Cylinder Reaming

[M. De Land]

Egg on my face here. I previously reported these numbers:

- Chambers: .357-.358
- Bore: .346

I had forgotten the critical step of setting 0 on the calipers. Remeasured the chambers, and they all measure .373-.374.

As noted above my bore measurement is not relevant. I have ordered some soft slugging bullets. After they come I'll post that measurement.

So your chamber mouths are about .017 bigger than the the barrel groove diameter? That's not a good thing at all, if so !

 

[PaulF70]

No, as I said, the barrel measurement was not valid. First of all the caliper was not calibrated. Secondly measuring with a telescoping probe and calipers isn't the best way to do it. I'll measure a slugging bullet (properly) that's been pushed thru the bore when they come and post. Then we'll have all good numbers, and I'll do whatever you guys tell me to the gun.

 

[M. De Land]

I have owned a half dozen percussion revolvers. I have never had one seat the ball with a noticable lop sided cut ring. When on half cock the cylinder is not locked in as in a vise and shifts to receive the ball adequately even. Maybe you have dealt with some very low quality products. I know about the Freedom Arms, but we are not discussing Freedom Arms, this is about affordable common C&B revolvers. I can guarantee you original Colts were not produced to FA quality specs but they did very well enough anyway. People of the C&B revolver period were more practical and realistic with their arms. If they needed a hundred yard shot, they used a rifle.

Chamber mouths have no coning to them,only a bit of chamfer to break the sharp edge if done correctly so if the rammer is out of alignment (even if smaller in diameter) and it has a hemisphere cut into its end it will secure the ball in the hemisphere and cut a lead ring off of an over size ball out of round. I used to attribute this to out of round cast balls and/or chamber mouths now I believe it's misaligned rammers doing it .
I've witnessed these out of round and often incomplete ball trimmings many times.
Remember misalignment is very often in the vertical as well as radial so it makes no difference if the cylinder is free wheeling or locked up by the bolt.

 

[M. De Land]

Egg on my face here. I previously reported these numbers:

- Chambers: .357-.358
- Bore: .346

I had forgotten the critical step of setting 0 on the calipers. Remeasured the chambers, and they all measure .373-.374.

As noted above my bore measurement is not relevant. I have ordered some soft slugging bullets. After they come I'll post that measurement.

You will need a plug gauge reading to get a real accurate read on the bore diameter and how level it is. If the rifling is even count then a good fully swagged out bore slug will give you a workable accurate read on both land and groove with a caliper used correctly .

 

[PaulF70]

So my slugging bullets arrived. They are .375" and there's no way I could push one all the way thru the barrel manually. Too tight. Don't want to risk it.

I'll have to order something else.

 

[M. De Land]

So my slugging bullets arrived. They are .375" and there's no way I could push one all the way thru the barrel manually. Too tight. Don't want to risk it.

I'll have to order something else.

One has to put the barrel in a padded vice and with a hard wood dowel, drive the slug into and flush with the muzzle then back out (open top )our all the way through the bore (solid frame cylinder removed), catch and measure. If it hits the floor make another slug. I use a two pound hammer and Hickory or Oak dowel (filliment tape the ends to keep from splitting) to drive them through.

 

[PaulF70]

Yeah it's a top-strapper so gotta go all the way thru.

Your method sounds good.

 

[M. De Land]

Yeah it's a top-strapper so gotta go all the way thru.

Your method sounds good.

If you would like you can send me a slug you've driven through and I'll mic it for you to confirm what you measure. It will only cost you postage each way.

 

[PaulF70]

If you would like you can send me a slug you've driven through and I'll mic it for you to confirm what you measure. It will only cost you postage each way.

I do have an accurate digital calipers... can that not do it?

 

[M. De Land]

I do have an accurate digital calipers... can that not do it?

Sure it will !

 

[Bad Karma]

I do have an accurate digital calipers... can that not do it?

does your barrel have an even number of grooves and lands?

 

[PaulF70]

Unfortunately it looks to be 7.

They are surprisingly difficult to count for some reason. (I can normally count to 7...)

 

[Bad Karma]

Unfortunately it looks to be 7.

They are surprisingly difficult to count for some reason. (I can normally count to 7...)

I would take Messr. DeLand up on his offer he can accurately measure the odd numbered lands and grooves on your sample. Meanwhile, since you have the .380 ball on hand, I would shoot a bunch of them. Maybe a hundred or so. Then you’ll know whether the pistol needs anything at all. You might just have a shooter which requires nothing other than powder, lead and caps. It happens more often than one would guess after reading a few of these threads.

 

[nkbj]

I measured the chambers and barrel of my Pietta 1858:

- Chambers: .357-.358
- Bore: .346

If I understand correctly, I do NOT want to ream the chambers, as they are already larger than the bore - correct?

That's perfect. You can use molds made for .38 Special and .357's.

Oh...
Saw you saying about forgetting to zero the calipers. I thought Pietta finally did it right!

 

[PaulF70]

I apologize for mucking up this thread with my bad measurement data. I do wish people would read thru before commenting on it again though.

 

[PaulF70]

I would take Messr. DeLand up on his offer he can accurately measure the odd numbered lands and grooves on your sample. Meanwhile, since you have the .380 ball on hand, I would shoot a bunch of them. Maybe a hundred or so. Then you’ll know whether the pistol needs anything at all. You might just have a shooter which requires nothing other than powder, lead and caps. It happens more often than one would guess after reading a few of these threads.

I think I may take him up, but would love to be able to do this myself!

I've shot the .380s a couple times. They are slightly more accurate with 20gr of powder than 25, and more accurate than the .375s (which don't shave any lead), but I am not too happy with the performance. *It may well be me* but I can't do better than 4-5" groups at 50'.

Part of this may be shooting in the basement where light is not great.

I think I'm just gonna shoot 'er outside. I live on a 4 acre semi-rural parcel. Neighbors won't care. I already pattern my shotguns here and a neighbor even shoots trap.

(I just hate going to ranges.)

P.S. Awaiting wood dowels from Amazon.

 

[PaulF70]

FYI, my barrels (I have two of these .36 1858s, both bought in the past year) look like the pic on the right here:

 

[M. De Land]

FYI, my barrels (I have two of these .36 1858s, both bought in the past year) look like the pic on the right here:

View attachment 171712

Looks like they switched from wide land narrow groove to wide groove narrow land. No reamer scratches on the land tops in the new style either. I'm wondering if it is hammer forged now as I see no indication of a reamer pass. Flats are milled.

 

[nkbj]

Yeah, got to be modern button rifling.

 

[M. De Land]

Yeah, got to be modern button rifling.

I don't see any sign of button chatter any where so I don't think it is button rifled but possibly. It actually looks like it's been hand lapped but that would not happen to a factory barrel. I'm back to hammer forging. I think EDM is only used on ovate rifling.