patch diameter ratio

[The other DWS]

is there a ratio of ball diameter to patch diameter for accurate shooting with pre cut patches.

I have a small arbor press and I am thinking of making a cutter out of steel tubing  somewhat like a harness punch that would let me cut patches out of multiple layers of patch fabric.

Since I'll be making patches for .54, .50, .40, and now .29 cal rifles  I thought that there might be a rule of thumb for proper patch diameter relative to the ball size.

[mjm46@bellsouth.net]

As a minimum size I wrap a ball with cloth and cut it off even with the ball like you were cutting it at the muzzle. then you can figure a patch diameter from that. As long as your making a custom size.

[smylee grouch]

I wonder if you could recover one of your shot patches and up that size by half inch or so.    Smylee

[SCLoyalist]

Try ball diameter times 2.57 for the same patch diameter as if you cut at the muzzle.   

[The other DWS]

2.57 eh?    thats the kind of ratio I was hoping for.   How did you calculate that?   surface area of a sphere?   I recognize it as a topological problem but I'm mathematically challenged---I know just enough to run and hide when I see it coming.

Obviously the patch has to wrap more than half of the ball but how much more that?  I suppose the muzzle cut patch has evolved as the optimum.

    I guess I could simply buy a selection of factory precuts for different calibers and measure them and calculate from that.   .54 .50 .40 are fairly standard I imagine.  just wondering about the .29---doubt I'll find many factory cut patches for that.

[T*O*F]

.30 - .39 roundball = 0.75 diameter
.40 - .49 roundball = 1.13 diameter
.50 - .59 roundball = 1.38 diameter
.60 - .69 roundball = 1.52 diameter

These sizes will give inclusive results for the calibers within their range

[SCLoyalist]

2.57 eh?    thats the kind of ratio I was hoping for.   How did you calculate that?   

If the ball is pushed down even with the muzzle, then the path the patch follows around the contour is:  1/2 the ball diameter down to where the ball is at full diameter,  pi/2*diameter around the ball, then 1/2 the diameter again back up to the muzzle.  You end up with diameter*(1 + pi/2) or 2.57*diameter. (The numeric value of Pi being 3.14159...)
 
The thing to keep in mind is that 2.57* ball diameter is the diameter of the patch you'd get if you cut at the muzzle.   If you've pre-cut the patches, you need to take some care that the ball is well centered on the patch.   Cutting with a knife at the muzzle the ball is automatically centered on the patch.

[bluenoser]

Thanks for the 2.57ratio.  I will store that in the old memory bank.  Then again, I should probably write it down.  The memory bank has a tendency to self-clear these days.

I have been determining the diameter by wrapping patch material in a U around the ball, marking it at the top of the ball and measuring it. That gives me the minimum patch diameter, but I don't hesitate to use patches cut for somewhat larger calibres - doesn't seem to affect accuracy.

I have a small arbor press and I am thinking of making a cutter out of steel tubing  somewhat like a harness punch that would let me cut patches out of multiple layers of patch fabric.

I haven't had much luck with the punch type cutters.  I had difficulty getting them to cut cleanly.  I made patch cutters to fit my drill press, and they will cut very cleanly through a good size stack of material.  I understand some folks grind the teeth off appropriate size hole saws and sharpen the edge - a whole lot easier than making a cutter on a lathe. DUH... why didn't I think of that!

Laurie

[Roger Fisher]

Heck,   don't   over engineer the thing. Cut in strips,    shove one end under your belt to be handy and cut em at the muzzle after applying a good dose of spit.  Much less ditzing around....

[LH]

There was an article in Muzzle Blasts several years ago by the Bevel Brothers where they compared pre-cut, square cut,  and cutting at the muzzle and there was a difference.  Not much and certainly nothing an offhand shooter would notice, but a repeatable difference.  Cut at the muzzle shot best.  Centering up pre-cut patches is the problem. 

[The other DWS]

This is all real helpful and educational.    And yeah, I do tend to over-think a lot of this stuff.  I get fascinated with the how and why of things.

I like the simplicity of using a strip and cutting at the muzzle.  I like knives a whole bunch too, so anything that gives me an excuse for a new one is welcome.   HOWEVER,  I am thinking about the problems that strips and cutting might present if you were to spend a day at the range.  I get dry mouth too easy as it is .

 How do you guys handle it when you are doing one of those woods walk/run matches---chaw on a wad of cloth while you are running.  with my luck I'd trip on a root, and wind half swallowing it and choke to death.

Since I'll be trying to get the "new-to-me" .29 fired up and running over the weekend--I hope, and of course the smaller the bore the more sensitive guns are to ANY variations.  I'm thinking more along the lines of pre-lubed patches    I guess the logical thing to do is to prelube strips or larger patches, keep them in a container, and then cut them at the muzzle.