KKM barrel accuracy concern

[Julien Boit]

Hi all,

I recently had one of my pistol rebarreled with a .40sw KKM bull barrel.

I had a hard time getting it fitted inside a STI slide, I had to remove lots of material to have a perfect fit.

I also had a hard time cutting the chamber. It seemed that the rifling was starting early in the unfinished chamber and I spent a lot of time to get the reamer cut the chamber properly.

The lock up is good, but the barrel seems inaccurate.

I recut the crown in case this was the culprit of poor accuracy, but it had very little effect so far.

I've yet to gauge the real inner diameter of it, but I'm unable to have descent groups.

Anybody have experienced something similar ?

[want2race]

Fun huh? Yeah, the KKM chamber isn't short chambered. It's rough chambered. Your finish reamer probably started to cut at the barrel hood right?

If this was the case, it is possible that the chamber was cut at a slight angle to the actual bore (if done by hand).

The area of the barrel that needed to be looked at is the width of the feed ramp area. That area is machined a bit on the wide side. Thin it out slightly and it will slip in the slide easier. Hopefully you found where is was binding. I've had slides so tight I had to open up the inside bore before the barrel would even start to fit into it.

Check to see if the barrel is in tension when locked up. Edited: Reread that you have a bull barrel, no bushing. Where did you take material off to get the barrel into the slide?

How deep did you cut the chamber? GO gauge? +.002? You could try a little free bore if you a throat (only) reamer. Some have had success with 10mm throat depth, with a .40 chamber.

There are so many variables that can turn an install ugly. I bought a "professionally built" pistol and found many areas there were LESS than ideal. Barrel fit was one. Very sloppy barrel install. Disappointed to say the least.

Edited November 20, 2007 by want2race

[steel1212]

HACK!!!!

W2R's "professional built gun" not W2R lol

Edited November 20, 2007 by steel1212

[dirtypool40]

My "mall ninja supremo" SV by Millenium has a bushing KKM in it and is a tack driver.

I don't know if it's a QC issue or something else. Contact Kevin, I'm sure he'll sort you out.

Edited November 20, 2007 by dirtypool40

[Julien Boit]

I had to get material removed in the locking area of the barrel.

I measured the inner diameter yesterday, and it's a .400, not a .401

I will make a gauge to check for chamber concentricity with the rifling.

As far as I can remember, I started to cut the chamber at the end of the rough chamber, not at the barrel hood.

I used a clymer reamer. I used it two times before, so the tool is in perfect condition.

Thanks for all the input guys

Edited November 20, 2007 by Julien Boit

[want2race]

I only get two barrels (KKM barrels) out of a finish reamer. The third one turns out bad. Manson reamers.

My first KKM had a short chamber, very easy to finish. Every barrel since has been rough all the way out to the hood (chamber reamer won't go into the barrel at all).

[dirtypool40]

is this a recent purchase? I think I heard Chcuk at Shooter's Connection talking about KKM tightening things up spec wise, and I know Dan Bedell uses a lot of them.

I would contact Chuck, Dan, and of course Kevin.

[shooterbenedetto]

I have a KKM barrel on my back up big match open gun in 9mm and it is accurate!!

[TrueDoubleTaper]

I agree, the KKM barrels have a lot of extra material and the chamber is very difficult to ream. I always have a couple of extra hours fitting these barrels but have not had any accuaracy problems.

[Julien Boit]

I made a gauge to check chamber and rifling alignment, it seems Ok.

I cleaned the inside to get the copper deposit (very light) out.

I will now try it again on bench and see what's next.

[Godzilla]

Just a thought....

The Schuemann AET barrels come with finished chambers!

[HSMITH]

I have built a couple Open 9mm guns with KKM barrels, and they have all been REALLY accurate. I run a KKM in my own 9mm major gun. There is a lot of material to move to fit them, and it does take longer. I haven't had any problem reaming the chambers at all though.

[chuckbradley]

Just a thought....

The Schuemann AET barrels come with finished chambers!

Only if the hood needs no fitting to the slide. Fit the hood to the slide and then it has to be reamed again which Schuemann says not to do but you have no choice. The AET and the finished chamber was designed to be used moslty in an SV slide with interchangeable breechface. They dont fit the hood to the slide. They just pick the best fitting breechface for the particular barrel.

[chuckbradley]

I only get two barrels (KKM barrels) out of a finish reamer. The third one turns out bad. Manson reamers.

My first KKM had a short chamber, very easy to finish. Every barrel since has been rough all the way out to the hood (chamber reamer won't go into the barrel at all).

I asked Dan about this. he hasnt had any problems and gets dozens of reamings out of a reamer but he uses a Clymer reamer. KKM's come with a short chamber so you can fit the hood then ream for your choice of round. If you got one with a rough chamber I would call Kevin and get it exchanged.

[ocx]

I have a KKM 9mm barrel in a custom STI and it is bullseye accurate. 1.5" at 50 yards out of a rest. Chamber is critical. So is the gunsmith.

[want2race]

My definition of short chamber is: Head space gage will go into chamber, obviously it's short so theres a bunch sticking out. Ream for correct depth.

My experience with KKM barrels have been (except the first one): Head space gage will NOT go into chamber at all. It's not only short, but it's narrow (or tight). This is really only an issue when reaming by hand. If the underside of the hood is is not cut by the chamber cutter of the reamer first it will not enter the chamber centered. This takes a lot of care when doing it by hand. The bullet will sit low in relation to the bore. If the barrel is reamed on a lathe then the hood gets cut first anyway, but because the reamer is not supported on all sides during the process it needs a slow feed rate at least until the reamer enters the chamber (IMO). I'm sure the reamer lasts longer when used with a lathe.

Even with the extra time involved (if reamed by hand) I still really like KKM's. One might not even notice a difference if the reaming is done on a lathe.

[steel1212]

I only get two barrels (KKM barrels) out of a finish reamer. The third one turns out bad. Manson reamers.

My first KKM had a short chamber, very easy to finish. Every barrel since has been rough all the way out to the hood (chamber reamer won't go into the barrel at all).

I asked Dan about this. he hasnt had any problems and gets dozens of reamings out of a reamer but he uses a Clymer reamer. KKM's come with a short chamber so you can fit the hood then ream for your choice of round. If you got one with a rough chamber I would call Kevin and get it exchanged.

little late now