I4895 vs AA2495 and Burn Rate

R

RC20

New member
First I know powder burn rates are not the same as direct match, but this one has me puzzled.

My understanding is that these two powders are duplicate (or AA duplicate of I4895)

I had one load I got stellar group with the 2495 and then ran out, can't find more, trying to do close to the same with the I4895

The oddity is that both H and I 4895 on the burn charge are listed as faster powder than 2495. Not a big spread with I4895, something like 5 or 6 powders with H4895.

However, the reloading books show 1.5 to 2 more grains needed to get the same velocity as 2495, that would indicate a significantly slower burning powder to me.

So anyone have any enlightenment on that?
 
When AA2495 first came out, I called Accurate Arms. The technical specialist told me that AA2495 was blended to duplicate the pressure curve of IMR 4895. I shot kegs of the stuff earning my Distinguished Rifleman Badge with an M1a, and I cannot tell a difference between the two, over my chronographs, that can not be explained with lot to lot differences. I shot over 27 pounds of AA2495 made in China, and the shot shot well. Accurate Arms changes vendors and I have not looked at the last keg I bought.

H4895 is supposed to be different, it is green, but again, velocity wise, I can't tell a difference. I recommend that reloaders buy by price. These powders are really outstanding in the 223, 308, and 30-06. The port pressures are appropriate for Garands, M1a's, AR15's, my PTR-91, and I assume AR10's.

The powders we use are blended, and Accurate Arms told me the industry standard was 10%. This tolerance band has disguised identical powders sold under different brand names. If you have read the literature for the past 50 years you will see this. For example, Ken Warner wrote an article about reloading for the 45 ACP. He praised to high heaven HP-38, it shot very well especially with light loads. But, he stated in the article, that he had "given up" on W231. He could not get his pistol to shoot W231. Well it turns out W231 is the exact same powder as HP-38, the only differences are lot to lot variances. You have to wonder about the impartiality, accuracy, and reputability of gunwriter tests when they can't get the same powder to shoot straight in the same gun with identical components. For powder charge differences in manuals, manuals are only guides. You have to develop your own loads. I frequently find tremendous differences between the velocities I get and the manual values. This will also be true for powder lot changes, as, the stuff is blended around an average. I assume the 10% tolerance means 10% plus or minus around the average, which would be then, 20% difference.

IMR 4895 was the powder used in the development of the 308 cartridge. Later the Army went to ball powders, but I have not found a good technical reason, and since ball powders are double based and have less than half the shelf life of single based stick powders, I am going to state the most probable reason the Army went ball powder was due to lobbying and post employment opportunities for the Army General who made it policy.
 
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The military bought train loads of powder. Batch to batch wasn't a concern as they went strictly by velocity. One batch may take 52 grs to get to 2700 fps, the next batch maybe 51 grs and so on.
Competition shooters in some disciplines will load up several batches of rounds for a given competition. The difference is half grs up and down from a proven round. This allows them to tailor that days temperature and humidity to the targeted velocity and use the appropriate load. On the other hand, some just look at the forecast and take the appropriate load for that with them, all well and fine unless the weather takes a sudden change.
Of course, in the end it's all how you hold your tongue!
 
AA2495 is made in Canada.

Accurate 2495 is a single-base, extruded rifle powder that was developed for the 308 Win and can be used over a wide range of rifle calibers. It is a very popular powder for 308 Win. NRA High Power shooting disciplines, as well as heavy bullet 223 Rem target applications. 2495 is a versatile powder with excellent ignition characteristics that provides excellent shot-to-shot consistency. Made in Canada.
Click to expand...
http://www.accuratepowder.com/products/rifle/?view=14&product=2495

Ball powders are cheaper to make. Your tax dollars at work.
 
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Slamfire said:
I assume the 10% tolerance means 10% plus or minus around the average, which would be then, 20% difference.
Click to expand...

This is about right for bulk powder. I once went through the list of National Match loads for 30-06 from 1957 through 1966, using QuickLOAD to adjust the powder burn rate to match the loads and velocities reported, and it turned out to be ±7%, or a 14% burn rate spread. Board member Hummer70, who worked at Aberdeen Proving grounds, said he once saw a lot of ball powder that had a burn rate off by 30%, but that otherwise 20% was the worst he'd seen (Mark, if you see this please correct me if my memory has slipped).

My Hodgdon manual says the IMR powder burn rates in canister grade are held to ±5%, but that manual's getting old now. Hodgdon says the ADI powders are blended to ±3%. Keep in mind they upgraded their QC system circa 2000. This was partly in response to complaints about inconsistency in lots of Varget. Western told me they keep all the Accurate and Ramshot powders to ±3%. I believe Alliant aims for that same number, but they're the only ones I haven't spoken to or read a published number from. As time passes and quality control methods improve, this stuff all tends to get better.

QuickLOAD's database is from measuring purchased lots, so it can be off by the amounts of the tolerance band at times, but here's what Herr Broemel measured (Ba is the burning rate coefficient for the start of the burn at the beginning of combustion; burn rate increases as pressure builds):

IMR 4895: Ba=0.5200
Accurate 2495: Ba=0.395
H4895: Ba=0.5571

So this agrees with the chart that say 2495 is slower. It may not have been slower at some previous point in time. Specs change over time and with the place actually making the powder. This is why old load data books are not to be trusted without cross-checking.

The gold color on some of the ADI powders is in lieu of graphite, probably to make it cleaner. I know all the graphite in Bullseye gets into every nook and cranny on my 1911's. It makes the powder seem sooty even if it isn't intrinsically so. But I hear they had complaints about the appearance and have started graphiting some of the Extreme line. It's strictly second hand, because I haven't finished up my old stores of it and had to replace any recently.
 
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