Px4 Full Size Velocity Abnormalities?

[arcfide]

So, I'm aware that different barrels and different bore diameters and the like are going to give all sorts of differences in velocity and accuracy for specific loadings. However, I've encountered a consistent pattern with my Px4 Full Size 9mm that I want to corroborate with the readership here who have Px4's.

In short, with every load that I've tried (commercial and hand loaded) with the Px4, it comes in at *significantly* reduced velocities over comparable barrels in other handguns, such as the APX, and much lower than expected velocities compared to the standard velocities listed in my reloading manual for barrels of the same twist and length.

One example is a Nosler +P 124gr commercial loading that came in at 1033 FPS, despite being labeled as closer to 1200 FPS "on the box." Seeing other chronograph tests of this ammo seems to indicate that this is a wide outlier on this particularly ammo.

Another is a handload that I worked up and comes in at around 1200 FPS for a 115gr Hornady HAP round. Out of the APX, that load tracks right along with the expected velocities in the Hornady manual. However, with the Px4, it's coming in at 1110 FPS, which is significantly slower than predicted by the manual and my testing out of the APX. In this case, the ammo was tested on the same day back to back.

I have a second Px4 that I could test against to see if this is just this barrel or something, but that Px4 is still NIB, and I'd prefer to keep it that way.

I was hoping that some of you would have done some chrono-testing of your own Px4's and could indicate whether this is also what you're seeing out of your own Px4's?

I've also had a weird phenomenon with 115gr Tac-XP Black Hills loadings out of the Px4. Usually the Px4 is reasonably accurate at 25 yards with any ammo. And with the HAP rounds mentioned above, it's still very accurate despite the difference in velocity. However, with this Black Hills stuff, it's literally not on paper at 25 yards against an 8" bullseye target on a letter-sized sheet of paper. Out of a 5 shot group I might get two that show up on the left side of the sheet somewhere. But put some other stuff in it, and I can get 2" - 3" groups right in the center without issue. Out of the APX that Black Hill load is one of, if not the most, accurate loading I've tested out of the commercial ammo I've tried.

I'm obviously over-thinking, but it would be nice if I could see the data that others have to determine how far within or outside of the norms my Px4 is.

[Leroy]

I would slug the barrel. Probably oversized grooves.

[olstyn]

I would slug the barrel. Probably oversized grooves.

Agreed. Didn't somebody on here say that Beretta 92/M9 barrels commonly shoot best with .357 and .358 bullets vs the .355 and .356 that are the standard size for 9mm because they tend to run a bit oversized? It wouldn't be a shock for another Beretta gun to be similar in that regard, and that could easily explain the lower than expected velocities.

[DAB]

likely the ammo boxes velocity is based on a full sized test barrel.

have a chronograph? other pistols (full size, 5") with longer barrels?

[arcfide]

likely the ammo boxes velocity is based on a full sized test barrel.

have a chronograph? other pistols (full size, 5") with longer barrels?

I thought this as well, until I took another Beretta brand firearm (APX) with a barrel length of very similar length (4.25" vs. 4") and found a huge velocity difference with identical loads on the same day. The 4.25" APX barrel was at or just a little above (as expected) the listed velocities for that loading based on the printed documentation (Hornady manual, based on a 1:10" twist 4" 9mm barrel).

[DAB]

if it's accurate, i wouldn't worry too much about it. if you are using it for matches where they check power factor, then it would be beneficial to do a chrono check so you know what velocity is expected.

[Bodhi]

Buy a new barrel maybe.
I did a quick search on the Beretta forum and found the exact same thread.
http://berettaforum.net/vb/showthread.php?t=132764
There is such a thing as over analyzing everything.
Are you going to go around and post the same thing on every pistol forum, just curious?
The responses in the same thread on the Beretta forum weren’t up to your expectations so you felt the need to post it here also?

Then the odd thing I discovered while searching on that forum was you’ve started 13-14 threads there on various subjects just this month alone.
http://berettaforum.net/vb/search.php?searchid=2897422

Best of luck sorting out all the various issues you are having. Seems a bit strange.

[arcfide]

Buy a new barrel maybe.
I did a quick search on the Beretta forum and found the exact same thread.
http://berettaforum.net/vb/showthread.php?t=132764
There is such a thing as over analyzing everything.
Are you going to go around and post the same thing on every pistol forum, just curious?
The responses in the same thread on the Beretta forum weren’t up to your expectations so you felt the need to post it here also?

Then the odd thing I discovered while searching on that forum was you’ve started 13-14 threads there on various subjects just this month alone.
http://berettaforum.net/vb/search.php?searchid=2897422

Best of luck sorting out all the various issues you are having. Seems a bit strange.

Hah! Yes, I posted the same thing on Beretta Forum. And I found the answers there about what I would expect. I'm not disappointed. And I just post on PF and BF the things that seem like they might both have relevance on either forum to get a wider response and to hear differences of viewpoint. I was hoping to get more data. I'm not really trying to solve a problem, but to understand the behavior and to situate that behavior amidst the distribution of behaviors exhibited by other Px4's. If I could, I would just go around and chronograph and slug all the barrels I could find and then develop some statistical estimate of the distribution of these behaviors across all Px4 barrels based on my sampling, but I can't really do that. :-)

I simply enjoy understanding and trying to get at the root cause of particular behaviors I see that deviate from standard expectations. I'm not disappointed with the Px4's performance, but I would love to have a definitive reason and justification for the behavior of the barrel relative to my APX barrel, for instance. I just don't want to buy 15+ Px4 barrels in order to get all the data.

And I'll admit, this month has been...above average in terms of starting threads on BF, most of them aren't "issues/problems" so much as things I've been thinking about and want to see what other people think.

[DAB]

any idea of the range of velocities in the same box of ammo?

[arcfide]

any idea of the range of velocities in the same box of ammo?

With the Nosler 9mm +P ammo I tried (I haven't tried it yet with the APX, but plan to do so), I got (1013, 1020, 1065, 1042, 1026).

With the handloads that I've tried (115gr HAP with 6.3 - 6.4gr of Power Pistol, COL 1.075", at 1200 FPS according to Hornady's manual with 1:10 4" barrel), I got a very consistent 1110 - 1116 FPS or thereabouts with my 5 shot group, but I don't have the exact numbers on me. I did test the same load with the APX on the same day and got 1170 - 1230 FPS or thereabouts, but I also don't have the exact readings for that one. They were mostly in the 1180 - 1210 range, though.

I tested some Black Hills 115gr TAC-XP +P from both guns, but only chrono'd from the APX last time, but it showed values in the same range as my handloads for the APX.

I plan to go back out and get more testing with some plated bullets that I have, as well as the HAP rounds and the Nosler rounds with both the Px4 and the APX to see if I can replicate my original numbers. I plan to get chrono readings of the Black Hills stuff as well, and see if I can finally figure out what sort of pattern the Px4 is shooting with that round, since it doesn't hit anywhere near point of aim with that load.