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Originally Posted by t45
I bought some H4198 today with plans to use it for my AR. It appears after doing some research that this powder has a burn rate a little fast for the AR gas system.
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Avoiding the sustained pressure versus burn rate arguments, I would say that you are discovering an uncomfortable reality.
in Richard Lee's "Modern Reloading"- 2nd Edition Both H4198 and IMR4198 are shown as a burn rate of 55. My experience is with IMR 4198 rather than H4198.
While their burn rates are in the same ballpark, I would treat them as different powders as far as load testing goes. Also my experience is with M-16 rather than AR-15. Again very similar but not the same.
I could not find a safe load (using 223 Rem SAAMI standards rather than the higher pressure EPVAT NATO test standards) that would cycle the action. To avoid talking about many other powders, I will focus in on IMR 4895. Every load level tested (I think I was using Lyman 46th Edition) from start to max listed would properly cycle the action (full auto M-16A1). This meant that the full Lyman load range was available for accuracy testing. The top load listed and about 2 or three tenths below top load inclusive showed slightly flattened primers, no other pressure signs. (Consistent across multiple guns)
I did not test H4895 but I suspect it will be very close to the satisfactory performance of IMR 4895. Just use H4895 load data if you go that route. They are similar but different. Work up the loads from data for THAT SPECIFIC powder.
The testing involved several bullets in the 50-55 grain weight range. The one closest to your choice would have been the Matchking 52 grain Sierra HPBT.