Ref: 6.5 CM
I've noticed that most people loading for the 6.5 CM use H4350 powder, and I have worked up a very accurate load for my 6.5 CM using H4350. I also noticed that Nosler in their Version 9 reloading manual list IMR4350 as their most accurate load, over H4350.
I have 5+ lbs of IMR4350 and have used it successfully loading for my 30-06 and I fall in the category that if it ain't broke, don't fix it. Before I burn up a few primers/IMR4350 & bullets I thought I would ask if any of you might have already been there, done that and have the T-Shirt on this matter? Your experience and opinions will be greatly appreciated - Thank you,

BTW - I live in Florida and it is always hot! So, I have heard that IMR4350 is temperature sensitive; however, in 30+ yrs of using it in my 30-06 I have not ecperienced any problems.

My 6.5 Creedmoor shoots great groups with IMR4350. This is with 140 grain class bullets. I haven't deliberately tested for temperature sensitivity.

I haven't used it myself as I have a good stash of IMR4451 and H4350, but my cousin uses it without an issue in his Creed.

Temp sensitivity comes into play with temp fluctuations. If your AO is "always hot!", then the only time you'd bother to worry about it is if/when you travel to somewhere not "always hot!". Even then, given your scenario, the only concern would be a slightly lower POI from your "always hot!" Zero. Simply work your load up within safe pressures for your shooting conditions and rock on.

IMR4350 and H4350 are close, but powders should never be considered interchangeable. H being one place slower than IMR on the burn chart. Work up safely whenever changing a component.

Edit to add: IMR4451 is another "close" powder and I used it a lot in my 243 PRS rifle when H4350 got really scarce, but the Enduron line of powders is discontinued, so when the existing stock runs out it's gone.

I use the IMR version with 120 Barnes in 6.5 Creeds and a 6.5mm-06. Great groups out of both. Loading for 3 Creeds, great in all of them.

My CM likes H4350 the best with 120 Sierra and 129 Hornaday SST's the Sierra's will group 3 shots under a dime in a Tikka rifle

Testing IMR against Hodgdon under identical equipment and conditions, 14# M70, Krieger, Berger Hybrids, Hornady match brass, Fed 210M's...I couldn't see any marked difference in 10 shot group sizes...H4350 gave a little bit more velocity, IMR 4350 gave less extreme spread. Only 20 shots for record and only one lot number of powder. Good enough for me...but to really tell I should have fired a lot more shots for record.

I load IMR with 129gr AB in a 260 Rem with great accuracy, but also load H4350 with 130-139 gr berger, Atip and scenar with great results too. Half dozen of one...

IMR4350 is somewhat more temp-sensitive than H4350, but it won't make any difference at temperatures from around 25 to 80. Just about any modern rifle powder won't be affected by temperatures in that range.

Also, temp-sensitivity depends on other things, such as load density (a little charge-compression usually helps) and primer. As an example a load I used for years in my first .375 H&H was 81 grains of IMR4350 with a 300-grain bullet--which was pretty compressed. Velocity didn't vary much at all from zero Fahrenheit to 80 degrees. But have also seen IMR4350 handloads vary over 100 fps in the same temperature range with loads that weren't compressed--and around 100 fps is where variations in point-of-impact can occur.

All of this is explained in greater detail in Chapter 10 in my Big Book of Gun Gack II, "Temperature and Rifle Powder." This also includes the temp-test results of a number of handloads in cartridges from the .17 Hornady Hornet to the .375 H&H.

This has been my experience with IMR 4350 as well. No issues with it whatsoever, but then again I fall into that 25-80 degrees category 90 percent of the time.

Panhandle,

How old are you?
Under 45, use H4350
Over 55, use IMR-4350
In between, use either.

@FLPanhandle

I live in Florida too. I get very good results with both, H4350 and IMR 4350, out of my 260Rem and 257Robts. The IMR 4350 is both faster and gives a bit more accuracy. I develop, load and practice all summer in the Florida heat, then hunt in Wyoming and NY, in teens and 20° temps. All good.

EDIT:
I just noticed this is in the Long Range group. That's not me. Me comment was for my experiences out to 300-350 yards.

I've also used IMR 4451 as a one for one swap for IMR 4350 with pretty much identical results.

Stammstr - LOL!! I turned 84 last July, so IMR4350, eh?

Mule Deer - Interesting - If I understand you correctly, Seasonal changes (temp. swings over time) are of no concern with the IMR4350, rather sudden changes, like 15 deg in the morning and 80 deg. at noon would be of concern? Thank you,

I’m 50 so this explains why I use them both about evenly. 😁

Have done the same thing with around a dozen cartridges, with the same results--though on average 4451 has done a slightly better--and includes a decoppering compound. Luckily, I stocked up before production was "suspended," but am hoping it won't be suspended much longer!

That's just plain funny.

How about those of us who are near 60 yet were using H4350 when it first hit the market when it was made in Scotland?

Brown jug for me. Love imr 4350. Shoot it in about everything. Favorite is a 6.5-06 and a 140 or a 30-06 and a 165.

80 degrees would be a cool day in Florida. Triple digits are common. I live in North GA and upper 90's are not uncommon during summer months when shooting at the range and temps in the teens are common later in hunting season. Single digits are not unheard of.

I've only used H4350 in 6.5CM and it has done so well I've not been tempted to try anything else. But I've used both in 30-06. Accuracy and velocity are nearly the same, but I prefer H4350 simply because of temperature sensitivity. It may never make a difference for me. But there are no downsides either. If IMR4350 were more accurate for me I would use it.

Hodgdon likely hasn't gone full blown public yet because there is probably still stock to sell, but ALL the powder distributors are saying Hodgdon has announced the end of the IMR Enduron line. So unless that is not infact true, there will be no more production of 4451. Little surprised you wouldn't know of this already, unless of course you know something we don't know. I for one would like to see 4451 stick around.

Imr4350, H4350 and 4451, I've used all and wouldn't have an issue subbing any over the other (not grain for grain of course).

IMO, people spend way too much mental time obsessing over powder and fiddling with stuff instead of shooting, or dinking at the bench.

Imr 4350 is so versatile, as is h4350. I've used it in a fast twist 22-250 all the way to a 300 win mag

Yep, IMR4350 is very versatile--one reason that way back when I could finally afford to buy powder in 8-pounders instead of 1-pound cans IMR4350 was the first.

But I don't even have any in my powder collection any more, for two reasons: Montana has the widest recorded range of temperatures of any of the 50 states, from -70 to +117--and I've actually hunted at -40 and +105. Plus, its long granules don't run through a measure as easily as the "short-cut" granules of H4350.

Couldn't agree more. Varget and h4831sc have quickly became my favorite. In western oklahoma we see minus 5 to 105.

I strongly prefer h because I live in Idaho and often work up loads in the summer to hunt with when it's cold. I also think h4350 meters better than imr 4350. H has also proven very consistant speed wise in a lot of my loads meaning low extreme spreads and sd's which matters a lot at longer range.

My favorite rifle powders are h4350, h4831sc, and H1000. I also love 8208xbr which is IMR but also made by ADI in Australia like H extreme stuff. The imr enduron stuff was interesting but I'm not sure why it was all discontinued so soon. Another imr I still use a lot is 7828. It works awesome in my 264 win and a few others.

Bb

I run 7828 SSC in my 243 AI and like it a lot.

IMR 4350 meters like doggie dodo, so I quit using it for small caliber applications like 6mm Creedmoor.

well I am in the age of the IMR LOL but I generally reach for an H version powders. maybe they're extreme marketing line got to my brain..

I used IMR4350 in the .243AI with 105s a bunch in the temp extremes we get here in Alberta, and velocity, variation, and POI were all amazingly consistent. And AB has an even wider range of recorded temps than Montana. I have been using 7828ssc in the 7WSM and 7RM with 162s and 180s for years, and it’s always been a great performer in that application. I also use a lot of H4350, 4451, 4166, H1000, TAC, etc., and they’ve also been very consistent. I burned out a couple of match barrels with R26, but moved away from it since it showed more temp dependence than some of the others. That, and the availability and price were less attractive than other similar powders.

Jordan,

I eventually arrived at the same conclusion about RL-26, and sold my last few pounds a year or so ago.

As noted in an earlier post IMR4350 can be very temp-resistant, especially if compressed, and used with a magnum primer. But eventually preferred the "easy button" of H4350, or IMR4451. Luckily I have a good supply of 4451....

John,

Why’d they quit making 4451 and the like?

Not Mule Deer but I heard that Enduron powders production was suspended due to the need for more military capacity at the General Dynamics plant in Valleyfield, Quebec, Canada where the Enduron powders were made. Here are some links to General Dynamics plant info:
General Dynamics Ordnance and Tactical Systems Plant Locations
General Dynamics Ordnance And Tacti...Energetic Materials Manufacturing Plant

Serious question here, is there any application for these powders where you couldn't use Big Game or perhaps RL16 instead?

I’m with you there, John. When I ran low on IMR4350, I found that H4350 and 4451 did just as well, and were easier to meter. Like you, I fortunately laid up a healthy supply of 4451 before it disappeared, though I have found that H4350 often gives less velocity variation.

Finally! Someone mentioned the biggest improvement with H4350 for those of use who don't like to trickle every charge.

A lot of very good comments have been posted and I have given consideration to all of them. To summarize, unless one live in an area that undergoes extreme temperature fluctuation (Mule Deer in MT) there is very little difference between H4350 & IMR-4350, except ease of measuring. As stated, I've used IMR-4350 in 30-06 loads for years and haven't noticed any temperature related problems;however, living in NW Fla. it's just hot most of the time, unlike MT, ID, etc. with their extreme cold - extreme hot fluctuations. I have an ample supply of both powders, so I will amuse myself and experiment for a while.
Again, thank you for your input.

The young guys call IMR 4350. “An old man powder”

I'm 68 hanco and basically quit buying imr 4350 25 yrs ago. H4350 much better. Mb

Not that easy, damn stuff is as bad as 4064 you'd think you were trying to run Lincoln logs thru the measure..mb

Both powders will deliver supreme accuracy in that cartridge!

Them young boys on my deer lease say IMR 4350 is an old man’s powder

I've used IMR 4350 for years in my 270 with 130 grainers, my 257 Roberts with 90 grain X-bullets, and used it once in my 7 RM with 145 grain Speer Grand Slams. All 3 guns shot less than 1" groups and have good velocity so I've never bothered to experiment with H4350. The way I see it, if it works don't mess with it.

I don't buy imr-4350 at all anymore h-4350 for the win..mb

Two similarities. I prefer IMR 4198 over H 4198 because it produces slightly better accuracy and velocity for me, the same reasons I prefer IMR 4350 over H 4350. Almost the same thing with IMR 4895 and H 4895 except for ease of metering. They are horrible to meter but I crunch em anyway, even down to the little 17 IV. Been shooting some X terminator and it's perfectly luverly.

A4350 works for me. Like that brown can, but got a deal on Accurate 4350 and been liking it.

One of my favorite smells in reloading during my teenage years was cracking open a brown can of imr-4350 to load up another box of 30-06 ammo. Couldn't resist taking a quick wiff before commencing with the loading process. Switched to H4350 for better accuracy and speed compared to the IMR version, but when dispensing from the automatic Lyman PDS the long grains of IMR-4350 don't matter.

Years ago I compared IMR4350 to H4350 before it was changed to the Extreme line in my 7mag with 140gr bullets and the IMR4350 was about 100fps faster.I've used IMR4350,H4350 and Accurate4350.All three of these powders have given me good accuracy.Don't know,maybe it's changed over the years,but I've read a lot about Accurate4350 being the slowest velocity of the three.When I compared it in my 30-06 with 165gr bullets shooting all three powders loaded with the same charge,Accurate4350 gave me the highest velocity,followed closely was IMR4350 and around 30fps or so behind them was H4350.Did this same test recently in my 308 Norma Magnum using 180gr bullets and my results were different.H4350 gave me the highest velocity,followed close to it was Accurate4350 and the slowest by around 30fts was IMR4350.I know powders can change a little from lot to lot,temperature and humidity can affect it as well,but it has me thinking case fill and pressure also can affect the results of velocity.Temperature is not a big factor for me because it's usually somewhere between 30-80 degrees.As far as accuracy goes,all three have given me good results if loaded right.

This is a pretty astute observation.

I'm a tweener.

Old farts simply refer to it as 4350

You guys forgot about AA 4450

I use both. Just depends on how they shoot in different rifles. Temperature stability here isn’t too big a problem but It’s in the back of my mind. H4350 for my elk loads in 30/06 to be used in Colorado.

Some readers may be interested to know that when H 4350 (AR2209) was created in the 80's it was released with an advertised burning rate being 95% the burning rate if IMR4350 so was a touch faster.

If you like drooling over the past you might like to know I had mates who bought powder in 250 pound kegs. Aussies tend to reload and shoot a lot more than Americans because of no game laws, no hunting seasons or bag limits, no Wildlife departments and no snow country for most.

Ah, the old days, we called it.

Much of my load testing with old favorites of mine was with the IMR version. I've been trying the H version and I think as far as accuracy goes the H version is likely as good as the IMR. If you have lots of IMR, I'd suggest working with that powder.

I guess I'm considered old school...

Here are the results of a test I made of the three 4350 powders, which was published both as a magazine article and as Chapter 9 of The Big Book of Gun Gack II, "Different Batches of the 'Same' Powder," using a 24" barreled .257 Roberts. The loads were identical except for the powder, and I used 45.0 grains with the same cases and primers, and 100-grain Ballistic Tips seated to the same depth. And yes, they were during the same range session:

IMR 4350, 3083 fps.
A4350, 2917 fps.
H4350, 2980 fps.

Obviously this might vary with different manufacturing lots of the three powders. The best-grouping powder in that test was H4350, but that also could easily vary with other lots--and rifles.

Good info. However, as I've stated before, when you and others bring up examples like this, on these types of tests is the one that hits on the best node is going to shoot the best: It's always going to be about OCW. I'll bet if you drop the charge weight (to say 43.5gr's for example) on the IMR a bit, to get it closer to where the H is running, it would shoot just as accurately and consistently. In my experience IMR shoots damn well, but you have to develop loads in the fall or winter, where the temps are close to where they will be when you hunt.

With that being said, my favorite powder is H4350 because of it's consistency all year around. Loads with this powder are not affected by temperature change, like the other powders mentioned (IMR and AA). One reason why my competition ammo is loaded with H4350. I don't have to mess with it, and I know I can trust it, regardless of the temp. That adds a ton of confidence and peace of mind.

Have both IMR and Hodgdon in several different powders. I use one or the other to develop accuracy loads for a cartride/ bullet combination and stick with that load for that cartridge. There is a bit of burn rate difference between IMR and H in the same numbers in the past but they are close. Has been about the same as a lot change in powder. As always , when you change lots, you start the accuracy load development again with a back off and the back up.

Well said BSA. The powder vs powder velocity numbers is good solid information...the accuracy information means nothing.

i guess since i am 70 yrs. old its IMR 4350 and that`s great it does seem to shoot well in my 30-06 Winchester. great information ha-ha ,Pete53

I’m 70 also, use lots of IMR 4350

Which I plainly stated in my post....

But they have to read your whole post, John, to catch this.

It's not long range hunting but I'm working up my 30/06 load with 220 grain Hornady roundnose interlock with H4350. For a baited grizzly hunt--shot should be @100 yards. I used my 30/06 with IMR 4350 & 220 grain Nolser partitions a few years but I could find either---so I'm using what I could find.

Yeah--and it was such a LONG post it obviously exceeded some attention spans....

Have temp tested IMR4350 in two of my 270’s, two 30-06’s and a 30-06AI. Several more 270’s and 30-06’s with friends who are brave enough to go with me on frigid mornings.
In every case IMR4350 was temp sensitive and in a few cases the ES was close to 100 fps, groups opened considerably, and POI changed, sometimes a little, in some cases a lot. Although I wouldn’t say the powder charges were all compressed, they were at least full.

On the flip side, in a pretty wide variety of cartridges H4350 has been quite stable. H4350 has the reputation of being among the most temperature stable powders out there.