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rodwha
10-16-2014, 03:56 PM
A discussion about the driving band of a ball in a standard Pietta's revolver chamber and the usefulness of using an oversized ball had me look into the cubic area that's created and how the differ. As the numbers were a bit over my head I went to a math forum and was given the formula, which is:

"Using Pythagoras, each flat spot's area is, for example, (.451 squared−.446 squared)pi/4 square inches."

My calculator didn't have enough characters for a complete pi number and so I went with what it allowed, which should have been rounded but being so far down the line I went with it.

This gives an area of 0.0035295" for a .451" ball,
an area of 0.0056548" for a .454" ball, and
an area of 0.0078013" for a .457" ball.

Interesting to note how much more surface area you get my increasing the ball's diameter such a small amount. That's more than a 50% increase with a .454" ball, and more than 100% with the .457" ball.

The greater friction caused by the increased area increases the pressures which in turn increase the velocity. This has been seen by a few people. I'm not sure that it actually increases accuracy though.

Driver man
10-16-2014, 05:37 PM
I shoot a .457 ball in my Uberti Remington .44. I get far greater accuracy with the .457 than .454 or .451.

rodwha
10-16-2014, 06:16 PM
I've never actually read of anyone claiming better accuracy until now. How much of a difference do you see moving up?

My Pietta Remington '58's chambers were reamed to .449" and chamfered so I cannot do any sort of accurate testing to compare with what stock might be. I did this, in part, because I wanted to share projectiles with my ROA and didn't want to stress the lever assembly, but also because I wanted to get closer to groove diameter. I can't say I notice anything dramatic though as far as accuracy improvements, but then I'm no pistolero either, and my shooting is at 15 yds offhand and with poor eyesight. I really need to break down and get glasses…

Have you choreographed your loads and their differences? I'm curious as to what others get.

fouronesix
10-16-2014, 10:22 PM
The greater friction caused by the increased area increases the pressures which in turn increase the velocity. This has been seen by a few people. I'm not sure that it actually increases accuracy though.

If this is true then those short C&B conicals oughta scream out the muzzle.

Driver man
10-17-2014, 08:27 PM
I shoot at 25m targets and load for accuracy which in the Uberti is 21grains of fff then semolina filler with the ball loaded on top. This is then covered with a lube/grease. The ball is pure lead I cast from a Lee 6 gang mould. The lube is made with petroleum jelly with a small amount of lithium grease added(Ive never measured the amount) Using traditional sights ie front sight and the groove in the frame it will shoot x ring 10 and 9 ring. About 2 inches duelling (one handed) is normal. Using 454 the group opens up to about 3.5 inches. I load the ball with the sprue down and have to aim 100mm (4 inch) low and 50mm(2 inch) to the left. It takes three fouling shots to settle but will then shoot consistantly all day. The semolina acts as a scourer and cleans crud out of the barrel with each shot. The only problem occurs with the cylinder binding after about 25 shots. A quick clean and lube sorts that out. I will say that the ball weight makes a difference. For competitions I weigh each ball . The consistancy of loading is vital. I find the ball needs to be as flush as possible to the cylinder with minimal jump to the forcing cone. I have never used a chrono on this load but might just for curiosity try this Sunday. We have a traditional and modern bp pistol shoot scheduled along with a std pistol ISSF and a Russian shoot at 50m with hand guns. Will be a busy day. Love it

rodwha
10-18-2014, 07:52 AM
The formula I was given forgot a step, and so the figures I posted weren't correct. A fellow on another forum pointed it out with this response:


"Not to be picky but I think your formula forgot to take the square root of something.


The way I calculate the width of the flattened surface on the ball uses a little different formula.


Flat width = (Ball diameter X Ball diameter)- (Bore diameter X Bore diameter) = a number I'll call J.


Now, I take the square root of J to give me the width of the flat that's formed when the ball is shoved thru the barrel.


For your .451 ball and a .446 bore (and the symbol ^2 meaning "squared") that would be:


.451^2 - .446^2 = J = .00449


The square root of .00449 = .06701 wide


Lets assume this is in a smoothbore so we don't have to mess with the effects of the rifling grooves.


OK. The bore diameter was .446 diameter so the circumference (distance around) the bore is .446 X Pi. Pi is 3.1416... so 3.1416 X .446 = 1.40115.


The width of the flat times the distance around the bore once gives us the area of the surface contacting the bore so I get 1.40115 X .06701 = .09389 square inches.


For your .457 diameter ball I get:


Sq root of (.457^2 - .446^2) = J = .09966


.09966 times the circumference of the bore = .09966 X 1.40115 = .13964"


This is the correction:


"His formula is correct, so I changed my previous answer.
As pi∗0.446=1.40115... and J = 0.004485, the resulting areas for ball diameters of 0.451", 0.454" and 0.457"
are respectively 0.0938 square inches, 0.1189 square inches and 0.1396 square inches (rounded to 4 decimal places).
Hence the percentage increases you wanted are 26.7% and 48.8% approximately."

rodwha
10-18-2014, 07:56 AM
Driver: "Using 454 the group opens up to about 3.5 inches."

What size ball are you using otherwise to get the smaller groups? I'm guessing, since you mentioned Uberti, that it must be a .457" ball as I don't think the .451" is large enough as I hear the chambers run ~.450" or so, with some claiming the ball will just roll out.

I'm also curious which powder you've been using, and what powders you typically see in these competitions.

Driver man
10-19-2014, 01:55 AM
Goex is the main powder available here. Elephant brand ,a swiss brand and a locally made powder are also used. The main powder used is the GOEX at NZ$60.00 a lb. The balls used by me are .457. Bad weather today meant some shoots have been deferred.

rodwha
10-19-2014, 09:06 AM
$60/lb! Yikes!

Little Boats
10-19-2014, 08:12 PM
Now, I take the square root of J to give me the width of the flat that's formed when the ball is shoved thru the barrel.
"

Mine always cuts a ring of lead going into the cylinder. Wouldn't the flat be created then?

rodwha
10-20-2014, 12:06 PM
It is created then. I'm not sure if this was intended to be a generic answer (chamber/barrel) or just a wrong term. It was the bearing surface created at loading in a chamber I was referring to.

KCSO
10-20-2014, 03:05 PM
Gee all that math and I just sized the balls and tapped them down the barrel. Wih a full load in a 44 I have not noticed that much of a difference in accuracy at 25 yards, on the order of an inch. but I use the bigger ball for the best seal on the cylinder.

rodwha
10-20-2014, 05:03 PM
So you've noticed an inch smaller group at 25 yds by using a larger ball?

curator
10-21-2014, 12:27 PM
Rodwha et al:

While a larger ball size does give more "bearing surface" with cap & ball revolvers, to get the best accuracy advantage your chamber diameters need to be the same size or slightly larger (preferred) than the bore's groove diameter. If you chambers are under groove diameter as so many Italian replicas are, the value of a larger bearing surface is somewhat negated. Using corn meal or semolina/farina cereal filler under the ball does help to keep the ball centered and seal off powder gas from leaking down the grooves, allowing an under-size (swaged to smaller chamber diameter) ball to shoot accurately for target work. However, full power accuracy usually requires the correct chamber/groove diameter relationship just as it does with modern cartridge revolvers and cast boolits in general. A compressed heavy load of FFg will sometimes give good accuracy with undersize balls as the slower burning powder will act as its own "filler' preventing gas leakage. In this situation sometimes a heavier ball may be more accurate as well. Original Cap & ball revolver "paper cartridges" I have examined mostly are loaded with a grain size a bit larger than modern FFg.

rodwha
10-21-2014, 01:32 PM
Fly reamed my Pietta chambers to .449" and chamfered the mouths. It's certainly better than it was I suppose.

I've read that Uberti chambers run about .450".

BAGTIC
10-21-2014, 01:43 PM
60 New Zealand dollars, not 'real' dollars. Need to allow for exchange rate conversion.

rodwha
10-21-2014, 03:26 PM
Today that is $47.67 American. Pretty hefty!

curator
10-21-2014, 07:26 PM
Measuring the bore/groove diameter on 5 and 7 groove barrels is pretty difficult. The bore diameter can be determined easily with a "plug gauge." Lacking the correct angle "V-anvil" micrometer, I have always resorted to testing a correctly made bore slug by seeing if it was a smooth slip-fit in the cylinder mouth. Most if not all Italian Cap & ball revolvers of the ".44 persuasion" are .450-.452 (or larger) groove diameter. .36s run from .375" to about .382." Exceptions are the Walker Colts and guns made by various short-lived Italian armories. I have a ASM Walker Colt with a .468" groove diameter. I could barely hit the barn from the inside until I reamed the chambers to .470 and used .475 round balls. My Uberti 3rd. Dragoon is .457" groove and came with .452 diameter chambers. I reamed these to .458 and shoot .460 balls for excellent accuracy where before I was happy to hit the target backing at 25 yards. The relationship between the chamber diameter and the groove diameter is critical to full power accuracy. Heavier (larger diameter) balls can help with accuracy under some but not all circumstances. The key to success is know the science, and to know your equipment. Cartridge revolver boolit guys know this stuff "fur sure", why don't we black powder enthusiasts? This ain't rocket science, folks!

Been fixin' replica C&B revolvers to shoot fur 50+ years until I couldn't stand the whining no more! Most nimrods can't shoot a handgun anyway--they're happy enuff if it goes "bang."

rodwha
10-21-2014, 07:49 PM
My Pietta is of a newer flavor with 6 lands/grooves. Ran a ball through it and found it to be .452".

I wanted to ream my chambers as close to .452" as possible both for a good seal, but also to share projectiles with my ROA. Fly only had .449" so I took what I could get. I do notice it doesn't take quite as much pressure to seat my .456" boolits as they're also chamfered.

I had no idea a Walker could have been given such a large bore!!!

I'm not great with a pistol, but I certainly keep them all in the black off hand at 15 yds, and likely at 25 yds too. Beyond that I'd probably need to rest it...

curator
10-21-2014, 10:38 PM
Brownells offers a .4525" chamber throat reamer with a removable pilot. I have one of these with several pilots of different diameter ranging from .445 to .451 diameter. I have shortened both the pilot and the pilot pin so they would bottom out in non-rebated cap & ball cylinder chambers. Rebated ones take a bit of extra effort but are still easily modified. I have a lathe, vertical mill and precision drill press but have found that doing this by hand is easier than setting up one of the machines if you are only doing one. The results are very good. My altered Pietta 1858 Remington New model Army revolvers are soda-can accurate at 50 yards when fed good quality components. If you have a couple of friends, you can split the cost of the tool then offer it on EPay or another online sales site to recoup your investment.

rodwha
10-22-2014, 08:43 AM
Is this the one I've heard about that you actually do it by hand? I've wondered how it can be dead on...

If I've spent the $$$ I'd likely keep it. My Remington has felt lonely, but I wouldn't put it past me to purchase another cylinder or three, and then there's my need for a Walker (who wouldn't want to hold on to thunder and lightning?)!

curator
10-22-2014, 09:05 AM
rodwha,

The currently manufactured Uberti Walker and 3rd. Dragoon both have .456 groove diameter barrels unlike their 1860 Colt and 1858 Remington that usually measure .451-.452. I have measured several that were brought to me to "accurize." With the larger barrels, I ream the chambers to .457 and use a .460 round ball (custom mould) Armi San Marco Walker bores are all over the place as are their cylinder chambers. Some of their earlier guns are right on with .452 chambers and .451 groove diameter bores. Most that I have seen are the later ones with .446" chambers and .462+ groove diameter bores. These shoot poorly but the shock & awe (and lever-drop) makes up for the lack of accuracy. Some of the 2nd Gen Colt Walkers were the earlier guns and had a good reputation. Later ones has serious quality control issues but were finished handsomely. With most handgun issues, a large proportion of shooters can't shoot accurately enough to gauge the quality of their handguns and ammunition so their opinions lack and scientific basis.

cpileri
10-22-2014, 09:15 AM
This formulaic stuff can be put into an excel spreadsheet, then all one has to do is enter the diameter of the ball and the bore and it will calculate for you.
C-

rodwha
10-22-2014, 03:12 PM
I find that strange that they give a .456" bore in the Walkers. I wonder if this is to help with over pressures with more energetic powders?

It seems it would cost them less to bore it the same as the others...

I had looked for a .460" RB mold for my ROA and settled on the .457" as I couldn't find one.

curator
10-22-2014, 04:31 PM
You can lap a Lee .457 single cavity round ball mould to .460 easily with a bit of valve grinding compound and a few hard lead balls using an electric drill on low speed.It takes less time to do than to talk about it. Not only bore size but twist rates are different for the Uberti Dragoon and Walker compared to their other revolvers. I suspect different machines making the parts. With some of the other Italian gun makers, there appeared to be a lot of equipment swapping as one or the other went out of the replica business. As with most of the replica arms makers there is more concern about what the guns look like than how accurately they shoot. Uberti cartridge revolvers have correctly sized chamber throats in relation to their bore/groove diameters and twist rates to match bullet selection so they obviously KNOW how to make a gun that will shoot accurately.

rodwha
10-22-2014, 05:02 PM
I don't use my RB mold much anymore as I have several designs made by Accurate. I'd almost prefer to see what could be done to make a Walker shoot my .456" bullets better or maybe just get another custom mold, though I had my Pietta's chambers reamed so as to be able to share.

Though I like the Walker mostly for it's historical significance (brought Colt back into business and supplied the TX Ranger's with firepower) I'd mostly use it for hunting from a fixed position as well as the shock and awe at the range!

I suppose it doesn't hurt anything to modify that mold to drop a .460" ball, though it may be a bit rough on a .449" Pietta… But then again I just don't use it anymore.

These are the reamers I've looked at but they appear to be used in a press. Are these the ones you were talking about?

http://www.brownells.com/gunsmith-tools-supplies/barrel-blanks-tools/reamers/throating-reamers/revolver-cylinder-throating-reamer-prod7700.aspx

curator
10-23-2014, 12:53 PM
rodwha,

The Mason reamer is the way to go. I have several. For use in the Cap & Ball cylinder, I shortened the pilot and pilot pin so it could reach deeper into each chamber. Be sure to get the correct size pilot. They come in .001 increments. Brownells sells a "T" handle to turn the reamer by hand. You are not taking off a lot of metal and the pilot keeps everything lined up. Go slow, use a good cutting oil, and don't turn the reamer backwards. The job takes less that 10 minutes. Once the reamer bottoms out, I remove the nipples, and the pilot bearing and get another 1/4" of depth to provide a wee bit of extra powder capacity. The typical .44 '58 Remington chamber holds about 35 grains of FFFg before reaming and about 38 grains afterwards. Still, that's a bit less than 10% for what that is worth.

rodwha
10-23-2014, 03:22 PM
I found everything I needed at Brownell's but their reamers have a pilot that's .448", which will work fine on my current cylinder (.449" chambers), but won't work on any new ones (.446"). $100 is a chunk to spend to make one work. Figuring I may eventually buy more cylinders and pistols I can justify it.

curator
10-24-2014, 09:43 AM
rodwha,

Call the Brownells folks. They did have pilots in .001 increments that were not listed in their catalog. Pilots are easy to make if you have a lathe. They are also easy to turn down a few thousandths using an electric drill motor and some emery cloth.

rodwha
10-24-2014, 04:28 PM
I went to their site to ensure I knew what I was looking for and used their chat service. I was directed to another fellow more experienced with what I was speaking of initially but called back when I noticed the pilot size issue. Maybe that fellow wasn't as savvy...

I have no lathe. But if I did I'd not feel comfortable enough to do such a precise surgery. I'm handy with tools, and I've found I can work on some of the issues with these repro's, but not quite enough that I'd want to do something quite like that or cutting down a barrel and recrowning it, which is something I've been considering. An A/C guy doesn't need to be quite as precise with things!

On my Pietta Remington I've opened up the loading window, filed the hammer nose to fit the safety notches, and cleaned up the edges on the hand and bolt, as well as reprofiled that large grip and refinished it a better color.