B-W, I currently own 3 cut rifled barrels from Grn Mtn.  I wrote a review for the SSR Journal about them approx. 3 years ago based on my experiences with the first two which I bought through normal, commercial channels.  The quality was and is exceptional even when compared to more expensive barrels.  My only difficulty with the first (.45-70 BP) barrel was the result of fouling on a hot, dry day...which I attributed then and now to poor lube choice, not the barrel.  The second (.32-40 with smokeless)  came to me with a tiny bit of scale in the bore due to the heat treating process that has since been improved to eliminate the problem and which I took care of with about 10 rounds of fire lapping.  Now I don't think I can MAKE that barrel foul.  Accuracy with both of these barrels is far better than I have ability to utilise. 
     I am currently fitting a light octagon bbl in .25-20 SS to a low-wall action and am fully confident that it will do just as well, but I have no data yet.
     As to button rifling, if the equipment is good and you start with a smooth, well reamed bore, the result will be quite good.  Is it as good as cut rifling? Is a Ford as good as a Chrysler or a Smith & Wesson as good as a Colt?  That depends, and someone will probably argue either side.  The barrels are good quality, they are priced very well, and they are usually available immediately in most bore sizes.  I like them a lot, but as with all things, YMMV!

Regards,
Charlie Shaeff
the Green Frog

PS  For 5a, try the first deHaas book, I think all of that information is there.  GF

PPS  At last report, I thought GM was only offering cut rifling on their 40+ cal barrels, did they start advertising they had a .38 bbl that was cut rifled?  GF

Charles,

  To try and answer your questions.......

1) I don't happen to own one but as you can see from the other replies they are well liked, and I don't recall ever hearing a bad word about them. Just be sure you get a barrel with the proper twist for cartridges and the bullet wgts. you want to use. Of course this would apply to any barrel you wished to get.

2) As mentioned by others this will of course depend on the machinery used, and the operator. Both are more than satisfactory if  properly done. See 1) above.

3) Nope! That's a pretty good price.

4) I would recommend looking at Douglas and Shilen barrels as being well worth the money too, but don't think either compares with GM as far as price goes. They might be a tad bit better as far as quality goes.

5a) Can't answer for sure, but I would suggest just calling C. Sharps and ask them what the threads are. They might be different than original Sharps.

5b) Either would be satisfactory altho you can get into some discussion as to whether the round barrel is more accurate than an octagon barrel. For anything more than the ultimate in accuracy either would be more than sufficient. It would more depend on what you think looks the best.

5c) Go for it! Sounds like a neat pair of projects.

PETE

To further add to what Ed  just said ......   I just realized that I have DS Cole being bbl'd in 45-70, a lowall in 22 LR being done both by Steve Durren -- a #5 roller in 40-65 being bbl'd by Glenn Fewless -- a Lowall being bbl'd by Bob Snapp. There is a Borchardt and a Wesson long range and a Wesson center hung hammer mid range that are to be bbl'd by Glenn Fewless.  ALL of these rifles will wear GM bbl's.  Hope this indicates how much I like them .   ken

Mr. Way:

I have a GM barrel on my silhouette rifle and find it to be everyting one could ask for.  Another nice feature about the GM barrel is that you can actually get one. Nothing wrong with a Douglas or any one of a number of good barrels, but no others are availablle in octagon. Cutting a round barrel octagon would cost the price of a GM barrel.

As for the Sharps, only the GM Sharps barrel will fit the rifle. I don't recall the Sharps barrel thread offhand, but it is huge and the 1-1/8" barrel is not big enough to fit to it. That is way the Sharps barrel costs so much more, it comes from a larger blank.

Glenn

The round section at the back of the octagon on a Sharps must be at least 1.25" The threads on a Sharps 1874 are 1.127" diameter shank, with 10 square threads per inch. The threaded section is .760" long. The Borchardt uses a 16V TPI and a much smaller diameter of .945"