Patch reading

[flatsguide]

First shots out of my Rice barreled English sporting rifle kit by Jim Chambers flintlock. The patches are torn pretty bad. Here are the stats.
Barrel crown was polished and the barrel was lapped with tight patches and JB compound to remove any microscopic edge burrs.
Only fired two shots.
Charge: 90gns Swiss 3f.
Patch:  .018” pillow ticking (cotton)
Lube: patch wet with straight Ballistol.
Bore dia.   .580”
Bullet: pure lead ball. .570” dia.  272 gns
MV:  1740 fps.  (Garman chronograph)
First bullet load in clean barrel, bullet was tight but slid down smoothly to powder charge. Second loading with fouled bbl was difficult (second patch).
Any idea what’s occurring?
I stopped shooting as I found out I need to make a fly for the tumbler even though it’s a single trigger.
Thanks for the help.
Cheers Richard

[smylee grouch]

More crown work, thicker patch with tighter weave, more or different lube.

[recurve]

you have a cut rifle barrel  with micro burrs that are cutting the patches you can shoot it smooth or you can take steel wool w oil on a jag 50 stokes clean and test repeat as necessary  ( Mr Dixon advised me )
with patches looking like yours




after with a good patch

[smylee grouch]

I think the JB might slick up the surface somewhat but the steel wool will do a better job on any burrs. I will guess that the riffling is about 16/1000 deep and you have 10/1000 windage in the bore ( 580- 570 ball ) so you probably are getting blow by.

[smallpatch]

New patch material, more lube.?

[alacran]

Your pillow ticking is the problem. I would try 10 oz denim or tightly woven canvas. I have never used Ballistol for patch lube so I won't comment on that. I personally use Bear oil. If I don't have that I use mink oil. I have tried Mr Flintlocks patch lube and that works well.
The reason your second shot was hard to load was because of all the blow by from the torn patches.

[flatsguide]

Thanks for the replies and suggestions, please keep them coming.
I made a mistake, I thought that I had a patch thick enough to fill the rifling. With the rifling depth of .016” and the patch material being .018” I thought the patch had an extra .002 thou filing the rifling groove but I forgot to account for the .005 thou of windage between the ball and the bore per side, that’s .005” windage, .016” rifling depth for a total gap of .021” inches. Have I got that correct?  So, I guess I should try a patch thickness of at least .022”.  With a .022” patch and .005 windage per side of bullet to bore that amounts to a compression of the patch to .017” won’t that be very difficult to impossible to load? Seems like awfully deep rifling.
Smylee, Recurve, thanks! I have some 4 ought steel wool that I’ll try on the bore.

Smallpatch, alacran, thanks also! I try and hunt down some tighter woven material at the local Joann’s. So much of that cloth has synthetic materials that one really need to read the label.
At present I have the lock apart doing the final finishing on it and will make the fly today from tool steel.
Thanks again Richard

[smallpatch]

I’m confused. Not unusual.
Why do you need to make a fly? All Chambers locks have a fly?

Also, 90g of 3f? That’s a pretty stout load.

[Hawg]

Also, 90g of 3f? That’s a pretty stout load.

Why do you say it's a stout load? It's not like he's shooting minies out of it. I use 90 grains of 3F out of my .54. I would say 120 grains would be a stout load.

[smylee grouch]

I would think there is more to consider about what is " stout " than just bore size. Barrel contour, weight, rate of twist, stock profile and shooter comfort just to name a few.

[Daryl]

Well covered.
Ball dia. + 2 X patch thickness should equal .002" to .005" over groove to groove dia. Even more is better than less.
I would be using 2F personally. 2F is more forgiving of weaker combinations than is 3F. Yes, to get the same vel. will require more 2F than 3F, however in the larger bore sizes, 2F can give better accuracy. This was true in my .50 and .69.

[alacran]

Stout is a subjective term. That is unless you are talking about a beverage.

[flatsguide]

My target velocity I guess I should say desired velocity is 1800 fps. It really does not matter whether it’s from 2 or 3 F, what ever gives the best accuracy close to that velocity. From what I can figure from drop tables, that speed give good mid range trajectory. Plus I need to make a rear sight and need to know the fixed and leaf blade bights.

[Daryl]

2FG of any "given" make will deliver that target vel. at lower pressure than will 3FG of the same make. Thus the ball and patch combination will not be as critical as with 3FG. It still needs to seal, though.
Instead of having a "target" vel. I think you should target the best accuracy load instead.

[Jerry]

2FG of any "given" make will deliver that target vel. at lower pressure than will 3FG of the same make. Thus the ball and patch combination will not be as critical as with 3FG. It still needs to seal, though.
Instead of having a "target" vel. I think you should target the best accuracy load instead.

Daryl, I’ll drink to that! Jerry

[flatsguide]

“what ever gives the best accuracy close to that velocity” ! Daryl I think you missed this in my previous post. Of course one could claim the old saw of “the ball weight should match the the animal weight your after driven at the speed of light”