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I'm not sure what screw you were originally referring to, but there is no such thing as an accurizing screw in an AR.
1. A tighter lower to upper receiver doesn't make an AR more accurate. It simply eliminates what some people consider to be excessive wobble.
2. An adjustment screw for trigger preset doesn't make an AR more accurate. It simply removes what some people deem excessive preset.
The only things that will make an AR more accurate are a good barrel, plenty of practice, and good ammo that is matched to the barrel.
Following that reply, came this one from Mr. Barnes:
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You are correct sir!
We call it an "accurizing" screw , because that it is what is has always been refered to in industry ....although it is a misleading/incorrect description.
Yes ......accuracy is contributed to-controlled by upper to barrel fit...not lower to upper fit.Screw used to take up "CREEP" of trigger is also USAMTU trick..and it lessens amount you have to pull trigger to drop the hammer...so , this CAN be an accuracy improver,especially if using high magnification optics and shooting for group size.....that is elementary.
What is first thing bolt gun guys do to improve /shrink groups??They do a trigger job(reduce creep and lighten up pull...and then reduce overtravel) as well as steel bed action to stock....and freefloat barrel. Those are the most common anyway.....that produce the biggest results.
We install this feature(like other premium grade lowers have) to tighten up feel from upper to lower when assembling.Those who know better ,(and most consumers ,with all due respect ,do not)realize Uppers are made within a tolerance range and so are Lowers ...and because of this tolerancing of parts you can get an "in tolerance" machined upper or lower ...and get more play than the ones assembled yesterday...that were also well within tolerances ..IT IS tHE NATURE OF THE DESIGN!!!!!!!!!!!!!Those who say a little play is an indicator of poor /unacceptable quality ,do not understand the way the weapon works ...or how Eugene Stoner designed it /meant for it to be made.Ever heard of an ACCUWEDGE????? Why do they exist????? Because issue has been around for many years ,and they( Accuwedge) had the first commercially available product to address it .I have seen Colts (the worst) Bushmasters/DPMS/Olympics/LMT's /Stag/Rock River/ as well as a lot of no names ...and they ALL exhibited a certain amount of play/looseness. Ours are no better/no worse....because we machine to the SAME TOLERANCES.That is also why some of these very folks tell us we machine a GOOD QUALITY/IN SPEC product that is indicative of common industry players.
If you shoot a high mag scope ...reducing upper to lower play might help tighten up groups because of less wiggle of upper once on target .(your heartbeat/breathing can affect reticle movement in this situation) ...and so can loose fitting upper to lower....it can effect group size , but it is not a "direct" effect as mentioned .
Weapon will exhibit a looser feeling the more rounds you put through it ,the more you disassemble it to clean it...and this screw gives you the option of tightening it up during the life of product.It is an old USAMTU (US Army Marksmanship Training Unit )trick that gunsmiths/armorers have been doing for YEARS....but no one until the last few years ,has been including it on production models.It is a method taught by most gunsmithing /armorers courses,as well as other "steel bed" methods,as taught by Mark Hunt at Montgomery Community College.
I did not come up with the idea ....we just decided to include it as a standard feature in our lowers ...along with hole for detent pin/spring for rear takedown pin being tapped for a set screw ...so you can do stock changes with out losing /dealing with detent pin/spring.These are just two of the things that make ours a Premium grade lower receiver in many peoples eyes...and since we do not machine uppers ....yet- it gives our customers the option of mating with ANY upper in industry ,while maintaining a tight fit.
Thanks for listening.
Now we know!!!!:)