IMR4895 unburned powder and accuracy?

[hithard]

What has been your experience with unburned powder in the barrel effecting accuracy?

I'm using IMR4895 31 grns. pushing a 200gr. GC in my 338 federal. I'm happy with the the groups, 10 shot's in 2" at 100. The thing that is hanging me up is there is unburned kernals basically from the chamber to the muzzle, and it is all sitting at the bottom of the bore. If you tip the barrel a few kernals will fall out, but the rest stay wear their at. Do you all think that this is hurting accuracy or just keep shooting as the grouping acceptable.

It's a pac nor barrel by the way, so I don't think I'm asking to much from it.

[runfiverun]

that load should be burning clean. [you are right on the verge with gas expansion/bore ratio]
you could change things or live with it.
if you backed the load down one grain of powder and replaced it with one grain of Dacron it could improve both groups and the burn.

[220swiftfn]

Well, if you have that much unburned powder left, I'd be willing to bet that if you shot over a chrony the deviation and spread would be high. You're not getting a complete burn because the powder is not in its "efficiency zone" and probably needs more pressure. You might want to re-work that load with a slightly faster powder if the velocity is where you want it.


Dan

[.22-10-45]

Hello, hithard..Not with H4895 powder..but I have noticed when working up cast loads in a .22 Hornet using H4227..as the charge is increased, the bore gradually becomes cleaner..at the point where there are few if any powder grains remaining in bore...usually that is where the best accuracy is. Now some calibers/cartridges due to bore expansion ratios will never achieve close to 100% fouling free condition..but the little there is shouldn't hurt accuracy.

[303Guy]

Perhaps the boolit is too light for that powder. Increasing the powder charge would help but may raise the peak pressure too high. The problem could be that the case volume is too high for the powder charge in which case some sort of bulk filler may be indicated. The advantage of such a filler is that it resists volume expansion on ignition, raising case pressure without raising the pressure acting on the boolit base as much. Just how much this effect actually takes place is speculation but tests I've done would seem to show a reasonable effect. I say this from signs of increased pressure as well as apparent consistent pressure without boolit base distortion that is observed with more powder. Need I say which filler I'd suggest? Wheat germ or wheat bran. Wheat germ seems to raise pressure less and is a lot easier to get into the case. The problem is that one has got to fill the case with filler - no in betweens but because the powder is not burning fully at all it is likely quite safe to simply add the filler. However, I would first try Dacron in varying amounts to see what happens, starting with just enough to hold the powder in place to a fair compression of the Dacron. If that makes no difference then perhaps consider the wheat germ. I have gone as far as corn meal and that really raises the pressure! That I won't suggest! (It might be OK but ... )

Oh, if you're getting 2", 10 shot groups at 100 with unburned powder there is a good chance you'll get better groups with less or no unburned powder.

[44man]

Testing 3031 from my 45-70 BFR showed a lot of unburned powder from the short barrel (10") but none at all from a rifle. It shows powder burns after peak pressures and adds to bore pressure.
Yet accuracy was very good. However velocity was also low from the revolver and increased a lot from the rifle.
More powder can help burn to raise initial pressure but like 303 said, it can harm the boolit. Fillers do help let powder get going without exceeding initial pressure as much as more powder. It is still a toss up because more powder burn at the start will raise initial pressures.
A few "experts" claim all powder is gone in an inch so the boolit just has expanding gas for push. This OP has shown it is not true and a boolit leaving before all powder is used means there is not time and distance to burn it all.
Pressure aids burn but once the boolit leaves the muzzle, pressure is zero. More resistance from a heavier boolit will keep pressure higher to burn more powder. A jacketed with higher resistance will burn more.
A grain of powder will not burn unless exposed to flame or pressure. (both in fact)
Peak means little, it is the trace after peak. If it goes to nothing it only means the powder was fast and is gone.
Powder is not an explosive, it is a progressive burn item that makes velocity possible. After peak, it adds to push.

[shredder]

I had the same experience with 4895 in the 8mm Mauser with the 237 grain Karabiner boolit and learned that is really performs its best at higher pressures. My solution was to work up the charge from 32 grains to 35 and use Puf Lon filler to keep the powder tight up against the flash hole. My crazy velocity variations disappeared as did the noticable hangfires and unburned powder kernels. In this case a moderately heavy crimp also seemed to help build up pressure before the boolit could begin to move and dissipate the pressure.

Months of experimenting (and some cursing!) condensed in to a small paragraph!

Since I could not be in the barrel when all the action happens, there is lots of educated guesswork here, but based on what I have read and experienced, 4895 seems to be best suited for your heaviest boolits and heaviest loads.

[44man]

I had the same experience with 4895 in the 8mm Mauser with the 237 grain Karabiner boolit and learned that is really performs its best at higher pressures. My solution was to work up the charge from 32 grains to 35 and use Puf Lon filler to keep the powder tight up against the flash hole. My crazy velocity variations disappeared as did the noticable hangfires and unburned powder kernels. In this case a moderately heavy crimp also seemed to help build up pressure before the boolit could begin to move and dissipate the pressure.

Months of experimenting (and some cursing!) condensed in to a small paragraph!

Since I could not be in the barrel when all the action happens, there is lots of educated guesswork here, but based on what I have read and experienced, 4895 seems to be best suited for your heaviest boolits and heaviest loads.
A great post. Nothing more needs said.

[hithard]

Jumping up in powder the group really goes haywire.

Will try a heavier crimp, pretty light right now. I'm also thinking of sizing to .340 up from the current .338

Sounds like the consensus is I need more pressure and burn time. I'm hoping one or both of these changes will cure the burn problem. I just hate to mess with all that filler, sounds like alot more work, and I plan on shooting this alot.

Thanks all

[skeet1]

hithard,
When reading this thread I was wondering if you had a crimp until I got to your last post. I think you have the right idea if you have a Lee FCD it might help. A wonderful die for crimping.

Ken

[243winxb]

Bigger bore = Faster Burn rate of powder needed.

[sthwestvictoria]

With the 30-30 and 150grain Lee FP, 19.0grains of AR3306H (H4895) I get a few grains of toasted powder in the bore but literally only a few - 4-5 if you counted them.
It does not seem to affect accuracy or cleaning.
Currently I am not crimping these, just straightening out the mouth belling so I'll both try going up and crimping to get rid of the toasted grains. I don't see it with the AR2205 (H4227) 16.5grains and 170grain Lee FP.

[detox]

I'm also thinking of sizing to .340 up from the current .338

Thanks all

Good simple thinking without over thinking. I like your idea.

[Larry Gibson]

that load should be burning clean. [you are right on the verge with gas expansion/bore ratio]
you could change things or live with it.
if you backed the load down one grain of powder and replaced it with one grain of Dacron it could improve both groups and the burn.

Concur.

Larry Gibson

[HangFireW8]

Once you find your clean bore, remember that cold weather can push you past your threshold again. If you still get good groups I guess that's OK, but you might not. If cold weather is in your plans, be sure to test for it.

[hithard]

update on using boolit sized to .341,

I don't have the pics. Well the unburned kernels are gone! the recoil definetly picked up...will have to chrony for speed. Best of all the fliers are gone, and the group size is down to 1.5".

I will also say I'm kinda impressed these boolits shoot that well. It's the lee 200gr. that ranch dog had made. The seam is easily visible and you can feel it no problem. When sizing you really can see the sizing marks heavy on one side and light on the other. Oh well, they may not look purdy..but the groups are.

Thanks for all your help guy's.,

[303Guy]

Thanks for the feed back. Good to know you solved the problem and so simply too.

[44man]

Yes, good feed back. Remember the cast boolit has lower friction to hold back powder.
It is said pressure makes powder burn but I have always had doubts. Fire must touch each kernel or it will not burn, pressure only keeps kernels closer together. Spread the grains too far apart and fire will go out. You can't light paper with a match from 6".
More powder or filler keeps grains closer. Heat source is either the primer or gr to gr.
I have funny thoughts but put two gr of powder on your bench, 1/2" apart, light one and tell me if the second lights. To have both light, they have to touch.
You guys work with electric with the common unhooked and expect the motor to run.