What is the slowest burning powder that is safe for Semi Auto 308 AR rifle?

[Three57]

I have a friend that is considering loading up 150 grain bullets and 4831 for his new DPMS LR308, as he has a few pounds of it laying around.
Is 4831 safe to use in this rifle or will there be port pressure problems?

I can't find information that has the range of safe powder burn rates for an AR 308 platform?

Thanks for all your help

 

[turbo54]

IMR and H4831 are not suitable for an AR10/LR308 in 308win.

It will work in a pinch (like SHTF or something) but we aren't deep enough into a components crisis currently to justify or warrant it.

Tell him he needs something more akin to IMR or H4895.

In my opinion, even Varget or IMR4064 are a little on the slow side for an AR10, though they work ok.

 

[ksthomas]

Three57,

There is no chart (to the best of my knowledge) on this, because it really isn't the problem that it is with the M1/M14 family. The op rods were the weak point in those designs where port pressure was concerned, and they would be damaged by excessively high port pressures . . . but I assume you know this already. The direct impingement system of the AR family isn't subject to the same sort of damage. I would expect to see excessively violent cycling, and possible damage to the BCG over time on a diet of such a slow powder, but not the sudden damage as you'd see in the M1/M14 systems. Turbo is spot on in his recommendations here, and something within this range will be a far better choice. You CANNOT go wrong with 4895 (either flavor) in a 308. Anything else in that general burn rate vicinity should be equally suitable.

 

[Three57]

This is exactly what I was thinking, I had also recommended using a faster powder. I was looking for a good second opinion. Appreciate the help, thank you.

 

[Paladin2147]

I go no slower than Varget with an adjustable gas block. But I think H-4895 is a better choice.

 

[squirrel_slayer]

I used PP2000mr with 168's in my lr308 pattern rifle (bushmaster orc 16"middy) box stock I was seeing noticable smearing on the brass where it was unlocking with alot of pressure still present. after going to a full length buffer tube, spring, and h3 buffer the smearing went away. was pushing a 168 a-max 2600ft/sec out of the 16" barrel.

 

[NoFail]

I go no slower than Varget with an adjustable gas block. But I think H-4895 is a better choice.

In fact I have tested and ocw'd with h4895, Varget, IMR 4064 & CFE 223 in my LR-308, 168 grain Amax's and SMK's. H4895 is probably my top choice because I achieved tightest groups with it. Velocity is superior to Varget and 4064. The CFE 223 is the slower burning of the bunch & I was creaming my brass upon ejection.

But with a 178 AMAX the CFE settled down with the brass destruction. Now I like H4895 for the 168's and CFE for the heavier 175 gr 178 or 180 gr loads. I like the CFE for superior velocity and I achieve low ES/SD #'s with it and the heavies.

The IMR 4064 I also get great results with & I'd have no problem recommending that one either. A 168 SMK's and 43.5 gr IMR 4064 in Win or Hornady brass is a winner in my LR-308.

43.6 gr H4895 and 168 AMAX in the same brass puts smile on my face too