Barrels??

[Scota4570]

seeing your picture raises another question in my mind and that's whether boring out your .45 $#@* barrel to .47 and leaving the rifling as is would give you a good shooter.

That would leave tiny rounded grooves with wide lands.  So, I doubt it. 

I speculate that a round rifling cutter would have less tendency to chatter than a wide flat cutter.  If it were sharpened right there would be wedging effect with a scrape cut that could lessen chatter?  Maybe the barrel makers push them for that reason. 

Neither Pope,Zischang.Oberlies or any of the Schuetzen rifle makers were thinking of close range shooting with a round ball
when they were making barrels.Ditto for the Brits with the Whitworth and Henry with their rifling systems from the mid 19th
century.
Bob Roller

I wonder if anyone ever tried to shoot patched balls in a Pope barrel?  The the twist rate would be too fast but it could be interesting with a light charge. 

I am one to re-invent he wheel.  I like the idea, and may try it to satisfy my curiosity.   Somebody mentioned using a slower twist.  Any guess as to optimum for 40 cal?  1:48 seems "standard" ,  try a 1:56 or even 1:66? 

[EC121]

The deep grooves are all marketing.  I'll take whatever is in a finished rifle, but to order a barrel it would be square grooves or shallow round bottom grooves.  I did use a few Colerain round bottoms, but I was getting them for $120.

[Daryl]

The problem I see with a small bore, with very shallow rifling, is velocity in relationship to the rate of twist & groove depth.  I think getting the ball to follow the
rifling without irregular stripping, might be the problem with anything short of a 80" twist. Even at that, getting it to follow might be a problem and I think 80"
is way too slow.  My .40 made 1/2" groups at 50 yards with a 48" twist and 75gr. 2F & 65.0gr. 3F, both producing roughly 2,240fps. .010" depth of grooves.
I guess the only way to find out for sure is to try it. Speculation is just that, a guess.

[DGB]

Hi,
Regarding "round grooves".....Confidence in your equipment is a large part of accurate shooting. If you are not happy with
what you are using, you can't do good work.
Build  what you like.
I have several Rice barrels, they all work great.

Dave

[Daryl]

I have a 44" .50cal.  Rice barrel on my Beck, however it is the "gun maker's" barrel and has squarish rifling.

[Ric Carter]

I've only used one round bottom barrel. It shoots okay, but myself and others have found they take a lot more work to get clean. Mine also demands being swabbed between each shot to maintain good accuracy.
I don't know where the deeper rifling started, but Jerry Cunningham was cutting some to .015 back 40 years ago, when he was making barrels for Montana Rifle Barrels, formerly Sharon.

[R Whittington]

I have always thought that upset of the ball is what seal, not patch thickness, groove depth. IMHO, a tight fitting ball, and proper load will seal regardless of rifling depth.

[Scota4570]

I don't think the shape is the problem.  I speculate that if the round grooves were wide and no deeper than regular it  would work fine and possibly be easier to clean.  Round coroner grooves?  The trouble with the one I threw away was the grooves very deep and the grooves were narrow.  No loadable combination could  make a seal.  I even tried wads.  As far as upsetting the ball with inertia, I am not sure especially on smaller calibers.  The pressure has to build to start the ball moving.  Gas will leak before acceleration happens?