Not enough crimp or something else?

[Raydee38]

I am having a issue in my 9mm AR build where I am seeing unburnt powder all over and the brass is very dirty on the outside. I am using Berry's 124gr bullets with 5.1gr CFE Pistol powder. I have been told that I may be under charged but I am leaning toward not enough crimp. I know it's hard to diagnose over the net but I am sure I can't be the first reloader to have this problem?

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[Solvability]

That is plenty of powder - any chance your brass was wet? Might try mag primers - how does it work in a pistol?

[jcc7x7]

sounds like its not sealing the chamber

i.e. The case isn't being expanded enough to fill the back of your chamber so gases are coming out the back and the muzzle.

Try a tighter crimp BUT plated bullets don't generally do well with a tight crimp since it deforms the plating and causes poor accuracy

IF that doesn't work start going up with the powder charge

I've not used CFE so make sure you reference loading manuals etc

Watch for the normal signs of over pressure.

HAve you measured the cases to see how much they've expanded?

[bowenbuilt]

A low charge is what it sounds like but in no case could it be the amount of crimp. Crimp is a misleading term for what the die does for an auto pistol, all the die is supposed to do is remove the flare from the case mouth. Anymore than this and it will undersize the bullet and cause tumbling and all kinds of other problems you don't want like dangerous set backs and the like. Keep the crimp to a minimum and maybe up the powder charge a few tenths until the cases start to seal in the chamber and the powder burns more efficiently.

[Raydee38]

That is plenty of powder - any chance your brass was wet? Might try mag primers - how does it work in a pistol?

I am seeing the same shooting through a pistol. The brass didn't get wet as far as I know.

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[Raydee38]

sounds like its not sealing the chamber

i.e. The case isn't being expanded enough to fill the back of your chamber so gases are coming out the back and the muzzle.

Try a tighter crimp BUT plated bullets don't generally do well with a tight crimp since it deforms the plating and causes poor accuracy

IF that doesn't work start going up with the powder charge

I've not used CFE so make sure you reference loading manuals etc

Watch for the normal signs of over pressure.

HAve you measured the cases to see how much they've expanded?

I have not measured the cases to see how much they have expanded, I am new to loading 9mm but I will measure them and see what numbers I am getting.

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[Raydee38]

A low charge is what it sounds like but in no case could it be the amount of crimp. Crimp is a misleading term for what the die does for an auto pistol, all the die is supposed to do is remove the flare from the case mouth. Anymore than this and it will undersize the bullet and cause tumbling and all kinds of other problems you don't want like dangerous set backs and the like. Keep the crimp to a minimum and maybe up the powder charge a few tenths until the cases start to seal in the chamber and the powder burns more efficiently.

Honestly I did exactly that, I crimped just enough to take the flare out and still drop into my case gauge. I am going to pick up some factory ammo and see how it shoots and compare them.

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[olemiss]

You might try a Lee undersized resizing die. That will do much better than just more crimp.

[IDescribe]

No, a U-die will have no impact here. And measuring the brass after the fact won't tell you anything useful. The brass "springs" back and shrinks a little after chamber pressure subsides, so all measuring the brass will give you is a number which you can assume your chamber is larger than.

What Bowenbuilt said is correct. Your load is under-pressured. When the powder ignites and starts building pressure, the brass expands outward and creates a pressure seal against the chamber walls. This keeps all those expanding gasses headed down the barrel. In your situation, the case isn't expanding fast enough, and hot gasses are being forced around the outside of the case before the case seals off completely, and what you're seeing is that residue from those escaping gasses. Start upping the charge weights a little at a time and see if it goes away or improves. Hodgdon's load data says you're good to 5.5 grains. If you can monitor with a chrono, you can probably go higher than that.

[Raydee38]

I have loaded up to 5.2 grains and noticed that the primers were starting to flatten out. I don't think they were over pressured, probably just soft primers. All my firearms cycled even at the lowest charge so I decided to keep my reloads on the low side. I will up the charge a little at a time and see where the sweet spot is to get the expansion I need to seal the chamber.

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[RPatton]

If all else fails I would try a faster powder.

[NickyC]

Just wondering if he could possibly lengthen his OAL so the bullet would have less of a jump which I think would increase pressure some. Depending on how long he loads might require upping the charge.

[Sarge]

Even with major loads my AR made really black filthy brass. There must be pretty generous chambers to enhance reliability?

[FULLMETAL]

Had the same issue in my Spartan 9AR went to 320 and a Mag primer has gotten a lot better