Action Runout Question

[k260]

Pics of what you are doing, If you are talking about suppressor alignment rods, There is no way that is going to not have a lot of flex and they are not used for what you are doing. Range rods can be put in pretty tight with the right bushing, They are tapered, The harder you push, The tighter they get. But range rods can't be used for what you are trying to do either.

You asked for opinions.

I did ask for opinions and you guys have greatly exceeded my expectations It's quite evident that you guys are absolutely concerned about precision and are forgetting that there's more than one way to smash a goat, this is more of a "hold his head habib, I got the back" kinda thing and not dinner and wine.

Just to satisfy my curiosity I put the precision ground 16" steel rod in the lathe (1/4" in each chuck) and put a test indicator in the center, gently set the barreled action beside the indicator on the rod and it moved .0065" so it's not the wild flex that you guys are assuming. Besides, what I'm trying to check is affected zero by the flex of the rod but apparently I can't explain what's in my head so I'll figure something out, it's raining and cold today so 'll have plenty of time to piddle with it.

And, "spinning" the action on the rod is spinning it by hand very slowly to watch the runout, not spinning it at 2000 RPM, so I'm not at all concerned about damaging the barrel bore.

 

[k260]

The runout of the outside of any action is meaningless no matter who made it.

Absolutely. But I guess what I'm trying to figure out is an easy way to see if the barrel bore is centered in the bolt bore before I start making chips, it's not a benchrest gun but I'd like it to be as good as I can get it. Like I said before, I may be over thinking this but it got in my head and I can't get rid of it.

 

[SKWERLZ]

I'm surprised an unknown action with an unknown barrel built by an unknown person, spinning on an unknown type of rod is only out 27 thou.

^^^^^

 

[Jud96]

If you want to inspect things, you need to have the right tools and use proven techniques.

At minimum you need a ground mandrel with bushings that fit in the action bore, and the best option would be ground 9-12” mandrels that are 0.700-0.705 in diameter in .0005 increments.

Take the barrel off, dial the existing chamber in and then put a long reach indicator just ahead of the throat to see how true the bore is running. Then you need to check the runout on the barrel shoulder face and see what it is. If the existing chamber is running true and the bore just ahead of the throat is running true, then the shoulder should be running true if the last guy did his job right. If it’s out even .0001 then the rear of the action 8” away is going to read .0008 more runout then it really has because the shoulder it’s against isn’t running true. If it’s .0002 out, now you’re adding .0016 of runout to the equation. You get the idea.

Thread the action on tight against the barrel shoulder, find the bushings or ground mandrel that fits the action bore the best, put a tenths indicator on the ground rod/mandrel just behind the tang and spin the chuck and check the runout on the rod.

Now you know the barrel bore is running true and you know the action face is square against the barrel shoulder that’s running true, so whatever amount of runout at the rear tang is purely from the receiver bore and slop in the bushings, which could be a few tenths. The ground solid mandrels work the best, but they’re not cheap and aren’t readily available.

 

[AlNyhus]

I'm surprised an unknown action with an unknown barrel built by an unknown person, spinning on an unknown type of rod is only out 27 thou.

Yep.

 

[LVLAaron]

If you don't have action mandrels, The next best thing you can do on a rainy sunday, is take a piece of old barrel, turn a shoulder and tenon on it... screw the action on without removing your stub from the lathe, now you can indicate the body of the action. Like others have said, it absolutely does not matter, but I understand the curiosity.

 

[Jud96]

Other than for curiosity sake, the OD runout has no correlation to the ID runout of the action, especially on a factory 700 action.

 

[Sniperhandle]

"hold his head habib, I got the back"

That's actually pretty funny!

Edit to add:

"Unless you're the Goat!"

 

[ELR LVR]

I'm surprised an unknown action with an unknown barrel built by an unknown person, spinning on an unknown type of rod is only out 27 thou.

thats why the barrel was cut down to 9"
to reduce the runout

 

[tobnpr]

Thread the muzzle on a chopped-down wartime 91/30 and you'll see some REAL runout

 

[ELR LVR]

Thread the muzzle on a chopped-down wartime 91/30 and you'll see some REAL runout

I threaded the muzzle on a Browning x-bolt
after seeing that
I will never own a Browning X-Bolt