Round Bottom Rifling?

[Smokey Plainsman]

Hello all! Another question, here. 

What do you folks think about round (or radiused) bottom rifling for gun barrels?

I’m hearing some say they’re easier to clean at the end of the day, and that they can allow more shots before needing to swab the bore, and things of that nature. As far as accuracy goes some of the top barrel makers claim between it and square bottom rifling any difference is so small as to be meaningless unless competing at the national target shooting level.

Any truth to any of this? That sure sounds good to me as far as the benefits go. I’m mostly interested in an offhand shooting and small game hunting gun for my .40 caliber. I have picked a swamped 42” round bottom rifling barrel by Rice for the TVM order I recently submitted. Hoping it was a decent choice and just gathering more information on the subject.

Thoughts?

[Pukka Bundook]

I don't think I have anything but round -bottomed rifling Smokey, and I like what I have.
My own rifling is round -bottomed.

[rsells]

I have used both types from Rice and they shot well.  You will not be disappointed.  I think that the ball size, patch thickness, and lube is easier to work out with the round bottom rifling.  I don't have any real technical basis to feel this way other than personal feelings.  I was using the square cut all the time unless a customer requested the round bottom rifling because I feel it is more correct for the type of rifles I like to build.  However, I have changed over to using the round bottom on everything now.  Both types shot great.  Good luck with your build.
                                                                                                                 Roger Sells

[stubshaft]

I have a couple of barrels with round bottom rifling.  I can't say they are more accurate than squared rifling but they seem to foul less in my .40 (might be my imagination) and cleaning is a breeze.  I like them so much that my Kibler Colonial wears a .58 barrel with round bottom rifling.  This was not determined by empirical scientific evidence but, just a gut hunch from over 40 years of making smokepoles and shooting them.

[alacran]

This last Sunday I shot a match with a .54 GRRW. barrel.  27 shots in all. Square bottom rifling. .018 pocket drill, bear lube 60 grains and 95 grains of Goex 2f. a.535 ball on top. Only cleaned once after one relay because we took a lot longer than normal to resume shooting.  Clean up , which I did at the range was no harder than cleaning the round bottom rifling on the .54 Rayl barrel that I shot fifteen shots out of yesterday. Same patching .530 ball 60 grains 2f Goex.  Personally I wouldn't pay the extra $40.00 for round bottom rifling. You will not get a significant cleaning advantage.  I've had other round bottom Rice barrels and saw no advantage or disadvantage over square rifling.

[Turtle]

 from my experience round bottom rifling defiantly cleans easier, but you need a thicker patch to fill the deeper grove's and a tighter load. I use square bottom now, but miss round bottom at cleaning time.
turtle

[Long John]

Friend,

I have radius groove rifling most of my rifles.  I think they clean-up easier.  I fired 51 rounds in a match one day with my 54 caliber hunting rifle, by friend was using my rifle to continue competing when the mainspring on his gun broke on the first shot, and didn't wipe the bore once.  I don't know that the radius groove rifling contributed to that - I think having the right load gets most of the credit.  After all that shooting the rifle cleaned-up just as easy as after a 12 round woods-walk.

I have heard that square groove rifling is more accurate but I am not a good enough shot to be able to notice.

My future rifles that I build for me will all have radius groove rifling.

Best Regards,

JMC
John Cholin

[Acer Saccharum]

you need a thicker patch to fill the deeper grove's and a tighter load.

With round bottom rifling, I have found that I need more patch thickness to make sure the grooves get filled completely with patch upon loading. With a thinner patch, the grooves don't get filled, and the gasses blow by, burning the patch at the grooves.

A muzzle contour like Darryl uses, helps immensely when trying to load a thick patch.

For smaller bores, I would tend to use square rifling, as I don't need so much patch. Calibers .60 and above, I like the round bottom rifling.

 

[Scota4570]

Interesting about caliber.  I tried one round bottom Colerain in 45 cal.  I don't like it at all.  I can not get really fine accuracy out of it.  I prefer regular square bottom and conventional to shallow dept.  Sounds like RB works better in larger bore rifles. 

I would really like to try Pope style rifling.  Because it has the shallowest possible grooves yet is a polygonal-conventional hybrid, it gets maximum purchase on the bullet.   The thin patches should work.   Unfortunately, I can not find anyone to make such a barrel for me.   

[Huntschool]

I just ordered two barrels from Rice and decided to stick with flat bottom rifling in each of then.  One is a .32 and the other will be a .54.

The only experience I have had with round bottom occurred many years ago when Hoppy Hopkins started making round bottom.  I built a gun with said barrel and can not say it shot or performed any better or worse then my flat bottom stuff.  Frankly, I don't remember it cleaning any better but it was a long time ago.

The one thing I do remember is during load work up I really had to fool with patch thickness and powder load, as has been mentioned above, in order to squeeze out its capabilities........

I am going to stick with flat bottom and tight patches.....

Just my thoughts.

[Dennis Glazener]

I just ordered two barrels from Rice and decided to stick with flat bottom rifling in each of then.

 I am glad that Rice is offering the 32 in flat bottom rifling. The last two 32's I got were radius rifled and at the time the 32 was only offered in radius rifling. I prefer flat bottom rifling.
Dennis

[Daryl]

As Acer Sac. noted, muzzle 'shape/condition' can help in loading a tight combination, usually needed for accurate and clean shooting in a rounded bottomed rifling.

Since most rounded rifling is usually .016" to .025" deep (some MUCH deeper than that) the patch thickness and ball size can be much more critical, especially is using heavier hunting-type loads.

The reason for that is increased pressure generated by heavier loads stress the ball/patch fit much more than lighter, plinking-type loads.

I have and have used a number of different barrels using both types of rifling.  After 46 years in this hobby, I find picking a ball and patch that will fit and shoot well, to be quite easily accomplished.

I prefer square rifling myself, from about .008" in small .30's bore sizes, to.010" to  .012" deep in larger .040 to my .69. I find this rifling cleans virtually the same as rounded rifling. I have no

 preference for cleaning. Both need 1 patch for pumping the water into and out of the bore, along with 4 or 5 drying patches afterwards. I always remove the barrel for cleaning and clean in a

container of water.

Here are a few groups fired with VERY deep rifling, some .028" deep. Note with the light 85gr. load, the accuracy was quite good with a .022" canvas patch.

 When we went to a heavier load, we used a heavier .034" patching and achieved similar accuracy.

The switch to thicker patching was an automatic change after just firing a couple shots with the lighter .022" canvas patch and checking them. We found shredded burnt patches resulted as the

thin patch did not fill the rifling even though we were using a ball only .005" smaller than  the bore.  BTW- the .034" patches we used were marked "reclaimed" as they had originally been

fired from my .69calibre rifle, picked up and kept for future use.  I maintain that if once fired patches are not reusable, they were not thick enough or of the proper material. 100% cotton or linen

works well, but must be of the correct thickness.

Note that in a .60 cal. rifle, 110gr. 2F is not a high pressure load, but enough over 85gr. to demand thicker patching.

[hanshi]

I have barrels with rifling from about .006" to .016".  Two of the barrels are Rice radius groove barrels, a .32 and a .50.  I like the round groove barrels especially for hunting and general "all around" rifles.  They do seem to clean a bit faster but I'd call it "inconclusive".  I also have 5 square cut barrels and like them as well.  About the only thing I'm sure of is that for a target barrel I'd pick a straight, square groove barrel.  But I can no longer see to shoot as well as I once did; so for me it doesn't really matter which one.

I like thicker patch material and it does indeed work very well in the rb barrels.  With the smooth muzzle crowns both types load easily for me and need no wiping until I leave the range.

[Acer Saccharum]

There are modified rifling styles, some with basically flat grooves, but with a small radius between the land and the groove, leaving most of the groove flat.

Does the top driving corner lose some of its ability to drive the ball accurately? And this would be a custom barrel maker most likely.

Is the juice worth the squeeze?

[Huntschool]

Dennis:

Those two barrels were ordered earlier this week and when I told Jason I wanted flat bottom in both barrels he never said anything about the .32.

[Smokey Plainsman]

Seems as if most prefer square bottom rifling...

I fear I’ve made a mistake ordering round bottom! I didn’t know round bottom rifling causes blown patches and so on. 

[alacran]

You will be fine with the round bottom rifling. You will be able to work out patching issues during load development.

[Dennis Glazener]

Dennis:

Those two barrels were ordered earlier this week and when I told Jason I wanted flat bottom in both barrels he never said anything about the .32.

I am going to check the Rice 32 that is on my Kibler kit 32. I hope its flat bottom rifling.
I am sure Jason would have mentioned it if they didn't offer flat bottom in a 32.

Back when I got my first Rice 32 I paid extra for it being a 32 (extra work to make) and only offered with radius rifling. That was probably over 5 years ago.
Dennis

[WadePatton]

You might also be interested in reading replies to similar inquiries from the past.  Here are 2 samples (and I'm quite certain there are more) where you can read previous discussions and save some guys some of the hassle of typing everything they said before.

2009 - http://americanlongrifles.org/forum/index.php?topic=2579.msg24861;topicseen#msg24861

2018 - http://americanlongrifles.org/forum/index.php?topic=49340.0

[Bob Roller]

Wide,flat bottom grooves and very narrow lands worked for me real well back in
my shooting days.

Bob Roller

[Scota4570]

Wide,flat bottom grooves and very narrow lands worked for me real well back in
my shooting days.

Bob Roller

That is Pope rifling.  I want to try it.  Does anyone currently do single point rifling to the customer's specifications? 

Scot

[Bob Roller]

Wide,flat bottom grooves and very narrow lands worked for me real well back in
my shooting days.

Bob Roller

That is Pope rifling.  I want to try it.  Does anyone currently do single point rifling to the customer's specifications? 

Scot

Bill Large made a lot of these barrels in 54 and 58 caliber.
Ed Rayl in Gassaway WV might make them now but I don't
have his contact info.I think Rice makes them for a German
customer for schuetzen rifles.

Bob Roller

[rfd]

i prefer radius groove rifling.  i do find cleanup is easier and little need for patched jag fouling control.  not a match shooter, never will be, don't see a difference in offhand accuracy 'tween radius and flat gooves.  finding a good patch/ball combination is also easier as well.  ymmv, as it should be.

[Smokey Plainsman]

i prefer radius groove rifling.  i do find cleanup is easier and little need for patched jag fouling control.  not a match shooter, never will be, don't see a difference in offhand accuracy 'tween radius and flat gooves.  finding a good patch/ball combination is also easier as well.  ymmv, as it should be.

Any experience with Rice round bottom barrels?

Seems when it comes to this, half of people are saying round bottom rifling is easier to clean, fouls less, loads easier, and is just as accurate as square bottom rifling.

But then the other half says you have to use such a thick patch and tight load combination in order to control fouling and blow by that it makes it actually harder to load, that there is no difference in cleaning, and that square bottom is more accurate...

 

[hanshi]

I use thick unbleached canvas and it fills out the deep rb grooves completely.  Actually, it's just a matter of finding the load your barrel likes.