GP100 adventures in leading and thread choke

[zomby woof]

I've been struggling with leading in my GP100. I was using a LEE TL 158 and getting horrible leading. I tried a commercial boolit and still got leading. I found the the throat was .3575. I got the throat reamer and forcing cone tools. I reamed the throats to .358 and cut the forcing cone. I was still getting leading. I came across a website that talked about thread choke. I got a set of gauge pins. The .348 pin went right down the muzzle and stuck in right around the threads.

http://www.hunt101.com/data/500/medium/100_8555.JPG

I embedded lapping compound into some boolits and fire lapped a bunch of boolits until the .348 made it through the barrel.

http://www.hunt101.com/data/500/medium/100_8557.JPG

Success!! I shot a bunch of commercial Magtech lead rounds and got no leading. Accuracy was still very good. Now to experiment more with the LEE TL and get them to shoot.

[runfiverun]

it should be easier this time around.

[williamwaco]

Good Job.

.

[Jim Flinchbaugh]

Welcome to late model Ruger land. My Redhawk was pinched at the threads
& under the front sight

[Jtarm]

I've read the same thing about the late model SAs. Fortunately, the youngest Ruger I own is a first-year Redhawk.

BTW, where did you get the throat reamer and forcing cone tools? I've opened throats before just using a drill and emery cloth, but if I ever have to do it on stainless, it's gonna take a month.

[geargnasher]

Excellent. I fixed on just like that a couple of years ago, buddy of mine bought it cheap from a gun shop with "a bulge in the barrel and the rifling shot out". After he peeled the polished layer of lead and copper out of it it turned out to be perfectly fine except for about .020" of thread choke and .3565" cylinder throats.

Just about all revolvers have "thread choke" to some degree. Ruger revolvers seem to have it worse than most (and some not at all) due to a unique process of selecting matches between a bin of barrels and a bin of frames, but the phenom is not limited to Ruger by any means.

My solution has been a combination of hand lapping, fire lapping, and reaming, same as Zombie Woof's. Those SS barrels are TOUGH, too!

Gear

[Crashbox]

This is excellent information, thanks a million for sharing it as my GP100 tends to lead very badly as well compared to my SP101 which leads very little.

[Willbird]

Excellent. I fixed on just like that a couple of years ago, buddy of mine bought it cheap from a gun shop with "a bulge in the barrel and the rifling shot out". After he peeled the polished layer of lead and copper out of it it turned out to be perfectly fine except for about .020" of thread choke and .3565" cylinder throats.

Just about all revolvers have "thread choke" to some degree. Ruger revolvers seem to have it worse than most (and some not at all) due to a unique process of selecting matches between a bin of barrels and a bin of frames, but the phenom is not limited to Ruger by any means.

My solution has been a combination of hand lapping, fire lapping, and reaming, same as Zombie Woof's. Those SS barrels are TOUGH, too!

Gear

.02" ?? WOW...:-)

Bill

[Lefty SRH]

Nice job, I'd like to hear more about your firelapping procedures.

[zomby woof]

Nice job, I'd like to hear more about your firelapping procedures.
I had several types of lapping compound laying around, 180, 280, 400 and 800. I first tried 10 rounds of each and 20 of the 800. That didn't seem to move the pin at all. I then loaded 50 rounds of 180. After 40 rounds the pin moved through the barrel. I rolled boolits between two pieces of metal with lapping compound on it, embedding compound into the driving bands. Then I loaded them into un-sized cases with 2.5 grains of Bullseye. I would shoot 5, clean and check. It did open up the throats a little to .3585-.359ish. The rifling was very rough on this pistol. It did seem to smooth out some of the roughness. The .348 was still nice and tight at the muzzle. This has been quite a journey with this gun.

[Lefty SRH]

Zomby, did you cast the boolits you fire lapped with? If so what alloy?

[zomby woof]

Zomby, did you cast the boolits you fire lapped with? If so what alloy?
I did not. I only have commercial cast, they were hard. I think a softer boolit would have taken the compound a little better.
A little cold to cast right now.