Rusty powder?

[cdoc42]

Only once in 40 years have I had a "bad" can of powder. And I mean, "can." IMR powder had been provided in metal cans, and at one time I opened the can and it was foul smelling, obviously not good and accompanied by a large amount of rusty-looking powder. I contacted IMR for advice and they suggested it deteriorated and replaced it.

Well, this occurred recently for the second time. A can of IMR 4350 did not smell bad, but I could see brown dust in the granules and when poured into a plastic container, then returned to the can, a brown dusty residue was in the plastic container.

Well, I loaded up 5 rounds for my 6.5 Creedmore with 40 gr of the rusty stuff and with everything equivalent otherwise, 5 more rounds with 40 gr of a new container, now plastic since IMR has been taken over by Hodgdon, of IMR 4350.

Just for the heck of it, I also loaded 5 rounds with H4350. Off to the range with the chronograph.

"Rusty IMR 4350" - 3 shots, 0.861"; 5 shots, 1.486" Ave velocity 2541 fps

"New IMR 4350" - 4 shots, 1.111" with one flyer Ave velocity 2576

So it appears there was no real difference in accuracy but just a 35 fps drop in velocity with the "old" rusty powder.

With H4350 40 gr: 4 shots, 2.0" with one flyer; ave velocity 2486 fps.

Would it make sense to increase the H4350 charge to obtain a velocity closer to 2540 to see if accuracy matches the IMR 4350?

 

[griz]

That small difference is not really more than what you might see from lot to lot variations. But it would be interesting to see if you have found the most accurate velocity.

 

[hdwhit]

cdoc42 wrote:
Would it make sense to increase the H4350 charge to obtain a velocity closer to 2540 to see if accuracy matches the IMR 4350?

No.

IMR-4350 and H4350 may have the same number, but they are different powders from (in this case) different manufacturers.

Well, this occurred recently for the second time. A can of IMR 4350 did not smell bad, but I could see brown dust in the granules

If the "bad" smell was not yet pronounced and the "rust" color dust was limited, the powder was in the early stages of decomposition.

As it decomposes, the powder's chemical make-up changes and this will affect it burning rate and resulting pressure. What those changes might be at any point in time are not really predictable and that's why it is recommended such powder be discarded.

If you choose to continue loading and shooting this powder, do it quickly before the decomposition progresses much further, but you really should toss it.

 

[243winxb]

What bullet is being used?

Would it make sense to increase the H4350 charge to obtain a velocity closer to 2540 to see if accuracy matches the IMR 4350?

Yes, but only if within the maximum powder charge listed in reloading manuals.

Not the same powder as said above, start low, work up as always.

 

[cdoc42]

RE:Would it make sense to increase the H4350 charge to obtain a velocity closer to 2540 to see if accuracy matches the IMR 4350?

To continue the responses by hdwhit and 243winxb, my question is based on the slight difference reported in the burn rate charts. I realize these burn rate charts are relative and not absolute and may change slightly during current and subsequent manufacturing of a given lot number.

However, I stock my 35 different powders in order of relative burn rate so I have a rough idea how they differ in that respect. The most recent chart I have has 149 powders listed. IMR 4350 is #115 and H4350 is #117, so roughly, H4350 is a bit slower than IMR 4350.

That relationship has been maintained since at least 2004. A list of 106 powders in 2004 showed IR 4350 as #112 and H4350 as #113 - again, a hair slower (maybe actually equal).

In a 2011 list, IMR 4350 was #112 out of 144 and H4350 was #113.

So my thought was, the slower H4350 powder should give a higher velocity with equal weights of the charge of 40 grains. Since it was slightly lower, I wondered if it would make sense to increase the charge of H4350 to, say, 40.5gr to see if the velocity would increase to the range of 2540-2576 seen with IMR 4350 where the accuracy was better.

I would be certain to watch for signs of excess pressure, but even though references I have seen don't have any max over 40 gr for either of the 4350's, discussions here and on other threads reveal some shooters of the 6.5 Creedmore are shooting over 40 gr.