Really, tearing up the breach face , that sounds ominous. What causes it ??

OK . wow , thank you !! Looks like it would be a great round . I can see that it would be a challenge to get a barrel made. But !! If the accuracy could be obtained. It would sure mahe for a great calling rifle. I wonder if 16" would be too long tho. Maybe something like 12" with a step barrel
With the frame mounted scope mount there would be some disconnect of the sighting and barrel system.
Lots to think about. Thanks again
    Glen.

 Are there any ? Seems like a 16" barreled 17 or 22 would make a good calling gun on a G20 platform . If it would be arrurate enough.

  Great,  thanks everyone. 

 Threoys abound with bear defense threads.  But flat charges are EXTREMELY RARE  !!!!!
Usually a bear that is a punk adolescent will root and beller around trying to work.up the courage to give u a go. Or a sow is protecting but mostly teaching her cubs how to deal with the 2 legged problem.  Over 90% of the time you have plenty of time to get your gun ready.  Just backing off teaches bears to push you.  Just like dealing with an aggressive dog.   
Thru my experience with brown bear,  I've learned that bolt rifles in 416 or 458 are the best tool to have.  For those new to dealing with bears,  if they are good buddies with their big bore rifle.  They will have the confidence torun the bear, bears off without a shot being fired. 
Ime the attitude and demeanor of a Marine Corps drill Sargent is the best to have to train brown bear to fear man. Which is the only correct response a bear should have with a human.  If all you have is a G20  then you just gotta have abit more intestinal fortitude.  I've done it several times with short barreled 357 mag revolver,  S+W Sigma in 40 S+W,  41 mag,  44 mag,  45 Colt and 480 Ruger handguns. 
Bumping into a bear the size of the one pictured is a very rare event. 
The most dangerous bears are the old ones that are starving.  They plan to eat you and only their death will stop them.  Those are the bears you really need to have your S#!+ together on.
Since a chambered,  safed  rifle in your hands is faster to get off an accurate shot than a handgun in a holster.  That is how I pack mine.  Also why I use the Ruger M77 Mk2 actioned rifles.  They are the safest rifles there are when on full safe and have the half safe feature if you (Think) something might happen around the next bend in the trail. 

 I have a lot of experience in densely populated brown bear country.  Quite remote.  . I've shot for my life with a 44 mag,  320gr Cast Performance WLN pushed by 20+ gr H110 from a 5 1/2" Redhawk.  Not a very big brown bear.  I didn't get bit ect.  But I was very underwhelmed with the handgun.  Finished that fight with my 458. I've also stopped charges with the 416s and 458 Win Mag.  Those are absolutely decisive  !
Not trying to start a rouw but the 12 ga. SUCKS at stopping/dumping brown bear.  Unless your using special slugs like the Heavy Brenneke high velocity slugs. Then its like a 45/70. With buckshot you will get very shallow penetration.  The typical deer slugs only penetrate 6-8" and won't smash a brown bears shoulder. 
A 375 works good but the 416s and 458 work spectacularly. 

I've been in far too many of these brown bear threads I usually avoid them anymore. 
I've had and packed revolvers up to the 480 Ruger Super Redhawk.  Which is one of my favorites as I can shoot it ok with a 400+ gr bullet at 1200 fps. 
The 500 Smith +Wesson with 400+ grain bullets at high velocity works very well.  Better than any shotgun I've ever seen.
  Tho I don't live and work.in dense brown bear country now. If I did I would pack my G20.  Loaded with the same 220 gr Hard cast Buffalo Bore TC bullet.  Just like I do here.  The reason is.  I get good hits with it.  Hits are what count.  But when Im in brown bear country I also pack a dead reliable crf bolt rifle in 338 Win Mag or larger

NOE,  ok.  I need to get another Chronograph.  Shot my last one last fall.    :'(
  I regret passing up the boxes of cast and plated 10 mm bullets at Sportsman's Warehouse last time I was in town.  I was unsure if plated bullets were ok in Glock or LW barrels .  From what I've read on here and Glock Talk.  They do great with them.
What do you use for a crimp die?  Seat and crimp or separate crimp operation? 

 Thank you!!  That's good to know!!!!   
Around here lead is not too easy to find as there are lots of bullet casters. 
Has anyone had any success with gas checked bullets in the 10mm?
Rim Rock Bullets supplies Buffalo Bore with the 220 gr TC hard cast for their ammo and sells the bullet as reloading components.  But they are a bevel base.  I don't have the equipment to slug my bores and was thinking perhaps gas checks might solve my leading problem.  ??

Great info!  One caution I have been told is that batteries are a bad source of lead.  Apparently the lead has been altered over time by the battery acid or electrical current or something.  I know some guys that use high antimony solder to increase the antimony content of their alloy.  I still have not got into casting but as I live in Alaska there are.lots of guys around that do.
I did get quite a lot of leading in my OEM G20 barrel shooting the Buffalo Bore 220 gr hard cast TC bullet loaded ammo that chronographed 1200 fps from my gun. Not as much leading in the Lone Wolf barrel. 

Ok. Thanks.  I don't have a huge selection of medium burn rate pistol.powder.  I used to use Lots of H110/Win 296 . Then started using 4227 for milder loads.  But,  I have got some 800X and Unique.  I use the Unique to fire form rifle brass.  So far the 800X has worked good with 155 gr XTP bullets and I want to try it with the 200 gr XTP.  It would be great to use them on black bear this spring. 

 I have some 800X and was wondering peoples experience with it. According to the Lew book it's the fastest velocity with 155 gr bullets.  And does well with 200 s.
   Thanks
    Glen.

Have you chronyed these loads yet. ?
The Lee #1 manual shows HiSkor 800X as having the top velocity with 155 gr jacketed bullets.  I have just been linking with them at 8.7 gr. Haven't chronographed them yet. The Lee manual shows going up to 11+ gr with the 155 jhp. For over 1400 fps.  Hornady also shows 1400+ velocity.

Hey all ;
New guy here from Eastern Central Alaska.  A G20 is my 10 tho I did have a S+W 1006 20 years ago or so. I prefer the Glock but the S+W was a good gun. I just wasn't in a situation to utilize it back then.  Still hadn't got over being hooked on large caliber revolvers. 
Anyway,  I'm looking forward to being on another cart specific forum.
   Glen.