Deep vs shallow rifling?

[backwoodsguy]

I've been doing a little research on different barrels and I am wondering what the main difference is between deep and shallow rifling? I was hoping maybe someone with a little more knowledge or experience could lend some light on the difference or purpose of the two?

 

[reddog]

Deep for patched round ball,,,shallow for sluggers.

Deep, shallow, round bottom, square bottom, Forsythe, ballard, gain twist, gain depth, and some more that I ain't thinkin' of right now.

What is it, exactly that you wanna know?

Welcome.

 

[Zonie]

Welcome to the Forum.

In my opinion, shallow grooves are made for elongated bullets which are loaded without thick patches. Some of the them are occasionally patched with paper but generally speaking they are just lubed before loading.

These bullets rely on the enlarging that occurs when they are fired to pick up the rifling and to seal the bore against the high pressure powder gasses. They are usually very close to bore size when they are loaded and because the enlargement they produce when they are fired is not very much, shallow rifling grooves are about all they can seal.

Most modern cartridge bullets (which we don't discuss here) are the same size as the rifling grooves or slightly larger before they are fired.

The rifling I'm referring to as shallow is usually .0015"-.003" deep.

Deep rifling grooves are ideal for shooting roundballs patched with a cloth material.

The size of the ball and the fairly thick patch are larger than the rifling grooves are so when they are loaded they not only get a good grip on the grooves but they seal them against the powder gas pressure.

The soft lead roundball compresses some during loading but it is the patch that does most of the work.
This deep rifling is usually between .007" and .016" deep.

A lot of the commercially available muzzleloaders use a compromise rifling depth of .004"-.007" deep.
Guns like the Thompson Center sidelocks and some of the Lyman guns use this kind of rifling.

This is intended to work well with either patched lead roundballs or solid lead slugs, some of which are solid lead and some using a hollow base.

These can work fairly well with either type of projectile but for best results the slug should be just slightly smaller than the bore size and the patched roundball should be patched with a very tight fitting cloth patch.

The very tight patch is used to get a good grip on the medium depth rifling grooves without slipping when it is fired.

 

[backwoodsguy]

Reddog thank you for the reply, right now I was just trying to understand the general difference between the purpose of shallow and deep rifling. The different styles of rifling you mentioned is an entirely (new to me) subject but one that you have struck my curiosity in. I would greatly enjoy any information you have on them.

 

[backwoodsguy]

Zonie, thank you for such an informed reply I think you covered the basics of what I was wondering and then some.

 

[zimmerstutzen]

Wow, wait til you start studying round bottom and other shapes and widths of grooves and twists.

 

[Dphar]

I've been doing a little research on different barrels and I am wondering what the main difference is between deep and shallow rifling? I was hoping maybe someone with a little more knowledge or experience could lend some light on the difference or purpose of the two?

Rifling deeper than .010 simply increases blowby.
I.E. its harder to seal and may have a shorter life especially when cheap steel is used in the barrel.
It does nothing to increase accuracy.
Dan

 

[zimmerstutzen]

where the lands are equal width with the grooves there is a greater chance of blowby with deeper grooves. Where the lands are, for instance, 1/4 or 1/5 the width of the grooves, blow-by happens far less frequently.

A patch material with a thicker knap, such as cotton flannel will prevent blow by in some deep rifled barrels

 

[nkbj]

Concerning the depth of groove, deep grooves width with approximately equal land / groove widths generally work well. As the land widths is decreased it usually means a tighter patch and ball combination gives best accuracy. Well, but not always...
This is a .58 rebore flinter before lapping it in. Been working on it since then and got her 95% slicked and crowned for loading patched ball now. I'm chomping at the bit to get her sighted in if I ever get to stop working 12-16 hour days.

 

[Dphar]

To expound somewhat. I do not think "bullets" when talking the typical MLs so I was speaking of cloth patched projectiles. "Naked" and PP bullets are apples and oranges to cloth patched projectiles.
Bullets such as those used in breechloaders can use much shallower grooves. But if taken much below .003 soft bullets may strip. Some 19th century Winchesters had very shallow rifling, not worn cut that way, and the 45-70 1886 I once had required jacketed or hardened W-W alloy to shoot well. Typical BP bullet alloys 1-16 to 1-40 would not work. With hard bullets it was very accurate.
Some 19th century BL arms had deep rifling. The Sharps percussion guns converted to cartridge by Meacham had very deep, probably .007 or more, Henry style rifling and shot pretty well and were widely used in the west though I have never had the opportunity test one. I would think they would be less efficient than the original Sharps rifling which was usually about .004".
The "naked" or PP bullet will work with shallower rifling since they do not have a cloth patch. The cloth patched RB does not physically engage the grooves the patch does. If the grooves are not deep enough to allow substantial engagement of the patch, if the patch material is weak, if the ball is too small the patch will likely fail and "blow" and may even catch fire.
Elongated bullets (the cloth patch will not allow bullet with long bearing surfaces) when fired with BP will, due to there inertia, expand to fit the bore and fill the grooves even if .015-.020 under groove diameter. If the bullet is properly designed they will shoot very well too. If the grooves are .003" or deeper stripping is very unlikely. So bullets can easily work better in relatively shallow grooves .003-.005" that would be useless to someone shooting cloth patched RBs or Picket Bullets.
So the minimum depth IMO for bullets at least those significantly heavier than a RB of the same caliber, can be perhaps 1/3 that needed for cloth patch projectiles since its very difficult to "strip" a bullet that fully engages the grooves at least at the pressures possible with BP and reasonable groove depth.
Dan

 

[Dphar]

where the lands are equal width with the grooves there is a greater chance of blowby with deeper grooves. Where the lands are, for instance, 1/4 or 1/5 the width of the grooves, blow-by happens far less frequently.

A patch material with a thicker knap, such as cotton flannel will prevent blow by in some deep rifled barrels

This is also true and I prefer narrow lands. They seal better and load easier than wide lands. I believe barrels with wide lands are the reason the myth that only soft lead works in MLs started. Hardened lead was the standard for MLs used for shooting large African and Asian game with both rifles and smoothbores.
I can shoot pure lead or W-W alloy in narrow land barrels. It shoots as well or better than pure lead in limited testing. Hard lead MAY require a slightly thinner patch. I use .015 linen in one rifle with WW and .020 cotton with pure lead. But it is a shallow groove barrel .008".

Dan

 

[Rifleman1776]

As long as there have been rifles there have been various theories about rifling. I'm sure these debates have been going on just as long as well.
I'm a deep (.010 to .012, or more) proponent. Others favor shallow. Now, let us examine, round, gain, fast slow, etc. No......let's not. I'm old already. :wink:

 

[backwoodsguy]

Well, now that I have opened such a can of worms, does anyone know of a source of information on what type of rifling a 1984 Charles daly .50 cal 1:48 would most likely have?

 

[nchawkeye]

Most likely shallow as production rifles are usually "button" rifled...(A button or star is pulled through the barrel and the grooves are engraved into the bore)...Custom rifles are typically cut rifled...Button rifling will run .006-.008 deep while cut rifling is typically deeper, like .0010-.018...

Most agree, deeper, cut rifling works a bit better for patching round balls...

 

[paulvallandigham]

Charles Daly imported guns made in Japan. They were well made, but the company took advantage of the spurt in interest that revolved around the Civil War Centennial, and then interest in Pre-civil war " mountain man" movies that came out in the 70s. I did not see these guns here in the midwest, altho I haunted gun shows hoping to see one to examine. They were well made, but I can't tell you anything about how they were rifled. I suspect that they mimicked the order of the day, and used square bottom rifling, in common calibers, all with ROTS to shoot Round balls. If I spend some time in my back issue of Gun Digest annuals, I am sure I can find information on calibers, and models of the guns. That is not what you are asking about, however.

 

[backwoodsguy]

This particular Charles Daly that I have came from Italy, it was made by Investarms. I believe it is the older version of what cabelas is now selling as "their Hawkens".

 

[reddog]

Slug it,,,easiest and fastest way to find out.

 

[Zonie]

If it is an Investarms, most likely it has the .005-.007 deep rifling that can work with either patched roundballs or solid lead slugs.

The twist is probably 1:48 but you can check this if you have a cleaning jag (grooved brass button)installed onto the end of your ramrod, a lightly oiled cleaning patch, some tape, a tape measure and a pen.

Run the cleaning patch on the jag down to the breech.
Wrap the tape around the ramrod flush with the muzzle.
Place a mark with the pen on the tape in line with the front sight.

Carefully withdraw the ramrod allowing it to turn with the rifling grooves until the mark has rotated 1/4 turn. (If it started at 12:00 oclock it will now be either at 3:00 or 9:00 depending on the direction of the riflings twist).

When the mark is at 3 or 9 oclock, measure the distance from the muzzle to the bottom of the tape.

Multiply this measurement by 4 and you will know the rate of twist.

Sometimes the patch or jag will slip so do this test several times and use the answer that comes up most often.

Have fun.

 

[C Barker]

Just curious, had anyone shot PA Conicals out of a Lyman Deerstalker?

 

[Herb]

That's a really good photo of a bore. What equipment did you use? And what does the bore look like now?