Hello everyone I'm a new member of this forum and today became the owner of a new Glock G20 Gen 4 10mm.  I got it to carry on fishing, scouting, and some hunting trips primarily for bear protection.  I started hunting Alaska last year and have plans to go back already made for 2020.  I also hunt western states in some areas with grizzly as well as black bear.  The chance of a problem is slim but worth considering I think.  I hunt with a rifle and don't always need to have a pistol but I try to do as much scouting as possible. For that plus packing meat the handgun often makes the most sense.  On some trips it's easier to hike with the rifle strapped to my pack and using trekking poles so my rifle is not quickly accessible. The 357 I've been packing is a discontinued model that keeps getting to be worth a little more, I figure maybe it should stay in the safe more often and I should pack the Glock.  The ability to put a light on the rail at night and add night sights are other reasons I'm looking at options other than my trusty revolver.  That and all the holster options compared to my old revolver.

I bought a box of the Underwood 200gr coated ammo because some say it's best in the factoy barrels of the cast stuff, and it was what I found on the shelf.  So far I have only shot 2 rounds of it and both hit the target, felt, and looked fine.  I also shot 30 rounds of Fiocchi 180gr JHP ammo rated at 1250fps.  I really enjoyed shooting my Glock for the first time tonight and it seemed to shoot well in my initial informal plinking session.

I have read a ton of information on using hardcast bullets in the Glock's factory barrel.  I'm willing to buy a KKM barrel if I need to, but am trying to get to the bottom of IF this is necessary or not.

I looked through the owners manual and unless I missed it there is nothing about lead bullets in there. It is mentioned on Glock's website under the FAQ section as follows:

Can I use lead bullets?

No, we recommend the use of jacketed ammunition only.


Also When looking for Glock 20 Gen 4 reviews I saw this one from American Rifleman that has the following paragraph in it:

Glock Gen4 G20 10 mm Pistol
The Gen4 G20 provides the stopping power of a Magnum revolver in a high-capacity semi-auto.
www.americanrifleman.org

"Accuracy testing was conducted from a bench rest using five, five-shot groups fired into targets set at 25 yards. Some readers will be quick to notice one of the rounds used for formal accuracy testing was loaded with hard-cast, gas-checked lead bullets. Glock warns against the use of soft-lead bullets in its factory barrels. This is because soft-lead bullets have been known to foul the rifling, which could in turn increase the pressures inside the barrel to an unsafe level. However, true hard-cast bullets, when properly lubricated, will not cause the problems of soft-lead bullets. That's why ammunition companies like Buffalo Bore, DoubleTap and Underwood Ammo provide hard-cast hunting rounds for use in polygonal rifling pistols like the Glock."

I emailed Glock yesterday but have not yet received a response.

I read the Glock algorithm post on here also that made more sense than anything else I could find on the internet, but still leaves me a bit confused.

What do you 10mm experts recommend?  New barrel to be safe or just shoot the Glock and clean it often?

Thanks for your help.

I do shoot my own cast bullets from my factory barrels, Mine are cast form older clip on wheel weight material about 14-16 BNH.  However I size them at 0.4015" and run Carnauba Red lube.  I have run some of them at velocities that equal those of UW, DT and BB without any leading issues.  When I load them I am careful not to over do crimping where that process can squeeze bullets to a smaller diameter.  The smaller diameter can be an issue for leading of the bore...  Glock factory barrels have been measured at 0.4015" and 0.4020" which is on the large side for cast bullets @ 0.4000" and even 0.4010".
I will also say that I have extra barrels with conventional rifling to play around with as well! 

I also shoot cast in my Glocks.

When shooting cast bullets size in king.  Lead has a low melting point compared to the gilding metals used in jacketed ammo, and this is why fit/size is so important.

Hold you hand in a 212° oven, and then compare that to 212° steam.  (don't really do this unless you like 2nd degree steam burns).  The constantly moving steam transfers heat to your hand far fast than the still hot air in the oven.

Same thing happens while the bullet is moving down the barrel.  The hot, expanding gas which has a high enough temp to melt lead does not as it  is trapped against the bullet base for a short time.  It is relatively static in nature.  However, if the bullet is at all undersize for the actual groove diameter, those hot gases can move around the bullet, and transfer far more heat.  It acts just like a plasma cutter.

As a result, the lead softens greatly, or even liquifies, and deposits heavily on the bore.

As The_Shadow has noted, Glock barrels tend to be far over spec for groove diameter.  Nominal is .400", actual is often .399" in traditionally rifled barrels, and Glocks run >.401".

Many of my cast bullet molds don't drop bullets bigger than .4015, so have to be lapped out to get a bit larger bullets.  And, putting a .402 or .403" bullet in a 10mm case often either swages the bullet back down to .401" or expands the case mouth so it won't chamber.

Powder coated bullets often provide a solution.  A good lube certainly helps as well.

Thanks everyone.  I decided to order a KKM 6" barrel for my G20 today.  I emailed Razco and had them adjust my holster order to allow for this extra barrel length.  There really wasn't much disadvantage I could see since the holsters were going to be longer to allow for the Streamlight TLR-1 lights anyway.  This will put the barrel out about even with the light instead of a bit shorter.


Thanks again for helping with my decision.

I'm happy with the factory barrel and a .401" moly coated bullet.

But at the end of the day if it works and gives you confidence then that's all that matters.

I would run a box or two just to confirm.

I have been shooting Underwood powder coated 220 grain HC through my stock Glock G40 without issue.

Though I see you have already ordered a conventionally rifled barrel so it shouldn't be a thought for you anymore.

Evening, My accuracy improved substantially with my G20 / KKM standard length barrel to justify the $160.00 expenditure. For others, maybe not so much, but I still really like it.

Ken

Two things:

There is a misconception that the hardness of the alloy is the ultimate determinant in leading or not leading. As has been correctly stated above, bullet fit is the most critical. Alloy hardness (strength) is down the list.

Many who swap to an AM barrel see better results with cast simply because the bullets they shoot fit better. The classic infamous example is Hickock45 shooting the 230 gr Double Tap hardcast. I've measured DT cast bullets to be sized .400. Too narrow for a Glock. If DT sized that bullet to an honest .401" the results would be different.

The KKM, might have a throat that will need to be opened a little to fit fatter cast bullets. Or a short overall length might be needed.

Thanks everyone.  The Glock will be going to my gunsmith for some trigger work he recommended and to get the night sights installed.  I will send the barrel along plus some 220gr HC ammo too and have him check it all out, make sure everything is good.  Then I'll start shooting it once I get it back, get the load picked out and sights perfected.  I don't plan to reload at this time for it.  I spend to much time loading for my rifles already. 

Cutting to the chase....

It is very unlikely your Glock is going to shoot commercial hard cast bullets well.  Commercially cast bullets are sized .401" and are too small for every Glock factory 10mm/40 barrel I have ever examined of heard of being examined.

Bullets in the 10-12 BHN range would be better than modern hard cast bullets, but again, commercially cast bullets are generally very hard.  Hard bullets and hard lube look good when a box is opened after being josled and banged in shipping, but they are far more likely to lead a barrel if every spec isn't spot on.

I hope you have good results with these bullets, but will be very surprised if you do.  Be sure to let us know how it goes!

Quote from: sqlbullet on April 23 2019 07:58:40 AM MDT
Cutting to the chase....

It is very unlikely your Glock is going to shoot commercial hard cast bullets well.  Commercially cast bullets are sized .401" and are too small for every Glock factory 10mm/40 barrel I have ever examined of heard of being examined.

Bullets in the 10-12 BHN range would be better than modern hard cast bullets, but again, commercially cast bullets are generally very hard.  Hard bullets and hard lube look good when a box is opened after being josled and banged in shipping, but they are far more likely to lead a barrel if every spec isn't spot on.

I hope you have good results with these bullets, but will be very surprised if you do.  Be sure to let us know how it goes!

This is a good post. Curiously, what motivated me to begin casting for my G20 was after shooting commercial cast Hi-Tek coated 180s. The maker used standard hard ball alloy, and they shot phenomenally well from my Glock. They were sized .401 on the nose.

Each barrel will tell it's own story, but mine have been very happy with about 8 different coated bullets (mine and commercial) bullets sized .401. I think HT and PC makes Glock barrels a bit more tolerant of fit. At least in my 40 SW and 10mm guns.

I use alloy around 12 bhn also heat treat to about 18 for the hot stuff. My Glocks like 'em PCed and sized to .401.

Oddly enough, Glock chambers are loose, except I find that mine are tight right at the case mouth such that rounds loaded to .402" are a bit fussier about the kerplunk. So .401 is what I've settled on a few thousand rounds ago.

Regarding traditionally lubed hard cast, Beartooth shoot better than DT components because they are sized a full .401 (or size specified) and DT aren't.