Are they interchangeable?

purt much.

I have found no diff. in my .222 & 223..

NO! They are quite different. It depends on the application you use them for.

Yep, check out the data on Hodgdon's site. It's also interesting to try them at different temperatures. IMR4198 ain't bad, but....

They are both made by Thales in Australia. The IMR version is AKA AR2215,IIRC. Hodgdon won't tell you ANYTHING about their powders, and the MSDS is very old.
So they could be the same, but differ on allowable variations; or could be different.

I have an old can of imr 4198 that I want use in my 30-30 with Barnes 150 grain bullets. Their load data uses H4198. That is why the question. Thanks

Really don't know much about either, my usage jumps from H-110 to Benchmark. So I had to look it up.
Very surprised to see how close the 4198s are in a burn-rate chart:

Burn-Rate-Chart

Adding the moot point burn-rate charts are NOT a powder substitute chart. Just interesting.

Having used both, to include the 30/30.. they are pretty interchangeable in the real world...don't load IMR's to max if you are shooting in very hot weather... but Hodgdon's is pretty much temp insensitive....

I used to use a lot of 4831 when I had a 270. The load charts, in general, showed IMR to be just slightly faster than H for the same powder charge. The difference was negligible in the real world.

I've used H and IMR 4198 in .223 and .45-70, with IMR being slightly faster in both cases.

They don't look the same, they don't smell the same (IMR is coarser, blacker, more solvent smell, while H is finer, shorter, almost greenish)…..they are quite different. They seem to burn to produce similar pressures and speeds in smaller bottle-necks like 222 or 30-30, but compare them in bigger straight-walls and the differences become more significant.

As far as burn rate charts are concerned, the Winchester chart cited above has

# 61 - Lil' Gun
62 - H110
63 - W296
70 - Rl 7
71 - IMR 4198
72 - H 4198

Lyman 49th Edition shows:

# 49 - H110
50 - W296
58 - Lil' Gun (an error/misprint perhaps?)
59 - IMR 4198
60 - H 4198
63 - Rl 7

Burn rate charts can be……………….interesting!

Klik, the latest batch of H4198 I bought was black, but still finer-cut than IMR.

It also seems to have retained the burn rate of it's green cousin.

H 4198 is AR 2205.
John

H4198 is AR 2207, at least according to Hodgdon's MSDS info; AR 2205 is H 4227.

And Hodgdon's MSDS info credits IMR 4198 manufacture to General Dynamics in Canada.

I have seen IMR4198, yes IMR, labeled from Australia.

Yeah, I have too, now and then, but the batch I bought recently is labeled Canada.

Yep. You are correct.
John