G29 Groove Diameter

[sqlbullet]

Have any of you Glock owners slugged the barrels to find the groove diameter?

I just pounded a slug through mine and it is definitely .401".  Which to me says there are any commercial cast bullets out there that are likely to run well through this barrel.  Yes, I know Glock advises against lead, but I plan to try it anyway.  I can understand the warning if their barrels generally run .001" over nominal groove diameter.

Just curious if others have had similar results to mine.

[The_Shadow]

My cast bullets run at 0.4015" and work pretty good.  I think bullet shapes to the polygonal rifling enough to work pretty good!

[EdMc]

Yeah, my G20SF was .401, also.

[Vice]

That really sheds light on the leading issue of Glock barrels with cast bullets.  Considering that your cast bullets should "normally" be  0.001-0.002" over bore. 
Gas blow by is melting lead around the bullet and depositing it in the bore due to lack of a good seal.  Unless of course the proper bullet hardness/softness allows for proper "bump up".

I'm sure most Glock owners assumed that their bores were .400 and thus ordered .401 diameter cast bullets from a commercial caster.

Another reason for Glock owners who do not order a "lead" aftermarket" barrel to be anal about cleaning their bores after EVery session!

[sqlbullet]

I shot 10 rounds of Lee 175 grain SWC TL at the end of my range session yesterday.  Bore as shiny and clean like you had just run a patch through it.  Those bullets were all .402-403" cast from isotope lead and water dropped.  Hardness according to my Lee hardness tester was 23.

Looks like I will be shooting a fair bit of lead through my Glock.

[Yondering]

My G21 barrel is right where it should be at .451", but my G19 9mm barrel is .357" instead of .355". Some research online shows this is pretty common, and that maybe all of the Glock 9mm barrels are .357". That would have a lot more impact on leading than the rifling style. Both of these guns do very well with lead that is correctly sized and the right hardness (I use .357" in the 19 for both cast and jacketed). I actually really like Glock barrels for lead, because they are so well finished inside that they don't tend to build up lead like a conventional rifled barrel with sharp edges and corners in the rifling.