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

AR/M4 AR Technical Discussion
1

I took an LPVO class a few weeks ago and developed some concerns about the new upper I was using. It had about 1k rounds through it, but I hadn’t gotten a chance to shoot it further than 50m at that point. The 100m groups we started out with were around 2-3 MOA, which was a little disappointing but I assumed it was either me or the older PPU 75 gr BTHP ammo that I was shooting. As we pushed the distance, it got worse, to the point that I couldn’t make consistent hits on steel at 200 and 300m. The instructors started watching me a lot closer and looking at the scope and mount to see what could be the problem. There were some theories that the 1.93 mount was making it hard for me to get a consistent cheek weld, but I wasn’t convinced that was the case, especially after one of the instructors shot it on paper and got some very odd results. Knowing that it’d be a while before I could do it, I sent the upper and scope to Robb Jensen, since he assembled it for me. His target is below, and he stated that he was surprised that it didn’t shoot better based off of his own BFH barrels.

Upper: BCM BFH
Optic: Razor HD 3-18x
Ammo: Hornady 75gr BTHP
Distance: 100 yards
Results: 1.99" five round group, 2.36" 11 round group.

I wanted to do some more testing on my own so after another week I finally got to the 100 yard range with my backup AR, a factory BCM ELW-F with original KMR. I think the round count is around 2,500 and while I’ve shot it at 100m before, its always been with an Aimpoint. I brought my primary lower with SD-E and swapped the uppers and Atlas bipod, but shot both optics. I also used a rear bag. Ideally I would’ve shot every type of ammo (I had several that I didn’t get to) at 50 and 100 with both uppers using the Razor, but I ran out of time. All groups were five rounds. Here are my results.

Target 1
Upper: BCM ELW-F
Optic: Razor 1-6
Ammo: FGMM 69 gr.
Distance: 50 yards
Results: 3/4"

Target 2
Upper: BCM ELW-F
Optic: T-2
Ammo: PPU 75 gr.
Distance: 50 yards
Results: 1 1/4"
Note: Ignore group one, that was my first one of the day so I shot it at 25 yards

Target 3
Upper: BCM ELW-F
Optic: T-2
Ammo: Gold Dot 75 gr.
Distance: 50 yards
Results: 1 1/4" for both
Note: windage zero target

Target 4
Upper: BCM ELW-F
Optic: Razor 1-6
Ammo: FGMM 69 gr.
Distance: 50 yards
Results: 1 1/8" and 1 1/2"
Note: elevation zero target

Target 5
Upper: BCM BFH
Optic: Razor 1-6
Ammo: FGMM 69 gr.
Distance: 50 yards
Results: 1 7/8"

Target 6
Upper: BCM BFH
Optic: Razor 1-6
Ammo: FGMM 69 gr.
Distance: 100 yards
Results: 1 3/4"

Target 7
Upper: BCM BFH
Optic: Razor 1-6
Ammo: PPU 75 gr.
Distance: 50 yards
Results: 1 5/8"

Target 8
Upper: BCM BFH
Optic: Razor 1-6
Ammo: PPU 75 gr.
Distance: 100 yards
Results: 2"

I thought I had shot the PPU with the Razor on the ELW-F upper so that I’d have two direct comparisons, but apparently I only shot it with the Aimpoint which means that targets one and five are the only direct comparisons. The ELW-F shot a 3/4" group whereas the BFH shot a 1 7/8" group. Also, while not a direct comparison, targets two and seven are similar and interesting because the ELW-F with a T-2 shot a 1 1/4" group while the BFH with the Razor shot a 1 5/8" group. So in the one direct comparison, the ELW-F with double the round count outshot the BFH barrel by a singificant margin. It also shaved off almost half an inch in the next closest comparison, despite the significant difference in magnification. Finally, the groups from the ELW-F are on average tighter with one flier, whereas the groups from the BFH are all fairly dispersed.

I’m surprised at how well the BFH barrel shot, considering how it did at the class. I was actually expecting five MOA groups because of how it did on paper when the instructor shot it. So here are some questions that I have.

  1. If I have an upper that will shoot 2" at 100 yards, how well does that translate to 4" at 200 and so on? I know its not a perfect science, but are there instances where it would suddenly open up considerably, like 6-8" at 200 yds?
  2. What’s the consensus on a newish BFH barrel grouping no better than 2 MOA? I wouldn’t expect 1 MOA, especially knowing that BCM barrels are often out shot by DD and Colt, but I’m pretty happy with the performance of the standard barrel, just not the BFH.
2

You won’t know how it will perform at any range until you actually test it at that range. In theory, a barrel/ammo combination that shoots 2 moa at 100 yards should shoot 2 moa at longer ranges. But that depends on what distance a bullet “goes to sleep”, how much precession it has and how close to destabilizing it is at any given point. Many experienced shooters will tell that you can’t tell how precise a rifle really is until you shoot for groups at two or three hundred yards.

In short yes, there are instances where groups will suddenly open up at longer ranges. You won’t know what they are until you shoot.

3

The “in theory” part goes along with; “in a perfect world/given ideal conditions”, re X-MOA being consistent at extended range.
We try and shoot load/rifle at 300 prone/benched to get some idea of what to expect.

4

@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.

Maybe I have low standards for accuracy, but I think that 2-3 MOA out of a regular production barrel is pretty good.

I would personally check things in the following order:

  • change ammo brand, try lighter a grain or a different bullet type.
  • scope 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.
  • barrel nut
  • check chrome lining for flaking/cracks, check throat erosion
  • muzzle device torque
  • change bolt - maybe that will tighten up a headspace (never seen this to be an issue personally, but heard somebody else mention that)

Keeps us posted. This is a very interesting case.

5

Yeah that’s what I kind of expected. Still, the groups that the instructor shot were at 100m and were very inconsistent. The first was 2-3 MOA, he made some adjustments to the scope, and then his follow up group was at least 5 MOA if I remember correctly. It was also way off, like double or triple the distance that it should have been based on the adjustment he made. We thought it was the scope until I sent it to Robb.

Sent from my iPhone using Tapatalk

6

Comments in bold, thanks for the ideas.

7

The fact that you and Rob both shot around 2 MOA at best makes me think it’s not a great barrel.

I am going to swim against the stream here and say that a $300 AR barrel should be capable of 1.5 MOA at 100 meters or less with ammo it favors and 2 MOA with any good ammo.

Edit - 5 shot groups, from a solid rest/bags.

Andy

8

Well, we’ll see what BCM says. I’d actually emailed them a week ago because of the tremendous increase when the instructor shot it on paper. I told them I wanted to do more testing and would keep them updated, which they were interested to hear the results of. I just sent them a follow up about half an hour ago with some of the data from here. I’m kind of expecting them to come back and say that 2 MOA is perfectly acceptable. I can’t blame them if they do, but it’ll be more motivation to get a KAC upper for my Razor and throw my spare EXPS-3 on this one.

Sent from my iPhone using Tapatalk

9

IIRC mil-spec is 4MOA. Certainly not a precision instrument, but still within spec.

10

2 MOA is within my expectations for that skinny, 14.5" long, chrome-lined barrel. As you probably know, PPU is not consistently match-grade ammo, and older lots of it can run very slow, e.g. 2400fps in a 20" barrel. A chrono test would be interesting and I suspect it may only be going ~2200fps from your 14.5" barrel, which would increase the effects of wind on your group size. Your FGMM 69gr results are interesting but I would also like to know what it does with FGMM 77gr and maybe something lighter as well. I would suggest focusing on Federal GMM, Black Hills, or Lapua for serious accuracy testing with factory ammo. I have also had good results with Norma and Nosler ammo in .308, FWIW.

11

Norma TAC-223 55 gr fmj has shot very well for me (shockingly well in one AR).

Andy

12

I had some FGMM 77 gr on hand, as well as the CBC and IMI 262 clones, and finally the FGMM with 73 gr Berger bullet. A second hour would’ve been very nice, but I just didn’t have the time unfortunately.

Interesting note about the chrono, there was some wind that day but I never heard it discussed with the class so assumed it wasn’t strong enough to be relevant. There were a few things they didn’t cover though so that may be a bad assumption.

Tracking that 2 MOA is well within spec, that’s why I said I can’t blame BCM if they dismiss it. The PPU was bought sometime within the six months before or after Sandy Hook, so it very well may have not been their most consistent loading. Unfortunately the closest range that I know of that goes beyond 100 yards is about three hours away. Not sure when I’d get the chance to head down there, and I’d probably want higher magnification for that distance.

Sent from my iPhone using Tapatalk

13

I don’t know if it’s feasible at your range but if I have it to myself, I’ve been known to shoot from the parking lot to squeeze an extra 20-30 yards out.

Safety first and all that.

14

It wouldn’t be, unfortunately.

BCM just got back to me with an interesting response. They want me to shoot more groups, discounting the first and last shots, and use either Hornady, Black Hills, Winchester White Box, or “other known good, domestically produced, factory new, brass cased ammo.”

I’ve never heard of discounting the first and last round, and I don’t have glass with enough magnification to do that at 100m. Also kind of seems like cheating. And 3/5 targets I sent them were either Federal GMM or Hornady Black. Apparently that’s not enough of a sample size?

I guess it’s better than them telling me to **** off, but at this point, I’m not sure it’s worth it since only counting the middle three rounds will probably yield a significantly smaller group, enabling the claim that it shoots great.

Sent from my iPhone using Tapatalk

15

Borrow a scope. And then shoot 7 round groups, discounting the first and last shots… :slight_smile:

16

I had a new, 16” 300 Blk upper from BCM.
It shot 5”/6” groups at 100 and was iffy keeping rds on a full size IPSC steel at 200.
I contacted them and after brief discussion and with my insistence, they said to send it back.
Their results mirrored mine and they sent a replacement barrel in my original upper, which shoots adequately.

The point; I am certain that all gun manufacturers deal with an agonizingly large number of limp dicks that have no clue what a reasonable expectation is, or actually know their way around a firearm.
You are not included in this group Wake.

I suggest you contact them and STRONGLY insist they send a return authorization so that they can sort this out for themselves.
My experience was that BCM was even handed and did “the right thing”.

17

The only reason I didn’t respond to that email and insist that they take a look is because I don’t have proof of it shooting terribly. I knew I should have taken a picture of the target that the instructor fired but I didn’t, so I don’t really have anything great to show them. I’m not confident in it, and 2 MOA is not where I want it, but all of the relatively controlled testing seems to result in acceptable results. That’s part of why I posted here, I’m trying to see if I’m off base.

18

Your 1-6x Razor is plenty magnification for shooting groups at 100M. Some of the best shooting I’ve ever done at 600 yards was with a 12x scope - roughly equivalent to using your 6x at 300 yards. Off a bench, with decent conditions, 6x is enough to find out how it’s shooting at 100 or even 200 yards. Use a front benchrest or good bipod, use a rear bag, go slow. Take a few minutes’ break between groups to minimize any effect of barrel heat.

I would load 7 as already suggested and use only the middle 5 for the group, aiming the first and last elsewhere. Although I haven’t had an issue with my ARs noticeably throwing the first or last shots, it’s conceivable given that the first shot is loaded differently (especially if someone rides the bolt, which is common, even if you don’t do it) and potential reaction to the last shot bolt catch. While I don’t think this is needed for a good shooter, I don’t think BCM is off base given that they don’t know you.

If you get repeated 2 MOA groups with these conditions then I think the barrel is meeting expectations. If you can’t reliably get under 3 MOA with match ammo, then I think a return to BCM is in order. Accuracy with non-match ammo isn’t that relevant because some of the blasting or milsurp ammo will do 3-4 MOA (or worse) in even the best precision barrels. Keep in mind that BCM offers heavy profile SS barrels for a reason, and their ELW is only claimed to be good for what it is, not a benchrest barrel. It’s slightly thicker than a pencil, chrome lined, 5.56 NATO chamber (which for BCM likely means a true, somewhat loose, NATO chamber), etc. This is your barrel, right?

https://www.bravocompanyusa.com/BCM-BFH-14-5-Mid-Length-ENHANCED-LIGHT-WEIGHT-B-p/bcm-brl-mid-14.5-elw-bfh.htm

I have some 16" barrels that shoot much better than this, but they are 50-75% heavier, have .223 Wylde chambers, and are nitride treated or bare SS instead of chrome lined.

One question - do you know if the barrel nut tightening for this upper was in the normal range of torque, and if there were any issues like trouble timing the nut, or loose, or excessively tight, fit of the receiver extension into the receiver? I note that you said Robb Jensen built the upper and I assume he is highly skilled at building uppers, but did he mention any issues like these?

19

The results are not surprising given the barrel profile. Look at Molon’s test of a Gov’t Profile BCM BFH using handloads for comparison.

[i]Three, 10-shot groups were fired in a row from the Bravo Company 14.5” barrel from a distance of 100 yards with the resulting extreme spreads:

1.58”
1.96”
1.50”

for an average 10-shot group extreme spread of 1.68”. The three, 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius of the 30-shot composite group was 0.49”
The smallest 10-shot group . . . [/i]

https://www.ar15.com/forums/ar-15/Accuracy_Evaluations_of_14_5__AR_15_Barrels_From_Colt__Noveske_and_more______/118-687913/?

20

The magnification at 100m was in reference to being able to see the first and last shots so that I could ignore them, though if I aim those elsewhere like you suggested, that becomes a non-issue. He didn’t mention anything about the barrel nut. I have wondered about it since it was mentioned before and the MK16 was rumored to have some issues with it, but again, I’m assuming that there were no issues with the install. For all of the lowers I’ve built, I’ve yet to mess with an installed rail, but maybe I’ll throw it in the vice to see if I can figure that one out.

Yeah I did look at his posts for comparison. The fact that those were 10 shot groups lead me to believe that they’d be somewhere between 1/8-1/4 of an inch larger than a five shot group. I don’t know how true that is, but if it’s a close estimate, it would tighten them up decently. If that’s the difference between ELW and Gov’t profile, then so be it, I like the little bit of weight savings out front. However, my backup non-BFH gun with the ELW-F barrel seemed to indicate that the accuracy could be just as good as with the gov’t profile. I wish I had another of each barrel to test for a better sample size.

Sent from my iPhone using Tapatalk