PRB thru a mod choke ???

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Trail Troll

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I have a CVA Trapper with screw in chokes and want to try a PRB. Can you run a PRB thru a mod choke ? Is it safe or just not the best (possibly) for accuracy? I am think of a 690 and the choke is about a .700-.705.

Thanks in advance !!
 
Trail Troll said:
I have a CVA Trapper with screw in chokes and want to try a PRB. Can you run a PRB thru a mod choke ? Is it safe or just not the best (possibly) for accuracy? I am think of a 690 and the choke is about a .700-.705.

Thanks in advance !!
Click to expand...
The ball If loaded on top of a fiber wad without the patch and with jute or flax fiber or top to hold the ball in place. I’d think it would be ok providing the fiber securely hold the ball in place. I wouldn’t expect much for accuracy, then again? BJH
 
Trail Troll said:
I have a CVA Trapper with screw in chokes and want to try a PRB. Can you run a PRB thru a mod choke ? Is it safe or just not the best (possibly) for accuracy? I am think of a 690 and the choke is about a .700-.705.

Thanks in advance !!
Click to expand...

IF you can get it past the choke, the choke will strip the patch off as the ball exits. The problem is that it will not uniformly strip off the patch, thus your accuracy will suffer more than using a wad and a cylinder choke.

LD
 
Billy-by-gosh said:
I used to have a 20 GA Imp/Mod choke that could do a 3 1/2" group at 50 yards from a bench firing 70 grains 2F black with a bare .570 ball with a one-piece plastic Fedral wad/cup
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Hmmmm , did you load from thru the choke with the wad/ball combo? I guess I am asking, would you size the ball so it will just pass thru thru the choke?
 
That pesky phenomenon known as obturation where the lead ball expands when suddenly forced into motion means that the ball will try to expand to the bore diameter at the breech, but soft lead will be forced to the bore diameter at the choke constriction. If one intends to use a round ball in a choked smooth bored gun, soft lead must be used. No wheel weights here!
 
Trail Troll said:
Hmmmm , did you load from thru the choke with the wad/ball combo? I guess I am asking, would you size the ball so it will just pass thru thru the choke?
Click to expand...
I trimmed the petals of the wad down pretty short, then loaded. Also used a 490 ball for faster loading, though it didn't have the good grouping of the 570. The .570 diameter ball didn't need sizing, it rolled right thru the choked portion of my 20 GA. (with a clean bore)
 
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Loyalist Dave said:
IF you can get it past the choke, the choke will strip the patch off as the ball exits. The problem is that it will not uniformly strip off the patch, thus your accuracy will suffer more than using a wad and a cylinder choke.

LD
Click to expand...
Well I ended up finding a couple of chokes on Flee Bay. I have a full , an improved modified ( never heard of it but thats what it measures ), and a second modified. So I threw one of the modified tubes in the lathe and opened it up to .720 ! So now I have a cylinder bore choke for PRB along with a mod, imp mod, and full. I need to get a mold next. Reccomendations ? I was thinking a 690 which would put it at a 495 grain or 1 1/8 oz load. That is what CVA says in the manual.

Thanks again !!
 
Last edited:
Trail Troll said:
Well I ended up finding a couple of chokes on Flee Bay. I have a full , an improved modified ( never heard of it but thats what it measures ), and a second modified. So I threw one of the modified tubes in the lathe and opened it up to .720 ! So now I have a cylinder bore choke for PRB along with a mod, imp mod, and full. I need to get a mold next. Reccomendations ? I was thinking a 690 which would put it at a 495 grain or 1 1/8 oz load. That is what CVA says in the manual.

Thanks again !!
Click to expand...

Yeah the cylinder bore should work, OR you might also try a bare ball with a 1/2" fiber wad between the ball and powder, and a crushed paper wad, or even another 1/2" wad over the ball..., with the final wad very well lubed.

So imp/mod and mod/full chokes came out over the years I'm told due to patterning of shot. Guys were finding better performance with slightly tighter chokes but not so far as to a proper mod or a proper full.

LD
 
Well I got my mold in and cast a few up. Wow, that 690 ball hits with some authority !! I was using a 015 spit lubed patch and it was very east to start in the choke. Recovered patches showed some burning but were no all torn up. I am thinking maybe try a thicker patch. Accuracy was maybe 4 inches at 25 yards, it was tough with only a bead. Some form of rear aiming point would help for sure.

More testing to follow, and the load was 1 1/8 ounce volume dipper of FFg, approx 75 grains I believe.
 

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