KKM Chamber Question

[Hatchet Jack]

I have a major 9 built on a Glock 22. It has a KKM 9mm/40 barrel. Ammo that drops freely in and out of the chambers of my Glock 34 and 17 fail to seat all the way in the KKM. Is this unusual? Does anyone know if this is unusual? Are the KKM chambers overly tight? I am using new Star Line brass. 125 grain Zero JHP and OAL is 1.142"

[SuperAWE]

Yes, the KKM and for that matter, most all aftermarket match barrels have a much tighter chamber, than factory glock barrels. Same thing happens on my glock 35 with the KKM barrel. I use a factory crimp die and tweak the crimp just enough so the loaded rounds drop freely into the chamber.

[Flexmoney]

You may...and it sounds like you do...have a barrel that hasn't had the chamber "finish reamed".

After-market barrels often come with "short chambers". The reason is that the barrels will be fit to the gun, then the chambers can be custom cut.

So, your chamber might be overly short for your ammo...and the bullet could be hitting the rifling. That will raise pressure if you shoot anything out of it. So, don't go blasting away with Major 9 until you get it addressed !!

[gm iprod]

You may...and it sounds like you do...have a barrel that hasn't had the chamber "finish reamed".

After-market barrels often come with "short chambers". The reason is that the barrels will be fit to the gun, then the chambers can be custom cut.

So, your chamber might be overly short for your ammo...and the bullet could be hitting the rifling. That will raise pressure if you shoot anything out of it. So, don't go blasting away with Major 9 until you get it addressed !!

Agreed.

Check and see if empty sized cases go in and chamber properly by hand. If so then make a few dummy rounds with varying bullet seating depth to find if the projectile is impinging on the throat.

If the sized cases do not fit, check that the sizing die is adjusted properly, then if no go get the gun to a gunsmith that you trust and get the chamber set correctly.

[Hatchet Jack]

You may...and it sounds like you do...have a barrel that hasn't had the chamber "finish reamed".

After-market barrels often come with "short chambers". The reason is that the barrels will be fit to the gun, then the chambers can be custom cut.

So, your chamber might be overly short for your ammo...and the bullet could be hitting the rifling. That will raise pressure if you shoot anything out of it. So, don't go blasting away with Major 9 until you get it addressed !!

Agreed.

Check and see if empty sized cases go in and chamber properly by hand. If so then make a few dummy rounds with varying bullet seating depth to find if the projectile is impinging on the throat.

If the sized cases do not fit, check that the sizing die is adjusted properly, then if no go get the gun to a gunsmith that you trust and get the chamber set correctly.

I took the barrel out and dropped some sized brass into the chamber. All fit, no problem. Heck even a belled case fits. Some ammo will chamber properly and some won't. I sight blacked the bullet of one of the rounds that would not chamber all the way and slid it into the chamber. Although the round did not fully chamber, there were no rifling marks on the sight blacking. It came out looking the same as it went in.

I also took a bunch of different rounds and measured the crimp at the case mouth and also measured the bullet diameter immediately in front of the case mouth. It probably doesn't mean squat, but here's what I found:

Legend -

Sample round

Crimp/Case mouth dia.

Does sample fit into chamber?

Bullet dia fwd of case mouth

Belled Star Line (empty) case

.3804"

yes

n/a

125 Zero JHP in Star Line case (1.142" COL)

.3783"

no

.3553"

115 Speer GDHP (1.066 COL)

.3766"

yes

.3476"

147 PD FMJ (1.142" COL)

.3768"

yes

.3532"

115 WW Silvertip JHP (factory) (didn't record COL)

.3766"

yes

.3541"

115 MG JHP (1.066" COL)

.3778"

no

.3520"

[Braxton1]

On my G-34 with a KKM, I had to run a Manson finish reamer thru it before it would run reliably with any sort of reloads. Out of the box, it would run with factory new ammo, but not reloads.

Most of the metal removed by this reamer came from the front half of the chamber, making me believe that the chamber had a bit more taper to it.

[Hatchet Jack]

On my G-34 with a KKM, I had to run a Manson finish reamer thru it before it would run reliably with any sort of reloads. Out of the box, it would run with factory new ammo, but not reloads.

Most of the metal removed by this reamer came from the front half of the chamber, making me believe that the chamber had a bit more taper to it.

That sounds exactly like what's up with my KKM. The fella who built it for me is going to run a finish reamer through it. I think the front end of the chamber is somewhere around .0015" too tight.

[the duck of death]

I built a open G34 using a KKM barrel. OAL of the cart. I wanted to use was 1.145, it wouldn't fully fit fully in the chamber. On calling KKM they said to send the barrel back and they would run the NATO reamer in the chamber---problem solved.

[Hatchet Jack]

I built a open G34 using a KKM barrel. OAL of the cart. I wanted to use was 1.145, it wouldn't fully fit fully in the chamber. On calling KKM they said to send the barrel back and they would run the NATO reamer in the chamber---problem solved.

Pretty much the same for me.

The KKM chamber is somewhere around .0015" too tight. I sent it back to the builder and he's going to use a finish reamer on the chamber. Looking forward to getting it back and getting on with my load development.

[Kristofer_G]

On my G-34 with a KKM, I had to run a Manson finish reamer thru it before it would run reliably with any sort of reloads. Out of the box, it would run with factory new ammo, but not reloads.

Most of the metal removed by this reamer came from the front half of the chamber, making me believe that the chamber had a bit more taper to it.

I have had two KKM Glock barrels, and still have one of them. I had no problems with either as KKM shipped them to me, but I did eventually run a Clymer SAAMI minimum reamer into both. It cut a substantial throat into both. I swear it softened the felt recoil as well, even with just ball ammunition. I noticed no decrease in accuracy, but I my shooting may not be the ultimate test of such things. I do recommend this for consideration to all who are planing on Major 9 builds with any "match" grade barrel.

Edited June 30, 2009 by Kristofer_G

[Hany]

Seems like they are tighter....just a question of how much. My G17 kkm works with everything, never had a problem, a 10mm G20, was much more sensitive to dimensions. All in all, I like them, but I dont shoot many handloads in my 17.

[Hatchet Jack]

The long wait is almost over. I just got the open Glock (with finish reamed chamber) back from the builder. Taking it to the range tomorrow with chrono and test ammo in tow. Will report on my findings.