Speaking of pistil groups.....

**William H. Shuey** · 09-09-2015

How much should the ball diameter exceed the bore diameter in a B/P revolver;

Ex: A 51' Navy with a groove dia. of .370, what would be the ideal ball dia.??

Bill Shuey

Doggone finger trouble. That'l teach me to read before I post!

**RaiderANV** · 09-09-2015

Scratching head......you have a .57 cal pistol??

**Don Dixon** · 09-10-2015

Second Raider’s comment.

But, back to your question. I can’t necessarily give you an answer without measuring your pistol. The larger problem is the relationship between the diameter of the chambers in the cylinder and the groove diameter of the bore of the barrel. In many of the Italian reproduction guns the diameter of one or more – sometimes all – of the chambers is smaller than the bore diameter. You could put balls into the chambers that shaved a substantial ring of lead when you loaded and still have balls which were too small for the bore. Too small ball = inaccuracy. All six chambers have to be larger – but not too much larger – than the bore of the gun. Then, you have to use balls which shave lead when you load the chambers.

Another problem with the Italian guns is that often one or more chambers do not line up properly with the bore. If you look down the barrel with a strong light you can see partial “moons” where the edge of the chamber does not line up with the bore. Cutting a forcing cone in the barrel is a partial solution to this problem, but it merely kicks a misaligned ball over into somewhat better alignment with the bore. That starts an interesting discussion on the impact of internal ballistics upon external ballistics.

The above are the reasons why accuracy gun builders – Tri-L and previously Tom Ball -- use(d) a .36 caliber cylinder to build .44 caliber pistols. They set the cylinder up in a jig and bore all of the cylinders out so that they are aligned with the bore and properly sized. The Italians could do this, but only a few of us are prepared to pay what a properly set up revolver costs. The Italians make guns in grades based upon the price the importer is willing to pay. Since the Germans shoot rather than reenact, they get better grades of guns than we do, but they also pay more. If you expect to get a $200-300 gun off of the shelf that will shoot you are sadly mistaken. One would not expect that of a modern firearm, and should not expect it of one of these reproductions.

Regards,
Don Dixon
2881V

**Maillemaker** · 09-10-2015

Is this the Tri-L that does revolver work?

http://www.tri-l.com/

Steve

**Don Branch 12592** · 09-10-2015

Originally Posted by Maillemaker

Is this the Tri-L that does revolver work?

http://www.tri-l.com/

Steve

No. Rob does not have a website.

**jonk** · 09-10-2015

In so far as no one has really answered the question... well it varies. Assuming you don't have the mouth of your cylinder belled to prevent lead shaving off, you want it to cut a nice ring for a snug fit. That said you still want the resulting ball to be at or over groove diameter. So let's say you have a .44 revolver and you load it with a .454 ball. You shave off a little lead, maybe 5/1000 or so, and have now a .449 ball. In that case I'd hope that the grooves on the gun were .445-8 in an ideal world.

What you can do is remove the nipples from the cylinder and seat a ball into each empty cylinder, then use a brass rod to tap them free from the nipple hole and measure. Then slug your bore and measure. That will tell you if you have undersized cylinders or not. Or if you want, you can buy some cerrosafe and make chamber casts.

There are a variety of things that can be done to off the shelf italian repros. Boring out the cylinders so they are over groove size is one. Adjusting timing so they align better is another, as is adjusting the fit of the cylinder to the frame so that it doesn't have such a gap up at the mouth. Throating the barrel is also a good idea. Some go whole hog and have the whole barrel replaced. Each of these costs money; the question is, is it worth it to you? Personally, given I shoot revolver 3 times a year, at nationals and early bird, my stock Spanish repro that can shoot about 1.5-2" from a bench is good enough for me. I bust some targets, miss some, and have fun. If you're in a region that still shoots revolver regularly, after making the chamber casts and such, you can decide where you want to go from there.

**Maillemaker** · 09-10-2015

What you can do is remove the nipples from the cylinder and seat a ball into each empty cylinder, then use a brass rod to tap them free from the nipple hole and measure. Then slug your bore and measure. That will tell you if you have undersized cylinders or not. Or if you want, you can buy some cerrosafe and make chamber casts.

What I did was push a ball into an empty chamber, then remove the nipple and knock it out as you suggested. Then I tried to fit that ball down the barrel. Discovering that it would not go, I assumed that it must therefore be engaging the rifling. To be more sure I could have tapped it down the barrel and examined the rifling on it.

Steve

**Mike McDaniel** · 09-10-2015

Remember, even if you are only a team shooter, revolver is unforgiving. Put a pigeon on a pistol target...you'll find that it is significantly smaller than the black. A 9 that touches the 8 ring at any point will not break a pigeon. You need a gun that will shoot a 2-inch group at 25 yards, at the most. Better than that if you mean to shoot individuals in Expert class.