View Full Version : boolit stabilization
11-29-2010, 10:42 AM
Receintly I started to cast Lyman 311284 boolit for my rifle. I cast pure lead 220 gr. boolit with water quenched base and GC(I haven't got hardness tester). The bore is .311 and has 1/9.45 twist. The cartridge 7.62X39 has COL 2.20. The speed was perfect - 930-950 fps .
I started my shooting session with 10 cartridges. Than came the shock! I coldn't hit the target from 50 yards.The accuracy was terrible. The boolit can't be stabilized.
Were am I wrong? The hardness? The COL or the twist ?
I'd like hear your comments!
11-29-2010, 11:47 AM
What is the cast diameter?,,,from what I have read, Midway list that as a .309 dia. mold, but not sure that's accurate. Is the boolit undersize??? I'm not sure water quenching does anything to pure lead,,thinking not.
I ran a ballistic program, it should be stabilized,,,,I did question where you were getting the rpm's needed under a 1000 fps. But your stability factor is over 2, so that should be good to go.
11-29-2010, 12:03 PM
water quenching pure just cools it off faster.
the 311 should pour close to 311 but with lyman number2 alloy, with pure lead it could be anything
heck with number2 it could be anything.
a chrome lined shallow grooved bbl too soft lead and a nose that don't fit ='s disaster.
11-29-2010, 01:06 PM
One of my pet loads is a 200 gn Lee boolit going along at 1000 fps fired from my single shot 7.62x39 bolt gun . The barrel I fitted has a 1 in 13 twist and I was surprised at the accuracy achieved ; 1.5 to 2 MOA with pure lead boolits and a touch smaller with wheel weights .
I would suggest you look at factors other than the twist rate of your barrel to sort out your problem . Boolit fit , powder choice , seating depth etc .
11-29-2010, 05:19 PM
I've shot that bullet cast very soft out of several similar twist rifles down to 300 fps with very good accuracy. Thus I do not think it is the twist or the hardness. However, at a COL of 2.2" you are putting an aweful lot of that bullet down in the boiler room of that 7.62x39 case.
"I coldn't hit the target from 50 yards.The accuracy was terrible. The boolit can't be stabilized."
Also at just 950 fps they are going to hit a lot low, very low compared to a standard 7.62x39 load, so were you just not on target or were the bullets keyholing? Or is the "terrible accuracy" just because you were not hitting the target? Would be nice to have some more specifics about the rifle used, the sights and zero and the specifics of the load. Hard to answer without enough knowledge.
11-30-2010, 11:25 AM
Thank you guys for the reply!
The problem was with the boolits' keyholings which were around the target - 20' left,rigth, up and down. Only one hit the target stabilized straight at 11 o'clock. In the same time shooting with the same speed of a boolit and the same rifle with cast Lee C 312-180-1R hit the target with very good accuracy and stabilized. This weekend I'll play with the COL with Lyman 311284.
12-06-2010, 03:30 AM
This weekend I increase the COL and the success came in COL 2.29' The boolit's keyholing were circles and accuracy was acceptible - 5 shots 50 yards - 2'
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