10mm Glock 20, cast, and pin gauges.

[subsonic]

I am looking to shoot cast in my Glock 20 10mm. Mine is old, one of the very first made in this caliber. No finger grooves, no light rail, etc. What I think is called a Gen 2 because they never made 10mms in Gen 1.

I have dabbled with cast and had decent, but not great results. As you folks may know by now, decent is not what I look for. I also want to use the stock barrel if I can.

So here we go.

I yanked the barrel out and started shoving pin gauges in it this morning before I ran out of time and had to go to work. I found some interesting info, the details of which I will relay when I get back to it tonight. To summarize, these things have a throat in them that is slightly tapered and kind-of oversize. The chamber is also quite oversize and tapered. Think .45 Colt Ruger for the chamber.

This is a cartridge drawing of the 10mm:
http://stevespages.com/jpg/cd10automatic.jpg

I know a .429" pin gauge started in the rear of the chamber. Larger might go.

I have a few .403" boolits from Sewerman and a .403" lubrisizer die from Buckshot. I greased them up last night.

[ebner glocken]

I have the exact same gun and used this mold for it. Lubed with javelena.

http://www.midwayusa.com/product/569185/lee-6-cavity-bullet-mold-401-175-tc-40-s-and-w-401-diameter-175-grain-truncated-cone

"Decent" is the best I got with ww231. I desired great but was not achievable w/o more time than I was willing to spend.

Ebner

[subsonic]

What alloy/hardness did you use and what sizes did you try?

[475/480]

I am using moulds from Accurate and mountainmolds in my G20 SF and Custom 10 MM-6" barrel. The Accurate mould is a 190 gr LFNGC and the MM mould is Custom 215 gr WFNGC- BOTH feed reliably in the G20 SF.
This past weekend I used a GB mould from 2 years ago- .412-200gr WC that I lubed/sized to .410 and then down to .401 in a Star sizer,shot 2" at 15 yards in the G20 SF.
Powder wise- I use AA7 in the 190gr and 215 gr loads, wc680 in the 200gr WC load (only because a have a LOT of wc680).
Here is a pic of the G20 SF and the Caspian 10MM, w/the 190 and 215 gr boolits, the extra barrel is a LWD 5.57" barrel- a tighter chamber.
The Glock chamber is cut to run ALL ammo.
Alloy - water dropped wheel weights. BHN 23

Sean
http://i184.photobucket.com/albums/x150/475480/Sheridan4-21-12119-1.jpg

[ebner glocken]

I sized down to .401" with water quenched and air cooled wheelweights. I played around with different combinations of the above.

Ebner

[subsonic]

So here is the info from the pin gauges.

What I did was stick pin gauges in and measure how far they went.

The largest pin gauge that would pass completely through the bore was .390".

.391" would drop pretty far in from the chamber end, to where I couldn't get ahold of it and had to use an ink pin to push it out. It would just try to start at the muzzle, but wouldn't go in.

The chamber would take a .431" at the rear just past the "unsupported" area. And a .424" was the largest pin that would hit the front of the chamber where the case headspaces.

A .403" boolit in a nickel Remington case measures about .423" and the case walls are .010"

If you trim cases to .982" (min) and have a 1.260" OAL, that gives you a boolit nose length of .278"

Then I took the 2" long pin gauges and started inserting them into the chamber end of the barrel and measured overall length of the pin and barrel - from muzzle to the back of the pin hanging out of the chamber end and got these numbers:

.424" - 5.615" as a baseline for where the chamber starts
.404" (largest that would start past the chamber) 5.585"
.403" - 5.575"
.401" - 5.455"
.399" - 5.400"
.397" - 5.34" <- this would be where the tip of the boolit seated @ 1.260" would end.
.393" - 5.200"
.392" - 5.150"
.391" was below the end of the chamber and could not be measured.

[subsonic]

If you load this thing with a .401" boolit, it has absolutely no support or direction upon firing with the stock barrel and I would bet is tipping on take off.

Playing with Mtn Molds website now to see what might give this some support without causing interference with slide closing/opening.

[MtGun44]

This is why they make "deGlocking dies" to resize the case head back down so it
will fit in a normal chamber. I suspect it also contributes to the periodic blowups
of Glock .40s with FACTORY ammo. I have seen a letter from the head of the
Federal Police (yes it exists) to Glock asking why they have had so many guns
blow up when they only were shooting 100% factory ammo.

WAY oversized chambers seemed to be the norm originally - I am not a Glock
person, so all is from friends that have them.

Bill

[frank505]

Here is some "real" world experience to those that care. New Gee Lock 20, all stock. CCI 300, Starline brass, Lee Deluxe dies, RCBS 180 grain cast boolet(weighs 191) and 13.5 grains of WC 820(lot 47320). Very accurate and reliable. Not chrono'ed yet. NO LEADING AFTER 63 ROUNDS. Like zero lead in barrel. Cases are NOT bulged either.
OAL 1.275

[subsonic]

Thanks for the input guys!

[MtGun44]

I think that the latest gen Glocks have an improved chamber - more support in the
feed ramp and less "huge" at the rear, at least that is reported to me by my more
knowledgeable Glocker friends. Second hand, so - for what it is worth.

Bill