Choke in a rifle barrel

[Roger Fisher]

GRRW purportedly had a slight constiction at the muzzle. I stress slight. Pop the the short starter and they went down easily. My choice over any other at the time for accuracy. Rumor had it that they got the idea from Bill Large. How is it bad if the barrel is easy to load and the patch ball combo tightens up as it leaves the muzzle.

When I made my first MLing rifle [1978] I used a .45 GRRW barrel--it was sold to me as a "choked bore" barrel--and it seemed to be so.  It was and still is the most accurate ML rifle I have shot.  All I can say, as I never measured it, is that the ball loads very tight for the first few inches, then slides down more easily. 

Well she would be tight there til we swage the ball to the grooves and lands then it is natural that the patched ball would move on down more easily

[David R. Watson]

The Germans had a "Squeeze Bore" rifle that was somewhere around 25MM at the breech and ended up somewhere around 20MM when it exited the bore. The velocity was incredable at the time and was used on armored vehicles. Of course this was a breech loader...

[Dphariss]

U guys just gave me an answere to a question Ive been kicking around. want to build a 22 cal cap and ball, was thinking of tapering the forcing cone to swage down #4 buckshot. By lapping the cone and continuing up the bore a bit it may just work..thnx ty

If you put too much pressure on the lead you will likely get MASSIVE leading of the barrel that cannot be prevented.

I learned this in trying to make a 45 colt shoot with .458 cylinder throats and .451 bore.
Shooting .457-8 bullets greatly improved accuracy, for about 5-6 shots, by then the barrel was  leaded HEAVILY for about 1" in front of he forcing cone.
Based on this I would not try shooting a .240" ball out of a .22 barrel. Better to make a die to push the balls through to size them to .004-.006 or so over groove size then have a cylinder that will size them to groove or just over.
Revolvers can shoot a ball that is slightly under groove diameter since as the rifling in engraved it will force the bullet/ball to extrude into the grooves. One of the best shooting C&B revolvers I ever owned had cylinder throats about .0015 under the groove of the barrel.
I would also consider that there might be a reason why Colt never made a revolver under .28. Not saying don't do it, saying think about this carefully before spending a lot of time on it.

Dan

[tyro]

I'm glad I found U guys. Every time I look I find more to look at.. and reasons as well. Thanx TY

[James Wilson Everett]

Guys,

Reading Gary B.'s earlier reply, I decided to measure the bore of the barrel I am working on at both ends.  I found the muzzle end to be 0.513 and the breech end to be 0.515.  The very slightly tapered bore is certainly the result of using the armory hone from the breech end to the muzzle end.  I believe this shows the compression of the paper shim stack and the wear of the wood backing piece as the hone travels from the breech to the muzzle.  The barrel has a tapered lead in, slight funnel shape, at the breech to aid in starting the reamers, the hones and the rifling cutter.  I really would not want to try starting any of these tools at the square muzzle end of the barrel.  

I believe that this also means that the rifling grooves are slightly deeper at the muzzle than at the breech as the rifling cutter head  use is not compressible as the armory hone is.

It is great how the comments on this site stimulate my unused brain cells!  Thanks guys!  Come to think of it, making a 18th c barrel without this slight taper, or choke, would be very difficult, indeed.

Jim

[t.caster]

I had a long discussion with John Getz about ten yrs. ago in which he said all his rifled barrels are "choked" due to starting the tools at the breech like Mr. Everett just explained. He said that was made them "better" than the rest.  I believe he said they are generally .005 larger at the breech. I know mine start tight and then slide down quite nicely.
Don didn't mention this earlier, so I hope I didn't let a trade secret out of the bag.

[Joe S]

Don King is a fan of choking rifle barrels a couple of thousandths.  On his advice, I lapped a slight choke into the bore of my .54 Green Mountain barrel.  It loads much easier, and will shoot a single ragged hole at 50 yards if I do my part.

[Pvt. Lon Grifle]

I have one of Warren Fitzgerald's rifles where he re-rifled the barrel differently from that of the original modern barrelmaker. As near as I can figure the first ten inches of barrel  is .460 bore starting at the muzzle ,  tapering  to about .456 at the end of the ten inches and by then has transitioned to a uniform bore at that diameter. The rifling  has grooves noticeably wider that the lands. I never checked the twist rate.
I had a chat with him early on and he later sent copies of his targets shot with the rifle. His groups were fair, mine were no better. I did however,  invent the twelve inch short starter during the  learning process  and still shoot the rifle for pleasure and the occasional hunt.  He advised that he rerifled many barrels over the years with differing dimensions.

His craftsmanship was excellent.   Lon

[Paul Griffith]

Tapering with the wood backed reamer is pretty much a given. As has been stated the wood wears away as it passes thru the barrel. But this will amount to only .0005 or so if you have things tuned up as they should be.  For a time I fooled with deliberately tapering bores a thousandth or two. They blew patches from the first trip to the range til I cut em up & pitched em in the scrap bin.

There's been numbers tossed around here refering to tapers up to .010. I can only speculate as to how this would be possible. If a conventional rifling head was used it would have full .010 deep rifling on one end before the other end began to cut any rifling whats so ever. Considering that .015 deep rifling is rather on the deep side & brings about its own bunch of problems, a hole such as this might have .015 rifling in the muzzle & .005 in the breech. A split down the middle head could be made where a single tooth cutter was held solid in one side & the other side was sprung against the opposite side of the bore. This could put a uniform depth groove in a barrrel of large taper. Although I've never heard of such a tool in use. And it would still bring about the problem of blowing patches caused by the extreme loosness in the breech. 

Another Idea that while I've never heard of anyone actually doing but would be possible would be a tapered groove rifling.  To do this the barrrel would be rifled on a sine bar machine. After rifling, the pitch of twist would be slightly changed, pivoting the sine bar exactly at the muzzle of the barrel. It would then be rifled again to the same depth as the first  rifling. This would produce a taper to the groove, wider at the breech. Although I think the cutter would at some point have a tendency to slip into the existing groove & not cut any more. Would have been a good system in the lead bullet days as the bullet would have been tight thru out the bore.

[James Wilson Everett]

Guys,

Great insight from 1Chunker here.  I really cannot imagine how difficult it would be to rifle a bore with any great taper.  Certainly with an 18th c type of rifling machine and cutter it would pose problems.  It takes me about 100 cuts to make a groove, about 700 pulls for the whole 7 - groove barrel.  This is an average of about 0.00015 inch per cut!  If the cutter was only barely contacting the bore at the breech, by the time the cutter travels to where the constriction is 0.005 on the radius, I don't think that I am strong enough to pull that!

Jim

[Don Getz]

What an interesting site, one could garner enough fertilizer to get a great crop of tomatoes.   I met Bill Large several times at Friendship, and am sure he could have helped that tomato crop.   Then we have a guy who can shoot 3/4" groups with a 40 cal. smoothbore at 75 yeard, holy cow, he could clean up at the Alvin York shoot.  I don't think I have
ever made a tapered bore barrel intentionally, may have been some out in the back room among the seconds.......Don

[Herb]

If you put too much pressure on the lead you will likely get MASSIVE leading of the barrel that cannot be prevented.
Dan
[/quote]
That likely explains my GRRW .54 barrel.  I got it used from a friend who had made it into a caplock and did not like it.  He said it was very accurate, don't know why he didn't like it.  He unsoldered the rib and said a lot of gunk came out of the bore.  He is a modern gunsmith and had the front sight 3/4 inch from the muzzle, 36" barrel.  I want mine back 1 1/2" and told him I was going to cut it off.  He said, don't do it, that is a choked bore.  So I tapped a .58 roundball into the muzzle and pushed it through the bore.  The slug felt normal but at 5.5"" in it hit a tight spot which lasted for about 9" then got loose for 21.5" to the breech.  This tight spot must have leaded for Bill.  I sawed the barrel to 32", deciding to shoot it and if it didn't work, then lap it.  So now I have about 1 1/2" of "normal" bore, a 9" tight spot, then about 21.5" of (I guess) "normal" bore.  I have the rifle finished, shot it a few times to regulate the sights, and I think it will be more accurate than most barrels.  I guess this makes it a choked bore, but the choke is due to a tight spot.  I had a .58 GRRW unbreeched barrel with the stamp on the end of the breech, which I made into a fullstock flint rifle.  It also had a tight spot midway in the bore that I lapped out.  It then shot very well.  I've had maybe 8 or 10 GRRW barrels and have not detected choke in any of them.  Have two more to build up that were examined with a Hawkeye borescope and they are premium, no marks at all.  But I will slug even them to see if the bores have tight spots.  I know half a dozen of the old GRRW employees, they say the choke is an artifact of how the cutter cut the grooves, not intentional.  They freely cut off GRRW barrel muzzles to shorten the barrels.

[Dphariss]

Guys,

Great insight from 1Chunker here.  I really cannot imagine how difficult it would be to rifle a bore with any great taper.  Certainly with an 18th c type of rifling machine and cutter it would pose problems.  It takes me about 100 cuts to make a groove, about 700 pulls for the whole 7 - groove barrel.  This is an average of about 0.0015 inch per cut!  If the cutter was only barely contacting the bore at the breech, by the time the cutter travels to where the constriction is 0.005 on the radius, I don't think that I am strong enough to pull that!

Jim

Lots of old rifles have chokes.
Have you read TK Dawson's description of the bore on the Hoffman and Campbell rifle in "Hawken Rifles..." by John Baird?
Possibly lapped but it takes a LONG time to lap .002-.003 out of a bore, maybe more strokes than your rifling. So...?
Might find an answer in the Warner-Lowe papers...
Brockway in "The ML Caplock Rifle" states that he used a square reamer, and that everyone did, but does not mention chokes.
The Warner/Lowe papers do mention chokes even to the point of how something in the dimensions of the choke will cause certain effects on the target. I have not read them extensively enough to find anything on the how part of the choke though lapping was and still is typical of a premium barrel.

It is unfortunate that people who did such things did not write them down. But many if not all of these guys were very secretive about certain things. Making accurate rifles was their living and the things they learned through a lot of hard work and experimentation they were not eager to share... I believe, in fact that Brockway fibbed to Ned Roberts on some things, shooting over snow to find unburned powder at least. But then I have never tried it with a 38 caliber slug gun.

Dan

 

[Dphariss]

If you put too much pressure on the lead you will likely get MASSIVE leading of the barrel that cannot be prevented.
Dan

That likely explains my GRRW .54 barrel.  I got it used from a friend who had made it into a caplock and did not like it.  He said it was very accurate, don't know why he didn't like it.  He unsoldered the rib and said a lot of gunk came out of the bore.  He is a modern gunsmith and had the front sight 3/4 inch from the muzzle, 36" barrel.  I want mine back 1 1/2" and told him I was going to cut it off.  He said, don't do it, that is a choked bore.  So I tapped a .58 roundball into the muzzle and pushed it through the bore.  The slug felt normal but at 5.5"" in it hit a tight spot which lasted for about 9" then got loose for 21.5" to the breech.  This tight spot must have leaded for Bill.  I sawed the barrel to 32", deciding to shoot it and if it didn't work, then lap it.  So now I have about 1 1/2" of "normal" bore, a 9" tight spot, then about 21.5" of (I guess) "normal" bore.  I have the rifle finished, shot it a few times to regulate the sights, and I think it will be more accurate than most barrels.  I guess this makes it a choked bore, but the choke is due to a tight spot.  I had a .58 GRRW unbreeched barrel with the stamp on the end of the breech, which I made into a fullstock flint rifle.  It also had a tight spot midway in the bore that I lapped out.  It then shot very well.  I've had maybe 8 or 10 GRRW barrels and have not detected choke in any of them.  Have two more to build up that were examined with a Hawkeye borescope and they are premium, no marks at all.  But I will slug even them to see if the bores have tight spots.  I know half a dozen of the old GRRW employees, they say the choke is an artifact of how the cutter cut the grooves, not intentional.  They freely cut off GRRW barrel muzzles to shorten the barrels.
[/quote]

The 54 sounds a lot like the bore described in "Hawken Rifles..."
I assume he was shooting "naked" bullets. Patched bullets do not lead.
I have a 54 that I have lapped some to improve the polish but found no loose or tight spots.
May lap a choke into it if I get ambitious. But have several other things in the works.

Dan

[pathfinder]

   Then we have a guy who can shoot 3/4" groups with a 40 cal. smoothbore at 75 yard, holy cow, he could clean up at the Alvin York shoot. 

Last shoot "Ole Wormy" won was in Freedom,In in '88. Hershall House wandered into my camp by accident and we talked about the.40 and how stupid accurate it is. My freind Anson Morgan built the gun and he knew Mr.Large back in the day and had him ream the barrel to these spec's. I'm not much of a bench shooter,a freind of mine is and with a different set of sight's,he shot that group. I'll look for the targets,4 moves since then!

When I read the Bill Large's Quote about the '88 being "choked",it reminded me of my buddy Tony. He was at camp with us and while we were watching satellites one evening,he said,"That's a Russian one". Tony's a really smart guy,so we figured he knew trajectories and stuff,so when I asked how he knew,he exclaimed,"The paint job!"! Yup.Lot's of gardening going on!

[t.caster]

A lot of smoke being blown around & up

[Dphariss]

I have a Bill Large .40 smoothbore barrel,13/16th,41",and it tapers down from .420 to .408, from the breech to @ 8" from the muzzle,then open back to .413 at the muzzle. Absolute tack driver. To 75 yds,she'll hold a 3/4" group with a .400 ball,.018 pillow tick patch,and 65grs of 3f. She was built by Anson Morgan in Avoca,Mi.

Every time I hear something like this I think of N. Kendall scratch rifling a barrel with coarse emery and taking all the turkeys at the SB only turkey match.


Dan

[Paul Griffith]

What an interesting site, one could garner enough fertilizer to get a great crop of tomatoes.

It is truely a gift to speak volumes in so few words.

[Herb]

Dan, that GRRW barrel that Bill had, he told me last night at our .22 gallery shoot that it was not leaded, that "gunk" was perhaps fouling.  He said it was very accurate, and I still don't understand why he took the barrel off.  When our weather warms above freezing, I'll get out and shoot this barrel.