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Old February 9, 2013, 10:09 PM   #1
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H4198 Burn Rate to fast for AR?

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. I was planning on using it behind a 52gr FMJ. Anybody have any luck with this powder?
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Old February 10, 2013, 05:13 AM   #2
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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.
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.
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Old February 10, 2013, 07:23 AM   #3
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It works fine in an AR, especially with 52-55 grain bullets. I went through about 8 pounds of it years ago but ended up settling on H-322 as my AR powder. It was accurate and fairly clean, as I recall. I forgot to say, I was using IMR, not Hodgens.
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Old February 10, 2013, 09:08 AM   #4
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You will just have to try it in Your rifle. Some have no issues with it cycling the action while many do. Do not go above Max charge if it does not cycle.
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Old February 12, 2013, 01:57 PM   #5
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I am debating the use of H4198 for my AR15 also. I tried 20.5 gr of H4198 with the Hornady 50 g ZMax. It did not cycle enough the strip the next round from the magazine. I next tried 21 gr of H4198. It cycled enough to strip the cartridges from the magazine, but failed to lock the bolt back after the last round in the magazine.
I may relegate this powder to my 30-30 rounds and stick to IMR 4895 for the AR15. I have IMR 3031 but haven't tried that with the AR15 yet.
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Old February 12, 2013, 10:15 PM   #6
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CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

IMR4198 is one of the powders Stoner used in developing loads for the AR. I'm sure he would have worked up to more like the NATO pressures, though. I think you'll find yourself landing about a grain higher, if you want to do that.
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Old February 13, 2013, 09:03 AM   #7
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AR and H4198

You wont know till you try it. The gas port pressure curve is a critical part of internal ballistics for cartridges used in gas operated firearms. Gas operated weapons are generally tailored to a narrow range of powder burning rates and characteristics. If the port pressure is too low the weapon will fail to function and if to high the weapon may function too forcefully or rapidly causing extraction or cycling problems. When using the fast H4198, the pressure peaks very fast and is done producing pressure sooner than your slow powders. With such a wide range of bullet weights from 40gr to 80gr, matching the gas port location and size is critical. If the gas port was moved closer to the chamber and drilled larger, H4198 may work. 40 gr Bullet.
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