Do I really have to work up a new load??

[Brno]

Pet load in my 7x57 has been 48 grains of IMR 4350 with a 154 grain Hornady Interlock for years. I've tested it up to 50 grains with no apparent problems, but settled on the 48 gr. load a long time ago because it's well under max in my rifle, consistently prints nice tight groups, and been a stone-cold killer on deer, elk and antelope.

I haven't had to load for this rifle in a few years, but now I need to whip up a batch of ammo for the coming big game seasons so I bought a new canister of IMR 4350 to duplicate my old pet load. Thing is- I've read that burn rates can vary from lot number to lot number in any given powder, and it's wise to work up to an established load when using a new lot number of the same powder - in this case, IMR 4350.

Really? I've never done that. And I've never noticed any difference in pressure signs or performance. Have I just been lucky?

All things being equal - same brass, primers, bullets, charge weight, seating depth, etc., what risk is there in just loading up with my old tried and true recipe? I'm also wondering if I can substitute H4350 for IMR4350. They look to be interchangeable (the data looks to be exactly the same in all my manuals).

 

[Magnum Shooter]

The lot to lot difference is rarely more than 3%. If loading at max or hotter you would want to work up, but for your load (as described), you might just want to load a few and check at the range.

I'm also wondering if I can substitute H4350 for IMR4350. They look to be interchangeable (the data looks to be exactly the same in all my manuals).

If you have data that is for the exact same caliber, bullet, primer, OAL, and brass. You don’t need to substitute anything do you?

 

[Ifishsum]

I normally do not re-work loads for each different lot of powder - the whole point of canister powder is to provide safe and repeatable consistency. That's not to say it can't vary a little from lot to lot but if it changed that much without advertisement or notice it would be a huge liability for the manufacturers. But if a number of years have past since purchasing, it seems prudent to compare the load with the newest data your can find, in case something has changed with the formulation since you last bought the powder. Data can also be updated with newer pressure test methods.

IMR4350 and H4350 are close, but they are not interchangeable according to my manuals. Hodgdon acquired IMR about 10 years ago so it may very well have changed somewhat since then.

 

[stubbicatt]

Depending on your needs, a chronograph may solve your issue. If you know your velocity from the old, tried and true, lot of 4350, see if you can duplicate the velocity with the new lot. This may require a little fettling with the load.

 

[243winxb]

If you were using Old Dupont IMR 4350 powder for your work up, you may want to reduce the change a bit if going to Canada made. But they should be the same? H & IMR are NOT the same. IMR 4198, 4227, 8208xbr are made in Australia. http://www.hodgdon.com/msds.html

 

[FROGO207]

I agree that the old and new lots are going to be close if made within a couple of years of each other so when I change lots I do a minimal workup (reduce my load by 1%) and load a few to try if not at MAX already. I now am in the position to buy in large quantities and the workups are far apart so I will be doing a full workup with those when the time comes however.
H4350 and IMR4350 are enough different that I would never trust just swapping in a can of the other brand. If you do a proper workup with a 10% charge reduction to start with you will most likely end up with a safe load using the other brands data if you feel you really need to. MY.02

243winxb has a valid point when changing lots after an extended time. I try to use the data from the time the propellant was manufactured to load with if possible using my library of old books.

 

[gamestalker]

If my load has been performing well and isn't on the edge of pressure limits, I don't re-work the load with different powder lots. If I change a component I might decrease it a bit, and then do a short re-work over the chrony, and on paper.

As for H4350 and IMR-4350, they are similar, but they are not the exact same animal. In that situation I would do separate work ups for each. And unless current reloading books are tabling two separate powders as being exactly the same, and it's supported by industry statements, I consider them different powders.

GS

 

[Brno]

Thanks, Fellas. I reckon I'll do the smart thing - load up a few starting low (prolly around 45 grs., creep back up to 48, and see how they shoot. Last IMR4350 I used was DuPont; this new stuff is Hodgdon. Ain't no sense in blowing my fingers off or wrecking a rifle to save an hour or two.

 

[rcmodel]

Last IMR4350 I used was DuPont; this new stuff is Hodgdon.

IMR-4350 and H-4350 were never the same powder.

H-4350 is slightly different then IMR-4350.

You can't use the two interchangeably without a load workup.

rc

 

[Brno]

Good to know, RC...

Reloading is a never-ending exercise in learning. Thanks.

 

[Arkansas Paul]

No, H4350 and IMR4350 are not the same. You can not use them interchangeably.

If you buy some IMR4350 and it has only been a few years since buying, I wouldn't mess with working up a new load. I buy powder locally, usually by the pound, so I would be working up a new load every 100 rounds or so. No thank you.

 

[PJSprog]

I've been using H4350 in my 7x57 loads for my '95 Mauser for some time, and with excellent results. I don't rework the loads with different lots, but then again I load closer to starting loads.

If you're going to change from IMR- to H-, though, you should definitely rework it. They are similar, but not the same.