Question: National Match BCG'S & other accuracy questions..

[Straight Shooter]

Im putting together my first build..a 20" rifle to be used for varmint/long range/hunting/target shooting/ammo testing, ect.
My research into accurizing the AR has led me to the subject of NM Bolt Carrier groups, ala Young Mfg & a couple others.
After finding out the physical differences between a standard bcg & a NM...Ive listened to some rather sound reasoning on why they should be used to get the N'TH Degree of accuracy out of a rifle.
So, my questions are: Are any of you using these? Can you tell or see results with them? Anyone tried them with no effect? Looking for actual users..NOT opinions or guesses.
For those of you with long range rigs...what other tips/tricks or advice can you give to get the most out of a Match barrel?
Also- for pure accuracy, what is the best way to attach a gas block as to not impede with barrel harmonics? And what muzzle devices should be considered on a long range gun?

[HelloLarry]

So, my questions are: Are any of you using these? Can you tell or see results with them? Anyone tried them with no effect? Looking for actual users..NOT opinions or guesses.

I shoot a lot of HP, including the Nationals and I am not aware of anyone using a "NM carrier". 'm sure they are out there, just nobody has made a point of mentioning it at a match or on any HP forums.

For those of you with long range rigs...what other tips/tricks or advice can you give to get the most out of a Match barrel?
Also- for pure accuracy, what is the best way to attach a gas block as to not impede with barrel harmonics? And what muzzle devices should be considered on a long range gun?

Have the barrel chambered with a specific bolt. Barring that, make sure the bolt you do have is not set up for a carbine. The extra force extractor doesn't help accuracy, according to Bob Whitley.
Gas block attachment - The accepted way to attach sight towers is with set screws & LokTite. However, I have seen a lot of clamp on gas blocks. I'd do whatever Whitley, White or Holliger does.

The only muzzle device I'd consider is a bare muzzle.

[MistWolf]

On an HP forum, I asked about NM carriers and was told they did nothing either way for precision.

[markm]

I didn't know those things were still marketed. That's some OLD SCHOOL stuff there.

[sinister]

"National Match" ANYTHING for the M16 is horseshit and marketing. There's a sucker born every minute, and many think it's a sin for them to keep their money.

The last United States Army National Match drawings and technical specifications were drawn up for the M1911A1, M1, and M14, and their respective cartridges. The USAMU specs out their own stuff for internal consumption by the Army, Army Reserve, and Army National Guard teams, as well as for requesting state National Guard teams. There are no formally published military National Match specs for the M16 and M9 pistol, yet the service teams shoot them at Camp Perry.

The Marines spec their own stuff, as do the Navy and Air Force.

[Ned Christiansen]

To me taking out carrier slop made too much sense to not try it, so I welded a ring around the carrier tail, ground it to, I don't remember but probably .997, put some flats on it, and ran it in my HP target gun. The carrier tail is otherwise about .070 smaller than the hole it runs in. This was probably early 90's. I did it knowing that it might compromise reliability but it sure never did. It pretty much triples the effective length of bearing surface taking out a lot of wobble. I also modified a buffer to help keep the carrier tail centered.

All the minutia that most people consider "necessary" to make a 1911 or Remington 700 more accurate, it surprises me that there has not been a big deal made about doing this.

Did either mod help? Honestly I didn't do comparative testing so I don't know, but I do know they didn't hurt. At least in theory, one or both mods "have to" help but if target competitors that are way more into it than I ever was don't do it, I have to wonder if there's any benefit..... but also, I ask, did they ever try it.

[sinister]

It doesn't hurt. Can't honestly say if it helps.

[rjacobs]

only thing I do on precision builds is get the bolt headspaced to the barrel. CLE offers this. JP offers this. I am sure others offer it as well.

I use 2 carriers: USGI phosphate or JP Low mass if I am using an adjustable gas system.

I use red loc-tite(loctite 660 retaining compound might be a "better" choice though) around the barrel extension and under the gas block to act as a sort of "shim" to take up any inconsistencies.

Besides that, using a high quality barrel(cut rifle is my preferred), and a decent free float tube and a NICE trigger is where its at.

Working up a load for your setup is probably where more accuracy can be gained than all the tricks in the book, at least on the AR platform.

[Straight Shooter]

It doesn't hurt. Can't honestly say if it helps.

sinister- what carrier is that?
Gents- all info & answers here are awesome, thank you so much. I do agree reloading would be a huge benefit- but I dont reload, so Im gonna try to build up as accurate a rig as I can afford. Also agree on getting a matched bolt, which I will do.
HelloLarry- Thanks for advice on the extractor spring & gas blocks.
Please keep any more info coming.

[titsonritz]

The only muzzle device I'd consider is a bare muzzle.

Would you consider a threaded barrel with a thread protector?