Originally Posted by
alx01
@Wake27,
It's a very interesting result you got. I don't think this is all that unusual to have groups open up past 200-400m depending on the barrel wear. In my experience it is typically indicative of a normal wear (barrel throat erosion) but I would expect it to occur no sooner than 10-12k rounds for a CHF barrel. That's how you get stories of people going 40k rounds on a CHF barrels - they rarely shoot it beyond 100m at that round count. You shouldn't have any of those issues (shooting 8-10moa at 200) before 10k rounds on a non-abused quality barrel, period. I actually had an issue like this before, which may be why I'm overhtinking this. There's a long thread on it here, but the Noveske upper this one replaced had a barrel with defective chrome lining and that was a mess. It wouldn't even consistently group at 100 yards though, so this definitely isn't on that level.
Maybe I have low standards for accuracy, but I think that 2-3 MOA out of a regular production barrel is pretty good. This is what I meant by overthinking. There are so many claims of 1 MOA guns on the interwbz without any proof that maybe I just have higher expectations than I should. But, since the standard barrel consistently shot better, I don't know. I know every barrel is a law unto itself and I shouldn't necessarily complain about a consistent 2 MOA gun, but I really would've preferred 1.5 or so, and who knows how it groups beyond 100 (which is the real question now).
I would personally check things in the following order:
- change ammo brand, try lighter a grain or a different bullet type. I wanted to test more options, but I think there is a good bit up there already. Three different brands and two different bullet weights, though they are both heavier. That's why I made sure I shot the 69gr stuff early, I wanted to mix it up from the 75 gr.
- scope mount Robb used an entirely different scope and mount.
- scope itself (reticle shift, etc.). Try doing a walkthrough on a target using turret adjustments: zero the scope, then select the initial point of aim and continue by adjusting in 1 moa increments left/right and up/down and repeat so you draw a square on a target using bullet holes. See above. Also, I experienced no issues shooting my backup gun with the same scope and mount I used in the class, though I shot purely for groups and didn't make any adjustments. The Razor did take a beating in December, so this would be a good thing to test regardless of what the barrel is doing.
- barrel nut I assume Robb checked this, but don't really know so that's a good point.
- check chrome lining for flaking/cracks, check throat erosion The bore is a bit cloudy, but smooth and nothing like the Noveske that I mentioned above. That had visible cracking.
- muzzle device torque Also an assumption that Robb checked this, I'll have to ask.
- change bolt - maybe that will tighten up a headspace (never seen this to be an issue personally, but heard somebody else mention that) Didn't even consider this since I don't remember ever seeing anyone discuss it, but I know headspace can be an issue and would've been an easy thing to check with my back up right there.
Keeps us posted. This is a very interesting case.
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