Lead "blow-back"

[biscot]

OK, I'm not sure exactly how to describe this, but I'm having a problem with my Browning Hi Power. I recently put in a new Olympic Arms barrel, and it's a pretty tight fit, but the action works fine when it's clean.
The load I'm using is a Lee 124gr TC boolit (water-dropped WW) over 5.4 gr Blue Dot with OAL 1.04.
It cycles fine, shoots great, clocks at 1060 fps. There's some leading, but it doesn't seem to get any worse and doesn't affect accuracy, even after a couple hundred rounds.
But, occassionaly I get a flake or two (like small oatmeal flakes) of lead blowing back out the ejector port, and a couple of times it has fouled up the action so the slide doesn't fully return. If I lock back the slide and wipe out the fouling on the underside of the top of the slide in front of the firing pin assembly, I'm back in action.
My main question is why I'm getting the lead flakes blowing back. Is this at all common or have I got something weird going on?

[cephas53]

Had something similar on my 45apc. Very occasionally I found that I had not opened the mouth of the case enough when seating the boolit. This shaved a very, very, small sliver onto the side of the case. Don't know if that's what happening with you but thought i'd pass it on. have a good one!

[trk]

Might try cycling a few rounds (not firing) through the action. Look to see on the bullets where (if) the flakes were scraped from. (To sort out the question, do the flakes come from cycling or from firng).

[biscot]

I'm pretty sure they're coming from firing - I can cycle without firing and don't get the problem. It's almost like (I could be way off here) it's lead that was plastered against the barrel that's getting blown out somehow.
I'm sure the cases are clean going into the magazines - I'm not getting slivers from loading.

[243winxb]

Try a different powder like Bullseye or Unique in your 9mm. You might be seeing unburnt powder. Old Alliant data (1999) shows a maximum of 8.2 gr of Blue Dot with a 125 L bullet-1190fps-29700psi Your load seems to give a very high velocity for only 5.4grs of Blue Dot, maybe its the barrel?

[biscot]

OK, I'll try a different powder. I've noticed that other people seem to use more BlueDot - how could the barrel affect this?

[Three44s]

Getting back to what cephas53 posted:

What he's trying to warn you about is not enough belling before you charge or seat.

The case mouth is cutting off some lead and it wads up between the inside of the case and the side wall of the boolit. When you fire those rounds ....... the now loose lead comes out and you can't distinguish what the origin is.

I have the same problem with revolvers ...... it's not an auto thing ...... it's a too little belling thing.

What I do:

I use a Very Low Drag case mouth champhering tool (VLD) ...... don't get too carried away though.

Then I use the Lyman "M" die ..... this gives me a more gentle belling ...... but more precise.

Of course this all has to be predicated on pretty uniform case length.

In a revolver, it's not a big sweat but in an auto ......... it's a big deal because you can't cut the cases overly short. ........ It ruins your headspace ........... (I load for 9mm in an auto myself) ........

This may entirely not be what is bugging you ...... but it's important to rule it out before you go looking elsewhere .........

Remember ........ always start with the simple solutions first!

Three 44s

[243winxb]

how could the barrel affect this?

Tight chamber maybe.

[HeavyMetal]

The 9 mm is such a pain to reload for because almost anything can go wrong in the loading cycle.

Because of this each gun must be viewed from an individual stand point.

In this case the OP is using a Lee TC design that seats a little deeper in the case than RNL designs so a lite load of Bluedot is giving him slightly better velocity.

So I'll make a few suggestions and see if I can help.

Are you using a Lee, or any one else's, taper crimp die? Mis adjustment can be a tough one to catch. Bottom line if you can see the "taper" crimp it is way to much!

Are you useing mixed case's? If you are stop and sort by head stamp.

Have you trimmed your case's so they are all the same length? If not do so after you sort them .750 Plus or Minus .002 is what you want but you may find all your 9mm brass shorter than that....adjust as needed. length isn't as important as having them all the same length!

I like Bluedot and use it a lot in my 9mm's but are you sure the flakes your getting are lead and not unburned powder?? I'd bump the load up a touch and see if the issue goes away IF your already doing all of the above.

Check expander ball size and make sure it is not under expanding the case. Many die sets for the 9mm are set up for ball ammo diameter and the expanders are about .351 or so. This can "size" the boolit as you seat it and what your getting could be a by product of poor case expansion.

Please be aware that case mouth "flare" is not the same thing as case expansion!

Is your TC mold a tumble lube design? If it is those little driving bands could simply be failing once in awhile as the load could be right on the boarderline of lube failure.

I think that should give you some food for thought and provide you with an answer for the issue.

[243winxb]

Lead shaving leaves a thin ring of lead on the bullet, right in front of the case mouth. You can remove it with a thumb nail. This sometimes happens during bullet seating when the seat/crimp dies inside diameter is on the small side. To avoid this shaving, seat bullet, then taper crimp is separate operations. Belling the case mouth correctly helps, but not always.

[243winxb]

Case trimming- Maximum length is .754" most never trim as brass does not seem to grow. RCBS gives max & trim length at .754" no trimming. Lyman is trim to .751" HeavyMetal makes a very good point, life is better when brass is all the same length. Seat bullet, then taper crimp in separate operations, this helps.

length isn't as important as having them all the same length!

Headspacing is on the case mouth, to short brass can cause misfires in autos, and for sure in Ruger Blkhawk convertibles.

[biscot]

Great - lots of ideas to sort out.
(I'll start with the simpler ones first - sorting headstamp, checking case expansion and belling, trying a different powder charge).
I just got a new Magma mold I'm going to try, also.

[fecmech]

biscot--I think you're getting unburnt powder back. That load with BD is very light and you can easily go to 6.5 with no problem and see if it clears up. Also are you loading the TL lee bullet or the one with the lube groove?? If the TL you might be shaving some lead on the seating. Bell the living daylights out of the cases and just turn them back with the taper crimp, there are bazillion 9MM cases out there!