Slugged my GPR Barrel today

[Birddog6]

You can measure the land diameter by simply making a plug gauge. Any one with a lathe can turn one in a few minutes. Just step it a .001 at a step. Groves can be measured with a simple calculation if you have thin enough calipers. Just measure from the land to the flat, then grove to flat. The grove diameter will be twice the difference added to the land diameter. It may take a few tries to find a land and grove that will give a straight measurement but it usually can be done. As a tool and die maker I use pipe mic,s and "anvil " mics myself but the simple plug and calipers will work.

I know where you're coming from.. my dad retired in '86 after 37 years as a journeyman tool and die maker.... when I was a youngster it was great... between the stuff I had access to in an R&D metallurgy lab where I spent 2 years as an intern, and the stuff he could do or have done .....he retired 23 years ago and passed away 13 years ago.. a lot of knowledge passed with him...

As another side note, just ran a 1/16" bit through the flash hole and it was a nice snug fit... Not need to drill her out, but I think I will cone the outside a bit as the screwdriver slot will end up vertical and the inside of the liner is already coned from the factory.

At any rate, this thread is just about to the :dead: stage... Time to finish the metal, put her together, and make smoke, fire, and brimstone. Will post some pics and add a range report once she's had a few loads down her pipe...

I have owned 5 GPR .54 cal rifle. Every one of them shot a .535 ball & . .015 to .017 pilllow ticking. One I shot over 4000 rounds thru it & it would still group 1.25" at 100 yards off the bench with peep sights.

That being said, you are making it ALLOT harder than it needs to be. Get some balls & go shoot it.... 500 rounds thru the barrel it will be slick as a whistle & save all of that lapping & etc. Also by 500 rounds you will KNOW the rifle & it's quirks.

Also, on the vent. Have coned over a hundred of them for guys with GPR's. Cone it with a #2 center drill & cone the inside & then the Outside slightly. Put a lil antisieze on the vent threads & just BARELY snug it in.... it ain't gonna come out on it's own. The vent hole to a .078 will make it Very consistant. YOu have to load with a vent pick then if using 3F, but it makes a Amazing difference.. Load it, run a large gem clip into the vent hole to clear it, fill the flashpan 1/2 full, 3/4" tom fuller english flint, you are good to go.
:thumbsup:

 

[fyrfyter43]

I still don't understand why he doesn't call Lyman and ask them for the bore dimensions. Its their barrel, and they should know the specs on it!

There's no need to even do that. I already posted the specs that are printed in Lyman's manual.

According to Lyman, the .54 GPR specs are: bore .542" and groove .558".

 

[hockeyref]

I still don't understand why he doesn't call Lyman and ask them for the bore dimensions. Its their barrel, and they should know the specs on it!

There's no need to even do that. I already posted the specs that are printed in Lyman's manual.

According to Lyman, the .54 GPR specs are: bore .542" and groove .558".

Fyrtyter... I did RTFM and didn't see those dimensions quoted anywhere specifically - I will go back and look again... As to why I have not called Lyman - Well quite frankly I don't want to know what the nominal factory spec is... I wanted to measure MY SPECIFIC BARREL and they sure aren't gonna send someone out to my house to do it... SO I FOLLOWED THE INSTRUCTIONS IN THE MANUAL for slugging the bore(with the diagram that shows a 6 groove, not a 5 groove. barrel) I never wanted to make a federal case outa this and fully realize that I need to dump powder down the bore, shove a cloth covered spherical lead cork down on top of the powder and then set fire to the hole in the side of the barrel. Enjoy the fire, smoke, loud noise. and sudden smack on my shoulder, & then repeat the process a few hundred times.
When I slugged the bore I saw something I didn't expect to see and commented on it.... Y'all are right, it ain't a big deal and I'll commence to making smoke and noise shortly and hope I don't waste too much money on balls, powder, and flint finding out just what "patience" likes to have her pipe filled with to keep her happy. :shocked2:
:surrender: :surrender: :surrender:

 

[BrownBear]

...hope I don't waste too much money on balls, powder, and flint....

Aint no such thing. The only wasted balls, powder and flint are the ones sitting around not being used.

Have a great time!