Rifling, round bottom vs. square bottom?

[Martin S.]

I am considering the purchase of a new custom rifle and I am working up my specs.

Can the experts here give me the pros and cons of round bottom rifling vs. square bottom rifling.

I imagine square is more historically accurate, but is there a difference in shooting accuracy?

Is there a difference in the ability to clean the barrel?

Any and all thoughts appreciated.  Mods, if I am in the wrong forum, maybe this belongs in the gun builders forum?

[WadePatton]

Probably a lot of old discussion on this in "Black Powder Shooting".  I'll root around.  I wanted to revisit the subject myself. 

http://americanlongrifles.org/forum/index.php?topic=3706.0

http://americanlongrifles.org/forum/index.php?topic=31422.0

http://americanlongrifles.org/forum/index.php?topic=2579.0

that arrta doo me. 

[EC121]

Since I have yet to find a barrel that I can outshoot, I'll take the least expensive one.  Really don't need more than .010" rifling.  Once I figured out that I was too lazy to do the work required to be a winning shooter, I started buying fancy rifles so I could, at least, look good getting my butt whipped.  Now I just shoot in the backyard and impress the squirrels. 

[WadePatton]

I suppose the question could be pursued by: building a gun with a radius-rifled bbl, developing a load and shooting a few thousand targets for a data pool, THEN having that bbl recut to square rifling, and shooting a few thousand more targets.  Numbers might be different.  Could be significant.  Could be not.

If all the winners shot the same thing this would be so easy.   

[sz]

Accuracy is not really a function of the shape of the bottom of the grooves.  It's all about the quality of the barrel.  If a set of grooves is deep and wide enough to hold the patch and keep it from slipping or "blowing by" they will serve to spin the ball.

Now evenness and straightness of the bore and the grooves, and the quality of the polish and concentricity of the bore....these all can have effects on the accuracy.

I have not done any rifle barrel making in over 20 years now, but when I was in Nevada I did quite a few of them.

  I did experiments with twist, number of grooves, and rifling geometry.  After about 25 such barrels made to compare one to the next I concluded that straightness and bore quality were important, but as long as the grooves were wide and deep enough to hold, not many other things were all that important.
 The faster the twist the more the bore fouls, but if I clean between shots I found that the barrel I made with the 1-14 twist was no more and no less accurate than the one I made with the 1-70 twist.
 The ones I made with round grooves shot just as good and no better then the ones I made with square grooves.
 Super fast twists are more finicky but when loaded right they shoot as tight a group as any other.

Having the bore and the grooves with no tight spots and no loose spots, with grooves at .006 to .014, and with 3 to 9 grooves, they all shot very well as long as the quality was good.
 

Now I will say that round grooves clean up a bit easier, and a twist for balls of 1-30 needs to be wiped a bit more then one with a 1-60 twist, so there are factors that may influence your decision, but none of them are really going to be about accuracy.  It's more about convenience.

[Hungry Horse]

 The hard cold facts are that very few shooters can shoot to the potential of their gun, if it is of any quality at all. I have seen great shooters outshoot other shooters shooting very expensive custom longrifles with kit guns, or production guns. I have also seen fantastic rifles sold for cheap because it was perceived that the gun wasn't accurate. Getting peek performance out of a muzzleloader involves a lot of time. Most shooters won't dedicate that much time to their chosen sport.
 I think the cost of a premium barrel makes most shooters feel they have to use it a lot to justify the expenditure, which makes them shoot better. So, I guess a custom barrel does make you shoot better.
 I'm not saying don't buy a custom barrel, just don't think it's going to work without some serious range time.
 So, go to the range every time your doctor goes golfing, or on vacation, and you'll do just fine.

      Hungry Horse

[oldtravler61]

H.H. love that last sentence. You hit the nail on the head. Practice makes perfect. Lots of it.

[Dphariss]

I am considering the purchase of a new custom rifle and I am working up my specs.

Can the experts here give me the pros and cons of round bottom rifling vs. square bottom rifling.

I imagine square is more historically accurate, but is there a difference in shooting accuracy?

Is there a difference in the ability to clean the barrel?

Any and all thoughts appreciated.  Mods, if I am in the wrong forum, maybe this belongs in the gun builders forum?

I consider the round bottom grooves to be of no benefit and, as some cut them far too deep, they may require a heavier patch to seal if they seal at all (also note that "seal" is a relative thing). As a result the "square" groove is less likely to "blow" patches than a deep round groove barrel. Also narrow lands and "square" grooves load much easier and seal better since a tighter combination can be used. Narrow lands (less than 50% of the groove width) and relatively shallow grooves are also more tolerate of hard or soft lead alloys so there is no need to use "pure" lead for projectiles. Grooves deeper than .010-.012" are not necessary.
But some people think the round bottom groove is "cool".
A uniform bore dimension, a uniform piece of steel and careful attention to cutting the grooves to a reasonable depth will make a good shooting barrel. Everything else is window dressing.
The smoothness of the barrel's internal finish is what makes a barrel easier to clean. There is no voodoo in barrel making IMO. Careful selection of material and careful attention to detail make a good barrel.
If you want the barrel the be accurate, other than relying on a roll of the dice, you need to pay for it. To further confuse the issue, the more machine work done on the exterior the more likely the barrel will have accuracy issues. So a straight barrel, all things being equal, will out shoot a swamped or 1/2 octagonal barrel.
Remembering that the sights on a traditional longrifle are generally the limiting factor. If you want to actually test a barrel but a 6-10 power scope on it, shoot at least 10 shot strings and learn a repeatable bench rest or over the chunk technique. Then do load development.
Practice will never improve a barrel that does not shoot accurately.
Dan

[Hungry Horse]

 Back in the day it was all about very deep cut rifling. Now, many years later, I find that rifling that is too deep can be more of a hinderance, than a help. As previously stated it is hard to get extra deep rifling to seal, and not burn up the patch. The only exception to this rule is Forsyth style rifling with wide grooves, and narrow lands, in my opinion. A friend had a Bill Large barrel in this configuration that had very deep rifling, that sealed up well, and shot like nothing I've seen since.

  Hungry Horse

[JBJ]

Well said Dan.

JBJ

[Marcruger]

I agree with Dan.  I've had a hard time sealing a round-bottom rifled barrel with deep grooves.  As far as round-bottom being easier to clean goes, if you are getting gas blow-by, they can be a booger to clean. 

I believe that square bottom is more forgiving.  Just my 2 cents worth. 

Best wishes,   Marc

[Scota4570]

I have both in 45 caliber.  They take different patch and ball sizes to work best.  If you have a bunch of guns you will want to keep a record of what works with what.  I got the round bottom barrel out of curiosity.  I now wish I had stuck with one maker and style to simplify patch and ball inventory.

[hanshi]

Having more than one of each I will say I can see no difference between them that's significant.  Round bottom, in my experience, does indeed clean up a little faster; but this should not necessarily determine barrel choice.  I have to agree that straight barrels make better target rifles than swamped barrels.  However, swamped barrels make better hunting and all around rifles.  The most accurate and easy to shoot rifle I've owned was a 42" straight, square groove, .50 barrel in a Virginia rifle.  My eyes are no good any longer so I can't shoot nearly as well as I use to; so any difference in barrel accuracy has to be pretty great for me to discern.  I use patches that measure from .022" to .024" and don't experience torn or burned patches in the round groove barrels with their very deep grooves.

[stuart cee dub]

Round bottom .No question for me anyway as a general rule  .

Especially if it's a long rifle and you're not pulling the barrel to clean it.(Which you shouldn't have to do anyway )

Both mine clean in about two thirds the amount of time as the square bottomed rifles do.
I can discern no practical difference on accuracy and less tendency to cut patches which is a problem with one square grooved barrel in particular .Still If I came across a good deal on a quality square bottomed barrel I wouldn't pass it up, just avoid extra deep grooves .

You can outshoot some barrels because some are just junk ,specifically on some old commercial guns no longer made.

 New made custom barrels are pretty good. Pick a good maker and move on to furniture etc .Talk to your gunmaker they have lots of useful experience and definite opinions .