Round Bottom Rifling vs. Square Bottom

[mossyhorn]

What are the pros and cons of round vs. square bottom rifling on a small .32 cal. and larger bores and please discuss accuracy, loading and cleaning ease.

[mossyhorn]

This will be my first build and I would like to know which is best. Decisions,Decisions, Decisions!

[jerrywh]

 If you only intend to shoot round balls go with round bottom rifling. Flat bottm or square rifling is best for elongated bullets. you can shoot both in a flat bottom rifling but it is a little harder to clean.

[Daryl]

Today's rounded bottom rifling requires a thicker patch with any ball chosen as the rifling depth averages about .006" DEEPER than rifling with what is referred to as square rifling.

Thus, the patch SHOULD be at least .003"to .005" thicker than what you would use standard square rifling or .010" to .012" depth.

For example, if you normally use .010", you'd need .013" to .015" in the rounded rifling, if you get my drift.

Also, a ball that is only .005" smaller than the bore would also be best to use in either type of rifling.

Taylor's .50 Virginia rifle has .016" deep rounded rifling. He uses a .495" ball and a .022" patch. Up to 85gr of 2F, this patch holds. Any load over that and the patches get burn lines due to the blowby in the grooves. Thus, for a more accurate load for heavier loads, he needs a thicker patch due to the rounded rifling.

 In square rifling, the .022" patch will withstand ANY load, including his 200yard load which was well over 100gr.  I just can't remember what that was. I'll probably wake up at 3AM tonight and declare to no one in particular, 115gr. 2F GOEX- or something like that!

I was just kidding about the .010" to .015" patches - they are even too thin for a handkerchief - in other words, useless - in my opinion.

You have to fill the grooves to the bottom + have some compression of the ball itself- cloth marks on the ball from each and every groove.

Rounded grooves usually clean easier than square - is noted by many people. However, if you use a load as noted above, there is no buildup of fouling in the corners of the grooves and the square rifling cleans very well.  All of my rifles have square rifling - they all clean up with one patch for pumping water in and out and 3 to 5 for drying and oiling.

If you are interested in competitions - even trail walks, you might be better off with square rifling .010" to .012" deep.  No serious match shooters use rounded grooves - wonder why?

[Dphariss]

What are the pros and cons of round vs. square bottom rifling on a small .32 cal. and larger bores and please discuss accuracy, loading and cleaning ease.

Wide groove, narrow lands between .008 and .012" deep will load easier and seal better than the typical overly deep excessively wide land round bottom barrel.
Narrow land barrels will also shoot hardened lead OK. Narrow groove barrels will not easily load with hard lead like wheel weigh alloy of range pickup lead.
It would take a lot of shooting the prove the more accurate style. But the wide "flat" groove gets my vote all other things being equal.
Dan

[rhbrink]

A while back I was looking to buy a barrel to build a match rifle and was talking to one of the well known barrel makers asking about the round bottom vs. square cut rifling. He ask me exactly what I wanted to accomplish and I expressed my desire for extreme accuracy and he flat out said "square cut rifling" and did not hesitate. And that's what I bought and have not be disappointed one little bit. But I wonder if a barrel were cut with more narrow lands and round bottom rifling .010 deep why would it not shoot as well as any thing else. I don't see the need for .016 deep rifling and think that it's just too hard to keep the barrel sealed good enough for great accuracy. Walking around the woods "plinking", bang and clang stuff, shoot all day and no cleaning with light charges OK? Maybe? Like posted about serious target shooters do not shoot round bottom rifling.

My experience your milage may vary!

RB

[Turtle]

 I chose square bottom rifling for my new rifle so I don't have to use such as tight a patch as my round bottomed barrel to achieve easier loading. I have an old rifle with a Green River? barrel with narrow lands and I love it. Accurate and easy to clean.
                                            Turtle

[Hungry Horse]

 The best shooting rifle I ever shot was an old used Hawhen full stock that had been converted to percussion. The gun was built by some unknown builder in Montana, with a Bill Large barrel, with wide grooves, and narrow lands. Bob Roller said Bill called these Forsyth style rifling. I don't know why you don't see more of old Bills barrels in this configuration, but suspect the may have been pretty time consuming to produce.

  Hungry Horse

[Acer Saccharum]

You've gotta fill the grooves with patch, or you'll get blow-by, fouling and burnt patches, not to mention poor grouping. In my opinion, I'd go for shallower square rifling on small calibers, as it's easier to get the grooves filled with a thinner patch.

[Pete G.]

I prefer square for the smaller bores because the thinner patches are easier to manipulate; round for .50 and up so as to carry more lube.

[mossyhorn]

Sounds like Square bottom for my .32 cal. is the thing especially with the replies from those about difficulty sealing with patch in round and accuracy problems. Also with target shooters using square and a squirrel rifle needs to shot good if I can do my part.?