Round Bottom Rifling?

[T*O*F]

Bit of a misquote Dave:  "Fat bottomed girls you make the rockin' world go 'round!" 

That's why I only listen to talk radio.  I can never understand the lyrics in most songs, so I make up my own.   

[hanshi]

The canvas, elkhorne, is by my measurement about .024".  Squeezed in calipers it runs about .030".  The way I measure with the caliper - don't have a micrometer - is to take both hands and squeeze the jaws with everything I have.  It's even thicker than canvas duck, which I like and use in certain guns.  Odd thing is that it seats easier than smoother, thinner material such as mattress ticking and even the duck.

I've had it for around 18 years and have used it from time to time but started using it in some rifles a good while back.  Canvas duck and ticking both get used a lot in a smoothbore and certain rifles.  I don't know where she got it and the original purpose was to protect walls in a small gym.

[Huntschool]

hanshi:

I suspect the "duck" you are referring to is actually Army Duck.... a very different weave then "cotton Canvas duck."  Regular canvas duck is a Fairleigh open coarse weave but is available in a number of different ounce weights.  The Army duck is a more complex weave and is also available in different ounce weights.

When we made tipis and tents we used a 10.38 oz treated army duck fabric that also had sizing in it.  It was quite water repellent.  Much more so then cotton duck. 

A good friend who shot a lot of trade gun stuff back in the day took a couple of strips of this material and washed it well to remove the sizing and then cleaned it (as in dry cleaning fluid) and used it in his trade gun.  He said it was the best patch material he had ever used......

I suspect one could find untreated army duct material at large canvas supply houses but I am not sure how big an order would have to be.  We bought it in 300 yard lots (36" wide) in bolts of 50 yards.  That would darn sure be a lot of patches.

Modern pillow ticking which I have sitting next to me measured as you do comes out to be .009.

Just some thoughts

[Scota4570]

Final thoughts from me on this subject:

The guys having positive results with RB rifling seem to be using larger calibers.  Larger ball = more mass = more momentum.  It has more ability to resist forward moment than a smaller ball.  Lead is equally soft regardless of caliber.  So, upon ignition, the larger ball slugs up better than a smaller one.  This compensates for the deep narrow grooves.  So, accuracy is sufficient despite the RB rifling, not because of it? 

[Ky-Flinter]

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...

 

Experience with Rice round bottom barrels?  Yes, 38" B-weight .50 caliber.  It's my deer rifle and off-hand match and woodswalk rifle.  I load it with 65 grains of 2F, .490 ball, .018 patch.  Spit for lube in matches, wonder lube for hunting.  Not hard to load and doesn't foul up.  It shoots more accurately than I can hold it.  Count me in the first group.

This discussion reminds me of the Miller Lite commercials with the chants, Tastes Great!  Less Filling!

-Ron

[Daryl]

Hello all! Another question, here. 

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

1/. I’m hearing some say they’re easier to clean at the end of the day, and 2/. that they can allow more shots before needing to swab the bore, and things of that nature. 3/.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?

1/.I have not found easier cleaning - but - I only have one rounded rifling barrel, all the rest are and have been square bottomed.
2/.I shoot all day with both styles of rifling - NEVER have to wipe during shooting, whether 20 shots or 100.  Loading the next shot is always the same.
3/.I have no experience with a cross-test - but note, "unless competing at the national target shooting level" - shows if wanting (REAL - not just good enough)accuracy, the rounded rifling is not the way to go-
admitted by some of the top barrel makers

So - there ya go. Your mileage might vary. How many guys here with comments in this thread actually tested to get the best accuracy out of their barrels, or merely
chose a load or powder and patch/ball combination and shot that & it was accurate enough, so done?

[JW]

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...

 

You will likely not notice a difference if you shot both side by side and if you did, you'd be splitting hairs. Most people will say they prefer whatever they have or make up a reason why they prefer one if they have both.

[hanshi]

You're probably correct, Huntschool.  It's been a while since I bought any and the only thing I seem to recall about it was the words "cotton" and "duck".  I have no way of knowing which one I bought.  I do know that the unbleached canvas really does well in my rb barrels.  I have a quantity of "mattress" ticking which is quite a bit heavier than pillow ticking, of which I also have a supply.  With several different materials for patches, I guess I'm set up for about anything. 

The two Rice rb barrels I have are a .32 transitional barrel and a "B" weight .50.  I can no longer shoot/see well enough - retina defect in my dominate eye - to compare the round vs square groove bores.

[bnail]

I think i read through all the responses but didnt see if round bottom or flat was used historically.

[Blacksmoke]

bnail:   More on the round bottom rifling - I have been hand rifling barrels for 35 yrs. now and for the last 27 yrs. have been proofing every barrel that I rifle, not for strength but for accuracy.  Some years ago a fellow came to me with a rifle that would not hold a group at 100 yds. so he claimed.  I took the barrel off of the stock and put it on my proofing bench to see if his story was correct.  It had , so called , round bottom rifling in it.  After I spent the entire afternoon putting every load that I had available to me through it - I proved that he was right.  No group smaller than 8" at 100 yds. The grooves were .012" deep.  I told him that I thought I could fix it.  So he left the barrel with me.  I put it on the Rifling bench and proceeded to cut wider oval bottom grooves to about .026" without increasing  the bore size or changing the twist.
 The attached target was the proof target for that re-rifling. Also I lapped a slight choke towards the muzzle.
    Hugh Toenjes   Yes there were some original barrels that were cut with rounded bottom rifling.

[Blacksmoke]

Finally managed to post a photo -see below.

[Daryl]

Many to most were very similar to this. I have never seen a rounded bottomed rifled original with the deep grooves. Most, at least in
NA, followed this upper example.
This is an early Longrifle barrel from the mid to late 1700's. I thought it was the worse case scenario of wide land, narrow groove going, until I found this one -
below. Might be hard to find a 'tough-enough' patch, but a tick patch and smaller ball might give 'decent' hunting accuracy.

[Blacksmoke]

When I speak of "round bottom rifling' I do NOT mean a radius profile groove. I mean that the grooves are rounded at the bottom in stead of flat across the bottom.  This was usually achieved by the cutter being slightly rounded because of wear.  Today's commercially rounded grooves are generally a radius designed groove.  The secret in designing an easy to load and accurate type of rifling is in the ratio of groove width to land width( The grooves are at least twice as wide as the lands) coupled with depth.  This has been my experience over the last 35 yrs.  This is the kind of rifling profile that I put in my barrels:
  Hugh Toenjes 

[Blacksmoke]

Here is the proof target for that barrel:
  Hugh  Toenjes

[little joe]

Hugh What were you using for sights?

[Acer Saccharum]

Narrow lands and wide grooves are a good shooting formula, from my reading, and your examples, Hugh.

One downside is if you don't protect the muzzle, the lands wear rapidly.

[Blacksmoke]

Tom:  Thanks for the input!  As far as land wear goes I have never found this to be a problem even after 12,000 - 15,000 rounds.
I can see it if you load real tight loads.  But with my configuration of rifling the extra tight load is not necessary. 
  Hugh Toenjes 

[Marcruger]

Hugh, I agree with the comment about the grooves being much wider than the lands for deep rifling to work.  From what I hear your barrels WORK. 

I had a round bottom barrel with narrower, deep grooves.  The problem was you couldn't stuff a tight enough load down the bore to ever shove the patching outward to seal the deep but narrow grooves. It would simply never seal, giving blow-by, velocity variations, poor accuracy and fouling. 

With wider grooves like yours Hugh, it appears to be much easier to fill those grooves to the bottom. 

Alternately, a person could go with Colerain's option of narrow-ish but shallow round bottom grooves.  I have shot my buddy's Tip Curtis rifles, and they will shoot tight groups with those Colerain barrels.  Easy to load and seal for sure.

All of that said, I have found Green Mountain square bottom rifled barrels to shoot like a house afire, and never seem to be fussy about the loads they'll shoot well. 

In all of the discussions about canvas and heavy patching, I have mentioned before that The Minute-Men patching company sells some really, really tough canvas material (get the untreated) that I have never had burn through.  Works super.  I would love to know their source!   :-) 

Your mileage on all of my comments may vary. 

God Bless,  Marc 

[Pukka Bundook]

Hugh,

I find it very interesting that in the above photo, you used a .562" in a .58" barrel.
I have used this same combination for decades and it does indeed work.   Yes, my old Don Getz has the round -bottomed rifling as well.

Very nice target in that photo!

[Blacksmoke]

Pukka: Thanks for the comment.  The undersize ball helps to keep it spherical when loading.  Every time one hammers the ball and patch down the barrel the once sphere is now deformed.  Any upset on the ball will have an effect on accuracy. 

  Hugh Toenjes

[Blacksmoke]

Little Joe:  I do not use sights when I am proofing I just clamp the barrel in the removeable jig and keep on shooting.  I only proof for accuracy of the barrel by eliminating the human factor of holding a rifle and pulling the trigger.   Hugh Toenjes