Possible issue with brand new HK Mk23

[Hootiewho]

I just got the tax stamp back on a KAC MK23 suppressor and I stopped by PSA Friday and bought a brand new HK MK23. I took it out today to do some factory load testing and then adjust the suppressor piston to try and get the POI as close to the pistol w/o the can as I could.

I shot all factory ammo:

FGMM 230gr
Amwrican Eagle 230gr
Speer 230gr Gold Dot
Win 230gr Ranger T
Win 230gr brown box ball
Hornady 230gr +P XTP

I’ve owned a first year Mk23 and own a HK USP Expert 9mm as well as a couple P7’s, VP9, P30’s...
The older Mk23 I owned would consistently shoot premium ammo into a 2.5” group at 50 yards from the bench. The USP Experts will too. This new Mk23’s best group without the suppressor was around 6” at 50 yards benched. Absolutely nowhere near what I’ve had other HK’s do. I also had a handful of brand new Federal Gold Metal Match cases split starting about 1/3 the way up from the casehead all the way to the mouth. The side where the split is was also visually bulged. I am not home yet to check them with the calipers but it looks like all the brass has a slight bulge on one side and is discolored from powder burn. The bulge also starts around 1/3 of the way up from the casehead and forward. It is not like what you would see in a Glock 40 cal where the casehead/base is not supported. Looking inside the chamber I can see heat discoloration on the chamber wall opposite of the ejection port.

Is it possible I may have a messed up chamber?

I’m not boastful, but I know what I can do with a rifle and pistol. I know when it is me and when it is equipment. When shooting today I would slide back over to my 9mm USP Expert and stack bullets on a 3” shoot n see at 50 yards.

Another thing I noticed with the American Eagle 230gr is every few rounds I would have one that would be wildly off, like 2 feet at 50 yards. That early mfg Mk23 I owned would NEVER do that. Unfortunately I sold it because I want to install an RMR on my Mk23 and I couldn’t bring myself to mill that beautiful prestine maritime finish slide. I guess I should have kept it.

Any insight is appreciated. I figured I’d ask here and see what you guys think it might be before I call HK.

[Campbell]

I’ve had a lot of HKs, several friends have older MK23s, even without the case issues that accuracy on THAT handgun would be unacceptable to me.
I’m interested to see what HK has to say, as well as the SME/ senior members here.

[Pappabear]

Oh man that sucks, I have always wanted a 23. I hope it works out.

PB

[Hootiewho]

Oh man that sucks, I have always wanted a 23. I hope it works out.

PB

Well this does suck. I got home and have around a 0.020 high spot in near every case. I have a machined flat surface at home and I can roll live rounds across it and they roll perfectly smooth. Looking straight under the case where it rolls there is no variation where the surfaces meet. If I roll any of the fired cases there is a definite high spot and you can see the warpedness of the case by the light shining through as it rolls along. It also does the speed up/slow down as it comes and goes over the high spot. I would say the chamber is slightly oval shaped by looking at this brass.

I’ll give HK a shout in the morning and get it sorted out. I’ll update what is found.

[og556]

I’m certain HK will take care of you. They have always gone above and beyond with the very few issues I’ve had over the years.

[Hootiewho]

I know they will. I’ve never had any problems before but any time I’ve ever called they have always been extremely helpful.

[azeriosu85]

My most recent 2018 HKs have all been hit or miss for QC. Blasphemy i know, but that seems to be on par with newer models. HKpro forums have alot of issues cropping up with new pistols that have never been seen before as well

[1_click_off]

When I get home this weekend I will roll and mic some of my brass from my Mk23. Will let you know if I see the same raised area you are.

[Hootiewho]

I got some cerrosafe in from Brownells today and just poured a cast of the chamber. Sure enough I have a variance of about 0.020” in the chamber right where the case split. I can rotate the mold 90 degs and get 20 thou difference in my measurement. I’m going to mail it off tomorrow and include the slug so they can use it to help them diagnose the issue.

I’ll post some pics shortly

[Hootiewho]

C05361DF-FEFC-40EE-AB5B-702728C4282E.jpg

This picture shows the high spot on a few factory new federal cases. I rolled them in ink with the case rim hanging off the ink pad.

2DE0D18B-0848-46AB-B087-2095011ED4D2.jpg

This is 180 degs from the high spot

90185FF8-1E60-4430-A7A0-431BB543EBB4.jpg

Blown out brand new federal 230 gr gold metal match

9D943050-C447-4E9B-9A4D-0A609F35FB64.jpg

Side view.

You can see discoloration on one wall of the chamber, and these pictures jive with the measurements I took off my chamber cast.