Round groove vs square cut rifling?

[Travis Gregory]

For those of you that have or have had both types of barrels is round groove rifling worth the extra cost? Also what are the specific advantages over square cut rifling if any?

 

[Stumpkiller]

Yes. I find round groove easier to clean. I also shoot 10 to 15 shots when the humidity is right between spit wipes (L.C. Rice barrel).

 

[M. De Land]

I just acquired a rifling machine and hope to make a couple of rifling heads for scrape cutting this winter so am curious about the difference.
I will use a radius topped scrape cutter and probably a bit of radius on each groove corner for lead bullet shooting.
Is it just the profile of the groove bottom that delineates the difference between round or flat bottom rifling, having nothing to do with the groove corners? Mike D.

 

[jdkerstetter]

Here's a picture for you Mike, just excuse the gun sleeve fuzz :redface: :



You can see that the grooves are deep with radius bottoms and the lands still have sharp corners. Enjoy, J.D.

 

[roundball]

For those of you that have or have had both types of barrels is round groove rifling worth the extra cost? Also what are the specific advantages over square cut rifling if any?

After my first Rice round bottom groove barrel in my .58cal Early Virginia, I was so impressed that I used round bottom barrels in .45/.50cals after that.
I found snug loads seated down easier, and the bores cleaned easier / faster. Also found the bores to be "roomier" with the .016" radius grooves and I had to bump up my patch thickness from .018-.020" to .022-.024".
For me, I decided it was worth the extra $30-40 bucks to go with round bottom grooves.

 

[M. De Land]

Oh, I get it,hemisphere grooving! I was thinking the difference was flat or groove diameter circumference arc ,groove bottoms with groove widths 3 to 1 to land width. Thanks JD, pictures really sink into my ole polish brain. Mike D.

 

[George T.]

I have only had the square groove type. However over the years talking around a camp fire with other shooters I have formed some thoughts.

The round groove is more forgiving and in the day where dry goods stores were few and far between they allowed the rifleman to use buck skin , canvas or what ever he could lay hands on.

This day and age where patches of several thicknesses and different sized balls are a click and card number away I am not sure they are needed.

That being said they are cool and I may well own one someday! But hey I like all guns! Geo. T.

 

[Many Klatch]

Don Getz talked me into a .54 rifle barrel with round bottom grooves and 1 in 55 twist. I have shot that rifle for about 25 years. I find that I can shoot without ever cleaning between shots and that the accuracy does not drop off when it is dirty. 75 grains of 3F makes a nice accurate charge.

Many Klatch

 

[M. De Land]

What are the disadvantages to round/hemisphere groove rifling.
I doubt the rifling form would work very well with lead bullet shooting because of the bullet deformation caused by bump up.
Makes lots of sense with patched ball use though. MD

 

[David W.]

if you're talking about seating conicals, you need to be using shallow groove rifling. A round bottom groove design is very good for PRB's, with deeper grooves. The part that grips the patch is the edge of the rifling. Fairly sharp , (but not too sharp as to cut the patches) lands grip the best.

 

[jdkerstetter]

What are the disadvantages to round/hemisphere groove rifling.....

Other than it being more expensive? None that I can think of....if you only shoot patched round balls. :wink:

Not so good for bullets, grooves are too deep. Enjoy, J.D.

 

[MSW]

I used a Colerain A- weight .40 on my last build ... radius grooves are great - easier to clean (and easier to load) ... well worth the extra money.


just one guy's opinion. free and doubtless well worth the price.

 

[roundball]

What are the disadvantages to round/hemisphere groove rifling.
I doubt the rifling form would work very well with lead bullet shooting because of the bullet deformation caused by bump up.
Makes lots of sense with patched ball use though. MD

I just spent last year successfully experimenting with a .40cal x 200grn REAL conical in a .012" deep square bottom groove round ball barrel. The typical conical doesn't 'bump up' enough to fill even regular .012" deep square bottom grooves...we're only talking about 7000-8000 PSI here, not 50,000-60,000 PSI as in a .30-06.
The issue with groove depth using conicals is gas seal and a properly sized lubed felt OP wad takes care of that as proven with the .40cal REALs in a standard deep groove round ball barrel.
As just mentioned above, the square corners of the lands are what grip a conical.

 

[hanshi]

I find them worth the extra cost. I have both styles and the rb grooves do clean easier.

 

[Travis Gregory]

So Roundball, What you are saying is that you believe that with a felt op wad that the conicals would work in a round bottom groove barrel as well. If that is the case then that would be the best of both worlds and there would be no disadvantage to that style of barrel. Sounds better all the time.

 

[M. De Land]

I don't have a hemisphere rifled barrel to test conicals against PB's in so it will be up to the guys that do for any comparative target results.
I was thinking in terms of what the conical would be shaped like after bump up and how it would react in the air with such a strange profile.
Guess it couldn't be any worse than a belted ball or a hexagonal bullet as in the Wenworth rifles. MD

 

[roundball]

So Roundball, What you are saying is that you believe that with a felt op wad that the conicals would work in a round bottom groove barrel as well. If that is the ca se then that would be the best of both worlds and there would be no disadvantage to that style of barrel. Sounds better all the time.

To be clear...I do not claim to be an authority on anything.
All I do is lay out the facts / results from testing and draw my own conclusions, share them...not a keyboard theorist, etc.
My personal opinion from using square bottom grooves for years in .40/.45/.50/.54/.58/.62cal barrels, then using round bottom groove barrels in .45/.50/.58cals to the present, given a choice I will now always choose a round bottom groove barrel.
Others mileage may vary...

 

[Travis Gregory]

I bet there are very few real "authorities" on here but you do have real world expierence with both types of barrels. That goes a long way with me and I respect your opinion greatly because of that. Thanks.

 

[David W.]

Well, I don't call myself an expert, but round bottom grooves loads easier after repeated reloads, and I don't see accuracy fall off either. No sharp edges in the grooves makes it easier to clean, too.

 

[nkbj]

Depth of rifling is relative to the bore diameter.
A bullet may be made to expand to the bore, depending on the diameter, the depth, the forces involved. This rifling is really pretty deep for the bullet but it works great. The gas cutting shown in the photo is caused by the gas check base on the bullet rather than the style of rifling. Shooting round bullets in a hexagonal barrel is a standard practice and that's a lot of reforming when it goes boom.