Loading the .30 Remington AR Pt. 2
Date: Oct 01 2010
I continue to be impressed with the .30 Remington AR out of the Remington R15 rifle. The cartridge is extremely easy to load for, and it seems to like just about anything you put in it. Since the last column, I’ve been experimenting with four new powders, and they all show promise.
One of the problems with both Ramshot Xterminator and Reloder 7 was excessive case head swipe when velocities neared maximum. Case head swipe is where the head of the case is scraped by the plunger-style ejector during the rotation of the bolt face while the case is being extracted from the chamber. This essentially means the bolt is starting to unlock before the case has let go of the inside of the chamber. It’s similar to an ejector mark on the back of a case fired in a bolt gun, but because of the mechanics of the AR, a bit more disconcerting.
With Reloder 7 and Xterminator I was getting too much pressure at the velocities I was generating with these loads. Gas from the gas tube was unlocking the bolt too soon. Hodgdon’s load data – the only currently available data for the .30 Remington AR, lists these powders: H-4198, IMR-4198, H-335, H-322, Benchmark and IMR-8208 XBR. This is a fairly narrow burn rate band of powders when compared to a cartridge like the .257 Roberts, which will work with everything as fast as H-4895 to as slow as Ramshot Magnum.
I selected H-322, Benchmark, IMR-8208 XBR and Alliant’s Reloader 10X and worked up loads with 110-, 125- and 150-grain bullets. As far as powder trends seen in this experiment, the most notable was velocity variation. IMR-8208 XBR was the slowest powder tested.
My rifle seemed less fond of IMR-8208 XBR than it did the other powders. Bill Wilson at Wilson Combat has been experimenting with the .30 AR a great deal, and he said he finally settled on Benchmark and a 150-grain Nosler AccuBond as his hog hunting load. But, he added it was a toss-up between IMR-8208 XBR and Benchmark. Now, keep in mind, Bill is using an SBR (Short Barreled Rifle – a rifle with a less-than-16-inch barrel – and a suppressor).
For me and my 22-inch barreled Remington R15, Benchmark produced very good accuracy with the 110- and 125-grain bullets. IMR- 8208 XBR produced better accuracy with the 150-grain bullet, but velocities were a bit slower than those with the faster powders. Also, with IMR-8208 XBR case capacity becomes an issue. The 40.2-grain load with the 110-grain Barnes bullet completely filled the case and the 40.0-grain load with the 125-grain Ballistic Tip was even more compressed because of the length of this bullet. The Barnes bullet has a cannelure for crimping, so this might circumvent bullet set out. I would be cautious compacting powder charges this much without a good crimp.