Jim
05-14-2013, 06:33 PM
I set out today to find the bottom of the pressure window for a Lyman 311410 over Bullseye in my new Mossberg .308 Winchester bolt gun. I started with 5 grains of BE and used large magnum rifle primers for the spark plugs. I've got almost 2Ks of the LMRs and as this is going to be toward a subsonic load, I figured I'd go ahead and use 'em up.
The 5 grain load gave a good report and a recoil but certainly not anything substantial. 4 grains wasn't much less. At 3 grains, I could tell the report was a bit quieter and the recoil got down to about like a 22 magnum. 2 grains reported a bit softer still and the recoil dropped to about like a 22 LR.
I went back in the house and made up a 1.5 and was prepared for the inevitable stuck boolit. I was very surprised that it fired! I made up a 1 grain load and it fired, too!
When I fired the test shots, I took the rifle out in the front yard and propped it on the wood fence. I have the top of a 55 gallon drum hanging in front of my berm which is 75 yards from the front steps.
I think the first shot hit the gong, but I couldn't tell. I could definitely hear the boolit hit the gong with the 4 grain load, although the report and the clang were very close together. There was a bit more time between the shot and the strike of the boolit with the 3 grain load. The 2 grain and the 1.5 grain load both hit the gong, also. I don't know where the 1 grain load boolit went. I'm guessing it just fell to the ground before it got to the gong.
That 1.5 grain load strike actually made me chuckle. Pop................clang!
I used my Graphlox to lube the boolits. The alloy is 1/3rd WWs and 2/3rds range lead with about 2 to 3% lead free plumber's solder added.
I didn't expect any leading at those low velocities, but I checked anyway. Except for the residual black from the graphite, the bore was clean as a pin.
The next step is to start at 2 grains and work up. My intention is to go up at about a grain at a time until I start seeing pressure signs. Then I'll drop back and work up at about .2 grains at a time in 3 shot groups looking for accuracy.
I'll let ya'll know how it goes as it progresses.
The 5 grain load gave a good report and a recoil but certainly not anything substantial. 4 grains wasn't much less. At 3 grains, I could tell the report was a bit quieter and the recoil got down to about like a 22 magnum. 2 grains reported a bit softer still and the recoil dropped to about like a 22 LR.
I went back in the house and made up a 1.5 and was prepared for the inevitable stuck boolit. I was very surprised that it fired! I made up a 1 grain load and it fired, too!
When I fired the test shots, I took the rifle out in the front yard and propped it on the wood fence. I have the top of a 55 gallon drum hanging in front of my berm which is 75 yards from the front steps.
I think the first shot hit the gong, but I couldn't tell. I could definitely hear the boolit hit the gong with the 4 grain load, although the report and the clang were very close together. There was a bit more time between the shot and the strike of the boolit with the 3 grain load. The 2 grain and the 1.5 grain load both hit the gong, also. I don't know where the 1 grain load boolit went. I'm guessing it just fell to the ground before it got to the gong.
That 1.5 grain load strike actually made me chuckle. Pop................clang!
I used my Graphlox to lube the boolits. The alloy is 1/3rd WWs and 2/3rds range lead with about 2 to 3% lead free plumber's solder added.
I didn't expect any leading at those low velocities, but I checked anyway. Except for the residual black from the graphite, the bore was clean as a pin.
The next step is to start at 2 grains and work up. My intention is to go up at about a grain at a time until I start seeing pressure signs. Then I'll drop back and work up at about .2 grains at a time in 3 shot groups looking for accuracy.
I'll let ya'll know how it goes as it progresses.