IMR vs H

[Thumbcocker]

I have read many of the posts concering lead in the .223 and it looks like H4895 has worked well for a lot of casters. I have 3 pounds of IMR4895. Burning rate charts put IMR and H at pretty much the same level. Is there a table or method to substitue IMR for H without a kaboom?

Thanks

[pdawg_shooter]

Back off 10% and work up.

[Bass Ackward]

At the pressures you are running, the loads will be very close to the same and well under kaboom levels. If the charge is say 17.5 grains of H, IMR might be 17.7 to get the same pressure.

But with that said, you know to always start low and work up.

[wiljen]

It looks to me like IMR generally starts out about 1gr lower than H 4895 data in the 223.

A quick check shows:

Maximum loads
Bullet IMR H
40gr 26.5 27.5
50gr 26.7 27.5
53gr 26.4 27.0
60gr 25.2 26.0
69gr 24.8 26.0
80gr 23.0 24.0


I wouldn't take this as gospel, but the pattern in the 223 would suggest to start by decreasing H4895 data by 2.5gr and work up.

It should be noted that in all cases IMR was producing higher pressures than H with the listed loads.

[405]

No expert here for sure. Start at minus 10% and work up is always good advice!

I've talked to a reputable source in the powder business about this and he says the same thing when comparing IMR to Hodgdon load data.

He also says that there have been some overlaps and flip flops in burn rates and pressure curves between IMR and Hodgdon of the same number designation.... particularly with some of the older and/or surplus types.

I have seen very little difference between the two but 99.9% of my shooting is far, far below max.... so the critical "too much pressure surprise" is never an issue. Only rarely will I approach max loads even in J bullet, bolt guns... and with cast loads really no need to go there.

[JeffinNZ]

I don't think it will matter soon as both will be coming out of ADI in Australia and will likely be the same.
IMR4227 is history now and H4227 the sole player.
I speculate we will see a lot of duplication disappear now that Hodgdon/IMR/ Winchester powders are all owned by the same company. EG: W748 & H335.

[Thumbcocker]

The load that is reccomended is 18.5 of H4895 with a 55 grn boolit. Since I have 3 pounds of IMR I would prefer to use it.

Thanks

[felix]

If you are talking condoms, that load is way too light. ... felix