The Glock Code Cracked! (Maybe??)

[Bigslug]

I need some peer review and confirmation here folks. . .

I wanted to apply my own scissors to cut through some of the mysticism surrounding cast bullets in Glock barrels. Today, I did some pin-gauging and bore slugging of several 9mm's. These included a new Gen 5 17 with the "Marksman" rifling, a Gen 2 19 with the polygonal bore, a Ruger P85, and a Springfield 1911-A1.

Chamber dimensions of the Ruger were a skosh larger (presumably deliberately sloppy for military applications), but both Glocks and the Springfield were exactly what you'd expect to chamber the cartridge blueprint shown in my Lyman manual - about .391" at the chamber entry tapering to about .382" at the front. Nothing unusual there

Now as for the bore:

It looks like both Glocks from roughly a quarter-century apart have tapered bores.

The Gen 2 19 will take a .346" pin gauge from the back, but it will only allow a .345" from the muzzle. I had a record of a previous slugging of this bore that gave a groove of .356" (don't recall if that was a chamber or full push through)

The Gen 5 17 is similarly .347" and .346". This gun also got a slug started into the chamber and then backed out, which measured .356", and a second slug pushed all the way through the muzzle came out at .355".

The other two guns were both .346" bore and .356" groove.

Seems that a .357" bullet solves the problem for all of the above.

It seems to me that if folks are basing their sizing diameters off of slugs that are pushed completely through these tapered bores, they will be reading the narrower muzzle diameter, and end up sizing possibly 0.001" smaller than properly desirable. Which might explain the leading horror stories that seem to circulate.

Such is my thinking. As I say, peer review and confirmation would be appreciated. Also curious if this tapered bore theory tracks across the other Glock calibers.

[shooting on a shoestring]

Interesting.
A tapered bore going smaller with boolit travel is a good idea in my view.

My experience with a G43 was bad. It’s problem was a sharp, unbroken edge on the shoulder at the muzzle end of the chamber where the cartridge head spaces. The sharp corner would shave lead rings which would often stay in the chamber and prevent the next cartridge from fully chambering.

The G43, a G42 and a G20 which I owned at one time all were bereft of a throat or leade into the polygonal rifling. Versus my HK VP40 which has polygonal rifling with a chamfered head space lip and a leade or throat into the rifling.

The G42 and G43 went down the road. The G20 got a new KKM barrel. It is still a candidate for trading.

I will say I’m not a Glock basher. I think Glock builds guns to compete for military and police markets first and civilian markets secondarily. They are combat oriented pistols and not finely built target guns. They are designed to be mass produced economically and sold as such for a market that needs such. In that realm they are successful.

I don’t participate in combat or policing so my preference is for more luxurious firearms.

There are people who shoot boolits from Glocks with great results. I think there are others who could but are afraid to. I hope this thread can help move more folks into the first group.

[W.R.Buchanan]

BS: No need to be afraid of shooting Cast Boolits in Glocks and there is an entire thread on this subject in the sticky section above. It has 635 replies so the subject has been discussed in detail.

http://castboolits.gunloads.com/show...locks-and-Cast

Randy

[44MAG#1]

I shoot cast bullets in whatever I have. I have Glocks (STOCK BARRELS no after market), Kimbers, Rugers, S&W, and BFR plus Contenders and Encores. If it doesn't "LEAD" it is good to go as far as I am concerned. I check my barrels often too as I am not "alloy controlled".
Some are just too overly worried about some things.

[bwframe]

Any further results on what others are sizing coated/cast boolits to for Glock Marksman barrels?

I've switched to all Gen5 guns with the marksman barrels, along with my trusty older G43.

I was sizing to .356 for a few years with seemingly decent results, but some leading snuck up on me in the G43. I think the issue was a crimp problem, cutting the coating. At the same time, I thought that moving sizing up to .357 would be more forgiving and a lot of casters were sizing to .357 as a norm.

It was great to see the OP here suggesting that I'm on the right path, sizing at .357. Just wondering if there are more Gen5 shooters out there using similar sizing to confirm accuracy and reliabilty? OAL also?

TIA. I understand I have work to do slugging and plunk testing my individual barrels. I'm just getting back into casting again after a couple years off, with a new 147gr mold to go along with my old 130gr.

[Coopaloop86]

I had horrible leading at first with all of my 9mm Glocks. Switched to .357 and never looked back. Now my barrels stay mirror shiny for 100 plus round range trips. That was cheaper for me than switching barrels and with a .357 boolit and PC, the stock Glock barrel is capable of accuracy that surpasses my skill level.

[root]

I have a blown barrel from 1995
A OEM barrel that is bulged and cracked from shooting lead.

I keep it as a reminder to always buy aftermarket barrels for my glocks.

Huge glock fan I have 6 of them all with threaded aftermarket barrels.
I shoot suppressed and with lead.

Never a problem.

Wanna shoot lead out of a OEM barrel have at it it's your gun.
I gave up after the 1st KB

[AndyC]

From 1995 - what caliber is it, out of curiosity?

[44MAG#1]

There were over 36,000 deaths, not counting severe injuries to slight injuries from vehicle accidents in 2019.
This comes under the heading of straining at a gnat and swallowing a camel.
There will always be firearms accidents but most of the times it is very hard to do a forensic analysis after the accident. Overcharge, excessively deep seating, wrong powder, who knows what.
I am sure other brands of firearms have been damaged, blown up and/or instantaneously disassembled with jacketed and/or cast.
What do we do now?

[Bazoo]

I been around glocks for only 15 years or so, never loaded for it though as I got rid of the last before I got into loading. I've heard the don't shoot lead thing many times. There is always a bunch of folks that do it without issues. Then there is a couple that had kabooms. I've always wondered, why? Why do a hundred people never have issues and one does?

I appreciate the heads up on glocks having tapered bores, I'll remember to check both ends if I get another.

[44MAG#1]

My Nephew was at an IDPA match and a guy there had a "memorable moment " with a 1911 and cracked the grips and cause him undue stress. A local indoor range wouldn't allow reloads but the only blowout they ever had was with someone with factory 5.56 ammo.
And so it goes in the day of shooting firearms.

[root]

From 1995 - what caliber is it, out of curiosity?

2nd gen G17

Replaced with a Chip McCormick match barrel and later replaced with a storm lake for the Octane 9 HD.

[Murphy]

My Glock, hasn't been made.

That would be a single stack that holds 8 rounds with normal 1911 rifling.

Murphy

[W.R.Buchanan]

I been around glocks for only 15 years or so, never loaded for it though as I got rid of the last before I got into loading. I've heard the don't shoot lead thing many times. There is always a bunch of folks that do it without issues. Then there is a couple that had kabooms. I've always wondered, why? Why do a hundred people never have issues and one does?

Because that one person was stupid? Actually one stupid person out of a hundred is pretty damn good odds.

Randy

[AndyC]

2nd gen G17

Replaced with a Chip McCormick match barrel and later replaced with a storm lake for the Octane 9 HD.

Ok, cool - I was wondering whether it was one of the famous .40-cal barrels with little support.

[root]

Ok, cool - I was wondering whether it was one of the famous .40-cal barrels with little support.

No

I still have and shoot the gun.

Same mold, 6 banger from lee. 121 truncated. ( also added the 150 358 6 banger sized to the same as the 121 accept for subs. about 12 years ago)

Same 450 sizer and sizing die along with same lube.

I shoot the exact same load out of a transferable UZI
Transferable M-10 with LAGE upper Max 10/31
2nd gen G19
Semi M11/9
and Scorpion EVO

So I'd say Mr. Gaston Glock was right about the polygon barrel thing.
He did say after all right from the start DO NOT SHOOT LEAD IN A GLOCK SERIES PISTOL.

All I do is buy high quality after market barrels and be done with it when it comes to the Glocks.
I have to buy threaded barrels anyways for Glocks so I can use the cans on them.
Kills two with one.
makes them suppressor ready and lead safe.

Maybe you will never have a problem with lead. Maybe you will.
Your gun, shoot rocks out of it for all I care.

Above post
Not directed at anyone just my exp. with the combat tupperware.
Well accept maybe the guy who said people blow their guns up with lead are idiots....

I think he's right it says right in the manual DO NOT and VOIDS WARRANTY
So maybe I was a idiot for shooting lead and thinking I knew more then the inventor.

[AndyC]

I bought a spare Lone Wolf barrel for a buddy's Glock as a gift a few years back so he could shoot the handloads I could make for him.

He had it less than a year before it vanished into the local PD's lockers, never to be found again - grrr.

[onelight]

You can get leading in any barrel . I wonder if the Glock barrel problems come from the guys who seem to take pride in how many thousand rounds they can fire without cleaning and tried the endurance run with misfit boolits.

[Tar Heel]

I believe the Glock leading horror stories began due to the polygonal rifling versus other (deeper and sharper) rifling. As a result of the polygonal rifling, the rifling has a difficult time "gripping" the softer alloy of a lead bullet. Jacketed bullets do not have that issue. Cast bullets CAN be fired in Glocks or other firearms with polygonal rifling but the bullets must be VERY hard. I have shot drop quenched wheel weight bullets out of Glocks with no leading issues at all.

Leading in Glock barrels is primarily due to bullet "slippage" in the rifling with cast bullets that are too soft for the rifling. At least that has been my experience.

[Bigslug]

Any further results on what others are sizing coated/cast boolits to for Glock Marksman barrels?

As of today, I added a Hungarian High Power clone to the short list of of guns I have both pin gauged and slugged. .348" bore on that one, but the same .356" groove as the other four. .357" bullet diameter does indeed seem to be the answer. I've also been pin gauging the chambers and the Glocks do not appear to be different in any regard - save the Ruger, which as I mentioned in post #1 is a little big in the chamber.

I shot some tumble-lubed NOE/Ranch Dog 135 grainers (cast at .357) through my Gen 5 today. Had some minor leading and some clear evidence of vaporized lead deposited on the top of my Streamlight's bezel. This was "pesky" leading, not catastrophic leading, of a level that can be corrected with the usual minor tweaks of right alloy, enough/proper lube, and making sure you aren't falling into the classing 9mm pitfall of having your brass size your bullets down. FWIW, it did foul a little more than the High Power clone and the Springer, but I think a little alloy and lube revision will do the trick.