Px4 Leading : MG FMJ 115gr & BullsEye

[arthury]

I shot about 250 rds of 9mm Montana Gold (MG) 115gr FMJ powered by 4gr of BullsEye and when I cleaned the barrel today, I saw quite a bit of leading which my regular bore brush cannot remove.
Had to resort to ChoreBoy on brush.

Anyone seen this before? I do not think the 4gr of BullsEye is overpowering the bullet, do you? Please be reminded the MG FMJ have open base and lead is exposed at the bottom. I'd expect super high velocity and magnum pressure can certainly melt the lead but 4gr of BullsEye?

 

[LiveLife]

The groove diameter of your barrel may be oversized and the base of the bullet may not be expanding enough to seal with the barrel and causing the leading. Typical factory barrels are .355"-.356" but some are oversized at .357"+, which will require you to use higher powder charge to expand the lead base of FMJ.

I'd expect super high velocity and magnum pressure can certainly melt the lead but 4gr of BullsEye?

High pressure powder ignition gas may melt lube around lead bullets but will not melt lead - instead, it will blow loose lead particles towards the muzzle end of the barrel. You need sufficient chamber pressure to expand the exposed lead base of FMJ to seal with the barrel. If the powder charge is not high enough, you may get lead particles leaking around the bullet as the bullet travels down the barrel causing lead deposits.

2004 Alliant load data lists 5.0 gr max powder charge for 115 gr FMJ bullet. I use Winchester 115 gr FMJ with 4.2-4.4 gr of Bullseye with 1.135" OAL. My various pistol barrels are .355"-.356" and I do not experience the same problem you are having. For your next range trip, you could load 10 test rounds of 4.2, 4.4 and 4.6 gr and see if the leading decreases. Take a cleaning kit with you and clean between incremental powder charges. +1 on copper scrubber (Chore boy) wrapped around an old bore brush - few strokes back and forth and leading is gone!

If higher powder charges do not resolve your leading issue, you could consider using CMJ or JHP bullets. MG CMJ bullet are FMJ bullets with a metal disk at the base to cover the exposed lead.

I have shot Montana Gold FMJ for match shooting and many have gone to JHP for cleaner shooting. My match load using 165 gr 40S&W FMJ (RNFP) vs JHP is comparable in accuracy due to mid-to-high range load data I use for target loads but in theory, at high-to-near max load data, the FMJ load has higher potential for accuracy due to the exposed lead base.

 

[arthury]

Thanks for the response.
The funny thing is that the same load did not lead my Beretta 92 nor the M&P9.
Like you said, these barrels could be slightly different compared to the Px4.

 

[LiveLife]

Slugging the barrel will determine the groove diameter of the barrel. If the Beretta Px4 barrel is larger than Beretta 92/M&P 9 barrels, it would explain the leading.

 

[arthury]

Yes, I have done that before when I was casting bullets for my 500SW.
Let me up the load for the BullsEye first. I may just keep with my WST instead if BullsEye continues to lead.

 

[918v]

You are trying to get a FMJ bullet of unknown core hardness to obturate? Not going to happen at any sane pressure.

 

[LiveLife]

918v, FMJ cores are softer than hard cast bullets. At high enough chamber pressures, the exposed lead base will expand to seal with the barrel (well, you'll still have some gas leakage through the voids as jacketing won't fully conform to the rifling of the barrel).

My guess is that the Beretta Px4 barrel is oversized (say .356"-.357"+) and he's leaking high pressure gas/lead particles around the bullet. 4.0 gr is fairly low powder charge and he could try higher powder charges to see if leading will decrease. If not, I suggested CMJ/JHP bullets to resolve the leading issue.

 

[918v]

918v, FMJ cores are softer than hard cast bullets. At high enough chamber pressures, the exposed lead base will expand to seal with the barrel (well, you'll still have some gas leakage through the voids as jacketing won't fully conform to the rifling of the barrel).

FMJ cores vary in hardness depending on manufacturer. Then there is NATO spec which is harder still. The most you can hope got is .001" at 35000 PSI and it prolly won't stop leading if his barrel measures .357" like the M9.