Criterion 300WM Neck Clearance

[brant89]

I have a Criterion 300WM SS Match barrel that I've had for a couple years and have gotten decent accuracy out of it but nothing to write home about. I recently had a piece of brass with a small nick in the case mouth (I messed it up during loading) that wasn't bad enough to scrap but I knew would hurt my accuracy. However, to my surprise it wouldn't even chamber which got me to questioning my neck clearance. My loaded case necks are measuring .335-.336 and my fired case necks are measuring .337-.338. I understand that there will be some spring back, but this seems pretty tight to me. At this point I'm wondering if this could be a contributing part of my accuracy issue. Norma brass, FL sized just enough to chamber, 4 firings, zero case growth up to this point (about .001 per firing). I ordered a 30 cal neck turning pilot today but I'm wondering if I should just skim them (can't hurt) or actually remove a couple thou. Thoughts?

 

[JMW67]

can you slide a bullet back into a fired unsized case mouth

 

[brant89]

I can but it's VERY tight.

 

[JMW67]

take a couple thou off and try again I bet your accuracy will be better thats one thou per side for a total of two

 

[brant89]

I've requested the reamer spec from Criterion but my experience has been that they don't seem to respond much to emails.

 

[JMW67]

You may have to take a little more after you try but it easier to take more then to put it back on

 

[GLTaylor]

A safe rule of thumb for a hunting rifle is .004 neck clearance from loaded dia to fired diameter. A bit more won't hurt. Surprised you haven't seen pressure problems...

 

[brant89]

77.2gr of H1000 under a 200 gr ELDX is getting me 2940fps from a 26" barrel with no pressure signs. Thought that was pretty much par for the course.

 

[brant89]

I only recently dived deep into the details of neck clearance and neck turning during my 22BR build. Previous to that I never would have questioned it.

 

[brant89]

Is Norma brass usually pretty thick or do I have an unusually tight neck?

 

[GLTaylor]

Brass varies in neck thickness from brand to brand and sometimes (lesser often) from lot to lot. You need a ball mike to check neck thickness so you don't get in trouble with a tight neck. It'll also tell you how much you've removed when turning necks

 

[DJ Fergus]

A safe rule of thumb for a hunting rifle is .004 neck clearance from loaded dia to fired diameter. A bit more won't hurt. Surprised you haven't seen pressure problems...

From what I understand, even alot of match shooters are getting away from tight necks & going for .004" clearance.

 

[brant89]

How much spring back do you think I'm getting after firing?

 

[GLTaylor]

.001+ is common. The only folks i know of that still routinely shoot true "tight" necks are benchrest shooters.