What kind of velocities are you seeing out of your grendel and factory SST's?
Acceptable Powder Charge variance
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What kind of velocities are you seeing out of your grendel and factory SST's?
I will have.to pull that.up on my computer when i get.home. i will post.it.tonight
Pull some bullets and measure the precision of the Hornady factory ammo powder charges. See if Hornady weighs their powder charges to 0.02 grains.
It's a virtual certainty that their cases are powder charged volumetrically, and that I'd be able to detect powder charge differences exceeding 0.1 grain on both my Chargemaster, and my 45yr old Ohaus balance beam scale.
I'm unaware of any major ammo manufacturers weighing out individual powder charges. Everything I've read is that they dispense powder charges volumetrically, and common tolerance exceeds +/- 0.1 grain.
And yet you consistently record SD at less than 10fps...
That's where I default, when all efforts to understand a cause and effect relationship continue to confound me: Magic!
Brian49
Member
I don't have anything to add to what has been said in previous posts, but what I didn't see and maybe with newer electronic scales this isn't an issue. I have an RCBS Micro Pro scale and through experience have found that the scale reading drifts anywhere from 2 to 4 tenths over time. I reload a lot as from Feb thru August I burn a lot of 204 and 22-250 shooting Belden gr squirrels. I recalibrate every time I start a session or after about 45 minutes because of the drift. When I calibrate the scale it checks out with test weights and reads the same as my balance beam, but by the time I've put BL-C (2) in twenty cases weighing every charge on the balance beam which doesn't take long the scale drifts low. I live 10 minutes from the RCBS plant and have asked about drift, their only recommendation is to use a dryer static sheet under the scale. So for along time I only use the electronic scale to dial in the powder dispenser and double check the balance beam setting.
average velocity of 2497 over 10 shots. Wrong about the SD. It was actually 7.
Thanks for the info, that's a good bit faster than mine. IIRC, I'm at 2450ish, also with an 18.
Mine is.a.JP lightweight
Lilja on my end. Woulda like a little lighter and faster barrel, but it shoots well.
I'm just understanding now that the Grendel isn't shooting a .223 Rem cartridge, and is likely a 6.5mm caliber. My research was specific to the .223 Rem cartridge, when I related some common Forum consensus of higher ES/SD compared to bolt (fixed) action rifles.
Occasionally I'd find someone claiming low ES/SD with their .223 AR. But there were multiple Posts expressing the experience, and expectation, of higher ES/SD with gas operated semi-auto .223 Rem AR-15s, compared to bolt rifles.
I never researched ES/SD on the 6.5 Grendel in semi-auto rifles, because my ES/SD battles were with the .224 caliber .223 Remington cartridge.
I weigh my charges to .1gr using a Charge-master. Loading cartridges from .223 to 300WM and have found that I've been able to achieve ES that is under 15FPS and SD's less then 7 with this level of precision. I do believe that it is imperative that the optimum node is determined when developing a load. I don't buy the belief of the gas operating AR15 producing higher velocity variations then a bolt rifle. I have owned and shot a 6mmAR(Whitely upper).in competition (300 yard egg shoots) for over 7 years. Using charges of Reloader 15, 28.2gr, 107gr SMK, BR4, Lapua brass, have consistently achieved ES of less then 15FPS, SD6. Velocity average is 2750FPS and accuracy runs .25MOA or better. My rifle has over 2000 rounds through it, and it has maintained this performance. I have seen this result achieved by other shooters using the Whitely AR in this caliber. As with bolt rifles, the quality of the build and the load makes a difference in performance.
I recall a US military study from many years ago conducted on the 30-06 using match grade rifles that claimed a .1gr variation in charge would result in an approximate .1 MOA change in POI at 1000 yards. I remember coming to the conclusion that if this proved true, it would suffice for my shooting needs. This has since proven to be the case
Recent test group of my 6mmAR at 100 yards.
I recall a US military study from many years ago conducted on the 30-06 using match grade rifles that claimed a .1gr variation in charge would result in an approximate .1 MOA change in POI at 1000 yards. I remember coming to the conclusion that if this proved true, it would suffice for my shooting needs. This has since proven to be the case
Recent test group of my 6mmAR at 100 yards.
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I agree that when you find that wide powder charge node variation in powder charge becomes much less critical.
Love my whitley turbo 40. But then again that rifle shoots just about everything i load up for it accurately
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.
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.
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