Acceptable Powder Charge variance

[Greyfox]

I'm waiting for AR .223 Rem owners to sound in on the ES/SD matter.
I'm hesitant to conclude your 6.5 and 6mm ARs are an apples to apples comparison to the 5.56 AR.
I've loaded for quite a few bolt actions, and chronographed many bullet speeds in the cartridges ID'd in my prior post. Never had a problem finding decent ES/SD loads in those bolt action rifles.

Your 6mm and 6.5mm cartridges differ in both caliber, and likely capacity. I haven't seen any opinions yet, based on AR .223 Rem experience. I can post about my experiences in bolt rifles with larger cartridges and calibers. But I have no ES/SD deficiency with any of them, so those experiences aren't particularly relevant.

Likewise, if you've not extensively chronographed .223 Rem bullets fired from a gas operated AR, your comparisons and conclusions aren't particularly valid.

If your personal experiences and opinions are based on recording the velocity of more than 100 AR .223 Rem bullets, then please make that clear, so I have a means of knowing what value to assign your opinions. I've recorded a couple hundred bullet velocities, and I gotta say the obvious. My opinion is based on much more 1st hand experience than either of you have committed to having within this Thread. My experience is real, and consistent with that of many other AR-15 .223 owners/operators.

The 338 mags I load for produce lower ES/SD with less effort than my 280s and 7mm mags. And the .223 is a peashooter, compared to the 280s.[/quote/]

I wouldn't declare myself an expert on the AR platform and surely don't feel the need to justify my expertise. I have owned and shot AR's of various types and will state that it would be an error to make a blanket generalization that they are incapable achieving consistent velocity performance.....whether a 6mmAR or 223. The AR comes in many different configurations, barrel lengths, barrel weights, twist rates, etc, that I suspect the performance varies greatly amongst the different formats. Perhaps you should better qualify you experiences and equipment. I have a 223 AR that delivers comparable ES(<10) and SD(<10) to my 6mmAR. It is built with the same 24" heavy barrel, 9:1 twist, and "care" attention to construction. It also delivers accuracy in the .25MOA range/2990FPS. I use Lapua brass, 69gr SMK, Br4, and 25gr of Varget. The average AR has some trouble getting to this performance, I will agree. But with the right set up good performance is possible.

200 yard 5 shots, 69gr SMK@2990FPS

 

[tbrice23]

This is only one chrono reading I have available right now of my AR15. The load was 69gr SMK, AR Comp and Rem.7.5 primers.

I'll search my log book tonight for more chrono data.

 

[Pdvdh]

Never asked anyone to justify their expertise, or value as a human being. I did solicit the description of the relevant experience with recorded bullet velocity from the 223 AR platform, which supports the basis for the expressed opinions. The only caliber and rifle my ES/SD issues pertain to is the 223 AR.

Let me clarify: The precision of my bullet clusters on target is completely acceptable across multiple powders and powder charge weights. Accuracy is fine with the 60gr Vmax. The only unique anomaly I experience is much higher ES/SD with this rifle and cartridge, compared to any other rifle and cartridge I have similar levels of effort and experience with. All the other rifles happen to be bolt actions with much larger cartridge capacity, and larger caliber.

My AR-15 was born a CMMG MOD4 SA. It has the CMMG 16" factory barrel and carbine length gas action and CMMG bolt and bolt carrier group. Aftermarket mods include the Vltor A5 stock, buffer, and buffer spring kit. A BCM-KMR-A13 free float handguard. A Geissele trigger. A BCM/VLTOR Gunfighter charging handle.

I've previously described the prep of the reloaded ammo. ES higher than 50 is the norm when recording velocity of eight or more bullets. I've had some loads with ES exceeding 100! And I've easily recorded more than 200 bullet velocities.

If folks are basing ES/SD on three to five shots, they're being misled to a false conclusion.

 

[Greyfox]

Phorwath, It's possible your issue could be the 16" barrel. My buddies are avid AR shooters and claim they can produce pressure consistency issues with the shorter barrels which can effect velocity spreads. I agree with the practice of using 10 shots to get a viable ES/SD. All my AR's have barrels that are 20-24". I have only bothered to chronograph my 24" AR's that are used for precision shooting/hunting. I don't see any problems.

 

[Pdvdh]

Appreciate that feedback.

I'm OK with what I've got for my uses of the rifle. It seems that it is what it is with this AR. It's curiosity that prompts me to have another go at it every now and then. Thanks

 

[Pdvdh]

Phorwath, It's possible your issue could be the 16" barrel. My buddies are avid AR shooters and claim they can produce pressure consistency issues with the shorter barrels which can effect velocity spreads.

Thought about this some more. The barrel length on the majority of ARs in use in the country are undoubtedly the M4 Carbines. Those ARs have 16" long barrels, and the gas port which drives the bolt and bolt carrier back is located closer to the chamber on the 16" long carbine model barrels than on 18", 20", or longer barreled models.

I don't know if the bolt begins moving before the bullets leave the muzzle on ARs or not. But the pressure on the 16" carbine gas actions hits the gas port earlier during bullet flight down the bore than on the ARs with mid-length or rifle-length gas tubes/ports. So the port location and port diameter on the 16" M4 carbine ARs, like mine, may be the culprit. If the pressure is more variable due to the carbine length gas port before the bullet leaves the muzzle, or if the bolt begins to move before the bullet clears the muzzle - either one or both combined could adversely affect ES/SD.

Perhaps that's why it's not too difficult to find a number of AR 15 owner's experiencing higher ES/SD. Most of them are shooting M4 Carbines with 16" carbine length gas tubes/ports. This is my running suspicion and theory for the time being. I presume you have a rifle length gas tube and port on your 24" barreled AR?

 

[rcoody]

Thought about this some more. The barrel length on the majority of ARs in use in the country are undoubtedly the M4 carbines. Those ARs have 16" long barrels, and the gas port which drives the bolt and bolt carrier back is located closer to the chamber on the 16" long carbine model barrels than on 18", 20", or longer barrels.

I don't know if the bolt begins moving before the bullets leave the muzzle on ARs or not. But the pressure on the 16" carbine gas actions hits the gas port earlier during bullet flight down the bore than on the mid-length or rifle-length gas tubes/ports. So the port location and port diameter on the 16" M4 carbine ARs, like mine, may be the culprit. If the pressure is more variable due to the carbine length gas port before the bullet leaves the muzzle, or if the bolt begins to move before the bullet clears the muzzle - either one or both combined could adversely affect ES/SD.

Perhaps that's why it's not too difficult to find a number of AR 15 owner's experiencing higher ES/SD. Most of them are shooting M4 Carbines with 16" carbine length gas tubes/ports. This is my running suspicion and theory for the time being. I presume you have a rifle length gas tube and port on your 24" barreled AR.

I have had good luck building precision .223 ar's with 20 to 26 inch barrels and a rifle.length gas system. None had a 5.56 chamber. The best had .223 match chambers.

I would not waste my time precision reloading for a 5.56 chambered 16" carbine. For my m4 i just shoot federal lake city bulk ammo and call it good.

 

[Pdvdh]

I would not waste my time precision reloading for a 5.56 chambered 16" carbine. For my M4 I just shoot federal lake city bulk ammo and call it good.

I don't argue with your position. It's a hobby. I have bolt actions rifles for long range hunting. I'm learning thru direct experience. I'm content with the precision of bullet POIs on target. I then continued to put in a lot of effort to improve precision with respect to ES/SD. Eventually accepted the fact it most likely wasn't going to improve. The one bullet I see lower ES/SD with is the cannelured Nosler Bonded Solid Base. I crimp into the cannelure, and perhaps that helps maintain more uniform chamber pressures??? A possibility...

My AR is well suited for what I purchased it for. I don't shoot or hunt past 300 yards, or compete with this rifle. I have shot it at 600yds, but just for kicks. It's scoped with a 1-4X variable. Not enough magnification for good crosshair placement past 200yds.

I typically chronograph and shoot targets at 280yds. Due to the low scope magnification, I purchase and place one of the 6" diameter blaze orange circular targets on a much larger piece of white backing material. I then do my best to center the reticle within the 6" blaze orange circle. Works pretty good. I've obtained some 1 1/2"groups at 280yds, so I must be getting a reasonably consistent hold on the center of target at that range.

 

[rcoody]

That is exceptional shooting with a 16" AR and a 4 power scope

Something all those AR shooters at the.local gun range could only dream of

They can't even shoot those kind of.groups at.50 yrds

 

[parshal]

I did a test once in a 22 Creedmoor using the Chargemaster only and trickling with the Gempro only. I found no discernible difference in SD or accuracy. That was 20 rounds of each. A small sample in one caliber but something nonetheless. I also have a Scott Parker tuned scale that I've not loaded with yet and intend to use that for my precision rounds. I intend to use the Chargemaster a couple tenths light and trickle on the balance scale. I figure it's not going to hurt.

I tuned my Chargemaster settings and throws charges much faster now. You have to tune it for your charge weight though. One cartridge uses 45 grains and the other uses 63 and the 'tunes' for each don't work for the other. I'll get overruns on one or the other if I don't change the tune.

 

[rcoody]

I have.a chargemaster, harrell powder measure, lee prefect powder measure and 3 gempro's

I have.found my fastest and most accurate charging method is to dump a charge a little short with lee dippers ($10 investment) on my gempro and trickle with my little dandy. Easy +/- .02 grains

Selling my chargemaster and going to try this auto trickler and high priced scale. Probably will be no more accurate but i like gadgets

Funny some loads i have i can just throw charges with the harrell without even weighing and some really tighten up with very accurate charges.

You can tell a lot about what to expect from a good ladder test