SQUARE CUT OR ROUND BOTTOM RIFLING?

I have 3 flintlock rifles with round bottom rifling , I have owned many others with square cut rifling . I never noticed any difference in accuracy but some in loading tight patched balls and in cleaning . Has any one done any research into the benefits or drawbacks in both types of rifling ?

I handed Hoyt an original underhammer to bore out and rifle and asked him about round bottom groves and he said square cut was a little bore accurate. When I got it back it had round bottom rifling which didn't bother me. No, I haven't shot it yet but I'll bet it's far more accurate than I am.

I don't find any difference in accuracy. I believe that the round bottom are easier to get completely cleaned.

I think square with stipulation that the lands are narrow relative to the grooves.

not going to be a difference in accuracy with a good fitting patch and ball. I find the round bottom to clean a little easier.

I have 3 round bottom rifles and 3 square cut ones. If I had a target rifle specially built for targets it would have square rifling and a straight barrel. But I was always a hunter/ recreational shooter and prefer them for the woods and all around shooting. Nowadays I can't shoot well enough to even begin telling a difference.

DuncNZ said:

I have 3 flintlock rifles with round bottom rifling , I have owned many others with square cut rifling . I never noticed any difference in accuracy but some in loading tight patched balls and in cleaning . Has any one done any research into the benefits or drawbacks in both types of rifling ?

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Like you, I’ve noticed no difference in accuracy. The round-bottom rifling seems to be much easier to clean, and doesn’t seem to foul as much as traditional square bottom rifling.

If nothing else I think the round bottom rifling looks better.

May be just me but my square bottom rifled barrels shoot a wide variety of loads accurately, my round bottom seems to like a narrow range of loads and hates others.

Unless one did a head to head comparisons between barrels made by the same outfit, same run of drilling and boring, same caliber, same twist, same depth and width of grooves, with the rifling cutter the only difference, there are too many variables that could be influencing the accuracy of a given barrel.

I tried a Colerain 45 caliber Round Bottom barrel...once. The grooves were semicircles. The lands were wide. No loadable patch and ball commination sealed the bore. The accuracy was so poor I scrapped the barrel. I replaced it with a Green Mountain square bottom barrel and it shot very accurately. My experience covers about 30 barrels.

Definition: Accurate means 1" @ 50 yards, benched, peep sight.

The biggest factor I fight is that patched ball barrels are all currently made with excessively deep grooves. I recently ordered a custom 36 caliber barrel with square bottom rifling that was to be 0.007" deep. I got semi round bottom that was 0.013" deep.

Most shooters can not appreciate an accurate barrel. The only ML barrels that have the accuracy potential I seek are Green Mountain. They are only 45 caliber and above. Of course occasionally you get a unicorn from the other makers.

Bottom line is that if you are an off hand shooter that is into trail walks and plinking, rifling shape does not matter.

Scota@4570 said:

I tried a Colerain 45 caliber Round Bottom barrel...once. The grooves were semicircles. The lands were wide. No loadable patch and ball commination sealed the bore. The accuracy was so poor I scrapped the barrel. I replaced it with a Green Mountain square bottom barrel and it shot very accurately.

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I tried a Colerain barrel in my last build. After getting the sights adjusted, my new barrel is quite accurate. The Colerain .50 calibre barrel seems to like a lighter load than my Green Mountain barrels when shooting targets.
Cleaning is easier too.

Narrow land square cut is what I always bring to table matches. Green Mountain or Goodoien. Yes I do have a couple round grooves that shoot good and a couple that suck. Maybe I could sell them too the (shoots better than I can guys)

I have a .62 Early Lancaster octagon to round TVM with their proprietary (not sure who made it) barrel with round bottom rifling- it shoots great and is not picky about powder charge. With Goex Ffg, .610" rb, iirc a .015" patch and a chunk of hornet's nest over the powder, it will shoot cloverleafs at 50 yards - have tested from 80-110 grains. This being from sandbags.

I get the impression that rb rifling is a bit easier and quicker for me to clean. Won't swear to that and I'm sticking to it....or not.

Most of the target shooters in my gun club prefer the square bottom grooves for target shooting and they have shot both types of grooves.

I'm not good enough to tell the difference.

1975 , I began shooting competition w/a round bottom rifling 44" barrel in .50. .012 grease patches , (Old Zip lube) , 80 gr. FFFG. ..In the 12 years shooting that rifle , two things changed to alter the consistency of it's splendid accuracy . First , The touch hole enlarged which changed the point of impact. Second , The barrel became slightly worn , causing me to switch to an .008 patch and a .495 lead ball. In both cases , accuracy was restored with touch hole replacement , and simply changing the patch , and ball sizes.. These incidents didn't happen at the same time , thank goodness , so it was easier to figure out what happened , in each case...... ........oldwood

DuncNZ said:

I have 3 flintlock rifles with round bottom rifling , I have owned many others with square cut rifling . I never noticed any difference in accuracy but some in loading tight patched balls and in cleaning . Has any one done any research into the benefits or drawbacks in both types of rifling ?

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Yes there are drawbacks between the two, but I think that's pretty much in the manufacturing process, not the results. There are a bunch of variables involved, width of the grooves, depth, the type of steel used, actual shape of the lands after the grooves are cut, number of grooves, polish after the grooves are made, etc etc etc

I have rifles with either type of rifling..., they all shoot better from a fixed rest than I can when shooting the rifles, so for me it's a moot point.

LD

There are many factors that make a good barrel. The bore must be uniform size (or choked), the twist must me uniform or evenly gaining, the finish must be reasonable. The percentage of land to groove matters. I never had a barrel with skinny grooves and wide lands that shot to my accuracy standards. The depth of grooves matters, it must be such that you get some compression of the patch in the grooves. And, way down list is the shape of the grooves.

Ease of cleaning comes with a good finish more than the shape of the groove, IMHO. It does not matter to me because I swab between shots.

My previously mentioned 36 caliber also had a poor finish, tight and loose spots and the grooves were too deep. I knew it was junk before I shot it. After about a pound of powder, a bunch of lead, and several trips to the range, and lots of lead lapping, I am setting it aside and moving on.

If you pay attention to the things I mentioned the odds of an accurate barrel increase. There are no guarantees though. Again I am talking about best possible target shooting accuracy. IF the shooting is done at 25 yards and/or off hand, you will not see any difference.

Can any of you experienced shooters say what your experience was (if you've shot one) or predict what experience I might have with my barrel I haven't shot yet?

Colerain 0.58 1" straight, round bottom, 66 twist, 0.016 groove depth.

Probably a silly question. But now I'm worried