Monolithic bullet in an AR-10?

[Ffjmoore]

I'm in California...I know it's embarrassing...So I have to shoot lead free. I want to be able to hunt pig with my ar10 so I'm developing a load using blc2 powder and barnes 130 ttsx for .308. Here's the data.

I started from min. and was working my way up using the recommended COAL of 2.735 at about 2 grains shy of max my length started to grow. I'm assuming because I was at the point where I am compressing the load. So I stopped there.
Now my question is, should I use the magazine length, 2.800, for my max coal instead of what's recommended? That would get me more room and I would have more powder before it became compressed. Anybody see a negative to that?

 

[zeroz]

The barnes bullets like to jump. I'd measure your BTO to the lands, and start with a .050 jump and go from there.

 

[TheOfficeT-Rex]

Make sure you have enough bearing surface left at your extended overall length. The way Barnes band's the bullets means you don't get much surface area in the neck when you start loading them out longer.

I used them in 6,5 and 8mm but found I got better performance (speed and accuracy) from PVA solids. Waiting to try some lapua naturalis for the 8mm this spring.

 

[Ffjmoore]

The barnes bullets like to jump. I'd measure your BTO to the lands, and start with a .050 jump and go from there.

It's an ar-10 there is no chance of getting close to the lands and still fitting in a magazine. I did measure the distance to the lands to confirm that.

 

[zeroz]

Thats fine, they like to jump. Ive jumped the shit out of them and they do fine.

 

[Ffjmoore]

What I found crazy was how much a difference the length made. I put a new scope on and zeroed it yesterday so any scope movement should be ruled out. I fired a few rounds before I did the reloads so the barrel temp was normal. Point of aim was the same for both groups. The second group i dialed the scope down to get it closer to the POA. So the first 8 shots were the top group and the second 6 were the bottom group.


Here are the velocities for each load. I was just testing for pressure signs so only 1 shot per load.

And here are the shots as fired from lowest first.


Im going to stick with the longer COAL and do some 3 shot groups of the fastest 3 and maybe go .5 grains farther.

I did find it interesting that the second group POI was coming down as velocity went up.
I dont know what to make of it all, maybe you do, but i found it to be an interesting day.

Faxon 18" 308 1:10 barrel