KKM vs LWD

[10mm-Admirer]

I've had 5 KKM barrels in various calibers. All have been flawless. I sent one in to have it shortened to stock length. They did it fast at no charge and refinished it in the process.  I buy KKM without hesitating if I want an aftermarket barrel.

[Texasbeanman]

I went with the LW, $99 shipped on eBay.
Works great with all my reloads so far!

[Ridgerunner665]

What is the actual modification KKM makes?

They open the throat .001-.002" and extend the freebore to accommodate oversize, longer bullets, WFN's, and higher pressures. You can do the same on any barrel, with some elbow grease and toothpaste (polishing compound) or fire-lapping, which is much more effective than machining.

I've spoken to KKM about this twice in the last couple of weeks...I was told they open the throat to give the oversize (.401"+) WFN lead bullets room to breakover into the chamber...they do not extend the freebore or anything else...just open the throat a little.

Doing so greatly improves feed reliability at the cost of a very small amount of case support...a necessary trade off I believe, if it won't feed case support is a moot point.

I'm not trying to call anybody out or anything, just sharing what I was told...it was this thread that led me to ask them the question....the way KKM put it was that Buffalo Bore, Underwood, etc. doesn't crimp those wide flat lead bullets...thats sounds a little strange to me but I don't have any to measure at the case mouth. It does however make sense when you consider that lead bullets are generally .001" - .002" oversize....the oversize bullets along with the lack of a good crimp and you have the need for a little more room in the chamber.

I elected to get my KKM barrel made without the "Underwood" treatment...he said if it ended up needing it due to feed issues, send it back and they'd fix it. I don't shoot lead much, if at all, preferring XTP's...so I don't really need it.

In case anybody is wondering...I ordered a 7" barrel for my G40 MOS.

[The_Shadow]

Well I do measure a lot of stuff when doing the pull-down documentations and I also measure the bullet in several locations as well as the casings in several locations.  I will even slip them into a case gauge at times if things seem out of spec.

Underwood 5 different Cast bullet cartridges  Very consistent with the different samples.

1) Underwood 220gr Hard Cast  Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
2) Underwood 220gr Hard Cast(reduced) Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
3) Underwood 220gr Hard Cast Crimp Diameter 0.4220", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
4) Underwood 220gr Cast WFN Crimp Diameter 0.4220", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
5) : Underwood 200gr Hard Cast Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"

Double Tap 2 different samples

1) Double Tap 230gr Hard Cast Crimp Dia. 0.4165", Bullet Dia. 0.4005" Crimp squeezed bullet to N/A Crimp squeezed bullet N/A
2) Double Tap 200gr Wide Flat Nose Hard Cast Gas Checked Crimp Diameter 0.4185", Bullet Dia. 0.4005" Crimp squeezed bullet N/A

Buffalo Bore 1 sample

1) Buffalo Bore 220gr Hard Cast Crimp Diameter 0.4225",  Bullet Dia. 0.4010" Crimp squeezed bullet to 0.4005"

Now I will say that I size my own bullets @ 0.4015" and has not been an issue and feeding has been great in all of my guns factory and the LWD and Storm Lake aftermarket barrels and they also fit the Lyman Case gauge.

If KKM's barrel chamber is less than 0.4230" then that would be smaller than a case gauge.   Most tighter chambers have been about 0.4275" 0.4280",  where Glocks run about 0.4340" (loose).

[Ridgerunner665]

Got any numbers for Hornady, Remington, Winchester, Sig, or Federal 10mm ammo...for comparison of the case mouth measurement? Jacketed bullets...

SAAMI says .423" for the case mouth and .424" for the front of the chamber.

[Duck of Death]

Put a Storm Lake in my G29.  Starline cases measure .4280 at the base after 13gr/14.5gr #9 /w 180gr cast/Zero bullets.

[Ridgerunner665]

Well I do measure a lot of stuff when doing the pull-down documentations and I also measure the bullet in several locations as well as the casings in several locations.  I will even slip them into a case gauge at times if things seem out of spec.

Underwood 5 different Cast bullet cartridges  Very consistent with the different samples.

1) Underwood 220gr Hard Cast  Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
2) Underwood 220gr Hard Cast(reduced) Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
3) Underwood 220gr Hard Cast Crimp Diameter 0.4220", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
4) Underwood 220gr Cast WFN Crimp Diameter 0.4220", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"
5) : Underwood 200gr Hard Cast Crimp Diameter 0.4225", Bullet Dia. 0.4010" Bullet Squeeze Dia. 0.4010"

Double Tap 2 different samples

1) Double Tap 230gr Hard Cast Crimp Dia. 0.4165", Bullet Dia. 0.4005" Crimp squeezed bullet to N/A Crimp squeezed bullet N/A
2) Double Tap 200gr Wide Flat Nose Hard Cast Gas Checked Crimp Diameter 0.4185", Bullet Dia. 0.4005" Crimp squeezed bullet N/A

Buffalo Bore 1 sample

1) Buffalo Bore 220gr Hard Cast Crimp Diameter 0.4225",  Bullet Dia. 0.4010" Crimp squeezed bullet to 0.4005"

Now I will say that I size my own bullets @ 0.4015" and has not been an issue and feeding has been great in all of my guns factory and the LWD and Storm Lake aftermarket barrels and they also fit the Lyman Case gauge.

If KKM's barrel chamber is less than 0.4230" then that would be smaller than a case gauge.   Most tighter chambers have been about 0.4275" 0.4280",  where Glocks run about 0.4340" (loose).

I didn't catch it the first time I read this reply (jet lag, rough couple days)...but what you've posted there agrees with what i was told on the phone.

He did not mention Double Tap as being one that needed the opened up throat....but he did mention Buffalo Bore and Underwood...your measurements show that DT has a tighter crimp than BB or UW....goes right along with what he told me.

[The_Shadow]

All of the ammo that has been documents is posted on this forum right here;http://10mm-firearms.com/factory-10mm-ammo-pull-downs/

With most jacketed 0.4000" bullets the finish crimp is usually 0.4215" to 0.4225"  I have also measured over crimped stuff below the 0.4210", then the bullets start to be affected by the crimp.  Plated bullets can suffer damage to the fragile jacket.
I have seen where the LEE FCD being used can reduce the size of a cast bullet which can cause leading issues, loose bullet fit!