Land and groove question?

[cynthialee]

Yeah that changes everything.

you can shoot what you want in the 1:48 barrel.

There will be a good performing PRB load and a good performing conical load.

 

[Tom Compton]

Lots o difference between a 1/48 twist w .004"-.005" deep grooves and a 1/48 twist w .010"-.012" grooves.

I believe TC made the 1/48 twist w shallow grooves to facilitate manufacturing and keep costs down by using button rifling vs cut rifling. An added benefit was marketing their proprietary Maxiball.

A round ball over heavy powder charges needs a tight ball/patch to keep from stripping the rifling. A conical won't seal well if at all in a deep groove arrest no matter what the twist.

Of the few original barrels I've been able to look at closely, most appeared to have deep grooves (no measuring was done) while some were so worn at the muzzle as to almost be non existent though noticeable further down the bore.

Discussing rate of twist without also considering depth of rifling is IMO fruitless.
TC

 

[Maven]

"It seems most people claim that a tight fitting patch equates to better accuracy. Some hammer theirs down it's so tight. That's too tight for me but then I don't shoot in matches."

{Slightly off topic] I just finished testing this very thing in my Lyman .50cal. cap lock, 1:60 twist on Friday. A few days prior to testing, I used a nominally .490" RB (.488" in fact) + a .018" (compressed) pillow ticking patch and couldn't hit my targets well. (Btw, that combination seated almost too easily.)

Last Friday, I decided to bench rest the rifle @ 25 yd. using a variety of RB diameters from .488" -> .497" (cast from Lyman, RCBS, and Lee molds) as well as .018" -> .020" patch thicknesses. Suffice it to say that the .488" RB + .020" patch shot better than the same dia. RB with the thinner patch. Additionally, the .492" (as cast) RCBS RB + a thicker, .020" patch shot best of all, followed by the Lee .497" (as cast) RB and a thinner, .014" patch. The larger ball + thinner patch, however, was very difficult to start (needed a mallet on my short starter). That larger ball with a .018" was even harder to start and seat, but a tad less accurate than that ball with a .014" patch. OTOH, neither of these combinations was quite as accurate as the .492" ball + .020" patch, which required moderate effort, i.e., no mallet to start and/or seat. (It would work very well for a follow up shot when hunting, for ex.)

In short, I couldn't demonstrate that a thicker patch always was more accurate any more than I could show that a larger ball was always the better choice. One needs to experiment with a variety of RB diameters and patch thicknesses to hit upon a repeatably accurate combination, factoring in how difficult it is to start said pairing of course.

 

[Rifleman1776]

I believe TC made the 1/48 twist w shallow grooves to facilitate manufacturing and keep costs down by using button rifling vs cut rifling

Right on. With mine I had to use a very thin, tight weave cotton material. The only thing that worked for me was airplane cloth and it did a fine job. Don't know if it is still available or what a satisfactory substitute might be. That barrel has now been a safe queen for 45 years. Did try maxis once. They slid up (towards muzzle) while carrying field hunting. Dangerous stuff. I think I gave away the mould. Nebber agin. :shake:

 

[smo]

I own a couple TCs myself most of them shoot round balls well with 60 to 70 grns of fffg. My 50 will still do ok with 90 grn of fffg. :thumbsup:

Start with a light load and see what it will do. :hatsoff:

 

[cynthialee]

With my T/C Hawken I shoot 80 grains of 3f, a .490 ball and a .015 patch but sometimes I use a .010 patch when I run out of the thicker patches. Seems to be the best load.

With my .54 Renegade it likes 90 grains of 3f. a .530 ball and a .010 patch.

 

[Tom Compton]

.490 ball +.015 patch on one side + .015 on the other = .520"

A true .500 bore with .004" grooves = .508" groove to groove.

.520 " - .508" = .012" compression. You are Filling the grooves that's good but I'd try .018" - .020" patch material. Might shoot a little tighter, might not. But if you are happy w what you are using keep on keepin on making smoke.
TC

 

[cynthialee]

I know I can get a better group with a tighter patch; it is just too much of a fight for me with the tighter patches. So I cheat and use an over powder wad or card. Forgot that part of the loads.

{I need to get me a rifle squire to load and clean my weapons...}

 

[Wes/Tex]

It's 1 in 48 I made a mistake ...
Dan

You'll hear a lot of talk still about the 1-48" twist. It got a bad rap in the 60's due to lack of knowledge and some of the mud still sticks. That shallow .003" rifling depth was developed in the 1850's for the Minie style conical bullet adopted by U.S. and European militaries. Originally, there were only three each lands an grooves that were very wide but stabilized the heavy conical slugs. When the Zouaves replicas first came out the Italian makers copied the bore down to the rifling. Those old farts of us who were playing the game then thought we had a grand .58 caliber ball tosser but groups looked more like buckshot patterns. In time we pin pointed the shallow/wide rifling and figured out it needed a fairly tight ball/patch combo and moderate charges. I don't mean so tight it takes a hammer but a good full fit.

I don't know the number of grooves and lands in your .50 but it sounds like it's definitely designed for the Minie/Maxi type slugs. Balls will work but heavy charges can cause the patched ball to slip across the shallow grooves which open up groups. They're surprisingly tolerant with a wee bit of pre-planning. Good luck. :thumbsup:

 

[pondoro]

Maven got it right, try various combinations. What works for others is a good starting point but may not be best for you. Unless the gun has a problem you should be able to find a few round ball loads and a projectile that it likes.

 

[Okie Hog]

My .50 caliber New Englander with its 1/48 twist shot round balls very well. Then i got it badly leaded firing conicals and round ball accuracy went away.

Got to finish cleaning that bore up.

 

[Wes/Tex]

Got to finish cleaning that bore up.

That's the secret...got to clean out all the bad pookie! :wink: :rotf: