Barrel Groove Question

[Idaho Elk Hunter]

Can anyone tell me what is advantage or disadvantage a barrel would have with six grooves vs. seven or even eight grooves in a barrel or less grooves than six? This is for PRB usage? Also depth of grooves for best patched round ball accuracy?

 

[Col. Batguano]

Round grooves are easier to clean, and don't trap fouling as much. I believe Rice cuts them .010 deep. More grooves give you more sharp edged to catch the patch/ball combo better, but because of the sharpness, they say to use a bigger ball and thinner patch with a round groove rifled barrel, and a smaller ball and thicker patch with square rifling.

Some modern guns (such as the 1903 Springfield) were made with only 2-groove rifling, so it's really not the number of grooves as much as it is the effectiveness of the lands / grooves to catch and impart spin to the projectile. The reason some of the old timers used an odd number of grooves had to do with their cutting tools that rode in the previously cut grooves to cut the new one, more so than any accuracy advantage.

 

[M. De Land]

There are numerous theories at play in rifling thought.
The odd numbered lands are cut that way so as to alleviate bullet distortion from the opposing land on the other side of the bore.
The object is to adequately grip the bullet with the rifling form that least distorts the in flight projectile in regards to drag and accuracy.
The Brits are big on odd number rifling and we also did so on some models like the 1863 rifled musket from Springfield.
Cutter teeth or hooks are proportioned to the bore diameter and number of grooves to be cut in that particular barrel.
They can be odd or even numbered and cut from the same machine with the appropriate indexing head.

 

[galamb]

Jim, I would suggest that unless you are a high end competitive shooter at the top of your game you would probably never see any difference between a 6, 7 or 8 groove barrel.

Now, I am not a prolific BP shooter - I do have a few rifles that I hunt with and shoot a few paper targets.

Colerain barrels have 6 grooves, Rice has 7 and Green Mountain has 8 grooves and I own all of these barrels (plus a couple of others).

They all shoot better than I can hold. My Colerain is super accurate and is my current deer rifle - but that's because of the caliber, not because it shoots more accurately than the Rice.

Likewise I have some round rifled and some square rifled - don't see any accuracy difference (or ease of cleaning difference either if I'm being really honest).

I do like the round rifled because it "seems" like successive loads go down the tube a little easier but that may just be the power of suggestion working.

In general you use deeper groves for shooting round ball compared with a conical. That's where the difference of opinions start.

Some say .008" is deep enough for RB, others will say "minimally" .012"

I have shot round ball barrels with rifling between .008" and .016" and can once again say that it never made a difference in the accuracy of "my shots".

Sorry - probably haven't help you answer any of your questions (or maybe that's an answer in itself) ???

 

[matt denison]

MD said:
"The odd numbered lands are cut that way so as to alleviate bullet distortion from the opposing land on the other side of the bore."

That is the explaination as I'v been told. Makes sense to me.

 

[mhb]

In my experience, there is no particular significance to the number of grooves in a rifle barrel, and no demonstrable advantage to any specific rifling profile, though barrels intended for patched round ball or picket bullets will likely perform better with 6 to 8 grooves of equal width to the lands or a bit wider, and not more than, say .010" deep. Fewer or more grooves offer no advantages in performance, and may actually be less accurate, or complicate the process of finding a patch and ball combination which works properly.
The important factors are the quality of workmanship in the barrel, and, to a lesser extent, the material of which it is made.
A good barrel MUST be smooth as to finish on lands and grooves, without burrs or rough patches, consistent in pitch, and uniform in diameter of bore and grooves from breech to muzzle, with a slight choke or taper being permissible, but not necessary.
Rifling pitch is another topic, and has been extensively discussed previously - the best procedure in ordering or selecting a barrel is to consult the maker for his recommendations. Exactly whose barrel to use is also a topic for discussion with other users, and also open to endless debate.
I am a barrel maker (re-retired), so offer my opinion based on experience, having made a VERY wide range of custom barrels to meet individual requirements, as well as the tools used in the manufacturing processes.
If you pick a reputable barrel maker, consult with him on your requirements, and follow his recommendations, you can expect good results. Advice on all other topics relating to good shooting is available from members of this forum and others like it.

mhb - Mike

 

[longcruise]

I once read that the odd number grooved barrels were done that way to allow the back of the cutter to rest against the land opposite it.

 

[Spikebuck]

Interestingly enough, I see that Rice, which I think most would agree is a high-quality barrel maker, uses 6 lands and grooves in it's small calibers (up to 40) and seven lands and groove in 45 and up. They use round-bottom groove cut .016 deep. I have one in .62 and it soaks up a LOT of patch!

I'm assuming they use fewer lands and grooves in the smaller calibers just because of the space issue?

I'm with Graham on accuracy and cleaning. I have both round and square, relatively shallow and deep, and they all shoot far better than I can. They also clean up the same for me.

 

[nkbj]

Can anyone tell me what is advantage or disadvantage a barrel would have with six grooves vs. seven or even eight grooves in a barrel or less grooves than six? This is for PRB usage? Also depth of grooves for best patched round ball accuracy?

For any given diameter I've come to think that the width of lands and grooves should look right. Yeah, big help, right? Please, bear with me a moment.
What I mean to say is that extremism in rifling design is typically to be avoided. Grooves about the same width as lands, kinda sorta. Neither real wide and not real small for whatever the bore is.
So the number of grooves is a matter of the length of the perimeter around the bore. For example, if you have a larger bore like a .58 or a .62, maybe you want a little narrower lands so you don't have to move so much metal when starting a ball. A smaller bore means less resistance. Bigger bore is more resistance. Smaller lands means less resistance so smaller lands in bigger bore can be a good thing if you don't want seating the ball to be a martial art.
Going into smaller bores you can get easier loading (in general) but it's still a matter of the lands width, the ball diameter and the patch thickness that all determine the degree of interference.
Hope I didn't confuse things.

 

[mhb]

'slayer:
That is somewhat true, in the sense that the cutter box will contact the land opposite the odd-numbered groove... BUT: in actual practice it makes no significant difference, and, in even-numbered grooved barrels, the cutter box is equally well supported by the corners of the opposing groove, which also helps to keep the cutter box (which is necessarily somewhat smaller in diameter than the bore) accurately located opposite the groove being cut, and prevents 'rocking' of the cutter box from side-to-side.
No advantage accrues to the odd-numbered groove schemes.

mhb - Mike

 

[longcruise]

Some target/match shooters fell that a barrel with narrow lands an wider grooves gives better accuracy. So, IOW, according to that theory, it's not the number of grooves but rather the ratio of land to groove width. Supposedly it allows the use of a larger ball and thus a tighter fit and better accuracy.

Guess it would involve a special order barrel to try it out. I'm pretty much an off the shelf barrel guy :haha:

 

[bpd303]

The old 58 caliber Jaeger that I rebuilt has only four lands & four shallow groves equal in width. Makes it look like a square bore. The twist rate is 1:28 and it shoots patched ball and minie's very accurately.

 

[Idaho Elk Hunter]

Thank you guys for answering my question...all are good......
Definitely some bright individuals on this forum and that is why I am here at age 62 and 38 yrs shooting BP guns and I cannot stress enough how much new information to my brain that I have learned from this site. Started in 2004 here and then was gone for quite some time and now back on forum and enjoy reading the posts through out forum. Some of you are really savvy to this sport of BP for sure!! Thanks again!
Jim

 

[M. De Land]

One has to understand how rifling heads work and how they are designed then it will be clear that the this statement makes no logical sense.
The cutter box/head is turned, hardened and ground round and generally kept no more than .001 under reamed and often lapped bore diameter.
The cutter tooth or hook is radially supported it's full length by the interior diameter of the bore. It makes no difference how many grooves (odd or even numbered) are cut as long as there is some bore diameter left,evenly spaced, around the interior circumference of the bore.
A micro groove configuration would support the head just as well as a two or three groove barrel would.

 

[longcruise]

I'm accustomed to making multiple non-sensical statements on a daily basis so I'm not sure which one you are referring to :haha:

 

[Zonie]

I'm not sure which one he's talking about either but I know that with the old fashioned single tooth rifling cutters, they used the bore, 180 degrees away from the cutter blade to support it.

That is why the old original guns always had an odd number of grooves. (With an odd number like 3, 5, 7 grooves, there will always be a uncut bore directly opposite the cutter tooth).

Cutters that cut multiple rifling grooves at the same time are a fairly modern invention.

 

[nkbj]

Some target/match shooters fell that a barrel with narrow lands an wider grooves gives better accuracy. So, IOW, according to that theory, it's not the number of grooves but rather the ratio of land to groove width. Supposedly it allows the use of a larger ball and thus a tighter fit and better accuracy.

Guess it would involve a special order barrel to try it out. I'm pretty much an off the shelf barrel guy :haha:

Both my Hoyt .58 rebores are that way. I asked him to give them his best round ball rifling. The lands are of fairly narrow width compared to the rhomboid curved bottom grooves. Both were criminally crusted up TC's, a percussion Hawken and a flinter Renegade. The Renegade is really a pretty handy rifle with more iron cut out of it.
http://vid791.photobucket.com/albums/yy192/SNARGLEFLERK/.58 Testing_zpsk4q11hxm.mp4

 

[M. De Land]

A cutter box or head as some like to call it is a cylinder five or six inches in length usually and is a close fit to the finished bore diameter.
Remember that all rifling is cut on a helix angle and the cutter tooth does not need a land at exactly 180 degrees opposite the tooth or hook to support it's cutting depth.
A groove opposite at 180 degrees will not effect the cutter support in the least.
That is why the same machine and head ( with a hook change) can be used to cut even or odd numbered grooves.
The only time the hook is not fully supported is when the head is half way inside or half way out,behind or ahead of the hook as it is introduced or withdrawn.
The groove will be slightly shallower at these two times for about a half inch or so.
This can be used to good effect in the muzzle as it amounts to a choke.