Hey All..no matter what i try...i just cannot seem to get 2400 to burn completely...there is ALWAYS unburned granules in the barrel even with MAGNUM primers in my 357...41 & 44 MAG loads...with either cast or jacketed loads...have tired cci 500...cci 550 & Rem 5 1/2...chrono speeds (LABRADAR) seem OK..www.LR..cci 300 & cci 350...
i dunno..i will get a string of 10 shots with less than 35 ES...and the next string will go 95FPS..usually with the 357 mag...i suspect my RUGER GP100 5 BBL has somewhat skewed oversized chamber...???? I will have to identify it..My Colt 2020 Python does not exhibit this annoying trait....???? The Ruger 357 5" GP 100 is really the one giving me fits re 2400 powder.....there is ALWAYS ONE SHOT in a string of 5..or 10 that is ALWAYS at least 70 to 90 fps slower than the others...?????
Am at my wits end....
Pete

I was having this same issue with 4227 in 350 Legend and cast bullets. I started using poly fill to hold the powder against the primer with three different loads, 14, 16.5 and 19 and all three of them shot consistently and the powder burns completely. All three loads were loaded with small pistol primers only because that's what I have the most of and am saving my srp's for jacketed bullets. The standard deviations were good with 14gr, better with 16.5 and with 19 it was 5! I'm going to test the 14 and 16.5 grain loads again and use enough poly fill to fill the air space and maybe even compress it a little to see the sd numbers again. I think they'll go down. I just need to get my bullets powder coated and sized so I can load some. Hopefully this week...

Same problem with 44 mag, 4227 and too light of a charge (19gr's) and a 250gr cast. I increased the charge to 22 gr's and while there is still some unburnt powder in the barrel, it's minimal. LPM primers in each load. I'm going to try poly fill in the lighter load next to slightly compress it and see if that ends the problem.

I tried 4227 in 222 with cast bullets, spp's, 12 gr's, (I think) and poly fill with good powder burn. All shots seemed consistent but I didn't have the chrony setup to prove that.

I don't know poly fill will help with 2400 but it can't hurt. I'm still searching for the "magic" load for my 44 mag (CVA Scout) and I'm going to try 2400 next. I'll use poly fill starting out.

Check the cylinder gap on the Ruger. if pressures drop too quickly with a slow powder like 2400 you will get an incomplete burn.
Also, don't bother with trying a heavy crimp, it's never worked for me.

Yeah, it sounds like a pressure issue which can be caused by a number of things. Cast bullets I’m shooting should be plenty big, .358 for the 350 legend and .432 in the 44 mag, but both rifles so no cylinder gap. That’s why I’m leaning towards case fill as a problem. It could be a combination of the two.

I agree with the heavy crimp thoughts, I’ve tried none, roll and lee factory crimp and saw no difference.

Hey FLINT....I checked the cylinder gap on all 6 cylinders....006" is a go....and .007" is a no go....I am weighing all charges 13.5gr of 2400 and using 158gr H&G #51 sized to .358"....
a string of 5 will show one shot at least 60 to 80fps slower than the other 4....
a string of 10 will show same..one is at least 70fps slower than the other nine....velocities are 1350 fps generally...accurate as all get out to 50yds....
Am going to up the charge to 14gr....

Ruger GP 100 5" 2012 vintage...
Thanks to all..
Pete

You will always have unburnt powder with 2400

"Unburned " powder has never been an issue for me.
I have many cleaning patches

The only issue I ever have is when a projectile doesn't
go where I want it to

+1 on this.

2400 tends to be dirty, even at full steam loads out of a rifle length barrel. As long as they're accurate, the cleanliness is irrelevant, imo.

2400 is my go-to powder in for full power 32 H&R and 327 Fed loads. Fairly dirty, but very accurate, and good velocity.

I have been using 2400 for 50+ years. It always leaves un- burnt powder. Don't worry about it. Also for most consistent velocities use standard not mag primers with 2400.

17-18gn of 2400 under a 240gn cast makes a nice .44mag load. Standard primers.

When you work with cast bullets try bumping your sizing diameter up 1/000 th larger. For my 45 Colt is the sized diameter is .454 for 45acp it's .453.

I think it's a good powder in several applications. To me, worrying about unburned powder is like worrying about having a dirty poop chute after you take a dump.

Have you checked the diameter of your expander plug? If you're oversize on the expander plug you won't be getting enough resistance and all the heavy crimp in the world won't cure it. It's no big trick to chuck the expander plug stem in a drill or lathe and take it down a thou or two with some emery cloth to get a tighter fit.