Rifle diagnostics

[DpdG]

I would also suspect some sort of internal failure in the scope, but just to be sure- no chance of some other variable between outings? I had a known decent nitrided barrel slowly degrade accuracy over outings and I was at the point of suspecting the worst. I disassembled the upper, thinking something had worked loose, but it turned out I had A) gotten lazy about cleaning so it was about 1k since last time I inspected the bore, B) been shooting "cheap" 2020 crisis ammo, and C) put that upper on a full auto lower for a few mags (200ish rounds over a half hour or so). By all those powers combined, the bore was massively fouled with the usual carbon plus pretty noticeable copper fouling.

My suspicion is that a nitrided barrel might be slightly more prone to copper fouling than chrome, especially with full-auto fire. Additionally, this was the first 1k through it and it hasn't shown a propensity for copper fouling since, so there may have been some rough spots getting smoothed out. Either way, I was able to restore its previous accuracy with a deep cleaning, including an ammonia based copper solvent and judicious use of a bronze brush.

[Wake27]

This is what it has done with 50 jhp and 50 vmax the two marked above the jhp is when I was adjusting the group. I’m not saying your wrong but it’s done cloverleaf so at 50 yards with other ammo. I still thinks it’s a bit odd to have one right where it’s supposed to go and two about 1”-1.5” to the right.

These groups were before or after you started having issues?


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[Grouse870]

The cloverleaf groups were before

[Lost River]

A few things:

At 50 yards I would shoot a few 3- 5 shot groups with iron sights to see what they look like and compare them in size to what the groups made with the scope looked like.

Find a scope of known quality, and put it on the rifle, and shoot at least 3-5 shot groups. Preferably further than 50 yards, but if that is what you have to work with, then roll with it.

If you are still trying to figure out if the scope you have mounted is causing issues, shoot a box drill.

If you are not familiar, you can youtube it, though I will explain my method.

Shoot an initial 3 shot group at your zero. This is not a test of group size, but of scope tracking and repeatability (so 3 shots are fine). Go up 4 mils/moa and shoot a group. Go right 4 mils shoot a group, go down 4 mils, shoot a group, then go left 4 mils and shoot a group. If your optic is tracking correctly, your last shots will be right back where you started from, and you will have shot a "box" type pattern. On a larger target/further away, you can measure the adjustment to make sure the adjustments are accurate. It can be very telling.

Now besides optic issues, you can also look at your mount and see if the optic mount is still tight, checking to see if the screws have become loose. I use marking paint on mine once they are torqued, so I can see at a glance if they have come loose.

Since this is an AR, one thing that can and does on occasion happen, though rarely, is barrel nuts come loose, especially after hard use, heavy firing, etc. I have seen it. Not often, but it does happen. It is far down on the probability list, but it is something to keep in mind if the optic and ammo proves to be OK.

Ammo is another area, but first I would confirm the optic. Buying a 10X or 20X SWFA and putting it in a good mount to use as a test optic for various platforms would not be a bad thing.

Hope this helps.

[Wake27]

I too would look at the optic, hard. I had a similar issue with a Razor after it had taken a solid fall. I thought it was good because I could still group it right after the fall but really struggled with consistency down the road. I think I’d often get three solid rounds and then a secondary group with the remaining two off to the side. This was at 50m and 100m I think too. While I agree that pushing it further can be worthwhile to a shooter, if you’re suddenly having issues at 100m or less, there’s a problem and I don’t know that going further will help you to diagnose it.

After doing a lot of troubleshooting (to include BCM replacing my barrel out of precaution), it turned out to be a detached reticle. Vortex of course took care of it.

You can probably find the thread I had on M4C detailing it, there’s a bunch of similar recommendations I think so it may be helpful. I’ll try when I get time if I remember.


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[TOTS]

While Vortex makes a good product and has amazing customer service, it’s not uncommon for the lower price point optics to need the CS.

However. Absolutely the first thing I would check is the torque on all the fasteners used to mount the optic.

I will add though, that when I’ve experienced the scope body slipping in the rings, the group size stays small but the poi has a repetitive shift. Which I don’t see in your instance.

[Stone]

Whats the twist rate of the barrel? Also, I would shoot 10 shot groups when shooting for accuracy and trouble shooting. It tells a much better story than 3 shot groups. How many total rounds on the barrel?

[Grouse870]

It’s a 8 twist barrel. Probably 1500ish. Agreed I’m going to try and mess with it after hunting season.