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

[SomeOtherGuy]

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.

Just throwing an idea out, but if you have the tools on hand this would be very easy to try, less work than packaging it up and shipping it to BCM. Which you can still do if you truly have an accuracy issue and nothing else fixes it.

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.

I think the bolded text is a reasonable estimate, but you don't yet have enough groups with quality ammo to really compare.

Individual barrels vary even from quality makers. It's possible your non-CHF is average or above average while your BFH is below average but still within spec and without a real defect.

[Jolr]

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.

Isn’t the point where a bullet “goes to sleep” the point where stabilization occurs and maximum accuracy is achieved?

[vicious_cb]

Isn’t the point where a bullet “goes to sleep” the point where stabilization occurs and maximum accuracy is achieved?

No, thats the wrong way to think about. Either bullet is stable or its not when it leaves the muzzle.

The "going to sleep" phenomenon is the bullet being initially disturbed by muzzle blast or barrel harmonics. Brian Litz showed that this initial "epicyclic swerve" both goes away rather quickly(definitely by 50 yards) and is insignificant.

In other words, group size increases linearly. Stop worry about "bullets going to sleep" because its not happening at 50 yards and its not significant enough to affect groups.

http://www.appliedballisticsllc.com/...clicSwerve.pdf

[Jolr]

No, thats the wrong way to think about. Either bullet is stable or its not when it leaves the muzzle.

The "going to sleep" phenomenon is the bullet being initially disturbed by muzzle blast or barrel harmonics. Brian Litz showed that this initial "epicyclic swerve" both goes away rather quickly(definitely by 50 yards) and is insignificant.

In other words, group size increases linearly. Stop worry about "bullets going to sleep" because its not happening at 50 yards and its not significant enough to affect groups.

http://www.appliedballisticsllc.com/...clicSwerve.pdf

I watched his video and came to the opposite conclusion. Over distance, the bullet displays less yaw and becomes more stable.

[Jolr]

The Army’s testing of m855 illustrated the phenomenon of the bullet going to sleep over distance. There is maximum yaw(instability) at the muzzle. Over distance the degree of yaw decreases. Bullets are least stable when they leave the muzzle

[WS6]

The Army’s testing of m855 illustrated the phenomenon of the bullet going to sleep over distance. There is maximum yaw(instability) at the muzzle. Over distance the degree of yaw decreases. Bullets are least stable when they leave the muzzle

This affects AOA, not group dispersion, and is partially responsible for terminal performance using fragmenting (tumbling) as a factor.

[sinister]

Looks like typical rack-grade rifle performance, even with match ammo.

There's nothing magic about hammer-forging -- it's a method of making lots of barrels quickly, not necessarily to bench precision standard. If not properly stress-relieved you'll get some group expansion and possibly zero shift as the barrel warms.

Chrome-lining takes a bit away from precision potential as well.

[MadAngler1]

Why don’t you swap the barrel out on the same upper for one made by Daniel Defense or Centurion arms? I know it costs more $$$, but maybe it’s a bad barrel. CHF barrels are very difficult to make right.

[MistWolf]

...CHF barrels are very difficult to make right.

The Remington 700 earned its reputation as a very precise rifle using hammer forged barrels.

[Wake27]

Why don’t you swap the barrel out on the same upper for one made by Daniel Defense or Centurion arms? I know it costs more $$$, but maybe it’s a bad barrel. CHF barrels are very difficult to make right.

Depends. If its just a 2 MOA gun and everything worse than that was shooter error, then its not worth swapping to me. I'm taking it tomorrow to test the remaining loads that I have but most of them are different variants of the 77 gr SMK so I doubt there will be much variation. I'm also taking my beater PSAs though, I think I was shooting just over 2" groups with a 4x scope and ball ammo so I'm curious to see how those compare.