August 30, 2009, 02:58 PM | #1 |
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Need help on IMR-4895
I've recently acquired a 30-06 built on a WWII Mauser bring-back action. Initial shooting, I kept 3 rounds of factory Remington 180gr rounds in 1.94" ctc at 100 yards, with an approximately 60 year old 4x scope.
Two weeks later, yesterday, I loaded up 5 groups of five rounds each. IMR-4895 powder that was at least 25 years old (but still in perfect condition). 46.4 to 48.4 grains, in .5 grain increments. I'm no marksman, so I'll just give the best 3 shot groupings out of each 5 (the 5-shot groups were still deer-kill-zone sized): 46.4 - 1.950" ctc 46.9 - 0.966" ctc (all 5 was 2.825" ctc) 47.4 - 1.400" ctc 47.9 - 1.555" ctc 48.4 - 0.862" ctc (all 5 was 1.671" ctc) The last three sets were all fired back to back, starting with the 48.4 group. No cool-down time between, as I was running out of light. __________________________ All that to get to these, my questions: My 1971 Sierra manual has flat base loads ranging from 44.4 grains (2600 fps) to 50.4 (2900 fps). Hodgdon has a starting load at 49.0 grains with a max load of 53.0 grains for a 150 gr Nosler boat-tail bullet. I'm using 150 grain Hornady flat-base bullets. Spire points on both. I know that when not using the exact same components as the recipes, start low and work up. However, it seems odd that Hodgdon would have a starting load for a longer bullet (BT vs FB and thus seated deeper) that is at almost the max load in the Sierra book. Has the formulation for IMR-4895 changed that much since my powder was new? If not - I'm confused. I can see them dropping upper limit recommendations due to lawyers et al, but not raising them. Or am I missing something else? Last edited by cpaspr; August 31, 2009 at 09:59 AM. Reason: specified weight on bullets I'm reloading |
August 30, 2009, 03:06 PM | #2 |
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Check the case brands and the bullet seating depths. Both affect pressure. The volume the case expands to in your particular chamber also changes the peak pressure (bigger being lower). Hodgdon uses Winchester cases. These tend to have the most capacity and produce the lowest pressures, therefore allowing for the most powder to reach a given pressure.
Your last load looks best, of course. I would increment up a couple more steps of 0.3 grains to see if it is your rifle's best accuracy load or not? Keep in mind that as helpful as load development is, if you have a rifle that has not been bedded to float the barrel, has not had its bolt lugs lapped for even bearing contact, has not had the muzzle recrowned, or its barrel lapped, or has a stiff trigger with a lot of over-travel, you may have enough other sources of error that the gun can't show the potential of the loads well.
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August 30, 2009, 04:17 PM | #3 |
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Join Date: April 20, 2009
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My 25 year old H4895 is slower than IMR. 53gr wasn't accurate, but 52gr was. I've gotten better performance and accuracy with 52gr of 4064 with 150 Sierra and Hornady.
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