December 4th, 2012

“Forgotten” IMR 4320 Powder Yields Great Results

IMR 4320 powderIn his Riflemans Journal Blog, German Salazar has authored an excellent article on IMR 4320 — The Forgotten Powder. German tested IMR 4320 and found that it produced outstanding results both in the .308 Winchester and the 30-06. This means that shooters have another very effective propellant option for their .308 and 30-06 match rifles. With H4895 and Varget being hard to obtain lately, you may want to give IMR 4320 a try.

German writes: “IMR 4320 falls right between 4895 and 4064 on the burn rate scale for most cartridges — in other words, right where Varget falls. Yet, despite having a very useful burn rate, 4320 has languished for decades while newer powders of similar burn rate have gained in popularity. I was interested in seeing what current production IMR 4320 would do in the .308 with the 155gr Palma bullets. My interest was sparked by the obvious fact that Varget and H4895 have been very hard to get lately while IMR 4320 sits on the shelves.”

German loaded up some .308 Win loads with IMR 4320 and moly-coated Sierra 155gr Palma bullets. German’s “practical max” load delivered 2990 fps in his long-barreled Palma rifle. This is certainly competitive speed-wise.

German observed that: “IMR 4320 has very small granules and throws very consistently from the powder measure — it is very much like Reloder 15 in granule size — so for those who prefer to throw charges it’s a good choice.”

Satisfied with the chron results, German loaded more rounds with the two most promising charge weights and used them in a 500-yard prone match at Ben Avery (ambient temps were 60s-80s F). Here is his report:

“As in the chrono tests, all IMR 4320 loads were with moly-coated Sierra 155 Palma bullets, Winchester brass and PMC primers. Powder charges should be reduced at least 1.0 grain for bare bullets. The load with 45.0 grains of IMR 4320 gave me a 199-12X with the single 9 being a high shot just off the 10 ring line at 12:00. Overall, I would rate that load as good, very useable for the intended purpose of 500 or 600 yard shooting (it’s 2844 fps) but no better than my H4895 load for that purpose.

Next I fired the heavier 47.0 grains ‘practical max’ load and that was an eye opener. The score was 200-15X in conditions that were windier than those in which the first load was fired. Elevation was noticeably tighter and shots were exactly on call. This load gives 2990 fps, so it has real potential as a Palma load. While no 500-yard test can ensure results at 1000, given the MV and reasonably low SD of this load as well as the good performance at 500, I won’t hesitate to shoot it at 1000 at the first opportunity. Warning: this was a STRONG LOAD and may not be safe in your gun.

Overall, I’m very satisfied with what I’ve seen in these past few days from IMR 4320 and plan to shoot it in some of our upcoming Palma and 1000-yard matches with the 155s. It appears to be a very useful alternative to some of the harder to get powders.”

IMR 4320 powder

CLICK HERE to Read Complete IMR 4320 Story (includes chron data and match test results).

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