1858 throat and barrel size/ reaming questions

After a few years of playing around I finally got around to slugging the barrels and throats on my 1858s (Pietta). I was pretty surprised at the results. Granted, they're pretty hard to measure accurately due to the odd number of grooves, but I believe I did a reasonably accurate job.

First I slugged the barrel with a .457 ball. I noticed right away it was pretty easy and the resulting ball didn't reach to the bottom of the grooves. I took another whack with a .490 ball. The resulting measurement was .460". Wowzers.

Next I did the cylinder with a .454 ball. The ball came out to a swaged/shaved .448". I checked a second cylinder and it was very close.

Third, I took the .458 cylinder slug and pushed it through the barrel. It pushed through by hand leaving barely noticeable rifling marks.

Finally, I pushed the barrel slug halfway into a cylinder. It all but removed the rifling.

My land diameter is a carefully calculated guess, but here's what I am getting:

Grooves: .460"
Lands: .446"
Throat: .448"

As final observation, both barrels are tight at the frame threads.

Well, that leaves me pretty well stuck as far as improvements. I'd hoped to ream the cylinder to .001 over groove diameter, but I'm not terribly excited about reaming it to .461.

At the same time I have only .001" rifling engagement! How sad is that?

Any thoughts on reaming cylinders to .4525? It would increase my rifling engagement by a couple thousandths, but still leave me several thousandths under groove diameter. Not sure if I'm solving anything with that approach.

How much metal would there be left between the reamed size holes in the cylinder and the outer diameter of the cylinder?

Personally, I think in your shoes that I would contact Pietta and see what they would do.

It may be less expensive and possibly safer to get a tighter barrel, rather than ream out the cylinders.

Gus

This pair of guns is at least 10 years old. I wouldn't think Pietta would be willing to offer much help at this point. The good thing is I paid $100 for the pair of them.

I checked into barrels just out of curiosity...$90 each, plus shipping and etc. I can ream them for about $20.

I haven't measured the meat between the cylinders. Based on a guess and matter of practicality (beyond .457 balls?) I don't really want to bore them to more than .4525". To reach groove diameter I'd be boring to .460"+.

If I did .4525" I would gain a couple 1/1000 in rifling engagement. Whether or not it's enough to matter is another question all together.

I might just decide to do one and see how it goes.

I am not sure you understand, so I will ask the following questions:

Have you measured the diameter of the cylinder holes and the outside diameter of the cylinder with a good pair of precision calipers at least?

With the same precision calipers to measure, how much metal is there now between the outer edge of each cylinder hole and the outer diameter of the cylinder?

The reason I am asking these questions is because though I may not have understood you, it seems to me you will be reaming the metal so there will be .005" less metal between the cylinder holes and the outer diameter of the cylinder and .010" between the cylinder holes.

Gus

Thanks. No, I understood, just haven't measured it. I don't have a caliber accurate enough to mean anything and my mics are too small.

I would be milling from .448 to .4525. If done accurately, that'd be .0045 less between the cylinders and .00225 less in outside wall thickness.

first I would find a accurate way to measure the barrel slug. there is a mic. for measuring three flute end mills. then there is a optical comparer.

There is not enough material between the cylinder chambers to take .012 out( .006 out of each side of adjacent chambers).
The chambers have enough material between the OD and each chamber and over the bolt notch as they are dual diameter ID and thicker in this area.
To accurately measure odd number rifling grooves you need a tri-Mic or a Powely gauge other wise it is only and educated guess.
You could sleeve the original barrel as well and get rid of the tightening under the frame threads.
The down sides is this leaves a very thin liner wall in the forcing cone.
I would re-barrel personally and ream all chambers to the same depth and diameter at or no more than .001 over groove diameter.

For what it's worth (and it might be good or it might be bad), the 2011 Dixie gun catalog lists several Pietta Remington New Army pistol barrel and cylinder measurements.

Many of these are standard Pietta production guns with DIXIE GUNWORKS stamped on the barrel but I have no reason to believe they wouldn't be typical of the Remingtons Pietta made/makes without the company stamping.

"Dixie Remington New Model Army & Kit"
bore = .440, grooves = .450 (6 grooves), chambers = .449

"Dixie Remington New Model Army Revolver" (rugged-look patina finish)
bore = .440 grooves = .446 (7 grooves), chambers = .446

"Dixie Remington New Model Army Revolver" (Oversize frame & grips)
bore = .440, grooves = .450 (7 grooves), chambers = .445

"Dixie Remington New Model Army" (stainless steel)
bore = .440, grooves = .450 (7 grooves), chamber = .447

"Dixie 1858 Remington INOX Target revolver"
bore = .440, grooves = .450 (7 grooves), chambers = .447

"Dixie Remington New Model Army "Shooters" revolver"
bore = .440, grooves = .456 (5 grooves), chambers = .456

"Dixie 1858 Remington Texas Revolver" (brass frame)
bore = .440, grooves = .450 (7 grooves), chambers = .445

Notice, the bore diameter on all of these is consistantly .440. If I were to guess a tolerance on this it would be something less than ±.0010.

The bore diameter of .446 that you arrived at makes me wonder about the accuracy of the groove diameter you ended up with.

As many have mentioned, it is very difficult to get a good measurement on a rifled bore when the rifling is an odd number. Opposite each land is a groove.

There are a number of smiths out there who rebarrel Remingtons, here is one who has done work for me:
http://www.hahnmachineworks.com/html/RevolverAccuracy.html

I have the chambers on all my revolvers reamed to .456" for a .457" ball and cut a new 11 deg. forcing cone. Still plenty of meat left in the cylinder (Colt or Remington).

I finally broke down and bought a set of hardened steel plug gauges to accurately check bore diameters and to find tight spots in a barrel to be lapped out.
The Powely gauge can be made by any machinest and is as accurate as a Tri-mic operating on exactly the same principle via a formula one plugs in after taking two standard mic measurements.

I know I'm weird but just for giggles I did a little calculating for measuring a round object with an odd number of grooves like a rifled barrel would have.

To try to explain what I did, imagine a slug with an odd number of rifling grooves on it.

On one side of the plug with the micrometer spindle or caliper blade directly in the center of the ungrooved outside, the opposite spindle or blade will be resting on the 2 edges where the groove meets the outside diameter.

Because of this groove, the distance from the edges to the exact center of the slug will be slightly less than it would be if the groove did not exist.

The effect of the groove is directly dependent on the width of the groove.
The wider it is, the smaller the distance to the center of the slug will be.

The figures I obtained are based on the idea that from the ungrooved side to the center of the slug will be exactly 1/2 of the diameter.

On the grooved side, the distance from the corners of the groove, measured perpendicular to the spindle face or blade of the measuring tool, to the center of the diameter will be the "base" of a right triangle.
Then, with the radius from the center of the slug to the outer corners of the groove will be the "hypotenuse" and 1/2 of the groove width being the short side of the triangle.

The length of the "base" is equal to the square root of the difference between the square of the hypotenuse and the square of 1/2 of the groove width.
The old B = √ A²-C² we learned in school.

Anyway, I selected .440" for the outside of the slug to do some figuring. (I probably should have selected something closer to .455 but that can be for another time.)

Using .440, if the groove width was .060 the measurement across the slug would be .438.

If the groove was .080 wide the measurement would be .436 and if the groove width was .090 the measurement would be .435.

OK you in the back row. Stop looking at Susan's bare arms and return to class now. :rotf:

Zonie said:

Notice, the bore diameter on all of these is consistantly .440. If I were to guess a tolerance on this it would be something less than ±.0010.

The bore diameter of .446 that you arrived at makes me wonder about the accuracy of the groove diameter you ended up with.

Click to expand...

Zonie, those Dixie specs are of interest, but there is absolutely no way on this planet that either of these barrels has a groove diameter less than .460"

The angle of the Powely gauge troth rests on some portion of land of the swaged slug which is the groove of the barrel. We always use a cylinder shaped slug as it will pick up the helix pitch of the rifling on the slug for better support on groove (land) flats.
The gauge thickness is measured with and without the slug. The difference is fed into the formula and the diameter of the groove will be calculated.
As long as you can pick up some portion of a flat at three points on the slug( two on the gauge and one on the mic anvil at the top the diameter can be accurately calculated.
The helix angle of the rifling imprinted on the slug in effect makes a wider measuring contact point on the gauge troth and in my opinion is the reason it should work on any odd numbered groove count in use 3, 5 or 7.
The gauge was made for five lands and grooves specifically but should work for any odd number as long as some portion of a flat can be picked up at the three contact measuring points.
You can prove the formula with a known plug gauge diameter, making the measurements and running the equation.

If anyone wants to make one of these gauges the angle of each side of the V is 36 degrees from horizontal.

To run the equation place in the gauge V a carefully measured round (plug gauge is good). The diameter of the round in multiplied by 1.1180 to find dimension B in the picture.
To find A use a common 1 inch mic. A minus B will give you dimension C for your particular block.The diameter for any other round (bore slug)is found by measuring A, subtracting C to find B.
B is multiplied by .8944 to find your slug diameter at the slug lands which is your barrels groove diameter.

What are you using this handgun for - if it's competition then just but the 1858 target model and forget "puttzing" with the standard firearm - you are wasting time & money on something that will MAYBE shoot accurately :v

Well, the guns are used for all sorts of things, none of them presently competition. I wouldn't rule that out, but I'd almost certainly do exactly as you suggested and buy a target model.

My biggest purpose in doing this was that I have several guns I want to slug and I wanted to take a hammer to a $50 pistol before a $1000 pistol.

So, in a nutshell, just putzing.

If I can improve them, then great. I also use one daily loaded with snakeshot. If accuracy goes to pot it'll still be good for that

I was able to find a few other folks that have had bores run this large. I think there's improvement to be had just not sure how much.

I ended up buying a .453 reamer this morning. That'll improve the rifling engagement substantially, and won't require a non-standard ball size, but I'll still be several thousandths under groove diameter.

This may sound stupid but the manufacturers should really be making firearms where all this aftermarket work is not required.
I am not looking for an "Ad" but are there any revolvers where the manufacturer usually gets it right?

I forgot to mention that with three and five groove rifling the lands can be measured on this gauge as well as the groove diameter if the the groove is not to deep to allow the three measuring points to be contacted.

Any one with a mill can make this gauge just as I did with a piece of mild steel and stamped the equation into the face so I wouldn't loose it.
Sure is handy, cheap and accurate, two of my favorite characteristics. :rotf:

I think there's officially more posts in this thread about your gauge than my pistols at this point...

My reamer should arrive tomorrow and I hope to have one cylinder reamed Saturday evening if the set up goes according to plan. If all goes well I plan to do some accuracy comparisons Monday or Tuesday.

I look forward to sharing.