Hello All:
Of the three different versions of the 5.56 caliber 77 grain ACC ammo
- OTM
- Sierra TMK
3, Sierra Matchking HPBT w/ cannelure
Which one is the best for long range target shooting?
Thanks
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Depends on twist. Buy a box of each and see what your rifle likes.
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I agree with TJ
Do a google search, theres a chart that shows your barrels twist rate with different bullet weights… higher twist rate is better with lower grain weight vs lower twist rate for higher grain weight or something to that equivalent
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Yep what they said 
the charts are a great but even so some rifles just like what they like.
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It’s hard to pinpoint and it, and make a blanket “This PSA AAC ammo is the hands down absolute Best ammo for long range”. Your best option here, buy 1 box of each, setup with whatever rifle you want to run this long range ammo in, bench rest it and shot some groups. Once you find which ammo your rifle/barrel really loves, buy it now and stack it Deeeeeeeep 
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OK I will buy all three versions and see which one the rifle likes best.
now it is a matter of when they come back into stock
thank you!
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Here are the generalized ideal twist rates for .223/5.56
Note that each value has a variable range around it where a close value may be the best for your barrel.
For example, where 1:8 says 69 grain, a range of 62-77 is a good span to try.
1:14, 40 grain
1:12, 55 grain
1:9, 62 grain
1:8, 69 grain
1:7, 77 grain
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I was out with a shooting buddy, prarie dog hunting, he had a 1/8 twist barrel shooting 36grain A-max “varmit gernade” projectiles. 4-6 out of 10 shots he was missing his mark. I subsequently noticed a shimmer as the projectile farmented 40-70 yards out from over rotation.
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One of the strongest performers for storebought 5.56/223 ammo is the Hornady Superformance 75 gn or 77 grain.
I bought 4 or 5 different ammo’s in that category - AAC, PPU, etc.
But have yet to try them all at the same time.
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What these fine folks said, but also to add…
Shoot a handful of each round with a cooler barrel and then with a warmer barrel. Things change with heat.
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@guyschwartz ( added a photo )
You are going to be very surprised with the AAC 77gr OTM load… it is a bargain for what you are getting.
The AAC 77gr OTM had the Same POI as the 77gr SMK , and stellar accuracy with the AAC made bullet, even from a barrel after 30ish rounds to warm it up.
This was shot yesterday at 50yds… Yes, the card was shot at the narrow edge, after those warm up rounds. The barrel had not been cleaned in months.
I was lucky, the first attempt , I actually did it !
Witnessed and signed by some Noble friends.
I would strongly suggest you buy more of the AAC 77gr OTM load.
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The answer is one of them will be better that the others. Accuracy of a barrel is determined by the harmonics of the barrel, the velocity of the load, which is affected by head space and bullet jump, and the effect of temperature on the residual stresses of the barrel. This is why long distance shooters develop their own loads.
You just have to buy some of each and see how they perform.
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YouTuber “Practical Accuracy” ( Practical Accuracy - YouTube) has a series of videos regarding bullet weight and twist rate. Heavier bullets do require a faster rate. That said, within the suitable twist rate, the individual rifle and ammo combination are the deciding factors in accuracy. Individual, in this sense means just that. Two rifles with consecutive serial numbers may have significant difference for the particular ammo best suited to each. The same may be said for individual lot numbers of ammo from a particular manufacturer.
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Welcome to the forum @DAVIEB1955 
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I stock both AAC 77gr. SMK & Precision, now I see a new third AAC 77gr. SMK tipped…
will try that as well in 18" Performance Center 1:8 button cut and a Aero QPQ 20"
M16A4 1:7 man what a shooter with just carry handle irons. PSA AAC 77 first iterations shoot
great so hopeful to make these ‘go to’ rifle rounds.
16" noodle Carbines here are 9:1 both Windham and DelTon and I have to say the Fiocchi 40gr
V-Max is so good I’m not considering others unless Fiocchi changes something with that cartridge.
Then a new 16" M4A4 1:7 not zeroed yet, looking forward running these 77gr. and compare
with the Fiocchi 40gr. 3600fps.
C&P below…
Sierra Tipped MatchKing® 77gr Projectile:
Sierra has enhanced a segment of the MatchKing® line by adding the acetal resin tip, thus crowning the Tipped MatchKing® (TMK) bullet line. The major advantage of adding a tip to the bullet is the reduction of drag, producing a more favorable ballistic coefficient. Another benefit is reliable feeding in magazine fed firearms. The 77 grain Tipped MatchKing® (TMK) allows seating to an OAL that permits cartridges to be loaded into M16/AR15 magazines. .80 cent per pop.
PSA has another new cartridge 70gr. Barns TSX.
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Follo Up.
I was able to get some of the 77 grain OTM and SMK, the HPBT was out of stock.
The OTM was good, however the SMK was great. Very tight groups, impressive!
Wonder if the SMK HPBT are as good or better. Anyone have any experience with the comparison between the HPBT vs. the regular SMK?
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The pressure spike of firing makes a barrel vibrate like a guitar string. Like a string, it has vibration nodes. If the barrel crown matches a node as the bullet exits you have maximum accuracy, if it doesn’t your groups open up. You tune your rifle by
a) using different commercial loads to compare accuracy.
b) clamping a weight (barrel tuner) to the barrel and moving it around to tune the barrel
c) hand loading different loads until you reach an accuracy node for a particular bullet.
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