H4895 to IMR4895

[kestak]

Greetings,

I need to know if I can switch the data from H4895 to IMR4895 to reload 7.7x58 Japanese.

Thank you

[Slamfire]

In my testing of H4895 in 308, if there is a real difference over the chronograph between the two, I did not see it.

There is not a big difference visually, other than H4895 is green.

Hogdon told me that H4895 was one of their extreme powders, so the chemistry is different. But I don't know if the pressure curve is all that different.





If you are loading maximum loads, then any change, lot to lot, case, primer, primer lot, will make a difference. But if you are loading mid range loads?, I doubt a change from H4895 from IMR4895 is going to make any difference.

I know loading manuals show different pressures, but then, you saw the same differences for H110/W296 and HP39/W231. But now we know these were the same powders. So the differences you see in loading manuals between similiar, if not identical powders, may be just the difference between lots.

[totaldla]

Standard common sense statement follows: Since you are changing powders, you need to back off a bit and work your way back to your pet load.

H4895 is much, much less temp sensitive than IMR, which is the main reason I like it. IMR powders tend to go boom in the morning cold and BOOM in the afternoon heat.

[steve4102]

To put it simply, they are not the same. They are similar in name only. If IMR called their powder IMR 4985 would you consider them the same? Probably not.

[Unclenick]

If I'm not mistaken, IMR does call their powder IMR 4895.

Yes, they are different. The temperature response difference alone means there is a good chance they will cross paths (produce the same peak pressure in a cold barrel) at some one ambient temperature, but no other. Same peak pressure, by the way, does not automatically mean same velocity, as that also requires same burn rate and same energy content per grain of powder weight, as well. Neither will match exactly, so velocity is not a suitable pressure indicator when swapping between the two.

I think it was Denton Bramwell who commented that once the barrel heats up, pressure rise in rounds often has more to do with the warm chamber passing heat through the brass case head to the primer than to the temperature of the powder (which takes longer to rise, as it is somewhat self-insulating (my explanation, not his)). This means, if the gun is hot, don't let rounds cook in the hot chamber before firing. Fire promptly after chambering a warm tube.

[steve4102]

If I'm not mistaken, IMR does call their powder IMR 4895.

Right, my post.

IMR 4985

[TXGunNut]

Had the same question with IMR4350 and H4350 awhile back while looking for a new 30-06 load. Optimal powder charges came out about the same but the results were different. Same with Varget and IMR4064, similar but different. Unfortunately this rifle never shot well enough to take advantage of any one good powder, maybe next time.

[Sport45]

They are close, but I wouldn't switch data between the two. Why don't you email Hodgdon and ask if they have load data for the powder and bullet weight you have?

[mehavey]

IMR is the (slightly) more energetic of the two powders

EX: for 25gr "4895" powder pushing a 52gr SMK out of a 223Rem case....

IMR has:
1.6% more energy/grain
6.4% higher pressure
2.4% higher velocity

[ronl]

I have a pound of H4895 that is really "hot". It is much hotter than the IMR 4895. Saw pressure signs that were not there with the same amount of the IMR. Perhaps that was just one lot of it.

[kestak]

Greetings,

Thank you all for your answers. I checked the different data for different calibers and always H4895 had a little bit less grains than IMR4895. When I aksed the question, I was in the impression the charges were closer.

I'll write to Hodgdon and ask if they have a load with IMR4895 for the Arisaka 7.7

Thank you

[Sport45]

Another resource for reloading data is Steve's Pages. I don't know where he gets his data and I don't trust it implicitly, but it is a good reference for checking loads. Anyway, he does show IMR-4895 data in the 7.7x58.

[emcon5]

Another resource for reloading data is Steve's Pages. I don't know where he gets his data and I don't trust it implicitly, but it is a good reference for checking loads. Anyway, he does show IMR-4895 data in the 7.7x58.

A quick check, his numbers match the published numbers in my Sierra 50th Anniversary Edition loading manual.

[Unclenick]

I think all of Hodgdon's data is online, and does not include IMR4895.

QuickLOAD thinks you need 2.5% more IMR4895 by weight than H4895 to match velocities in a 26" tube with either the 150 or 180 grain Sierra SP's, and 3.4% more IMR4895 to reach the same peak pressure (but giving a little more velocity; this happens because IMR4895 is about 6% slower burning according to the QL database). The low velocities achieved by Hodgdon suggest the gun they used was pretty loose. They have no pressure data, so it wasn't a test barrel.

[Slamfire]

QuickLOAD thinks you need 2.5% more IMR4895 by weight than H4895 to match velocities in a 26" tube with either the 150 or 180 grain Sierra SP's, and 3.4% more IMR4895 to reach the same peak pressure (but giving a little more velocity; this happens because IMR4895 is about 6% slower burning according to the QL database). The low velocities achieved by Hodgdon suggest the gun they used was pretty loose. They have no pressure data, so it wasn't a test barrel.

Such small numbers are well within the manufacturing technology of powders. Then the different lots are blended.

Accurate Arms told me they blend powders to 5%, (pressure curve I think), and that was half of industry standards.

I really don't know if there is a big difference between H4895 and IMR 4895 that cannot be explained by lot to lot differences.

Other than the green color. That is different.

[mehavey]

xx

[TXGunNut]

Interesting, Unclenick. Wonder why they didn't list the IMR powders for this cartridge? Could be old info from before they acquired IMR and they haven't taken the time to test the IMR offerings.

[Blue Grass]

If you're using IMR powder, use IMR data. If you're using H powder, usr H data. Some powders are interchangable. Most aren't.

[TXGunNut]

I figure if Hodgdon and IMR powders were the same Hodgon would have quit making the "duplicate" IMR powders by now.

[Jim Watson]

Hodgdon doesn't make anything (except Pyrodex and 777 fake black.)
They are the US distributors for IMR powders made in Canada at a plant owned by General Dynamics. The H- branded powders are mostly made in Australia. The "Spherical" powders are made in St Marks, Fla. in a plant owned by General Dynamics, same place the Winchester Ball powders are made... which are also distributed by Hogdon.

They HAVE simplifed the dual lineup down at the 4227 and 4198 range.

[TXGunNut]

I stand corrected, Jim. Thanks. I make my living in the automotive business and know the name on the package has little to do with the manufacturer.
For clarification, they wouldn't bother marketing two identical powders when one would fill the need.

[Jim Watson]

I have since looked up some loads. There will be as much as 3 grains difference in charges of IMR 4895 and H 4895 for the same gun. A conventional 10% reduction to a starting load would probably take care of it but they are not the same.

The H is a newer formulation from ADI supposedly less temperature sensitive. But there are so many established loads with IMR that it really pays them to keep selling it.

[Unclenick]

Temperature sensitivity doesn't turn out to be all it's cracked up to be. This article is interesting.

Originally Posted by Slamfire

Such small numbers are well within the manufacturing technology of powders. Then the different lots are blended.

Accurate Arms told me they blend powders to 5%, (pressure curve I think), and that was half of industry standards.

Actually, its burning rate they blend to, so you can see why the order of powders on different burning rate charts aren't always the same. It depends what lots were measured for the chart. A lot of spherical propellants can vary 10%. I believe a Hodgdon tech said their stick powder lots are blended within 3% of standard (meaning the Extreme line of powders). Performance in the gun, however, doesn't depend just on burning rate. Indeed, burning rate changes with pressure and can change order among powders at pressures different from the one at which burn rate was measured in the caloric bomb. So it's messy. Knocking down 10% and working up is about the only option if you don't have a Pressure Trace to get a matching pressure reading with.


TXGunNut,

When Hodgdon acquired IMR and took over marketing for Winchester powders, it looks to me like they incorporated a lot of the load data already developed by those two brands into their data. Apparently IMR never developed any data for 7.7×58, so it doesn't appear in the Hodgdon load data, either. Even the Hodgdon data listed has no corresponding pressure listing, so I don't think they own a pressure test barrel for it. If they no longer have the rifle they used to work up the original Hodgdon data, they may never work up any IMR data for it.

[brickeyee]

H4895 and IMR4895 started life as different batches of the same bulk powder.

Hodgdon got its start selling surplus powder, very likely produced for the military by Dupont.

Canister grade powders have tighter specs, so to keep things the same H4895 and IMR4895 standardized.

Since the original lots the came from are different, the canister grade ends up different.

[TXGunNut]

Thanks, Unclenick. Now I'm wondering how many loads on the Hodgdon site were carried over and how many are the results of recent testing. Is it possible the IMR loads on a given chart were tested using different equipment from the H or WW loads? It's a great site but it seems to me when they say "max" they really mean it. Not a place for folks who start @ the top and work down. Powder is one of the more fascinating aspects of our hobby.