Need Info on Truing an Upper Receiver

[GaCop]

If not you should have prior to purchasing another barrel if cash is tight as they very likely would make it right.

I'm not the original purchaser of the barrel. I've contacted the person I received the barreled upper from and he is going to contact BCA. I did install the KM Tactical barrel and shot the rifle yesterday. Hornady Black 123 gr ELD-M grouped into 1.6" at 200 yards. Big improvement over the shotgun patterns from the BCA barrel. 23 rounds fired through the KM barrel. Hornady 123 gr SST grouped into 2.18" at 200 yards, adequate hunting accuracy for deer or hogs. I figure the new stainless barrel will be broken in after about 150 rounds and accuracy should improve. A good cleaning yesterday didn't yield any copper fouling.

[sschefer]

3holes 1222018.jpg5.56 long range.jpg
Took my lapped and squared 5.56 out today with the new S&B PMII scope. It was on the paper at 25 yards with the scope at factory Zero. At 100 yards it was .3 mrad right and since it has a 20 moa mount it was 9.5 mrad high. Here's the group I shot after 60 break in rounds of green tips and then Hornady SuperPerfomance match 75gr BHTP. This gives plausibility to the need for lapping and truing. It also busts the myth that you need glues as fillers or lubricants. This barrel slid in easily but was installed using a reaction bar so it is centered in the hole and did not move one bit after 100 slow fire rounds with not appreciable cool down time.

Looks like three holes but it's actually 4, look really close.

[NugginFutz]

Nice shooting, and glad to see you built an accurate rifle.

Not sure, though, how you can unequivocally state that the idea of bedding is busted. If your barrel needs none, then all the better. If it can benefit, then again, all the better.

In the grand scheme of things, what works for your rifle is what works for yours.

Here is what works for mine.

BHW 22" 264LBC
Lapped (horizontal)
Bedded with LT Blue (Cured overnight)
Scope rings lapped (to 70% contact)
Vortex 6-24x50 Viper PST Gen 1
Hand Loads (123 Amax, 28.2 gr 8208, seated 2.250")

39136749614_48e1bc49dc_o.jpg
Three shot group @ 100 yards

39814419132_cd46066c24_o.jpg
5 shots @ 300 yards.

Do these groups prove bedding will cure your accuracy ills? Of course not.

Have others benefitted from bedding? Yes they have. (Don't ask me, ask them.)

http://www.65grendel.com/forum/showthread.php?14147-Accuracy-fixed

http://www.65grendel.com/forum/showthread.php?1791-Building-for-accuracy

(take note of post 12)

Will everyone get an accuracy boost? Not in my lifetime.

Can it hurt to bed a barrel? I can't see how.

Long and short of the subject of bedding is that there is no "right for every situation" answer to it.

[GaCop]

Considering the great improvement in accuracy just changing barrels and using blue Loctite on the barrel and gas block, I'm going to hold off on lapping the upper and do more break in and load development/accuracy testing at 200 yards and beyond.

[LRRPF52]

[ATTACH=CONFIG]10871[/ATTACH][ATTACH=CONFIG]10872[/ATTACH]
Took my lapped and squared 5.56 out today with the new S&B PMII scope. It was on the paper at 25 yards with the scope at factory Zero. At 100 yards it was .3 mrad right and since it has a 20 moa mount it was 9.5 mrad high. Here's the group I shot after 60 break in rounds of green tips and then Hornady SuperPerfomance match 75gr BHTP. This gives plausibility to the need for lapping and truing. It also busts the myth that you need glues as fillers or lubricants. This barrel slid in easily but was installed using a reaction bar so it is centered in the hole and did not move one bit after 100 slow fire rounds with not appreciable cool down time.

Looks like three holes but it's actually 4, look really close.

Call up the AMU armorers and every accuracy shop that is known for building precision AR15s and tell them bedding is a myth.

I find it interesting to listen to guys who have spent their entire professional lives chasing accuracy in the AR15 all agree on tightly fitting the extension into the upper somehow, whether it be thermo-fit, shimming, bedding, or combination of these techniques, but still see those who refuse to acknowledge cumulative centuries of accuracy work by armorers who are paid to chase every fraction of an inch of accuracy they can supporting competitive teams and shooters.

Some of the most accomplished engineers in this field also acknowledge the benefits of bedding the extension into the upper, along with balanced torque on the nut, as proven techniques they have tested across large fleet samples of rifles that showed demonstrable changes in group sizes as a trend in the fleet, not anecdotally with one or a few rifles.

It doesn't mean that you can't build an accurate rifle without bedding, but I have yet to see a valid argument that shows how bedding does not increase accuracy, and certainly have never seen a coherent argument that bedding hurts accuracy.

In all the rifles I have bedded-both AR15s and AR10s, I have seen group sizes shrink, sometimes from 1.7 MOA 5rd groups down to .75 or better with a random load not even tuned for the gun.

.223s are very easy to get to shoot because of the small mass projectile causing minimal whip and recoil effects-very forgiving.

Once you spit a larger projectile with more mass, the guns are very unforgiving of build approach and fundamentals of marksmanship.

For those that want to learn more, watch these videos.

[Sticks]

For those that want to learn more, watch these videos.

I watched all three, then did some mental note taking on other user reports here, and some YouTube vids with Muzzle devices, suppressors, MagnetoSpeed et al. Bedding aside (I believe in it) the crap attached to the barrel does make a difference. My 18" Barlitien with an Odin Atlas 6.5 muzzle brake has significant whip to it (caught it in a frame by frame of a vid). Enough that the slightly canted PF mounted Adj gas block was contacting my Samson handguard, enough to rub off the cerakoate , prompting me to tear down, lap, bed (only had blue locktite around the flange, and consequently into the threads . I have not had adequate time to see final results, other than remounting the scope resulted in a 1.5mil change in windage (15 clicks).

[Klem]

, but still see those who refuse to acknowledge cumulative centuries of accuracy work by armorers who are paid to chase every fraction of an inch of accuracy they can supporting competitive teams and shooters.

I'd be cautious implying there's only one way to do anything and everyone who questions it is a fool. We see the same intransigence with over-zealous believers of religion. It's only by questioning and curiosity that we develop and improve.

[bj139]

Considering the play between the barrel and receiver in a AR I am surprised there are not barrel based scope mounts being used by those in search of ultimate precision.

[Klem]

Considering the play between the barrel and receiver in a AR I am surprised there are not barrel based scope mounts being used by those in search of ultimate precision.

[Kswhitetails]

Haha. You never know how much quality costs until you find out you don't own any?

[bj139]

I was thinking of TC Contender barrels where the scope is mounted to the barrel, not the receiver.

Quality is in the eye of the beholder.