338 Fed Barrel Chambering issue

[mioduz]

I am chambering a barrel for 338 Federal. Ruger M77 action

I have the barrel trunion, and chamber all set using a Forster 308 Go and NO Go Guages.
Bolt handle drops Totally free on the GO gage, and locks up solidly on the NO GO

Everything felt really good but as a second check before removing the barrel from the lathe I dropped in a live (federal factory) round
It was VERY Tight. I could have forced it close.....but did not
I tried a second live round from box and same result
I pulled the bullet from the Federal Case and tested just the Case with same result
To check my sanity I have a second 308 PTG GO Gage that cleared smoothly

Not sure where to go with this next.

What do I need to learn to make this right? What did I do wrong?

 

[Supersubes]

Run the chamber out further. You didn't do anything wrong, accept you didnt account for how long the factory ammo is in the headspace dimension. There’s .005 between go/no-go. You probably have a few thou more to go to reach no-go. After opening the bolt on a tight case, does the case come right out of the chamber, or does it stick. If it sticks, its a diameter issue.


There are a few other things that could be going on, but we can go there when you respond if needed.

 

[mioduz]

There is .004 between my gages i beleive.

There is some "stick" on the live round (now empty case). I have the bolt stripped without a firing pin or extractor. I can pop the go gauge out with a short pop of compressed air down the muzzle. The brass i have to pull the action to get it back out

 

[Supersubes]

Figure out what that interference is first, as thats a diameter issue, not headspace. That case should fall right out with zero interference. Is this a saami reamer, or a custom? Hopefully not PTG. You can sharpy a case and see where its rubbing. If its the base of the case, you can hone that portion easily. Sometimes the reamer has too small a radius at the neck shoulder junction, and that fouls on the radius of the case neck/shoulder.

You have any shim stock to see how much longer the chamber is than your GO gauge? You may be several thou from the nogo. Go/nogo is somewhat arbitrary by the reamer manufacturers. The prints call out a .010 window for headspace which would be considered GO at the short end, and “field” at the long end. The reamer manufactures split this in half for nogo

If you have a variety of factory ammo, id check all of them. End of the day, if factory ammo is the diet, and its all long compared to a GO gauge, the chamber should be run to the ammo, not a gauge.

 

[Steel head]

Figure out what that interference is first, as thats a diameter issue, not headspace. That case should fall right out with zero interference. Is this a saami reamer, or a custom? Hopefully not PTG. You can sharpy a case and see where its rubbing. If its the base of the case, you can hone that portion easily. Sometimes the reamer has too small a radius at the neck shoulder junction, and that fouls on the radius of the case neck/shoulder.

You have any shim stock to see how much longer the chamber is than your GO gauge? You may be several thou from the nogo. Go/nogo is somewhat arbitrary by the reamer manufacturers. The prints call out a .010 window for headspace which would be considered GO at the short end, and “field” at the long end. The reamer manufactures split this in half for go/nogo

If you have a variety of factory ammo, id check all of them. End of the day, if factory ammo is the diet, and its all long compared to a GO gauge, the chamber should be run to the ammo, not a gauge.

Before I cut a chamber I always measure the go gauge to the brass or ammunition that I plan on using.
In the end the brass dimensions are more important than the go gauge dimensions.
It’s a nice convenience when the go gauge in a few thou bigger than the brass/ammo.

 

[cb186]

Use a piece of Scotch tape on the Go gauge. Its .002" and lets you dial in the headspace more accurately. I don't even bother with No-Go gauges.

 

[celltech]

A cheap spark plug feeler gauge is great for small pieces of shim stock...

 

[Wannashootit]

Whenever I want to know the exact clearance between boltface and gauge, I stick a piece of Plastigage on the boltface.
I think C. Dixon mentioned he uses a piece of soft solder, then mikes it.
Tape on the gauge gives a good approximation, but Plastigage tells me exactly what it is.