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measuring Rate of Twist

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paulvallandigham

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I Had an experience with my brother that made me think to share with others, how to measure your Rate of Twist in a barrel, when you are not sure. My brother took delivery on a new .45, and the gunmaker could not remember what the rate of twist it had. When he got the gun home, my brother attempted to measure the ROT, and sent me an e-mail saying it was 1: 43 or 1:44. I didn't think this was right, and he tried to measure it again while I was on the phone with him, today. I had him use a tape measure to measure 30 inches from the muzzle, mark the ramrod with tape, and then draw it out of the barrel the 30 inches, and see where his mark was. His first attempt gave an odd measure, because he tried to stop at 15 inches. He got something like 1:52 inches this time!

Then, I thought to ask if he was using a jag with his patches, or a brush with a patch? He said he was using his jag. That was the problem. The smooth jag was slipping as he started pulling on the rod to back it out of the barrel. He took much more care the next time, and got a half turn in 30 inches, or the 1:60 ROT I was expecting he had.

If you are going to measure your ROT in your barrel, please remember to use a brush with a oiled patch in front of it. The bristles will stay to the grooves, and keep the rod from turning or slipping, while it slowly follows the rifling grooves when you back the rod out.

Another thing to remember is when you first push that brush into the muzzle, stop and pull back on it, so that the bristles form to the back pull motion you will use when you draw it out. If you wait until the brush is all the way to the breech of the gun, it may be very difficult to get those bristles to reverse directions, and you will need two men and a boy to get the brush and rod back out!

If you do get it stuck, twist the rod clockwise as if to tighten the brush on the rod end. This will cause the bristles to turn out of the groove a bit, and free the brush up enough to draw it out. There are some nylon or synthetic brushes made for .45 cal. barrels, usually for modern cartridge gun barrels. You may not find such for the .50, .54, .58, and .62, or larger calibers but for .36, 45, and even the .32, you should be able to find pistol cleaning brushes made of nylon you can also use in your ML rifles and pistols. Like most old guys, I am accustomed to using copper coated steel brushes in my guns, but they are really only needed when you are going after lead deposits. For the BP crud that gathers in rifles, the synthentic bristles work just fine, and are cheaper, to boot.

Does anyone else have a better way to measure Rate of Twist in a barrel?
 
You've got the idea.
I use a jag with a tight patch. Push it all the way down the barrel. Put a piece of masking tape around the rod at the muzzle and place a reference mark on the tape. Pull the rod out until the mark has moved 1/4 turn. Measure how much rod came out and multiply by four.

Ex: 1/4 turn in 12 inches.
12 x 4 = 48
1:48 twist.

HD
 
HD: I think the secret to what you did is that " Tight Patch". My brother did not double up on his patching, or use a thicker patch, he just used his standard, flannel cleaning patch. That allowed his jag to slip and he could not even feel it. He also used the wooden rod for the gun, instead of using one of his steel range rods. I get much greater sensitivity of feel using a range rod to do this kind of thing. He was screwing up so badly doing a quarter turn, I told him to do a half turn, and to measure out 30 inches in front of his muzzle, ( as I suspected the ROT would be 60 "). Sure enough, he came within a half an inch of that 30 inch tape, andI told him no one makes a 1:59 twist, so he still must have allowed the jag to slip some, and that the barrel was, as expected, a 1:60. That is a perfect twist for a RB. .45 cal. rifle. His first shots were with 65 grains of FFg., a wonderlube patch and a .445 round ball. His last shot of the day hit a buffalo bang plate at 130 yds, right where he aimed to hit it. So, at least his sights are zeroed, and he can now play with the powder charges to see if he wants to shoot something different. Thanks for the post.
 
paulvallandigham said:
HD: He also used the wooden rod for the gun, instead of using one of his steel range rods. I get much greater sensitivity of feel using a range rod to do this kind of thing.

Paul,

I've had the best luck with a cleaning rod with a ball-bearing handle. It allows the rod to turn freely while pulling on the handle. And like you said, a tight patch is necessary. Every barrel I've checked had a 1 in 48" twist. :hmm:

GW
 
Paul, I've tried to measure twist rates with a cleaning rod and gave up due to the impossibility of saying just when the rod has turned exactly one quarter or one half turn and not a bit more or less.
I made a tool for this purpose from 1/4" square stock. Fitted it with a ball bearing handle and a 2" diameter disk with matching 1/4" square center hole to slide on the square rod. The disk is marked in eight segments so I can zero the disk to a reference point such as the front sight and clearly see when it has revolved exactly 1/4 or 1/2 turn. The square rod is also drilled and tapped to accept 8x32 jags or brushes.
Even with this tool my measurement of a slow twist barrel may be off by an inch or two, I'd be hard pressed to tell the difference between a 70" of 72" twist. Of course, in practical terms, there is no difference. :grin:
 
I had a lot of trouble trying to measure TOR in my english oval-bored Lancaster :cursing: until I realized it was progressive bored :shocked2: :redface: (actualy not done yet with measuring but will make a new try soon).

ARILAR :grin: :hatsoff:
 
Wow! That gun has to date from the late 1880s to the 1890s, when " Gain Twist" popularized by the famous Barrel maker, Harry Pope, was all the rage. The Italians used gain twist in their first smokeless powder military rifle, the now infamous 6.5 mm Carcano, brought out in 1891. In that gun the twist starts out at about 1: 20" , and finishes at 1:9" approx. I will be curious to find out what the rate of twist is in your gun. Keep us posted.
 
Around 1860 I guess? Here two pics. If interest I can get back on this gun later on in a new thread.

Lancasterright02.jpg

Lancasterclose-up.jpg


Regards,
ARILAR :grin: :thumbsup:
 
Glad to hear I was wrong. It is an earlier gun now that I see the pictures. I know that Harry didn't " invent " gain twist, and he never claimed he did. He did work out mathematical formula for determining the optimum ROT for various calibers, and popularized the practice with target shooters. The progressive twist was an early version of the gain twist he popularized. Still a very interesting gun, and it looks good enough to be a shooter, or museum piece, one or the other. I would not shoot it if its clean enough to keep its collector status as a new, unfired example.

I have a museum quality pepperbox pistol, from the 1840s or earlier, and as much as I would like to shoot it, I haven't.

Nice gun, and thanks for the pictures.
 
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