AR15 Accuracy Standards, technique, blah, blah, blah

[mtnbkr]

As discussed here, I decided about a year and a half ago to build an AR for shooting off the bench. No specific reason why, I just wanted a range plinker.

I've had a few missteps and changes along the way, but this is what I ended up with:
Anderson Lower
BCM Blem Upper
Larue 20" Stealth Barrel, 1:8 twist, Wylde chamber, no muzzle device
Brownells BCG
BCM Charging Handle
Larue Trigger
Generic lower parts kit
A2 Stock, buffer tube, and standard weight buffer
Adjustable gas block with gas turned down so the gun just cycles and the bolt locks back when the mag is empty.
Aero Precision Quantum Handguard
Magpul Bipod
Burris 3-9x40 scope
Nikon scope mount
Magpul pistol grip
Magpul 10rnd magazine

Missteps were mainly using a different upper receiver that was on the large end of spec while the Larue barrel's extension was on the lower end of spec, resulting in a very sloppy barrel/receiver fit. Even using green Loctite and greater barrel nut torque (per Rob at Virginia Arms) didn't get me where I wanted to be (best it could do was 1.5"@100yds). I bought a BCM blem upper and a better handguard/barrel-nut and that's where I am today.

What I have now is a gun that will shoot most commercial loads into 1.5" or less for 5 shots. It'll shoot most 73gr+ loads into less than an inch or better for 3 shots and just under to just over 1" for 5 shots (Nosler SSA 75gr is sub 1" even for 5 shots). I'm surprised at its preference for heavier bullets as I expected the 1:8 twist to be more ideally suited to bullets in the 60-70 range. Even stranger is that I found a couple 55gr loads it likes about as much as the heavy bullet loads. It doesn't like anything I've tried in the 63-68gr range. If the bullet weight starts with a "6", it's wrong apparently.

This is what I shot this morning (the loads it seems to like):
American Eagle MSR 55gr: .89" average for 2 3-shot groups, over 1.5" for 5-shots on my last trip
Nosler SSA 75gr OTM: .66" average for 2 3-shot groups (also did sub 1" 5-shot groups my last trip, but I don't recall the exact measurement)
Hornady Match 73gr ELD: .931" for 2 3-shot groups and 1" for 1 5-shot group
PPU M193 55gr: .716" for 2 3-shot groups, but was well over an inch for my last trip where I was shooting 5-shot groups
Hornady Black 75gr BTHP: .553" for 2 3-shot group and 1.5" for 1 5-shot group. Could be shooter fatigue as that was the last of 17 groups.

It does not like loads with bullets below 55gr or in the 60-69gr range. It doesn't like most 55gr loads, but did well with the AE MSR load for 3-shot group (did poorly with 5-shot groups on my last trip).

Question time:
1. Should I do anything with the gun? While the barrel fit this upper better than the old upper, it's still not snug (ie I didn't have to heat the upper for it to slide in). Should I Loctite it?
2. The Aero Precision instructions provided a torque figure for their barrel nut lower than most folks suggest, presumably because it's aluminum instead of steel. Should I torque it to a higher value anyway?
3. Does an AR need to "break in"? It seems to be getting more accurate, but maybe I'm getting better at shooting it.
4. Is there a specific technique to shooting ARs off the bench? I did notice if I put too much downward pressure against the bipod, groups would shift. Once I started minimizing this pressure, my groups would be more consistent and smaller. I was using the bipod up front and a sandbag in the rear.
5. What is the "correct" number of shots in a string to judge accuracy? Three is typical for a hunting rifle, but what about an AR that is used for target shooting? Five? Ten?

I'll be happy if the consensus is that I just need to learn how to shoot the gun. I don't have a lot of experience with centerfire semi-autos, so if the technique is different, I'm ignorant.

Chris

[NH Shooter]

Sounds to me like you're near or at the precision potential for this configuration.

[littlejerry]

5. What is the "correct" number of shots in a string to judge accuracy? Three is typical for a hunting rifle, but what about an AR that is used for target shooting? Five? Ten?

I'll be happy if the consensus is that I just need to learn how to shoot the gun. I don't have a lot of experience with centerfire semi-autos, so if the technique is different, I'm ignorant.

Chris

3 shot groups are typical for bad shooters and/or rifles, regardless of type.

You need a statistically significant sample size to assess accuracy or rather precision. Some people like 3 10 shot groups, others do 5x5. Some even do single shots at multiple bulls. There are reasons for all of them, but the takeaway is you need ~30 rounds in target to really make any kind of claims.

Individual cherry-picked groups are just that: proof that this one time the stars aligend and 3 rounds landed pretty close. It is not at all indicative of future or typical performance.

[Nephrology]

I am pretty happy with this rifle that I just put together. RRA Predator Pursuit 20" complete upper. Aero lower, White Oak Armory LPK, Larue MBT 2S, plus furniture.

Scope is a Leupold Mark 1 Mod AR 3-9x40 with their illuminated tactical milling reticle. It's fine for now but I can tell I will want a 3-15 of higher quality at some point in the near future.

My shooting is still inconsistent but the rifle is certainly sub-MOA with the right ammunition. Still teasing out what it likes, but I have had good luck with PPU 75gr and Federal GMM 77gr so far.

[LittleLebowski]

You need to reload to reach full accuracy potential.

[mtnbkr]

Sounds to me like you're near or at the precision potential for this configuration.

How so?

3 shot groups are typical for bad shooters and/or rifles, regardless of type.

You need a statistically significant sample size to assess accuracy or rather precision. Some people like 3 10 shot groups, others do 5x5. Some even do single shots at multiple bulls. There are reasons for all of them, but the takeaway is you need ~30 rounds in target to really make any kind of claims.

Individual cherry-picked groups are just that: proof that this one time the stars aligend and 3 rounds landed pretty close. It is not at all indicative of future or typical performance.

In my hunting rifles I find multiple 3-shot groups an adequate test for (bolt) guns that won't be fired more than once or twice a day, if not a season. But, it's not a 3-shot group and done, it's normally 5+ after working up a load to get to that point.

However, in this gun, it will see more rounds downrange, so I need a different take on what's good enough to say I've found the right combination. 5x5 or Nx10 seem reasonable. Does it matter how much time one takes between shooting strings?

The results listed above were not cherry-picked, they were the factory loads that gave me repeatable sub-1" groups. Now that I have that list, I can buy enough of each to run through multiple 5-10 round strings. I didn't want to do that initially because I'm not made of money. Some of the stuff I've purchased has not performed as well in this gun as expected.

I am pretty happy with this rifle that I just put together. RRA Predator Pursuit 20" complete upper. Aero lower, White Oak Armory LPK, Larue MBT 2S, plus furniture.

Scope is a Leupold Mark 1 Mod AR 3-9x40 with their illuminated tactical milling reticle. It's fine for now but I can tell I will want a 3-15 of higher quality at some point in the near future.

My shooting is still inconsistent but the rifle is certainly sub-MOA with the right ammunition. Still teasing out what it likes, but I have had good luck with PPU 75gr and Federal GMM 77gr so far.

Why do you want the higher mag scope? At what distances are you shooting? My only ranges are 100yds, so a 3-9x is all I need. I want a higher mag scope, but I don't know that I'd get any benefit.

The PPU 75gr load, is that the semi-hard-to-find target stuff? I shot some of it in my carbine a few years ago. It seemed fairly accurate, but wasn't really necessary in that gun. I'd like to get some for this 20" rifle and see what it does.

You need to reload to reach full accuracy potential.

That's the plan once I zero in on what it likes. I fully expected it to shoot well with 60ish grain loads (I happen to have a bunch of 62gr BTSPs on hand). Trying chase an accurate load with those might have been frustrating. Partially because I built this gun, I'm not 100% confident if any deficiency is the gun, me, or the load.

Chris

[Nephrology]

How so?

Why do you want the higher mag scope? At what distances are you shooting? My only ranges are 100yds, so a 3-9x is all I need. I want a higher mag scope, but I don't know that I'd get any benefit.

The PPU 75gr load, is that the semi-hard-to-find target stuff? I shot some of it in my carbine a few years ago. It seemed fairly accurate, but wasn't really necessary in that gun. I'd like to get some for this 20" rifle and see what it does.

I find it hard to distinguish 1" square at 100yd from my crosshair (ultimately what I am trying to hit a lot of the time). The scope i capable of giving me hits on an 18" gong at 550yd but it would be a lot easier with a little more mag and better glass.

re: ammo, PPU is in stock at SGAmmo right now. I'm trying out a couple other loads in the near ish future but it did very well wih 77gr PPU at the range the other day. So far my best shooting has been with the 77gr FGMM.

[TGS]

I don't think that is anywhere near the accuracy potential of that rifle if built properly. Personally I'd be pissed if that's all I was getting from that build.

Shooting off a bag prone at 100 yards, both of my run of the mill BCM 14.5" middies shoots 1.3" in 10 round groups with Hornady 75gr TAP .223, looking through a Burris MTAC 1-4x24. So, there's some component that's amiss here with your rifle. Shooter or defect (manufacturing or assembly). Before anyone looks at my post and thinks I'm one of those stereotypical internet shooters who always claims 1" groups, I'll very openly say that my two K31s gets 3/4" 3 shot groups and opens up to well over an inch with 5 shot groups, and I dropped $700 putting an authentic Yugoslav Army scope on my Yugo SKS for historical reasons (the JNA pressed the SKS into service as a DMR in 3 distinct versions, not to mention the plethora of Yugoslav civil wars field expedient versions), and regardless of the money I spent on it and how cool it is, it fucking sucks at shooting with 2" wide by 6" high groups at 100 yards. So, I will fully admit what a rifle's accuracy is and is not, regardless of the money I put into it.

Nephrology brings up a good point, but you may want to find a target that complements your reticle when doing accuracy testing to achieve the same effect. When doing accuracy testing with mine using the Burris, I used a Shoot'n'See target that had a big circle, 3" I think. That mated up very nicely with the MTAC's 2 MOA center dot, making it very easy for me to have repeatable accuracy by ensuring there was equal bull around the dot......same as the "equal height, equal light" concept for my Highpower Service Rifle and USMC guys that might be reading this.

[mtnbkr]

I find it hard to distinguish 1" square at 100yd from my crosshair (ultimately what I am trying to hit a lot of the time). The scope i capable of giving me hits on an 18" gong at 550yd but it would be a lot easier with a little more mag and better glass.

re: ammo, PPU is in stock at SGAmmo right now. I'm trying out a couple other loads in the near ish future but it did very well wih 77gr PPU at the range the other day. So far my best shooting has been with the 77gr FGMM.

Ahh, gotcha. I'm able to distinguish the two in my scope, but my crosshairs are duplex and quite fine in the center. The bold portions, if I recall correctly, come close to the 1" square, so they kind of "point" to the square when things are aligned.

Thanks for the heads up on the ammo.

I don't think that is anywhere near the accuracy potential of that rifle if built properly. Personally I'd be pissed if that's all I was getting from that build.

Shooting off a bag prone at 100 yards, both of my run of the mill BCM 14.5" middies shoots 1.3" in 10 round groups with Hornady 75gr TAP .223, looking through a Burris MTAC 1-4x24. So, there's some component that's amiss here with your rifle. Shooter or defect (manufacturing or assembly). Before anyone looks at my post and thinks I'm one of those stereotypical internet shooters who always claims 1" groups, I'll very openly say that my two K31s gets 3/4" 3 shot groups and opens up to well over an inch with 5 shot groups, and I dropped $700 putting an authentic Yugoslav Army scope on my Yugo SKS for historical reasons (the JNA pressed the SKS into service as a DMR in 3 distinct versions, not to mention the plethora of Yugoslav civil wars field expedient versions), and regardless of the money I spent on it and how cool it is, it fucking sucks at shooting with 2" wide by 6" high groups at 100 yards. So, I will fully admit what a rifle's accuracy is and is not, regardless of the money I put into it.

Nephrology brings up a good point, but you may want to find a target that complements your reticle when doing accuracy testing to achieve the same effect. When doing accuracy testing with mine using the Burris, I used a Shoot'n'See target that had a big circle, 3" I think. That mated up very nicely with the MTAC's 2 MOA center dot, making it very easy for me to have repeatable accuracy by ensuring there was equal bull around the dot......same as the "equal height, equal light" concept for my Highpower Service Rifle and USMC guys that might be reading this.

How would you go about discerning shooter vs manufacturer defect vs assembly defect and why would you say there's an issue here (not arguing, just wondering what the clue is)? Are there any symptoms to look out for aside from poor accuracy obviously? I used good quality parts where they made sense (barrel, upper receiver, bolt, trigger), but cut corners where my reading indicated it wasn't as critical (lower receiver, small parts, stock/buffer tube/buffer). Is there a specific "technique" to shooting a gas operated gun vs bolt or single shot (most of my experience is with bolt/single)?

As I mentioned, the barrel nut torque value specified by the manufacturer was a bit on the light side compared to most assembly specifications or best practices I've read. Also, some build articles I've read suggest using red or green Loctite to further lock the barrel into the receiver. I'm not opposed to trying either Loctite or more barrel nut torque (or both), but I'd rather rule out the shooter or ammo first.

Regarding the target commentary, I do something similar using this target. My duplex crosshairs mate up nicely with the center 1" box (the bolder portions of the crosshairs come nearly to the box).

I have enough of the better-performing loads left to shoot 2 5-shot groups. I may pick up a fresh box of the SSA load since it did well for 5-shot groups (2 groups under 1", but I don't have the exact measurement) and 2 3-shot groups averaging less than .75"). Every group I shot with SSA, 3 and 5 shot groups, was under 1" whether the barrel was hot or cold. I only had a partial box though.

Chris

[ST911]

Some things that help me...

Shooting from the bench, ensure that you're anchored/bagged securely, stock weld is good and you're in a firm seated position behind the gun. Many people sit too high, close, or far and end up hunkering behind the gun. If you're bipod is on a smooth surface, a high friction pad under the legs (or a wet towel) sometimes help. There's a lot of float that can go on that you're not aware of. Shoot it prone to compare.

The more rounds you shoot, the bigger your group gets. Unless your three round groups are tiny and consistent, one shot is good, one is bad, and one is one of the others. I like 5 rounds for zero and comparison. Ten might tell you a bit more, but you have to accept a larger group. The larger the group, the more time, impatience, eye fatigue, etc.

Experiment with different targets that offer contrast and framing for your reticle like a box or a circle. I'll use a larger shoot-n-see type target for quick zero confirmations or some load swaps, but hard work goes on small targets.

Shoot at longer distances to see if the loads are performing better than you think. It's a bit of a mind bender, but load that's +/- whatever MOA at 100 may get a little better at distance, or hold that accuracy longer than others.

My (16") 1/8 Stealth barrel likes several 60-60gr bullets, and even 77s, and is sub-MOA (5rds) with them at 100. It can stay MOA out to several hundred rounds.

Pretty capable guys I shoot with unbox new guns and shoot them, no break in. Most don't clean them with any regularity, just the BCGs and trigger groups.