Gunsmithing Tight chamber?
- Thread starter Dlwheel
- Start date
Go +.0005” will drop on a go gauge and not on a no-go. In spec is in spec.
Run it! Built numerous guns that are set up go+.0005. Nesika Bay Precision set up every rifle they built like this. World record guns!
Well if it is a .308 win and you want to be able to chamber third world 7.62x51 ball ammo I would say that it is a bad plan, otherwise Rubicon is 100% correct
Understood. It just seems to me that if virgin brass comes in at go spec or slightly less, that chambering .0005 from go would eliminate any stretch of the virgin brass. However, as I have measured some of the 6GT brass at a recent match, it is surprising to me to see chambers at .004 - .0045. Was just curious to understand if there was a reason the chambers would be cut that long or it is just a sloppy job.
A bad plan would be shooting third world .308 in a custom built gun.
So you were comparing fired cases to a Go gauge?
Well, when i chamber at go + half thou, my fired brass measures the same. I was just Wondering why a smith would chamber at go + .004.
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i understand, but what I’m asking is how you determined the 6gt brass you measured from multiple guns was plus .004-.0045?
Acording to the reamer spec using .350 gauge, the spec is 1.360” (min/max of R=1.360). That is precisely what I get when I measure the go gauge. When i measure my fired brass it comes in +/- .0005 of that spec. However I measured some fired brass that was 1.3645.
Again, in spec is in spec. I don’t have the 6GT print in front of me at the moment, but if there’s .004” between go/no-go, anywhere in between there isn’t sloppy, it’s in spec. Measuring brass, fired from different rifles, chambered with different reamers, checked with different gauges, isn’t a clear representation of chamber quality or spec.
Tolerances are there for a reason. Now, if you want tighter tolerances than the standard/SAAMI, that’s up to you and it needs to be discussed with your builder in advance, or dealt with accordingly if you’re your own builder.
OP hadn't specified purpose of rifle. Not all custom rifles are precision bolt gun. If you are making a shtf scout gun/jacknof all trades type rifle, ball ammo might be on the menu.
Gas guns are another area where chambering go+.002 is probably a good idea....
Understood. The 6GT reamer spec is fairly narrow as it is very new. only JGS & PTG are doing reamers for it and the prints are the same. Was just wondering if there was any reason for cutting a chamber at the far edge of the spec vs. the short edge.
For sure. I should have specified that this is for bolt guns. Thanks for the clarification.
I recently had issues with my 6XC with Peterson brass. After 3 firings bolt lift is chronic. Very frustrating. No matter how much I bump and/or reduce load there is unwanted bolt lift. One of my thoughts was that the Peterson brass didn’t like the tight chamber. Just a thought. Since I’m using ’Tubb brass’ and Tubb sizing die, I figured that a bad die would not be the issue.
My guess is they are not trying to do anything other than be within the allowed spec. I doubt many are standing at their machine saying “I think I’ll make this one go +.0045””
Got it. Since I only do my stuff and a few others, I’m pretty anal about indicating and chambering. My living is not chambering barrels.
You need to polish your chamber.. your chronic bolt lift problem will disappear.
dies are the big reason running headspace at go causes issues. a lot of mfg dies wont bump shoulders at go and the die will need shortened or a custom die made. in reality there is no reason to set it at go on a field or comp type rifle. go plus .002 is where I typically set them. keep in mind as well that you will have some loss from crush/torque typically.
