Cast .308 fun

[44Blam]

Well, I cast some nice hard boolits and finally got to shoot them today.

My results are interesting. I was shooting out of an AR10 style 308 with a 1:10 twist. It has a 20" barrel that slugs at .308.

I made 50 boolits: 25 sized to .311 and 25 sized to .309. These boolits are 174 grain cast from 3:2 ww:linotype and they are very hard. I gas checked and powder coated them.

I had feeding / cycling issues with the .311 boolits even after testing for function. I shot a couple with good accuracy but decided they were giving me too much problem and were a little too fat/seated wrong/etc.

So, I shot the ones sized to .309.

I found good accuracy and a good spread around 2300 fps. The spread for that load was: 2321,2369,2324,2353,2322 So, three shots in the 2320 fps range. For the 5 shots, my group was all within 1" with one I pulled that was about 2" away from the group.

Interestingly, 1 grain lower in powder gave me horrible accuracy and wild spreads in velocity: 2201,2277,2301,2267,2292 A couple boolits were close together, but one was 5" to the right and I don't know where one went.

Also, 1 grain up gave me a nice spread, but not as good accuracy. The spread was: Err, 2419,2417,2360,2432 They were all within 2", but a bit spread out.

I ran a scope up the bore and I found flakes of powder coat in the bore but no leading. After cleaning, I had a nice shiny bore with no lead. I also had no lead at the muzzle break. I did not have any signs of high pressure on any cases either.

I think I'm going to try to just lube the boolits instead of powder coating and see if I can size a little bigger, get them a little faster and get a little better accuracy.

[Rcmaveric]

Yeah powders can be wonky. They tend to like a certain amount of pressure to burn consistently. Thats why we use faster powders for cast bullets and our smaller charges. I noticed that the slower the powder the more inconsistent it likes to burn at lower charges. When you get into heavier bullets that random shot thats 100 fps fast or slower get told on by the chrono why it was flyer outside the group. You can try a faster powder but the slower ones have the pressure curves you need to cycle the action. There is a lot that has to be in harmony for gas guns to function.

Speaking of harmony, you got to have the right pressure curve for the action, right harmonic node for the barrel and the rights rpms for the bullet. I would be ecstatic for that kind of velocity and accuracy.

You found the sweet spot load for that powder and gun though. I would mark it as a keeper. Give it a consistency check with 25 rounds. If it passes the consistancy test you got that guns load. With 2300fps thats a good hunting load and longer range target work.

Compare your greaed bullet groups to your PC groups before you decide which to use. It always seams that my greased bullet groups are better.

Sent from my SM-G950U using Tapatalk

[popper]

I run my 165s @ 310 and get 2400 fps from 16" carbine, H4895. MOA @ 200. HF PC. You could probably drop back a bit on the lino & heat treat. Never found any PC flakes in any of my barrels but don't use a brake.

[44Blam]

I run my 165s @ 310 and get 2400 fps from 16" carbine, H4895. MOA @ 200. HF PC. You could probably drop back a bit on the lino & heat treat. Never found any PC flakes in any of my barrels but don't use a brake.

I probably should horde the lino... I just watch ebay for lino at $1/lb and I win a little too much... I think I've got 120 +/- lbs at this point...

[Forrest r]

FWIW:
I wasn't sure about what alloy to use with high pressure/hv rifle loads. So I tested 3 to 1 ratio of 3 parts range scrap (I make range scrap in 100# batches/stays pretty consistent batch to batch) and 1 part mono-type & used that as a base line. Tested a 4 to 1 ratio range scrap/mono-type and found no difference. Any lower on the the mono-type and things went south when I got into the 2500fps+ range.