IMR4350 vs H4350

montana09 · April 2, 2020, 08:26 PM

What's the difference between IMR 4350 and H4350? Is the load data interchangeable or should they be treated as separate powders?

TX Nimrod · April 2, 2020, 09:00 PM

They are not directly interchangeable. Hodgdon lists slightly different data for each powder, so use data specifically for each one. That said, the differences are generally only 1-3 grains between the two.

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ligonierbill · April 2, 2020, 09:05 PM

Pretty close, but if I switched from one to the other, I would redo the load workup. If you have a good load for one, run out of powder and can only find the other, your workup should come out fairly close. But interchange them directly? I would not.

jmr40 · April 2, 2020, 10:20 PM

I've used both and will get virtually the same velocity and accuracy with slightly different powder charges. The data isn't interchangeable, but close.

A max load of IMR4350 is one grain more than a max load of H4350 with 165 gr bullets in a 30-06 according to my manuals. It could be slightly different in another manual. They show H4350 with a 4 fps advantage, which is nothing.

I prefer H4350 because it is more stable under a wider range of temperatures. And that is the only reason. Most powder, including IMR 4350 will see 2-3 fps velocity change for each degree temperature changes. H4350 is closer to 1/2 fps for each degree temperature changes.

If you develop a load at 70 degrees and fire it at 20 degrees IMR4350 could be 100-150 fps slower. H4350 would only be about 25 fps slower. That is the only real difference.

old roper · April 2, 2020, 10:35 PM

H4350 is one of Hodgdon's Extreme series. I would treat it as different powder.

I switched over to H-4350 in all rifles I was using IMR-4350. I think maybe older H-4350 before change they where pretty close.

Rimfire5 · April 3, 2020, 10:10 AM

+ 1 Old Roper

H4350 velocity changes about 12 - 15 fps over the range of 0 to 125 degrees F.
IMR4350 velocity changes about 155 fps over the same range of temperatures.

On a normal summer's day at our range, temperature in the shade changes on the order of 20 - 30 degrees from 8 AM to mid-day.
That equates to a max of 3.6 fps increase for H4350 or 37.2 fps for IMR4350.

Some of the extreme powders perform even better than that.

montana09 · April 3, 2020, 01:16 PM

The main reason I'm asking is I'm reloading and having a hard time finding data for .270 Winchester with H4350 and 140gn Nosler BT. Noslers website lists data for IMR 4350 but not H4350

ligonierbill · April 3, 2020, 04:03 PM

Yeah, Nosler 8 lists only IMR-4350 for their 140s. Oddly, the next page of 150 loads lists H4350, but not IMR.

Anyway, I checked Quickload. Setting the case volume on QL to match the velocity Nosler got with their 140 gr IMR-4350 max load (52.5 gr./2,858 fps), I changed the powder to H4350, same charge weight. QL projects 350 psi pressure decrease and 6 fps velocity decrease, essentially the same. As always, work up slowly.

Also, compare this to Nosler's 150 gr H4350 max load of 52.0 gr. Pretty close. Have fun.

montana09 · April 3, 2020, 04:40 PM

Thanks! I loaded 10 rds with 50.5 gr H4350 and am going to give that a whirl to start out with, they're going in a Ruger M77 MKII.

ReloadKy · April 4, 2020, 06:52 AM

I am glad you started this thread. My 270 likes IMR4350 a lot. However, I am out of it and I doubt I am able to get some anytime soon. I do have over a pound of H4350 that I need to see how the rifle likes.

April 2, 2020, 08:26 PM	#1
montana09 Member Join Date: April 30, 2018 Posts: 55	IMR4350 vs H4350 What's the difference between IMR 4350 and H4350? Is the load data interchangeable or should they be treated as separate powders?

April 2, 2020, 09:00 PM	#2
TX Nimrod Senior Member Join Date: November 27, 2009 Location: Zona Posts: 432	They are not directly interchangeable. Hodgdon lists slightly different data for each powder, so use data specifically for each one. That said, the differences are generally only 1-3 grains between the two. . __________________ .22LR - .223 - .22-250 - .243 - 6mm REM - .25-20 - .25-35 - .25 BB - .250/3000 - .257 WBY - .260 - .30 M1 - .300 BO - .30 Herrett - .300 Savage - .32 H&R - .303 - .338-06 - .338 WM - 9mm Para - .35 REM - .38-55 - .45 LC - .45-70 - .50-70

April 2, 2020, 10:20 PM	#4
jmr40 Senior Member Join Date: June 15, 2008 Location: Georgia Posts: 10,976	I've used both and will get virtually the same velocity and accuracy with slightly different powder charges. The data isn't interchangeable, but close. A max load of IMR4350 is one grain more than a max load of H4350 with 165 gr bullets in a 30-06 according to my manuals. It could be slightly different in another manual. They show H4350 with a 4 fps advantage, which is nothing. I prefer H4350 because it is more stable under a wider range of temperatures. And that is the only reason. Most powder, including IMR 4350 will see 2-3 fps velocity change for each degree temperature changes. H4350 is closer to 1/2 fps for each degree temperature changes. If you develop a load at 70 degrees and fire it at 20 degrees IMR4350 could be 100-150 fps slower. H4350 would only be about 25 fps slower. That is the only real difference. __________________ "If you're still doing things the same way you were doing them 10 years ago, you're doing it wrong" Winston Churchill

April 2, 2020, 10:35 PM	#5
old roper Senior Member Join Date: June 11, 2007 Posts: 2,164	H4350 is one of Hodgdon's Extreme series. I would treat it as different powder. I switched over to H-4350 in all rifles I was using IMR-4350. I think maybe older H-4350 before change they where pretty close. __________________ Semper Fi Vietnam 1965 VFW Life member NRA Life Member

April 2, 2020, 09:05 PM	#3
ligonierbill Senior Member Join Date: May 20, 2007 Posts: 2,648	Pretty close, but if I switched from one to the other, I would redo the load workup. If you have a good load for one, run out of powder and can only find the other, your workup should come out fairly close. But interchange them directly? I would not.

April 3, 2020, 10:10 AM	#6
Rimfire5 Senior Member Join Date: January 2, 2009 Location: Northern Virginia Posts: 982	+ 1 Old Roper H4350 velocity changes about 12 - 15 fps over the range of 0 to 125 degrees F. IMR4350 velocity changes about 155 fps over the same range of temperatures. On a normal summer's day at our range, temperature in the shade changes on the order of 20 - 30 degrees from 8 AM to mid-day. That equates to a max of 3.6 fps increase for H4350 or 37.2 fps for IMR4350. Some of the extreme powders perform even better than that.

April 3, 2020, 01:16 PM	#7
montana09 Member Join Date: April 30, 2018 Posts: 55	The main reason I'm asking is I'm reloading and having a hard time finding data for .270 Winchester with H4350 and 140gn Nosler BT. Noslers website lists data for IMR 4350 but not H4350

April 3, 2020, 04:03 PM	#8
ligonierbill Senior Member Join Date: May 20, 2007 Posts: 2,648	Yeah, Nosler 8 lists only IMR-4350 for their 140s. Oddly, the next page of 150 loads lists H4350, but not IMR. Anyway, I checked Quickload. Setting the case volume on QL to match the velocity Nosler got with their 140 gr IMR-4350 max load (52.5 gr./2,858 fps), I changed the powder to H4350, same charge weight. QL projects 350 psi pressure decrease and 6 fps velocity decrease, essentially the same. As always, work up slowly. Also, compare this to Nosler's 150 gr H4350 max load of 52.0 gr. Pretty close. Have fun.

April 3, 2020, 04:40 PM	#9
montana09 Member Join Date: April 30, 2018 Posts: 55	Thanks! I loaded 10 rds with 50.5 gr H4350 and am going to give that a whirl to start out with, they're going in a Ruger M77 MKII.

April 4, 2020, 06:52 AM	#10
ReloadKy Senior Member Join Date: February 23, 2018 Posts: 191	I am glad you started this thread. My 270 likes IMR4350 a lot. However, I am out of it and I doubt I am able to get some anytime soon. I do have over a pound of H4350 that I need to see how the rifle likes.