, refined animal fats (lard) which hardens as it cools, leaving a thin, slick surface on the bullet. (messy and slow).
b. The modern method: moly coated bullets apply to bullets your self or buy direct from the factory.
c. Caution: jacketed bullets in subsonic loads risk becoming lodged in the bore with less than 6 grs. of N310, N312, Bullseye, Clays, Titewad, HP38, Red Dot pistol or shotgun powders when loading jacketed bullets.
6. To prevent lead cast bullets from leading:
a. Cast bullets will lead above 1300 fps unless gas-checked.
b. A hard cast bullet, that doesn’t have a gas check, can be used by
i. Cut a small disk of bullet base size from thin polypropylene and glue it against the base
ii. This stops fouling almost as well as gas checks in sub-loads.
That's very interesting. So you're basically making a perfect match with the barrel length and the load so the powder has time to completely burn up before the bullet leaves the barrel.
For those who haven't played in this realm before, here is the definitive primer on subsonic loads.