What tool do I need !!SOLVED!!

[ar15barrels]

No, just using feeler gauges. With the cylinder full the measurements change from .008 to .006 and from .009 to .008 so it still appears the crane is out of alignment.

I've polished the face of the forcing cone using a Dremel (I know that's a scary word) with some jeweler's rouge on a felt cone tip so we'll see what happens next time I get to the range.

If it doesn't lock up after multiple cylinders fired I'll call it good notwithstanding the gap variances.

Have no problem sending it back to S&W in any case. I think the problem is with an out of spec crane and will request they replace that part.

How are you seeing the variance in gap?
Is that from rotating the cylinder and measuring the gap on the same side at each hole?
The cylinder rotate on the crane.
The crane does NOT rotate as the cylinder rotates so you can not see a variance in gap as being the crane being bent.
Once the crane is closed, the crane is just the post that the cylinder spins on.
The crane being bent should show up as the ejector rod being misaligned or even the chambers being misaligned with the barrel in extreme cases.
The crane being bent won't change the gap for different holes.
The gap being different for different holes is differences in thrust which if you are using ammo, then it's differences in rim thickness.
Check the gap on each hole using the SAME headspace gauge and see what you get.
The cylinder would have to be thicker on one side (easily measured with a micrometer) or there is a difference in carbon/lead buildup at a specific hole or there be some difference in the hand cuts which causes the hand to push the cylinder forward differently for there to be a difference in the gap on different holes
0.006" is a good gap.

[Featureless]

How are you seeing the variance in gap?
Is that from rotating the cylinder and measuring the gap on the same side at each hole?
The cylinder rotate on the crane.
The crane does NOT rotate as the cylinder rotates so you can not see a variance in gap as being the crane being bent.
Once the crane is closed, the crane is just the post that the cylinder spins on.
The crane being bent should show up as the ejector rod being misaligned or even the chambers being misaligned with the barrel in extreme cases.
The crane being bent won't change the gap for different holes.
The gap being different for different holes is differences in thrust which if you are using ammo, then it's differences in rim thickness.
Check the gap on each hole using the SAME headspace gauge and see what you get.
The cylinder would have to be thicker on one side (easily measured with a micrometer) or there is a difference in carbon/lead buildup at a specific hole or there be some difference in the hand cuts which causes the hand to push the cylinder forward differently for there to be a difference in the gap on different holes
0.006" is a good gap.

That's a lot of detail. The gap is different on each side. The gap on the right side is less than the gap on the left side in all cylinder positions. What are the possible causes?

Well, the barrel face is a constant. Maybe the cylinder is not flat as in perfectly 90 degrees perpendicular? I will measure the cylinder with calipers as I don't have a micrometer.

That might eliminate a bent crane as the cause, especially since the lockup is perfect.

You said

Once the crane is closed, the crane is just the post that the cylinder spins on.

If that post is off center and not perfectly aligned with the barrel the result would be variances in the gap from one side to the other.

There is no carbon or lead buildup when I took the measurements. Everything clean as a whistle thanks to Hoppe's an multiple cleaning with cotton patches.

I don't have headspace gauges and think feeler gauges in increments of .001 are more precise anyway.

Differences if ammo rim thickness would not be a factor IMO.

[eaglemike]

That's a lot of detail. The gap is different on each side. The gap on the right side is less than the gap on the left side in all cylinder positions. What are the possible causes?

Well, the barrel face is a constant. Maybe the cylinder is not flat as in perfectly 90 degrees perpendicular? I will measure the cylinder with calipers as I don't have a micrometer.

That might eliminate a bent crane as the cause, especially since the lockup is perfect.

You said

If that post is off center and not perfectly aligned with the barrel the result would be variances in the gap from one side to the other.

There is no carbon or lead buildup when I took the measurements. Everything clean as a whistle thanks to Hoppe's an multiple cleaning with cotton patches.

I don't have headspace gauges and think feeler gauges in increments of .001 are more precise anyway.

Differences if ammo rim thickness would not be a factor IMO.

Sounds like the back end of the barrel isn't square. I don't think there is any way the cylinder and crane assembly could be out of square enough to get that amount of difference.
As Randall said, .006 is considered pretty normal.
I suggest you not do any more dremeling on it. Some companies won't honor warranties when there is evidence of home gunsmithing.
I don't know where you live, but I think it would be a good idea to get someone to look at it that has some experience with S&W revolvers.

[offrdmania]

Looks like the same shape as my locking lug nuts

[Featureless]

Sounds like the back end of the barrel isn't square. I don't think there is any way the cylinder and crane assembly could be out of square enough to get that amount of difference.
As Randall said, .006 is considered pretty normal.
I suggest you not do any more dremeling on it. Some companies won't honor warranties when there is evidence of home gunsmithing.
I don't know where you live, but I think it would be a good idea to get someone to look at it that has some experience with S&W revolvers.

It does sound like the back end of the barrel is not square. That is the simplest explanation. One would think the S&W warranty tech would have noticed that.

I'll get to the range this weekend and try it one more time. If it still locks up, there is a gunshop in Templeton who has a gunsmith, I'll check with him before sending it back to S&W again.

[Featureless]

Looks like the same shape as my locking lug nuts

That's interesting. Looks like that lug nut IS the tool.

[Dan_Eastvale]

my S&W Model 28 Highway Patrolman did this when new. Heat expanded the cylinder enough to catch the forcing cone after three reloads. Sent it back to them. They planed off a small amount from the cylinder face. It fixed it but they didn't redo the dull blue finish on the cylinder face.

[ar15barrels]

If the gap is 0.002" different across the breech end of the barrel, then my first guess would be a little burr on one side.
I would be looking at the breech end of the barrel insert for evidence of hand stoning or hand filing as opposed to the lathe turning I would expect there.

My first thing to do would be to dykem the breech end of the barrel use a pull-through facing cutter to scrape some of the dykem off and see if it happens to come off the tight side.
If the rear of the barrel cuts unevenly, I would cut it until it mostly cleans up and then I would clean everything and check it with feeler gauges again.
I would have a headspace gauge in the top chamber to make sure the cylinder is thrusting against the recoil stop and not against the crane how it does when there are no cartridges in the cylinder because simply pushing the cylinder into the frame from one siide while pushing the cylinder out of the frame from the other is going to give you different measured gaps.

That's a lot of detail. The gap is different on each side. The gap on the right side is less than the gap on the left side in all cylinder positions. What are the possible causes?

Well, the barrel face is a constant. Maybe the cylinder is not flat as in perfectly 90 degrees perpendicular? I will measure the cylinder with calipers as I don't have a micrometer.

That might eliminate a bent crane as the cause, especially since the lockup is perfect.

You said

If that post is off center and not perfectly aligned with the barrel the result would be variances in the gap from one side to the other.

There is no carbon or lead buildup when I took the measurements. Everything clean as a whistle thanks to Hoppe's an multiple cleaning with cotton patches.

I don't have headspace gauges and think feeler gauges in increments of .001 are more precise anyway.

Differences if ammo rim thickness would not be a factor IMO.

[Featureless]

Problem gone!! Trip to the range, ran multiple cylinders full (lost track after 10),
ZERO LOCKUPS.

Since the last trip to the range all I did was polish the face of the forcing cone so I'm thinking maybe a rough surface was gathering powder fouling?

Could it be that simple?

[Featureless]

If the gap is 0.002" different across the breech end of the barrel, then my first guess would be a little burr on one side.
I would be looking at the breech end of the barrel insert for evidence of hand stoning or hand filing as opposed to the lathe turning I would expect there.

My first thing to do would be to dykem the breech end of the barrel use a pull-through facing cutter to scrape some of the dykem off and see if it happens to come off the tight side.
If the rear of the barrel cuts unevenly, I would cut it until it mostly cleans up and then I would clean everything and check it with feeler gauges again.
I would have a headspace gauge in the top chamber to make sure the cylinder is thrusting against the recoil stop and not against the crane how it does when there are no cartridges in the cylinder because simply pushing the cylinder into the frame from one siide while pushing the cylinder out of the frame from the other is going to give you different measured gaps.

I think you nailed it right there the problem was at the breech end of the barrel and, apparently, polishing the face of the forcing cone solve the problem (small burr, rough surface).

[IVC]

I think you nailed it right there the problem was at the breech end of the barrel and, apparently, polishing the face of the forcing cone solve the problem (small burr, rough surface).

Glad it worked out, it's extremely frustrating to have to do these types of simple finishing jobs that should've been done at the factory.

[ar15barrels]

I think you nailed it right there the problem was at the breech end of the barrel and, apparently, polishing the face of the forcing cone solve the problem (small burr, rough surface).

It's almost like I work on guns for a living or something.