Predicting revolver flyers?

[keppelj]

How effective is the range rod at predicting which revolver chamber sends flyers? I am getting quite tight groups with my 686, but regularly get a 1" group with a flyer 2" away, usually to upper right of the group. I tried numbering the chambers and plotting the target holes to identify the errant chamber, but the results weren't clear enough to convince me that it might not also be my bullets.

 

[keppelj]

How effective is the range rod at predicting which revolver chamber sends flyers? I am getting quite tight groups with my 686, but regularly get a 1" group with a flyer 2" away, usually to upper right of the group. I tried numbering the chambers and plotting the target holes to identify the errant chamber, but the results weren't clear enough to convince me that it might not also be my bullets.

 

[john traveler]

A range rod only physically confirms bore-to-chamber alignment with the cylinder at firing position. The potential measurement error of course, is the depth of the rifling groove.

The other element of revolver mechanical accuracy is correct timing. The firing chamber must be in locked position at the moment of ignition. If timing is off, even perfect bore-to-chamber alignment won't give consistently good groups.

If you are already getting tight groups, but regularly get a flyer, the likely cause is bullet quality. Are you using commercial cast, or your own? You might try some commercial swaged 148 grain WC to check on bullet quality. Usually, they give the best groups compared to most other cast bullets.

 

[bountyhunter]

Originally posted by keppelj:
How effective is the range rod at predicting which revolver chamber sends flyers? I am getting quite tight groups with my 686, but regularly get a 1" group with a flyer 2" away, usually to upper right of the group. I tried numbering the chambers and plotting the target holes to identify the errant chamber, but the results weren't clear enough to convince me that it might not also be my bullets.

If one was seriously off, it could affect accuracy. IMHO, the chances are probably about 99.99% that it's ammo related.

 

[keppelj]

John, Bountyhunter, thanks for your thoughts above. The two bullets I've found to be accurate with this 686 are Winchester 158gr Match SWC and my own loads of Montana Gold JHP. Outstanding with both of those, no flyers, so you are likely right, it's not the gun. I've wanted to find an accurate SWC I'd load hence my efforts with these bullet in question, TVB 158gr SWCBB which have a good rep. I have some Hornady 158 SWC's which I have yet to try. John, those are commercial swaged aren't they? I did try 148gr Winchester WC with this gun and it was better with the heavier bullet, the Win 158. Of course, I can only identify a flyer if the groups are pretty good to start with. I gather both of you would say the range rod is not worth trying.

 

[john traveler]

I believe all lead bullets by the larger manufacturers are swaged. That would include Hornady, Speer, Remington, and Winchester.

 

[shovelwrench]

If timing is off, even perfect bore-to-chamber alignment won't give consistently good groups.

Is'nt "bore to chamber alignment" what timing really is?

 

[retired2006]

Something else to check would be the "throats" of the cylinder. Measure them to ensure that one is not undersize. You should be able to use a dial caliber to do this.
The throat is the end of the cylinder where the bullet leaves the cylinder.
There have been problems in the past with certain revolvers that would have an undersize throat, which would affect accuracy on that hole in the cylinder.

 

[shovelwrench]

Very true about the throats, problem with dial calipers is they'll be off by at least .001, telescoping gueages and a micrometer, or a pin guage set is about the only way.

If you have access, measure them. I they are not, at the least, .001 over the bore size for a given caliber, they should be reamed.

Cylindersmith.com

 

[keppelj]

It's not the throats. I have a pin gauges and they are uniformly .357-. A sampling of the bullets measure .357 also. They are as they should be, a stiff working push into the throats. I could check a larger selection for size irregularity though. The gun doesn't lead or spit with the TVB.

 

[Wayne M]

If your flier doesn't come consistantly from one chamber the problem is you or the bullets and from what you've already told us it sounds like bullets.

 

[keppelj]

I'm using a ransom rest. I've measured the bullets in diameter and weight and they are all .358 and within a tenth of a grain of each other. There may be some variation in my loading, but I don't know what that would be. Grain weights are identical. Same head stamps, same case lengths and close OAL. I think I'll go back to some good factory bullets to determine for sure that the cylinders are all the same. Thanks again for your thoughts.

 

[tomcatt51]

Originally posted by keppelj:
I'm using a ransom rest. I've measured the bullets in diameter and weight and they are all .358 and within a tenth of a grain of each other. There may be some variation in my loading, but I don't know what that would be. Grain weights are identical. Same head stamps, same case lengths and close OAL. I think I'll go back to some good factory bullets to determine for sure that the cylinders are all the same. Thanks again for your thoughts.

What are your group sizes at what distance?

Your throats should be .358" for .358" lead bullets. .357" jacketed will like .357" throats better. The only 38/357 S&Ws I have currently are 627's and they have .358" throats. .357 mag guns will usually shoot better with loads in 357 mag cases than .38 specials because of the case to throat jump.

Many hard cast bullets are too hard for the pressures generated from "target" loads. They won't obdurate properly at the low pressures of target loads. Swaged 148 WC or HBWC are usually better for bullseye type target load accuracy.

This is much more common with Rugers than S&Ws but sometimes the barrels are crushed excessively where the barrel threads into the frame. This does not help accuracy. The "fix" is firelapping or cutting a Taylor Throat in the barrel.

If there's a problem with the barrel crown you'll usually see it as an UNEVEN carbon/crud pattern on the crown after shooting. You should see a nice even symetrical pattern.

Good luck.

 

[bountyhunter]

Originally posted by shovelwrench:

If timing is off, even perfect bore-to-chamber alignment won't give consistently good groups.

Is'nt "bore to chamber alignment" what timing really is?

Sort of. I think most people refer to timing as carry up, which means does the cylinder rotate all the way into lock when the hammer falls. Cylinder to barrel alignment is checked with a range rod when the cylinder is locked in place. A gun wuth a carry up problem may have good alignment when the cylinder is locked in, but not lock in on every cylinder tube when the hammer falls which definitely can cause flyers.

 

[keppelj]

Tomcatt, this 686 is shooting well with the right bullet. The issue I raised here is a 1" group of 5-6 bullets with a single bullet 1.5 -2" away, all by itself, at 25 yards. I'm happy with the group. I'm trying to understand the flyer and eliminate it. I arrived at this grain weight by shooting 3-5 to 4-3 of Universal, and the sweet spot is 4.0 to 4.1. The groups got tighter and tighter except for usually one bullet tho sometimes two.

 

[keppelj]

Sorry, I meant 3.5 to 4.3. It's getting late in my workday.