Round groove vs square cut rifling?

[Zonie]

If I may ask, could we please stick to the subject mentioned in the original posts title?

It deals with round groove vs square groove rifling and I'm sure the intent was to find out what the benefits of each are.

I'm sure our members have learned a lot about the science and methodology of manufacturing rifling grooves but that discussion IMO is more suited to the Gun Builders Bench sub-forum.

Perhaps a new thread should be started there for us technically interested people?

 

[mhb]

M.D.:
We use CM 4142 and stainless 416R, and buy it in large lots from steel suppliers in the Southwest, different ones depending on price and availability at the time of purchase. To accommodate finished barrels of different diameters, bar stock is purchased in 1", 1 1/4" and 1 3/8" diameters, mostly, but a few 1 1/2" bars are on-hand.
Both steels are specified as 'BQ' (barrel quality), which, according to my metallurgical engineer partner in crime is a higher purity spec. than aircraft steels.
I have made a few barrels (rimfire) from 12L14, but do not like it - it is really too 'tender' a material, and subject to easy deformation and quicker wear. I have not used 1137, but, cost considerations aside, would always prefer the alloy steels.
Steel is purchased at a specific hardness spec., and desired physicals, which are certified by the supplier. The bars may or may not be stress relieved before delivery, but we stress relieve them in-house.
Bernie (the engineer) always tests new lots of steel to verify they are what they are supposed to be.
After stress relief, the steel is expected to be within the range of around 26 to 32Rc for both types.
The stainless is the 'friendliest' material to machine, giving fine surface finish and longer tool life, while the CM is a bit harder to work with, but perfectly satisfactory.
In rifling, the 416 chip is usually a thin ribbon, folded into the cutter box, while the more recalcitrant CM gives partial full chips and much that looks like steel wool.

mhb - Mike

 

[M. De Land]

Good point Zonie, I am one of the worst offenders of getting off subject and onto related bunny trails. I'll work on this and appreciate the correction as I absolutely own the responsibility for the diversion. Mike D.

 

[Rokon]

I find that the most accurate match barrels are cut square. The rounded groove barrels require a smaller ball and a thicker patch to shoot well and they do not shoot as well out to 100 yards as a square rifled barrel with a 0.005" undersize ball and a .015-.018" patch. Frankly, I own both and on the basis of accuracy, not ease of cleaning, I definitely favor a square form of rifling for all applications.

 

[roundball]

"...rounded groove barrels require a smaller ball and a thicker patch to shoot well..."

First time I've ever heard of this...would like to understand it in detail as I've used both type barrels for some time now.

Please post a link to the source data.

 

[hanshi]

First time here, too. I also have both and am unable to tell any accuracy difference. I use the same .024" patch as I use in the square cut bores.

 

[estas]

I'm not sure I understand your explanation of varying depth of rifling grooves due to lack of support of the cutter in the cutter box.
I am a barrel maker, and make my own rifling heads, so have a good understanding of the design, geometry, fit and function of the parts.
The depth of cut is controlled by the contact between the cutter and the screw-driven wedge which supports and raises it in its seat in the cutter box/rifling head.
Hook cutters ride up the wedge to the full height permitted by the adjustment of the wedge and the hook's contact with the rear of the cutter box immediately on contact with the barrel on the cutting stroke, and are held there by the forces exerted on it in making the cut and the spring which pushes it rearward through the forward plunger which supports the 'toe' of the cutter. Any movement of the cutter in its box aside from this will be sideways, due to a less-than ideal fit in the cutter box, and can result in a 'tipped' cutter, which will make one side of the groove deeper than the other. Hook cutter rifling heads without the extra mechanism designed to retract the wedge, lowering the cutter for the return stroke still permit the cutter to ride down the wedge on the return stroke, but the forward spring and wedge will return it to full height for the next cutting pass.
Scrape cutters are usually supported by the wedge directly under the cutting edge, and, again, cannot ride down in the box below the height at which the wedge supports it for the cut.

mhb - Mike

Hi Mike , I dont learn mesaage at forums . I need a information for cut rifling ..Can you help me please ..Can you send me a mail ?? [email protected]

 

[mhb]

Hi Mike , I dont learn mesaage at forums . I need a information for cut rifling ..Can you help me please ..Can you send me a mail ?? [email protected]

E-mail sent.

mhb - MIke

 

[Okie Hog]

Rounded groove bores are easier to clean. They're easier to load with patched round ball. i currently own two rifles with rounded groove rifling:

1. A Navy Arms Hawken style rifle that was bored and rifled to .54 caliber by Mr. Hoyt. Rifling rate is one turn in 66 inches. That rifle puts five round balls in one inch groups. at 78 yards.

2. A TC .54 New Englander with a roached bore was bored and rifled to .58 caliber by Mr. Hoyt. Rifling rate is one turn in 66 inches: My go to hog rifle.