Gunsmithing Headspacing and bolt clearances

[cast1]

Hello all. I've built a few rifles in 6.5 Creedmoor with good results so far but have come to a question. My PTG go gauge is EXACTLY the length of 140 ELD match. Bolt will close on a round but I am essentially running zero headspace if I get it just deep enough for the gauge to clear. Is that a problem, and if so, how much headspace is ideal for the PRS/tactical style rifle?

Also, on a Remington, are there hard guidelines on bolt nose clearance? The worksheets that Bob Pastor developed with brownells produce .010 nose clearance and .010 circumferential clearance, but Hinnant's book says that half this distance is the MAX allowable. What is safe?

Many thanks as always,
Brian

 

[DAVETOOLEY]

Are you're comparing the go gage to a loaded round ? If it's factory ammo you don't know where the contact point is in the chamber. Many times there is an interference fit at the junction of the shoulder and neck. Each will have a different radius in that area. With that being said +.004" on the go gage won't hurt anything.
As far as clearance I like .010" in front and .015-.020" on the diameter. Remember nothing is concentric in a Remington. Even after truing. If the bolt nose touches the rifle will be as wild a billy goat.

 

[cast1]

Awesome Dave. Thanks for the advice. I am comparing the go gauge to a loaded round. Is there any worry about pressure in a setup where the bolt is basically compressing the round prior to firing?

 

[Danny1788]

I shoot for .002-.003" over go gauge when chambering and checking headspace with the barrel still in the lathe just hand tight. I use these little disc shims from McMaster Carr https://www.mcmaster.com/#disc-shims/=189l1s2 when checking head space and a go gauge. Then when the barrel is torqued down I'm in the zero to .001" range on head space with proper barrel to action thread fit.

This has worked very well for me when chambering, O I had to trim one down for the .473" bolt face because the 1/2" is the smallest they make.

 

[DAVETOOLEY]

Awesome Dave. Thanks for the advice. I am comparing the go gauge to a loaded round. Is there any worry about pressure in a setup where the bolt is basically compressing the round prior to firing?

As long as the neck isn't an interference fit in the chamber it's won't be a problem. Take a magic marker and mark the neck at the shoulder and cycle the bolt up and down several times. Bring it up through the extraction cam. I'll bet you see a ring around the neck. The simple test for neck clearance is will a bullet go back into a fired case with some room to spare.

 

[spife7980]

Awesome Dave. Thanks for the advice. I am comparing the go gauge to a loaded round. Is there any worry about pressure in a setup where the bolt is basically compressing the round prior to firing?

Not anymore than for those people who neck size only.

Make sure the neck has the diameter clearance to actually let go of the bullet is the only thing to worry about as Dave said.

 

[Supersubes]

So are you camming closed on these rounds, or bolt closes with no effort, and has no thrust(zero headspace)?

I believe there should be some space. If you have zero clearance, youre just asking for issues. A little dirt, a carboned up chamber, a slightly long round(or bigger radius at the neck/shoulder), all mean a hard close at some point. Great way to screw up a string of fire in a match.

I agree with dave, the .004 window is a perfectly acceptable area to run in, wherever you end up in it.