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Action Runout Question

k260

Silver $$ Contributor
I have a 700 action with a 9" barrel fitted (that work was done by somebody else) that was brought to me to turn the barrel OD, it looked a bit kinky when I set it up but I know barrel blanks aren't true so no big deal. I decided to check it with an alignment rod so I ran a rod through the bore and chucked one end of the rod in the chuck and the other end in the tailstock chuck, spinning the barreled action on the rod the receiver has .027" runout behind the recoil lug. Should that be less? Shouldn't the barrel bore be pretty much centered in the receiver bore? I've never run into this so I don't know if it's an issue but it's got me thinking that maybe the threading/chambering is a bit off center. Thoughts?
 
k260 said:
I have a 700 action with a 9" barrel fitted (that work was done by somebody else) that was brought to me to turn the barrel OD, it looked a bit kinky when I set it up but I know barrel blanks aren't true so no big deal. I decided to check it with an alignment rod so I ran a rod through the bore and chucked one end of the rod in the chuck and the other end in the tailstock chuck, spinning the barreled action on the rod the receiver has .027" runout behind the recoil lug. Should that be less? Shouldn't the barrel bore be pretty much centered in the receiver bore? I've never run into this so I don't know if it's an issue but it's got me thinking that maybe the threading/chambering is a bit off center. Thoughts?
Click to expand...
a 9” barrel?
 
How’s the alignment rod centering itself in the barreled action? Bushing(s) in the bore?

If the rod is small enough to fit through the rifle bore and you have all of the weight of the barreled action hanging in the center, I think that would cause some big deflection and would be the cause of a lot of runout
 
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Jud96 said:
How’s the alignment rod centering itself in the barreled action? Bushing(s) in the bore?

If the rod is small enough to fit through the rifle bore and you have all of the weight of the barreled action hanging in the center, I think that would cause some big deflection and would be the cause of a lot of runout
Click to expand...
It's a 338 bore so the rod is pretty stiff, I'm spinning the barreled action on the rod that is supported between two chucks. I don't think the runout of the action is caused by the slight (if any) bend in the rod.
 
k260 said:
It's a 338 bore so the rod is pretty stiff, I'm spinning the barreled action on the rod that is supported between two chucks. I don't think the runout of the action is caused by the slight (if any) bend in the rod.
Click to expand...
What is keeping the rod true in the barreled action?

That’s a lot of weight on a rod that’s less than 3/8” and is over a foot long
 
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Jud96 said:
What is keeping the rod true in the barreled action?
Click to expand...
Nothing, but the slight bend in the rod doesn't affect the runout of the action as much as I'm getting, if any. I'm not spinning the rod, the action is spinning on the rod.
 
So how is the alignment rod centered in the bore? If nothing is centering the rod in the bore of the barrel, then how would you take an accurate measurement? Some pictures of this setup would be helpful
 
Jud96 said:
So how is the alignment rod centered in the bore? If nothing is centering the rod in the bore of the barrel, then how would you take an accurate measurement? Some pictures of this setup would be helpful
Click to expand...
The rod is a precision ground alignment rod made for the 338 bore, it's .001 smaller so it will slip through the bore to check bore alignment on suppressors.
 
marazzi59 said:
Can you make 2 drive dogs that ride on centers to take out the aliment rod from the equation? Or just remove the barrel from the action
Click to expand...
I'm trying to figure out if the barrel bore and chamber are centered in the receiver bore so removing the barrel would defeat that, I think. I might be overthinking this whole thing. I'm just wondering if it's possible for the receiver to be out that much but everything internal line up like it should.
 
A 700 ... from my experience ... there's likely little or nothing wrong with your barrel. It's more likely the action is a POS.

Not that that's necessarily a problem. I've trued and rebarreled several, and they'd shot just fine before.

When you set one up and your indicator doesn't have enough travel.... hard to not break out the truing fixture, just in case.
 
Dude, The way you are going about this is just wrong. Put your action in a truing jig with an action mandrel and dial it in with the barrel off. Spinning the barrel around a range rod that is not turning is not right, And yes you are going to get all kinds of flex like that.

Show a pic of what you are doing so it's not so confusing, Because it does not sound good at all.

Also it sounds like you are measuring the outside of the action, That is meaningless, You want to measure the center axis of the action and all subsequent machining needs to be concentric with that.
 
Sniperhandle said:
Also it sounds like you are measuring the outside of the action
Click to expand...
I am, I'm trying to figure out if the 700 receiver is that bad or if the barrel was cut wrong. I know we don't indicate the outside of the receiver to set up for chamber work, what I'm trying to figure out is if the receiver is truly that much out of round or not.

An alignment rod is not a range rod, a range rod is a very loose fit in the bore. An alignment rod is centerless ground steel and is .001 smaller than the bore, if there was as much flex as you guys seem to think there is it wouldn't spin freely.
 
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.
 
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