Don't reinvent the wheel--- > cast bullets in 308/ m1a m305, m14
Check out
ht tp://castboolits.gunloads.com/showthread.php?t=3558
the originator of that thread has several Thousand cast bullets down the barrel of his m1a and shoots them at long range too with full function
Several pages of information are on the castboolits site
Note the twist on his rifle is 1:11 so you will not get his exact same performance with a 1:10 twist (velocity/groupsize/pressure/function)
For your information I shoot cast in a norinco
the worst thing you can do in a semi is
1)if the nose is too long/big and touches before the bolt is closed
(slamfire/open bolt fire)
2)use the wrong powder
3)use too much of the correct powder (leading inaccuracy)
Hints Facts on cast bullets that one of my friends has given me and has taken more time than any other rifle I have loaded for
4)
1/10"
With this twist using 150 gr cast you will have trouble maintaining accuracy at an acceptable level (upwards of 1950 fps) while maintaining 100% functional reliability. Reason being by the time there is sufficient gas port pressure for functional reliability the fps will be above 2000 fps.
Functional reliability can be had with medium burning powders and very good accuracy with the 170 - 200 gr bullets in the 1800 - 1950 fps range. Given a well fitting bullet of appropriate alloy and design the RPM threshold is going to be in the 1900 - 2000 fps range with this 10" twist. Accuracy will begin to deteriorate once the bullet crosses it's RPM threshold.
Slow burning powders can be used with the 200 gr bullets but ignition consistency can be a problem if velocities are to be kept under 1950 fps (about where the RPM threshold will be with a 10" twist, a good load and good cast bullets).
1/12" twist;
The RPM threshold for this twist will allow (given appropriate bullet fit, alloy and powder) very good accuracy upwards of 2200+ fps, sometimes 2300 - 2400 fps if all is right on. Thus functional reliability can be had with medium burning powders with all of the bullets mentioned including the 150s. However, the slower "medium" burning powders up through RL19 or AA4350 will probably give better accuracy above 1900 fps than say, 4895 or 3031. I find the RCBS 168 gr silhouette bullet or Lyman's 311299 to be very good bullets for higher end 7.62 loads in milspec chambered M1As with 12" twists.
I do every thing you should not do
I shoot cast
I neck size (with the odd full length/aneal thrown in) 10-20 loading on the same set of 50 brass
During the summer I shot 400 cast rounds with out cleaning and it was still clean