For a few fellow forum members that MAY use IMR 4198 for some of their varmint cartridges, particularly the 222s and 223s, I was reading in the Hodgdon Annual Manual, under its description that it has added something to make it temp insensitive!

For those of us that might shoot it in cold temps or real hot temps in the summer.. I thought it was important enough to know, that it should be passed on...

I haven't seen anything anywhere else about it now being temp insensitive.....Hodgdon Has touted H 4198 being temp insensitive, among others for quite a while... but like others I have preferred the IMR version....

Didn't see that accolade given to any of the other old IMR standbys, like 4895, 4064, 3031, 4320, 4350 4831....

Im using the 'old' version of IMR 4198 in the deuce and have heated them up pretty well. No problemo...

I have used both.. and I have seen little difference from cold to hot weather.. BUT I don't use my .222 or .223 much during the winter.. They are mostly turkey, gopher and p. dog guns..

My concern isn't during winter time...

its when you are out shooting varmints non stop and its 95 to 105 degrees outside... a scenario that is why I don't use H 335....

It's fine for any climate on this planet!

I've seen made in Australia on IMR4198 containers, just like H4198, unlike other old IMR standbys.

I have had no issues with the "old" imr 4198 from 20 degrees to 80/90 degree summer days.... The stuff just works good threw the .223, it was my 'go to' powder for the .223 for quite awhile.

Also use it in the 45-70 with 350 gr. Hornadys. No isues there neither, things just tip over hot or cold.

That's been listed that way in the annual manual for quite a few years now.

I've always suspected that it was a "cut and paste" typo (swapping the Extreme version description for the IMR).

No, not a typo. Hodgdon is converting some of the IMR powders to the Australian-made Extreme versions. The latest IMR4895, for instance, is made in Australia rather than in the Canadian IMR factory Hodgdon acquired a few years ago.

That said, while the traditional IMR powders are less temperature-resistant than the Extremes, they're still single-based extruded powders, which normally don't gain as much pressure in heat as traditional ball powders, or some other double-based powders.

My present supplies of IMR4227 and IMR4895 are made in Canada, and I don't plan on replacing them with the Aussie versions until they're gone....

Is it safe to assume that an IMR powder produced in Australia is indeed "extreme" in its temperature resistance?

I wouldn't go that far, but so far all the recent IMR powders made in Australia have been listed as temp-resistant.

Yep, they've said that since at least ...2010? 2008-2009? It's been long enough that I no longer recall which year it was that I first noted it.



HUH?? You mean the General Dynamics facility where most IMR powders are manufactured for Hodgy? Or are you saying that Hodgy has recently bought that facility from General Dynamics?

He got the Cart before the horse there.

Hodgdon has ALWAYS been a reseller/blender.
The Canadian formerly IMR plant, is owned and operated by General Dynamics, not Hodgy.

Although I wouldn't put it past Hodgdon to claim otherwise.
http://www.hodgdon.com/new_prod.html
That powder (SMP 842) was developed for the military by GD near 15 years ago. However the "technology" to combat copper fouling; was developed by the French around 1900...

Given the Radford change, and GD keeping things moving; they aren't getting out of powder production anytime soon.