Round vs square

[hortonstn]

For competition purposes is a square groove barrel more accurate than round groove barrel?

[smylee grouch]

There might be some round grove barrels on the bench and cross x and chunk gun ranges but every one that I know there shoots square cuts.

[Carl Young]

Back in the 70s, I made a couple of barrels for one of the top NMLRA benchrest shooters. I used an approximately "U" shaped cutter to cut the 7 groove barrels after Harry Pope's style. There is more to groove geometry than "round or square".

Regards,
Carl

[Eric Krewson]

My take from having shot both kinds of barrels, my square bottom barrels shoot anything I put down them well, my round bottom rifles barrels are picky but very accurate once I find out what they like.

[GrizG]

The subject line triggered me...  This as I spend time on an arborist web site and there is a long running battle of square filing vs. round filing chainsaw chains... I use an Alaskan Chainsaw Mill to mill small quantities of hardwood lumber (e.g., ash, cherry, walnut, maple, oak) and to maintain 11 miles of rail trail so playing with chainsaws and various chain types and filing is another hobby of mine. I keep looking for curly maple but sadly haven't encountered anything useable yet... I have a 10/4 slab of walnut sitting here that may be used for a fowler at some point if I ever find time! A maple blank has suffered a similar fate...

[Bill in Md]

The most "accurate" rifling is the rifling that is properly sealed with a good patch and ball combination.

[Daryl]

Rounded grooves tend to be deeper, thus are generally more difficult to fill with "lead and" patch.
Bill in Md spells it out.  A load that does not fill/seal, will not generally be as accurate as one that does.
Look at what the winners in the BR, chunk, plank and cross-stick competitions are using.  As well the
shallower the rifling that works(still deep enough to work), will be generally more accurate due to less
deformation of the ball. This was also Harry's Pope's belief along with his style of rifling and although
he was using slugs, 'physics' are 'physics'. The more deformities of the ball greater the potential for
something that interferes with good stable flight. As Forsyth would say, the more the atmosphere has
to work with.

[smylee grouch]

When I have had the chance to give a good look at some old originals I have seen those " U : shaped cuts where the break off from bore to grove is square like the square flat bottom grove type. It seems to me that the modern round grove type has a less abroupted or more gradual " valley " shape to the whole cut. 

[Daryl]

Today, the rounded grooves are wider (most of them) and up to .028" deep as per H. Toenjes, but .016" in most. I've seen some Getz rounded grooves that were
more U shaped, but without the squared, hex or octagonal bore shape of many originals where the grooves were in the corners. Those are a bit weird looking. imho

[Scota4570]

Get the square bottom and be sure the lands are narrower than the grooves. 

The round bottom barrels I seen have wide lands, and narrow deep grooves.  IT does not matter round or square if the barrel is made like that.  None of the barrels I have owned with narrow deep grooves shot well enough to satisfy me.  I recently had a barrel rebored after only 100 shots.   It was pretty hopeless. 

I recently had a barrel cut to my specs, the one referenced above.  Wide grooves, narrow lands, 0.010" deep, 40 cal.  It is now well finished and there are no tight or loose spots.  IT now shoots very accurately, no fuss at all. 

I'm not saying all round bottom with deep narrow grooves will not shot accurately.  Each barrel is an individual.  I do believe such a barrel has less accuracy potential, all else being equal.

Accuracy is relative.  Some guys may be happy with a 4" @ 50yd barrel.  IF you do trail walks, plinking, and don't clean,  that may be fine.  I am not happy unless 5 shots are around 1 1/2" or less @ 50 yd. 

I have no interest in seeing how many shots I can get before cleaning.  I think a smooth finish achieves easier cleaning more than round or square anyway.

[hortonstn]

scot
My consern is benchrest accuracy we shoot open sights , benchrest 60 yds at a 3" target to win it takes 3 out of 5 in the center (a nickel)

[Dphariss]

scot
My consern is benchrest accuracy we shoot open sights , benchrest 60 yds at a 3" target to win it takes 3 out of 5 in the center (a nickel)

We shot string measure when doing 60 yard rest matches.
 “Square” grooves narrow lands. Don’t need to be more than .010” deep.

[Daryl]

Dan, those lands are even narrower than my Goodoien .40 - NICE!.
A short starter is not needed to load a 10 ounce denim patch and bore sized balls in either of these barrels.
I use one though, as it's faster and easier on the rifle's wrist.



.36 Rice is nice too.

[hortonstn]

Daryl I had the honor of owning one of Jims .565 bore benchrest barrels 2-1/4 dia with false muzzle
Underhammer really enjoyed it until I hurt my back now I'm trying to repeat its accuracy in a lighter
Version thanks for your input

[Dphariss]

Its 1 1/4” x 44” 50 cal gain twist by Jim McLemore. Jim told me that when he tested it (he uses a percussion action with a scope rail to test them) that with 120 gr of FFF and a teflon patch it would shoot the same hole at 100.
I also have the same contour in 45 caliber but its still in the rack.

[Daryl]

No doubts in my mind that it wouldn't/. Love the rifling profile. Wish ALL of mine were the same.

[WadePatton]

Hypothetically speaking (or perhaps this has been done a time or two), if you had a rifled bore with roughly equal width lands and grooves and it wasn't shooting to your satisfaction, how much extra work would be involved in cutting the grooves wider?  Would this be impractical to do in a freshing out procedure? Is there a better way to rework one to the land/groove profiling preferred?

Of course there's more to accuracy and bore parameters, but let's assume a good gentle taper to the muzzle, lapped/polished, and no tight spots. And rate of twist verified to be steady or increasing at the muzzle, with a perfect crown.

[Daryl]

This one has shot 1" to 1 1/2" 5 shot groups at 100yards with my sitting and using sand bags as a rest, with the rifle's Express sights.
Wider grooves simply makes for easier loading of tight, accurate loads, is all.
In this rifle, shooting those groups, I was using 165gr. 2F GOEX, 12 ounce .030" denim patching and a .682" ball in the .690" bore. The
grooves are only a little wider than the lands & are .012" deep.