ShtrRdy
Well-Known Member
Wow, those are good runout numbers. It sure sounds to me like it has a bedding problem or the scope/mount isn't solid. Do you have another scope to try?
Concentricity Question
- Thread starter Deputy819
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Deputy819
Well-Known Member
I only loaded/checked 6 cartridges, but I when I saw how little runout there was I figured I would've seen it somewhere in those 6 if it was indeed a problem. The only other scope I have is currently resting atop my 338-06 and I'll take a beating before messing with it. When my Willis headspace gauge comes in on Monday I'm gonna do my best to try and crank out the most consistent ammo I can and see what happens. If the results continue to show INCONSISTENT groupings then this rifle is definitely going back to the Smith for a look-see. I'll even have him check the lapping job he did on the scope rings and everything......
Deputy819
Well-Known Member
Okay guys....I loaded up one and fired it out the back door (pouring rain here) just to check the concentricity of the neck of a FIRED & UNSIZED case. The gauge went to .001 as you can see. Would you guys have a problem with this if it was your rifle?
ShtrRdy
Well-Known Member
It wouldn't concern me. Let's hear what others think.
Barrelnut
Well-Known Member
Deputy,
Looks like you are measuring neck wall thickness with that setup? Not neck runout/concentricity.
Looks like you are measuring neck wall thickness with that setup? Not neck runout/concentricity.
Deputy819
Well-Known Member
@ Barrelnut
Yes. I read that after firing any imperfections on the outside of the neck would be pushed to the inside of the neck and that the result would give a fairly close indication of how well (concentric) the chamber was cut. I'm missing something, aren't I?
Yes. I read that after firing any imperfections on the outside of the neck would be pushed to the inside of the neck and that the result would give a fairly close indication of how well (concentric) the chamber was cut. I'm missing something, aren't I?
Barrelnut
Well-Known Member
@ Barrelnut
Yes. I read that after firing any imperfections on the outside of the neck would be pushed to the inside of the neck and that the result would give a fairly close indication of how well (concentric) the chamber was cut. I'm missing something, aren't I?
Interesting, that makes sense, I guess. Never tried to measure that directly. Usually that sort of gauge setup is used to measure the wall thickness of the neck. I think having the mandrel inserted in the neck would just cause a bit of neck wobble because the neck wall variance is now pushed to the inside? So not certain how valid that measurement is. Also, if neck wall thickness varies around the neck, you would think that brass spring back would vary around the neck too and skew the results somewhat. Seems the high spots in the neck would have to be turned, so the necks would be the same thickness all the way around.
Deputy819
Well-Known Member
That's kind of what I thought, too. Although, I must admit I hadn't thought of the brass springback concept, but that makes sense. I don't remember what website I read that on, but it also said that while it's not as precise as the indicator a Smith would use to actually check chamber concentricity checking an unsized/fired case neck would be the next best thing....
ShtrRdy
Well-Known Member
Oh, I see what Barrelnut said - it looks like your measuring neck wall thickness. I looked up the instructions on the Forster website and you need to use that silver blacket with the "V" cut into it for runout measurements.
Deputy819
Well-Known Member
Ha! You're right. Yeah, I just hit myself upside the head. I actually used that V bracket to check the runout on the loaded ammo earlier....wasn't paying attention to what I was doing when I posted that last picture. Please completely disregard that thing. Stand by....
Deputy819
Well-Known Member
There we go. That fired/unsized case didn't even go to .001.
Deputy819
Well-Known Member
10-4! Gonna wait till my Willis headspace gauge comes in tomorrow before loading anything else so I can make ABSOLUTELY sure my brass is consistently head-spaced from shot to shot. I'll check those loaded rounds and post my results. Thanks man!
Deputy819
Well-Known Member
Absolutely need Barrelnut and ShtrRdy on "standby" to make sure I use my equipment properly during the process.
