Gunsmithing Range rod runout

[A-Rok]

Hey folks. It's my first time threading a muzzle, and I have some questions.

Anyway, I'm using a PTG range rod/bushings for this project. I dialed the range rod in with two .0001" resolution indicators, and I got everything running within .0001". Now, for some added assurance, I decided to take a look at the chamber end in my outboard spider to make sure it was also running true. The chamber end was visibly running out, so I took a measurement, and it was running out about .030". Is this normal/acceptable? This is an ER Shaw barrel, so I'm not expecting the bore to be straight as a laser.

Now, here's my question. I have read that the bore of the barrel will naturally wander a few thousandths, and the last 4" of the barrel is really all you have to worry about, because that's where your accuracy comes from. Should I not worry about the chamber end runout, and just make sure the last four inches are running true?

This is for a Form 1 can, and I really, really don't want a baffle strike the first time I take it to the range.

 

[Straight Shooter]

Re: Range rod runout

The main thing is being aligned with the bore on the end you are working on. Forget what the other end is doing. I have seen barrels runout near .140". When using range rods I cut nothing until the setup is repeatable. Remove the rod and reinstall. If it still runs out .0001" or less in two places you are good to go.

 

[A-Rok]

Re: Range rod runout

Thanks for your response, that's a load off my mind! Might post pictures tomorrow of all goes right, lol.

 

[LRI]

Re: Range rod runout

10+ years of indicating a muzzle with an indicator 1:1. (Meaning no widgits).

No strikes, no accuracy issues, no problems.

Just two olympic gold medals. I wish it were three.

 

[HPLLC]

Re: Range rod runout

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hired Gun</div><div class="ubbcode-body">The main thing is being aligned with the bore on the end you are working on. Forget what the other end is doing. I have seen barrels runout near .140". When using range rods I cut nothing until the setup is repeatable. Remove the rod and reinstall. If it still runs out .0001" or less in two places you are good to go. </div></div>

That makes good sense. The Germans made a bent barrel accessory for the STG 44 in WWII that allowed people to shoot around corners. The bullet is going to go where the end of the barrel is pointing.

Some of the barrel manufacturers straighten barrels (Savage does this).

Others like Krieger kryo them so that the metal machines better, claiming they can get the drill to follow a straighter path. Krieger then grinds the OD of the barrel into concentricity with the bore I believe. Theoretically that's supposed to create a barrel that has more even harmonic disturbance which is thus more accurate.

 

[trigger time]

Re: Range rod runout

Just screwed together a 260 with a Krieger that was the most crooked sob I've ever worked on. Back end was flopping around like a fish, but I have no doubt it will be a hammer.

 

[Sleeper]

Re: Range rod runout

Sure hope so, if not I'm calling Krieger

 

[wnroscoe]

Re: Range rod runout

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: A-Rok</div><div class="ubbcode-body"> I'm using a PTG range rod/bushings for this project. I dialed the range rod in with two .0001" resolution indicators, and I got everything running within .0001". The chamber end was visibly running out about .030". </div></div>

That’s normal with most barrels when double indicating at the chuck. Work one end of the barrel at a time (at the chuck) and let the other end do as it wishes (at the outboard spider)

You'll be fine.

 

[Straight Shooter]

Re: Range rod runout

Once dialed in just for fun check the runout on the outside of the barrel you just dialed. I have found the bore to be offset in the barrel by a small degree in lots of factory barrels.

 

[2156SMK]

Re: Range rod runout

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hired Gun</div><div class="ubbcode-body">Once dialed in just for fun check the runout on the outside of the barrel you just dialed. I have found the bore to be offset in the barrel by a small degree in lots of factory barrels. </div></div>

And for even more fun, cut down a factory 26" barrel to 20" and check the runout of the outside...

 

[JFComfort]

Re: Range rod runout

When we get the chamber end dialed in we mark the high spot on the muzzle end clock it at 12. I've been meaning to read up on the other method of dailing in barrels and trying it.

 

[skog]

Re: Range rod runout

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2156SMK</div><div class="ubbcode-body"> And for even more fun, cut down a factory 26" barrel to 20" and check the runout of the outside... </div></div>

Did this to a 700p barrel. 0.165" runout at crown while chamber was run dead nuts. Guns shoots after all was said and done though.