lot variation with 3n38?

[motosapiens]

trying to figure out some strange numbers. I bought a pound of 3n38 online several months ago, and liked it. worked up a 172-ish pf load with 9.2grains for mrs moto's open gun. Loaded a bunch of them. bought a 4lb jug locally. kept loading. mrs moto wanted to try a slightly hotter load to see if it would settle the gun more. i checked some weights before making any adjustments and the press was throwing about 8.9gr now (!!!) with the new jug. so we did some chrono testing and found that all the old rounds were consistently at 171-172 (with single digit sd's), but the box of rounds with the new jug. was unsurprisingly lower, with some rounds under 1300fps (around 160-161 pf!!).

 

so I cranked up some more powder to test, and 10 rounds with 9.2gr of the new jug gives me 1344fps average (166pf, SD=6). It *appears* that the new lot is both fluffier (same volume weighs less) and not as hot (same weight produces lower velocity).

 

The other possibility is I did something horribly wrong somewhere, but I've been reloading for a long time and chrono-ing regularly, and normally experience very very consistent results. Once I find a load i tend to leave the press alone and make no adjustments. Same lot of cci small rifle primers used for all testing. Interestingly, i could not feel or observe any difference in the 171-172 pf rounds with the old jug vs the 166 pf rounds with the new jug, both of which are theoretically 9.2gr. I can *definitely* feel a difference with the 160-ish pf rounds from the old jug, and many of the rounds barely eject from the gun, with the occasional stovepipe, which is what caused all the head-scratching and testing in the first place.

 

thoughts?

 

I think we're on the right path now, but I'll just have to load more like 9.4gr with the new jug I guess.

[shred]

I wouldn't be surprised if powder makers added filler to different lots to get charge weights where they are supposed to be for retail powders.  Even though everyone throws powder by volume.  Outside of wherever they test, its not implausible the filler changes the burn characteristics a little as well.

 

[MikeyScuba]

My guess is they are running flat out and/or having supply issues requiring different raw materials.  I'm surprised anything is coming out of Europe given the ongoing war.

 

[Jim Watson]

Back in the 3n37 days I read a loader to say he bought a year's supply at a time so he would only have to redevelop his load once a year.  Seems like they have a good bit of lot variation.

[zzt]

That seems to be an extreme variation.  Several powder manufactures told me the Canister Grade powder they sell to reloaders can vary within a 25 fps and 2500 psi range.

 

The only powder I've used that exhibits zero lot to lot variation is Aliant e3.

[motosapiens]

3 minutes ago, zzt said:

That seems to be an extreme variation.  Several powder manufactures told me the Canister Grade powder they sell to reloaders can vary within a 25 fps and 2500 psi range.

seems that way to me too, but I can't think of another explanation that is consistent with my observations. I've never experienced significant variation lot to lot with *any* mfr, but then I have traditionally bought 30-50lbs of powder at a time for limited and CO. I guess I should go back to the local dealer and get a couple more 4lb jugs out of the same box.

[shred]

The IMR powders that were the hotness for open last century-- 4756 and 7625 would vary quite a bit lot to lot.  Some of the Shooters World powders do too.  Always a good idea to retest when changing lots anyway.

 

[outerlimits]

definitely happens with HS-6 as well.

[zzt]

3 hours ago, motosapiens said:

I guess I should go back to the local dealer and get a couple more 4lb jugs out of the same box.

 

If you are happy with the results you are getting, yes.  Just make sure they all have the same lot numbers,

[Farmer]

On 5/29/2023 at 2:03 PM, shred said:

The IMR powders that were the hotness for open last century-- 4756 and 7625 would vary quite a bit lot to lot.  Some of the Shooters World powders do too.  Always a good idea to retest when changing lots anyway.

 

Yep, had the same thing happen with 7625. Had a perfect load from a small can, bought 4# and it went to pot. Have had same issues with N550 also. Worst one was a pound of H110. Have a 44 mag hunting load with 24.5g that gave a consistent 1400 fps. New jug dropped to 1300 and I couldn’t get the vel back no matter how much I tried to stuff in the case. Gave it to my bro who had a 14” bbl and it still was slower than the batch he had but not as bad. Started buying larger quantities after that.