Interesting results after grouping my standard and BFH BCM barrels - update 02 JUN

[Wake27]

Coming late to the party, but I got a very decent group at 100 with 77gr Black Hills OTM, around 2" ... using only an Aimpoint Comp M5 and 3x magnifier.

I haven’t been able to find BH in stock at my typical vendors the few times I’ve ordered match ammo recently. I was actually hoping to find that one first and settled for the FGMM, but that has typically done very well aside from today, even in the suspect barrel.


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[alx01]

I'm a bit confused by the whole storyline now and what was causing the accuracy issue.

Please correct me if I'm wrong anywhere. To recap:

======================
OP tested a well broken-in (over 1k rounds) BCM upper with various loads at different distances (most common being 100). At least another qualified person confirmed really bad accuracy past 200.
Poor accuracy was observed using both 1-6 Razor AND another scope.
Lower had a Geissele Trigger from what I recall (might not matter that much).
Some loads fared okay 2.5-3MOA, some did around 4 MOA at 100.

OP also tested a brand new KAC upper (not broken-in) on the same lower, same lots of factory ammo, and the same Vortex 1-6 scope and was getting better than 1MOA on many groups, and generally a much better groupings even in the worst case scenario. <=== THAT ALONE WOULD INDICATE TO ME THAT THE PROBLEM IS NOT THE SCOPE. Am I missing something here or you did this test with another scope?

BCM possibly replaced a barrel in the upper, but OP was still getting roughly a 2-3 MOA groups with Razor 1-6. From what I understand this is a slight improvement over the original groups, but can also be indicative of a subjectively better shooting day.
Groups improved using EOTech, some significantly so. That can also indicate a barrel breaking in vs earlier groups with a Vortex scope.
============


I don't know if you can purely blame this on a damaged Razor scope. There are just too many variables to positively identify the issue (barrel, ammo, scope, something else or a combination). Maybe a new barrel is just getting broke in, maybe you shoot better with EOTech. Maybe 2-3 MOA is just as good as you'll get out of this CHF barrel. Not a KAC barrel accuracy you were getting, but not too bad for a combat rifle IMHO.

Try to narrow down the issue:
- If you have another scope try using it side by side with Razor using the ammo from the same box
- Don't use 10 different ammo combinations, initially stick to 3 factory loadings you're comfortable with or had the best results so far
- Try using a single magazine for everything and shooting a larger group: warm-up 5 rapid rounds, 10 round group, scope change, again 5 rapid rounds followed by a 10 round group. <=== that might be an overkill, but at least that would level a playing field between the groups as much as possible.
- Again, maybe not an appropriate suggestion for your application, but try a regular M855 62gr just for curiosity's sake to see what you'll get with it.

[Wake27]

That’s mostly correct. The FGMM 77gr was supposed to be my control group since I had shot it in both the original BCM upper and the KAC. It was the only load that shot well in the BCM but as you can see, shot terribly in it now that I got it back from BCM. I was planning on shooting it with the EOTech so I could directly compare it but apparently I forgot. Same with the PPU.

You’re also right that the KAC shot very well with the Razor, but I don’t have a lot of groups on that one to know for sure because it was having feeding and extraction issues and is back at the factory. I guess there is a chance that the first few groups through the BCM were bad because it was a new barrel that needed break in, but if that’s the case, the break in only took about 30 rounds and just happened to be complete at the same time I switched optics. Possible, but seemed doubtful to me. Looking back through the targets again though, aside from the group where I mentioned that I had a faster cadence and the following one that was shot with Freedom reman, the groups got better the more I shot it so maybe the break in does have some validity. Pair that with me warming up as a the shooter and maybe that’d explain it?

I had so many different loads because I wanted to test a wide variety and see how it’d perform so that it couldn’t be blamed on the ammo. This wasn’t as helpful as I’d hoped since I’ve forgotten to shoot certain combinations as I mentioned. For the future I’m sticking to FGMM as the quality match round, Win 62gr OTM as my training ammo, and I have enough PPU to burn through that I can continue to test that until it’s gone. My HD gun is loaded with 75gr Gold Dots but that’s hard to find in stock so I don’t plan on using anymore of it for this.

Unfortunately this is my only LPVO and mount. Eventually I want one more AR to put another one on, but that’s a ways down the road.

The thing that still confuses me and was making me think it was the scope is the dramatic shift in the groups from the BCM that happened before and after its visit to the factory. It’s only happened with that upper and that optic combo, but like I said, I’m fairly confident that BCM replaced the barrel so that’s essentially two different uppers that it’s happened with. I’ll shoot BCM an email to see if they can confirm that the barrel was replaced.



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[Wake27]

Double.

[Wake27]

BCM got back to me and confirmed that they did replace the barrel and gas tube.


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[RHINOWSO]

I'm a bit confused by the whole storyline now and what was causing the accuracy issue.

////////////////////

There are just too many variables to positively identify the issue (barrel, ammo, scope, something else or a combination). Maybe a new barrel is just getting broke in, maybe you shoot better with EOTech. Maybe 2-3 MOA is just as good as you'll get out of this CHF barrel. Not a KAC barrel accuracy you were getting, but not too bad for a combat rifle IMHO.

////////////////////

Try to narrow down the issue:
- If you have another scope try using it side by side with Razor using the ammo from the same box
- Don't use 10 different ammo combinations, initially stick to 3 factory loadings you're comfortable with or had the best results so far
- Try using a single magazine for everything and shooting a larger group: warm-up 5 rapid rounds, 10 round group, scope change, again 5 rapid rounds followed by a 10 round group. <=== that might be an overkill, but at least that would level a playing field between the groups as much as possible.
- Again, maybe not an appropriate suggestion for your application, but try a regular M855 62gr just for curiosity's sake to see what you'll get with it.

I had a long reply typed out last night but an internet glitch dumped it and I didn't retype, but basically this.

Minimize the variables with one rifle, one optic, and far fewer types of ammo.

Also remember a box test can confirm if your scope is toast. I'm a simpleton so I start at 25 yards for accuracy and a box test. Even a shit 4 MOA barrel will have rounds inside an inch at 25 and you can rapidly confirm / deny an optic - mount issue.

[Eurodriver]

I had a long reply typed out last night but an internet glitch dumped it and I didn't retype, but basically this.

Minimize the variables with one rifle, one optic, and far fewer types of ammo.

Also remember a box test can confirm if your scope is toast. I'm a simpleton so I start at 25 yards for accuracy and a box test. Even a shit 4 MOA barrel will have rounds inside an inch at 25 and you can rapidly confirm / deny an optic - mount issue.

I like you.

[vicious_cb]

That’s mostly correct. The FGMM 77gr was supposed to be my control group since I had shot it in both the original BCM upper and the KAC. It was the only load that shot well in the BCM but as you can see, shot terribly in it now that I got it back from BCM. I was planning on shooting it with the EOTech so I could directly compare it but apparently I forgot. Same with the PPU.

You’re also right that the KAC shot very well with the Razor, but I don’t have a lot of groups on that one to know for sure because it was having feeding and extraction issues and is back at the factory. I guess there is a chance that the first few groups through the BCM were bad because it was a new barrel that needed break in, but if that’s the case, the break in only took about 30 rounds and just happened to be complete at the same time I switched optics. Possible, but seemed doubtful to me. Looking back through the targets again though, aside from the group where I mentioned that I had a faster cadence and the following one that was shot with Freedom reman, the groups got better the more I shot it so maybe the break in does have some validity. Pair that with me warming up as a the shooter and maybe that’d explain it?

I had so many different loads because I wanted to test a wide variety and see how it’d perform so that it couldn’t be blamed on the ammo. This wasn’t as helpful as I’d hoped since I’ve forgotten to shoot certain combinations as I mentioned. For the future I’m sticking to FGMM as the quality match round, Win 62gr OTM as my training ammo, and I have enough PPU to burn through that I can continue to test that until it’s gone. My HD gun is loaded with 75gr Gold Dots but that’s hard to find in stock so I don’t plan on using anymore of it for this.

Unfortunately this is my only LPVO and mount. Eventually I want one more AR to put another one on, but that’s a ways down the road.

The thing that still confuses me and was making me think it was the scope is the dramatic shift in the groups from the BCM that happened before and after its visit to the factory. It’s only happened with that upper and that optic combo, but like I said, I’m fairly confident that BCM replaced the barrel so that’s essentially two different uppers that it’s happened with. I’ll shoot BCM an email to see if they can confirm that the barrel was replaced.



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This thread has become pretty confusing.

So let me get this straight, you got the BCM rebarreled and the TLDR results are basically you are shooting better groups with the Eotech than the Razor @ 50yards?

[Wake27]

This thread has become pretty confusing.

So let me get this straight, you got the BCM rebarreled and the TLDR results are basically you are shooting better groups with the Eotech than the Razor @ 50yards?

Very basic summary of it, but yes. I started with a ton of variables because nothing in the equation was known to be good. Limiting myself to few variables would have been a waste of time since anything could have been the problem. The way I see it now, there are two possibilities:

1. The new BCM barrel needed to be broken in which explains why my first shots out of it sucked. However, that break in only took about 30-35 rounds, at which point the groups tightened significantly. And the better groups just coincidentally corresponded very closely with switching from the Razor to the EOTech.

or

2. Something in the optic combo is off because I’ve only gotten a significant shift in POI, mid-group, with the Razor. The fact that I put up solid groups with the Razor and my KAC would contradict this theory, but there are only two five round groups that actually fit this criteria. I only had three rounds of IMI so that group doesn’t mean shit. The PPU groups were bad, but I had blamed that on the ammo, until I shot the re-barreled BCM and still saw that same shift in other loads.

Either way, nothing is consistently off, it’s only maybe half of the time or so. But seeing as how the Razor and G mount did take a solid beating on concrete, and the POI shift has only happened with that optic, I think that’s the problem. Between talking to Jimmy from Vortex and the fact that my next range day won’t be until the 21st, I’m probably just going to send the Razor to them to get checked.

At this point, I’m not sure that the BCM was anything worse than a 2 MOA gun.




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[SomeOtherGuy]

The way I see it now, there are two possibilities:

1. The new BCM barrel needed to be broken in which explains why my first shots out of it sucked. However, that break in only took about 30-35 rounds, at which point the groups tightened significantly. And the better groups just coincidentally corresponded very closely with switching from the Razor to the EOTech.

or

2. Something in the optic combo is off because I’ve only gotten a significant shift in POI, mid-group, with the Razor. The fact that I put up solid groups with the Razor and my KAC would contradict this theory, but there are only two five round groups that actually fit this criteria. I only had three rounds of IMI so that group doesn’t mean shit. The PPU groups were bad, but I had blamed that on the ammo, until I shot the re-barreled BCM and still saw that same shift in other loads.

***

At this point, I’m not sure that the BCM was anything worse than a 2 MOA gun.

Chrome lined barrels don't really break in much, and not to the extent I would expect a measurable difference in group size.

The Razor is a quality scope, but ANYTHING can break, so it's worth looking into. Not my first guess though.

How good are you at keeping a repeatable eye position relative to the scope? And do you find the Razor's crosshairs too thick for the type of targets you're using?