308 headspace

[Halcyonhal]

Hi,

I have an old ruger american 308 that I switched to a preferred barrel blanks (the company) prefit barrel.

I installed it myself following their YouTube and some clymer go/no go gauges. The fitting went just fine (closes on go, doesn’t close on no go).

Testing the rifle using federal gold medal match 178gr and there are clear over pressure issues (swipe marks on the case head, heavy bolt lift). I check the headspace using a hornady OAL gauge and a modified case and the headspace is definitely *way* too tight. The federal factory ammo is be being jammed against the lands.

Can anyone suggest what to look at first? Tempted to get another set of go/no go’s but not sure what else to look for. Current set are 1.630”/1.634” are described as “match spec”.

many thanks
Ben

 

[celltech]

Sounds like the new barrel has a shorter throat than the Ruger OEM...I think your headspace is fine. Talk to PBB about what specs they make the chamber to...

 

[iceng]

Remove ejector pin, remove firing pin, cycle a live round in, close bolt, extract. It should not be hard to close. The bolt handle should drop under its own weight. If not, there could be an issue.

Texta (sharpie) on the bullet, and it may show some drag marks on lands, this will indicate a shorter throat.

I have a 308 reamer spec'd for 155s and 175s. A loaded 178gr will chamber in the 155 chamber, but certainly is jamming on lands. Causes pressure spikes and hard bolt lift.

 

[308pirate]

Testing the rifle using federal gold medal match 178gr and there are clear over pressure issues (swipe marks on the case head, heavy bolt lift). I check the headspace using a hornady OAL gauge and a modified case and the headspace is definitely *way* too tight. The federal factory ammo is be being jammed against the lands.

You don't know what you're talking about Headspace has nothing to do with how far it is from bullet ogive to the lands.

 

[Halcyonhal]

Sounds like the new barrel has a shorter throat than the Ruger OEM...I think your headspace is fine. Talk to PBB about what specs they make the chamber to...

Many thanks cell tech. Have sent them an email.

 

[Halcyonhal]

Remove ejector pin, remove firing pin, cycle a live round in, close bolt, extract. It should not be hard to close. The bolt handle should drop under its own weight. If not, there could be an issue.

Texta (sharpie) on the bullet, and it may show some drag marks on lands, this will indicate a shorter throat.

I have a 308 reamer spec'd for 155s and 175s. A loaded 178gr will chamber in the 155 chamber, but certainly is jamming on lands. Causes pressure spikes and hard bolt lift.

Many thanks… will try those steps out in the morning.

 

[Halcyonhal]

You don't know what you're talking about Headspace has nothing to do with how far it is from bullet ogive to the lands.

Yeah, you’re right. I didn’t explain what I was seeing with the OAL gauge very well… mind you, you didn’t add anything to conversation either

the other posters have been helpful and have me looking in the right direction I think. Thanks anyway.

 

[918v]

Try seating the bullets deeper.

 

[f>b25]

HS is the distance of bolt face to brass base; hornady OAL gauge is not designed to measure HS. The problem was not your explanation. You checked with go/no go and all was copacetic yet, .004 b/w go and nogo is a surprisingly tight tolerance. Given some of the confusion, can you describe how you measured the go/nogo gauges or is the measurement stamped?