I have an Impact action with Stuteville chambered 6bra barrel that I just put on. The bolt will not close on a Manson 6bra go gauge. I put a piece of Virgin Lapua 6br brass in and the bolt closes with a bit of resistance. Thoughts?
Bolt not closing on 6bra go gauge
- Thread starter shaun1826
- Start date
Generally speaking, you’ll get better results with headspace gauging if you remove the extractor and the ejector. Sometimes you can start the bolt closed with the gauge already under the extractor, but in any case make sure you’re not getting any interference there, that’s causing the issue. Check out the attached picture for information on the difference between ackley improved and parent case go gauges. That was why I asked that question.
Too much headspace is a much bigger concern than too little. If the bolt closes on the brass, with a little resistance, you are fine. It should be a .004” crush fit. Measure a fired case (or better yet a 2x fired case) to learn your chamber’s actual dimensions.
Too much headspace is a much bigger concern than too little. If the bolt closes on the brass, with a little resistance, you are fine. It should be a .004” crush fit. Measure a fired case (or better yet a 2x fired case) to learn your chamber’s actual dimensions.
Think the slight resistance on Virgin Lapua brass is good enough?
I used a comparator tool and checked the go gauge, no go and Virgin Lapua shoulders
No go = +.006 more than go gauge
go gauge = +.004 more than Lapua brass
No go = 1.2135
Go gauge = 1.2075
Virgin 6br Brass = 1.2035
As oregun said, an ackley improved should be a .004” shorter than the parent carriage neck shoulder junction to ensure it’s held against the bolt face to properly blow the shoulder out.
That it’s got slight resistance on a virgin case sounds optimal to me.
That it’s got slight resistance on a virgin case sounds optimal to me.
If it closes on your brass I’d run it, only issue I see is sizing die might be a bit of an issue but that’s easily remedied.
The original design of the 6BRA was to use the 6BR GO gauge as the BRA GO gauge. At some point the spec was changed to the "more traditional" spec of ackley improveds which is headspace of parent case -.004". We continue to chamber 6BRAs with the original spec meaning use 6BR GO as your BRA GO. All in all, if your virgin brass chambers properly, go with it, and set your sizer appropriately
Try coating the entire case with a black marker & try again to see where the case is tight. Don't assume it's always headspace that is the issue as the case web is always touching in my chambers.
You never know. If they keep all their BRA reamers together, the machinist may have accidentally picked up the die reamer.
The chamber is maybe just a tad shallow might be all. Never know, could be a good thing so long as the brass fits.
Everything I've seen on the 6BRA since it became popular around 2017 has suggested that the 6BRA should be chambered 0.004" short of a 6BR go gauge, like any traditional Ackley cartridge, so that it is a crush fit on virgin brass. I don't know what the OG benchrest guys like Sam Hall and other BR shooters did 10 years ago when they were experimenting so I can't say what the "original" design is. I can say that when Alex Wheeler and Tom Mousel and others were popularizing the cartridge in the BR world in 2017 and it started setting world records, the recommendation was 0.004 crush on a BR go gauge. That would mean that the 6BR go gauge should be used as the NO go gauge for 6BRA.
All my 6BRA Barrels have matched this spec, including one of my Stuteville barrels.
From your description it sounds like your Stuteville barrel is perfect. Don't know if your Manson gauge matches the BR -0.004 spec or not.
All my 6BRA Barrels have matched this spec, including one of my Stuteville barrels.
From your description it sounds like your Stuteville barrel is perfect. Don't know if your Manson gauge matches the BR -0.004 spec or not.
