"Accurizing the AR-15"

[TWR]

After zeroing the gun this morning with the new Troy sights and no red dot on the gun, it is but a smidge to the left. I know better than to try and zero them to the dot, shooting is the only way.

It also shot good enough at 200 with my 1-4 Trijicon that a better barrel is not needed but Black Friday deals might talk me into it anyway. But for now I have a red dot, irons and a scope zeroed and really killed my desire to take it back apart.

[Cool Breeze]

Myself, I don't think many manufacturer's would share their "secret tricks"... kinda like a NASCAR team sharing their secrets.

But I have applied many of Criterion's recommendations , and IMHO they do help.

This is 10rds, at 100yds, scoped, benched, bagged.. etc> PSA upper and lower, Criterion 22" 6.5CM , Hornady AG 140gr... various Criterion "Tricks" applied during assm., Yes , I blew the flier.

Attachment 110868


This group, is also same as above, but 308 18" Criterion barrel, 155gr Horn AG , same everything else.
Note I blew this flier as well...

Attachment 110869


IMHO, I would build / assemble one, if I can do it, anyone can.

Great shooting!

[Cool Breeze]

Has anyone ever seen a difference in lapping the upper?

I like BCM’s thermo fit uppers and have bedded barrels in looser fitting uppers before but I don’t buy into lapping.
First, I’ve not seen an upper not square enough to make contact all the way around yet.
Second, a loose fitting guide inside the upper is subject to cutting off center when done by hand.
Third, I don’t like to remove anodizing.

I’ve seen a few attempts trying to prove it does work only to not make any difference. But it would be hard to see any improvement until 300 yards or so anyway. Just wondering if this has been proven or just something else to sell.

The only tips I’ve got is to start with a good barrel, limit barrel nut torque to 40’ lbs. Just snug the muzzle device after loctite has been applied. I have swapped a bolt once that passed a field gauge but accuracy did improve with another bolt.

The lapping (via the brownells tool method is the one I'm most skeptical about for the reasons you mentioned as well as me wondering if a $30 tool is really "more square/precise" than what is done by the machining of a good quality upper. If done on a lathe, that might be a different story.

[Cool Breeze]

I've never tried any of it but d. Wilson does offer bedding/shimming and receiver truing services.

I didn't realize he did this. Thank you! That may be the easy button for me if I don't feel like getting all the tools to do this myself.

[Cool Breeze]

FWIW... the SOLGW upper is also a MUCH snugger fit on every lower I tried.
IMHO a tight fit between the upper and lower makes it far easier to wield the AR more consistently.

BCM lower was TIGHT. As in had to "slap" the 2 parts apart.
Colt was inbetween TIGHT and snug.
SanTan lower was snug.
Rainer Arms lower was snug.
PSA was a much better fit, compared to PSA uppers.

I tried the SOLGW upper on other make lowers, but I don't remember which ones.

Interesting - I had a somewhat different experience. I have Triarc matching serial set and its TIGHT. My SOLGW uppers and lowers can move ever so slightly but not noticable unless you try to move it - its not as tight as what is on their youtube video though. A BCM Mk2 upper and BCM lower was the looses of the group. That being said, I like the BCM Mk2 upper being that its thermal fit and the "newer" design. I am not sure if SOLGW is considered thermal fit as the youtube video says undersized and then he hammers it in with a mallet. Maybe that means the same thing as thermal fit?

[Cool Breeze]

I use a Brownell's lapping tool and have noticed the same thing which I thought was the whole point of lapping.

I pretty much use nothing but BCM blem uppers. I tend to use Green Mountain Barrels when they have what I want, but have also used others. Fit to receiver is snug, but I've never had to thermal fit. Is that unique to the blem uppers?

Are you using mk2 uppers or mk1? I've only heard the mk2 being referred to as thermal fit but that is not to say the mk1 uppers are not.

[mmc45414]

The lapping (via the brownells tool method is the one I'm most skeptical about for the reasons you mentioned as well as me wondering if a $30 tool is really "more square/precise" than what is done by the machining of a good quality upper. If done on a lathe, that might be a different story.

IMO/E making something like that tool is simple, cheap, and on a modern CNC it will be accurate. And if you just want the ID to be in perpendicular alignment with the front face of the receiver this sure seems like a straightforward approach.

Reading this thread over on SH seems to indicate the glue (or shim) might be more important than the facing, since the barrel extension is just a slip fit anyway. But the facing might clean up any variation in the anodize. There was also thought that it might help square up the bolt lugs, but that would just be gravy.

So my take on this is that there are probably not big enough gains (for me) to bother paying a professional (and UPS, twice) to fixture it up in a lathe and then measure for and cut and install a shim. I would probably not take an upper apart just to do this, but I am getting ready to do four uppers I plan to buy the tool and the glue. It will only add ~$10 each, just seems like it is too easy and cheap of an opportunity to skip, even if it actually nets me nothing.

[littlejerry]

Years ago I went through the process of accurizing my Sionics upper:

• lapping the receiver face
• free floating gas tube
• shimming and gluing barrel to receiver

I did it all at once so I don't know which ones made the difference.

My testing before and after showed that good loads didn't really improve significantly but some of my previously "bad" loads got a lot better.

To put it another way, the changes didn't raise the ceiling for my accuracy potential, but it did raise the floor on what I could expect when shooting commercial ammo.

[DDTSGM]

Are you using mk2 uppers or mk1? I've only heard the mk2 being referred to as thermal fit but that is not to say the mk1 uppers are not.

These are the ones I've been using:

BCM® M4 Flat Top Upper Receiver with cosmetic blemishes. Most have scratches or scuffs.

The upper comes unassembled, but complete with BCM forward assist assembly and ejection port cover door assembly.
You must assemble it. (Assembly required) (all parts, but you will have to assemble together)

THESE ARE USED/DEMO UPPER RECEIVER ASSEMBLIES. All will have several nicks, scratches, and marks on exterior finish. NO HANDPICKING.

This receiver has the M4 feedramps machined in. This is to be used with barrels that include the M4 barrel extension.

Built to the correct Mil-Specs.
(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.)

I bought a Mk2 when they first came out, but didn't need to heat it either. Do they even make them anymore?

[Cool Breeze]

IMO/E making something like that tool is simple, cheap, and on a modern CNC it will be accurate. And if you just want the ID to be in perpendicular alignment with the front face of the receiver this sure seems like a straightforward approach.

Reading this thread over on SH seems to indicate the glue (or shim) might be more important than the facing, since the barrel extension is just a slip fit anyway. But the facing might clean up any variation in the anodize. There was also thought that it might help square up the bolt lugs, but that would just be gravy.

So my take on this is that there are probably not big enough gains (for me) to bother paying a professional (and UPS, twice) to fixture it up in a lathe and then measure for and cut and install a shim. I would probably not take an upper apart just to do this, but I am getting ready to do four uppers I plan to buy the tool and the glue. It will only add ~$10 each, just seems like it is too easy and cheap of an opportunity to skip, even if it actually nets me nothing.

That makes perfect sense to me. Nice thread link btw - interesting read.