Dirty 9mm Brass

[Pbaker]

Hello all,

I’m having issues with dirty 9mm brass. I’m loading cast PC 147gr RN boolits (actual weight is 151), sized to .357, on top of 5gr of HS6 powder, OAL 1.110 (ish). This load doesn’t appear to be sealing the chamber as I have dirty brass. Additionally the fired case is not being fire formed (will fit in a case gauge still). This load should be on the high end of the load spectrum, but obviously it’s not achieving proper pressures. I have not chronographed these loads as I don’t have a chronograph. Weapon is an 8.3” AR9, which is noticeably fouled around the breach, which caused subsequent light primer strikes.

Not sure if I have a component issue, or if I should increase the load. Any advice or expertise is much appreciated.

[popper]

It's a blow back, going to get dirty.

[Pbaker]

Most, if not all, 9mm guns are blowback. I’ve never had fouling like this in my handguns so bad to the point it would cause light primer strikes (due to the amount of build up). What concerns me is this load is on the high end, and it’s still not building pressure to seal the chamber.

[Mal Paso]

My manual says 5.5g Max for HS6 and 147g bullet, I wonder if it is a problem with the powder.

[Dusty Bannister]

Do you have a faster burning pistol powder to try? That might clean things up and expand the case in the chamber. It would be a concern also, that your brass might just be too hard. What is the HS or are you mixing them all up?

What manual are you referencing since I see two different max loads?

[Pbaker]

It’s all mixed brass, and I fired roughly 100 rounds. All with the same signs of under pressure. I’m loading to my Lyman manual for cast 147gr, states max load is 5gr with HS-6. Considering my bullets are coming out at 151gr after powder coat, I would say this puts me well above a pressure range required to expand the case.

I was left with white powder fouling (ammonia?) on the bolt face, likely causing my light primer strikes. The loads are not crimped, only enough crimp to remove the belling. I’m think I should put a heavy crimp now, or possibly consider pulling the rest of the rounds. Not really sure what my issue might be…

[DCB]

It may be low pressure? "only" I would pull a few rounds and double check and see if they are actually 5grs of powder.
Check the length of the brass. " short brass" may not seal the chamber.
You don't need a crimp on a 9mm. Case tension is what is supposed hold the bullet tight.
I sort my 9mm brass by head stamp and OAL case length.

[Larry Gibson]

Lyman says 6 gr is max with a 147 gr cast.

I also suggest a faster burning powder.

[shooting on a shoestring]

So I see your AR 9 is indeed a blow-back action. That’s in contrast to a typical 9 mm pistol using a locked breech delayed opening action, aka Browning tilting barrel action such as Glocks, 1911’s, Sigs etc…

Using heavy for caliber boolits and a slow for caliber powder, your AR 9 might be pushing its bolt open early lowering your chamber pressure by increasing the apparent volume.

[Moleman-]

What buffer weight are you using? Often increasing the buffer weight on a blowback AR9 over the standard 5.6 ounce buffer will help clean up the cases. I'm using 8 ounce buffers in my blowback AR9's, but they go up to 10 ounces. If you're not already using a longer 9mm buffer now is the time to swap for the longer to protect your bolt latch & heavier to delay extraction 8ounce buffer. Faster powder will also help as others have mentioned.

[Pbaker]

I’m using a 7.5 oz buffer. It’s an Aero EPC, so I’m using all Aero parts and pieces recommend by them. I did pull a few bullets and discovered they are be swagged during the seating down to .353”, so I need to figure that out first. Being that undersized will never allow me to achieve pressure, so everything else is just a secondary issue at this point. Not sure how I will correct the sizing issue. I may look into a “M” style powder funnel that sizes up the neck of the case.

[popper]

pushing its bolt open early - and burning the PC off the base.
Happens with slow powder, get some 231. And the white is burned PC that is collecting on the bolt.
Get a long spud for sizing 9mm with those heavies - they seat deep in a tapered case!

[bruce381]

as said h6 too slow go faster powder

[Winger Ed.]

I've never used HS6, but for 9mm, I'm big on Unique or Bullseye.

Something that might be worth checking---
If the powder is OK, is there any chance your scale is lying to ya
and making you drop a too light of a charge?

[BNE]

The loads are not crimped, only enough crimp to remove the belling. I’m think I should put a heavy crimp now, or possibly consider pulling the rest of the rounds. Not really sure what my issue might be…[/QUOTE]


THIS.

[poppy42]

It may be low pressure? "only" I would pull a few rounds and double check and see if they are actually 5grs of powder.
Check the length of the brass. " short brass" may not seal the chamber.
You don't need a crimp on a 9mm. Case tension is what is supposed hold the bullet tight.
I sort my 9mm brass by head stamp and OAL case length.

I’ve never sorted by head stamp, check the Length, or trimmed any 9mm brass! I’ve loaded and shot, I don’t know how many thousands of rounds. In many 9 mm semi autos. Personally I don’t know anyone who does. As a matter of fact the only trimming of any semi auto brass I’ve ever done is when I trim 1 mm off 9x19 brass to make 9x18 (Makarov) brass. But to each his own I guess.

[JimB..]

Do figure out your sizing issue, not enough info to be sure, but you may want to try a larger M-style expander.
My 9mm AR suppressed load for a 147gr RN powder coated bullet is 3.4gr of titegroup, I forget the OAL. Suggest starting at 3.2 and working up. You’ll find things easier with a faster powder.
I forget the weight, but I used a very heavy buffer before switching to the JP captured spring setup with a heavy spring.

In my experience, the 9mm AR takes a lot more tuning than expected. Keep playing with it and you’ll find a solution.

[gifbohane]

The loads are not crimped, only enough crimp to remove the belling. I’m think I should put a heavy crimp now, or possibly consider pulling the rest of the rounds. Not really sure what my issue might be…


THIS.[/QUOTE]

You should continue to crimp to remove the bell, only. Your load is a little light and the OAL could be boosted to 1.120.

[Pbaker]

I settled on a .358 powder die. My barrels all slug @ .356 (+/- .0005), so I think at .358 I definitely get enough squeeze to seal the chamber. Crappy part is now I have to melt down all the bullets I sized to .357 and start over.

[AlHunt]

I settled on a .358 powder die. My barrels all slug @ .356 (+/- .0005), so I think at .358 I definitely get enough squeeze to seal the chamber. Crappy part is now I have to melt down all the bullets I sized to .357 and start over.

Powder coat them again, that should add .0005 all the way around, at least.

[Hanzy4200]

Possibly check your brass quality, and there is the good chance your chamber may be oversized. Is it a bargain bin upper? I've seen some pretty rough chambers in the cheaper gun show upper.

[Hanzy4200]

I settled on a .358 powder die. My barrels all slug @ .356 (+/- .0005), so I think at .358 I definitely get enough squeeze to seal the chamber. Crappy part is now I have to melt down all the bullets I sized to .357 and start over.

Unless your REALLY need the alloy, or if it's a large amount, you might want to just hang on to them. 9MMs vary widely in bore diameter. You might get another 9 in the future that likes .357's.

[Pbaker]

I have approximately 1,000+ rounds that I sized to .357. It would be easier to just scrap them and melt them down with a batch of COWW. It’s much easier to size everything to .358 for now, and then size again to .356-.357 when/if needed.

My upper is an Aero, as well as the barrel. From my measurements/estimate, the throats will accept anything smaller than .3605”. So sizing to .358 should work out just fine.

[David2011]

I have to disagree that 9mm doesn’t need a crimp. It should be taper crimped to 9.65mm/0.3799” at the mouth. I measure “a hair’s breadth” behind the mouth to be sure I’m not measuring on a burr. The taper crimp assures adequate case tension.

[AlHunt]

I have to disagree that 9mm doesn’t need a crimp. It should be taper crimped to 9.65mm/0.3799” at the mouth. I measure “a hair’s breadth” behind the mouth to be sure I’m not measuring on a burr. The taper crimp assures adequate case tension.

And gives you a better chance of consistency. Not that the short distances people seem to shoot 9mm at require match grade ammo but I like to crimp.

[Pbaker]

On a side note/issue, has anyone tried to custom fit their seating stem using JB Weld? I’m getting the olé smiley face on the tip of my RN bullets. Thinking about re-profiling it with some JB Weld :roll:

[bangerjim]

Faster powders are your solution.

Dark brass.....no problem. Dirty brass (with rough crud on it) needs to be cleaned but shiny new IS NOT required for any load!

[Pbaker]

The reason I settled on HS6 is because I’m using an 8.3” barrel, so I figured the slower burn would be good for this setup. Many people use HS6 for many pistol applications, so it’s not particularly a powder issue. I definitely have/had undersized bullets, possibly mixed with a light load. I need to mix up some more loads with larger bullets and see where that gets me.