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While 140gr bullets may not be the optimum size for the Grendel, they are certainly capable of being shot from it. To me the biggest issue is the amount of appropriate burn rate powder capacity that is lost in able to allow them to fit in an AR15 magazine. Nevertheless, I bought a box of Hornady 140gr Amax bullets that were on sale to at least expand my understanding of the caliber using upper end payloads a little further. Worse comes to worse, I have them for my .260 Remington.
A philanthropic member of another caliber specific forum sent me an 8lb keg of the new AR-Comp powder to experiment with and while we have plenty of good choices for the Grendel already, I've also been trying to find a fit for it that offered some benefit to Grendel fans. ATK has not released a QL powder file for it, only some recipes for common calibers (not the Grendel). I have tried reverse analyzing loads I have already done with it to arrive a appropriate parameters to use in QL for modeling, but the powder changes characteristics a lot from caliber to caliber, for the ones I have loaded it in. By and large, it has good burn characteristics consistent with heavier bullets in the Grendel, but and this is a big but, It's density sucks. Add to that the fact that it being an extruded powder, it does not integrate too tightly into the Grendel case, even when given a ride on my vibration plate before seating the bullet.
With deference to those observations, I tried a quick pass over four loads and given it being branded as a "faster Varget", I also shot a comparison string with Varget.
Here are the results:
Noteworthy is the fact that in the upper 3 loads, I could hear granules cracking as I seated the bullets, which qualifies in my mind as compressed loads. More noteworthy is the fact that the 26gr load of both AR-Comp and Varget are both all I could fit in the case and still get the bullet to seat to 2.29, so they are maximum (by volume) loads. None of the loads exhibited any excessive pressure signs and several were unduly sooty indicating that perhaps they were not sealing as well as I would have liked.
I had removed my normally fixed mount scope to give the receiver and barrel extension a trip through the parts cleaning tank in order to prep it for a secondary test involving a new lubricant I got a sample of, so I had to dial it back in. I used the Varget string for sight-in and it is reflected in it's 100 yard group. Three of the four AR-Comp groups showed promise despite my range visit being against a time limitation as I had somewhere else to be. My hasty presentation or lack thereof on the bench shows in the groups. All of that aside, AR-Comp does show promise with 140gr bullets. Especially considering it is spec'd for -20 to +160 degrees with only a 20fps change. The POI shift in the last two groups may be a function of hitting a poor barrel time as I did not change the scope from the first two groups.
Interestingly, when I reverse analyzed the load results into QL, I had a near perfect match with AA2520. Now you have to take that with a grain of salt as I have never had QL accurately predict resulting velocity and pressure for any load I've tried it with. That is, not without tweaking some of the parameters. That's another story altogether. So, the fact that AR-Comp nails QL's predicted performance of AA2520, doesn't have as much merit since a load worked up with real AA2520 does not match QL's predicted performance for it, without massaging some of its parameters. It is however useful information in case you want to use QL to predict how AR-Comp would behave with your 140gr bullet loads using Remington 7 1/2 primers. All that and a $1.59 will get you a cup of coffee at Starbucks.
PS: In case someone wonders, yes, the 24gr group is 5 shots.
Hoot
A philanthropic member of another caliber specific forum sent me an 8lb keg of the new AR-Comp powder to experiment with and while we have plenty of good choices for the Grendel already, I've also been trying to find a fit for it that offered some benefit to Grendel fans. ATK has not released a QL powder file for it, only some recipes for common calibers (not the Grendel). I have tried reverse analyzing loads I have already done with it to arrive a appropriate parameters to use in QL for modeling, but the powder changes characteristics a lot from caliber to caliber, for the ones I have loaded it in. By and large, it has good burn characteristics consistent with heavier bullets in the Grendel, but and this is a big but, It's density sucks. Add to that the fact that it being an extruded powder, it does not integrate too tightly into the Grendel case, even when given a ride on my vibration plate before seating the bullet.
With deference to those observations, I tried a quick pass over four loads and given it being branded as a "faster Varget", I also shot a comparison string with Varget.
Here are the results:
Noteworthy is the fact that in the upper 3 loads, I could hear granules cracking as I seated the bullets, which qualifies in my mind as compressed loads. More noteworthy is the fact that the 26gr load of both AR-Comp and Varget are both all I could fit in the case and still get the bullet to seat to 2.29, so they are maximum (by volume) loads. None of the loads exhibited any excessive pressure signs and several were unduly sooty indicating that perhaps they were not sealing as well as I would have liked.
I had removed my normally fixed mount scope to give the receiver and barrel extension a trip through the parts cleaning tank in order to prep it for a secondary test involving a new lubricant I got a sample of, so I had to dial it back in. I used the Varget string for sight-in and it is reflected in it's 100 yard group. Three of the four AR-Comp groups showed promise despite my range visit being against a time limitation as I had somewhere else to be. My hasty presentation or lack thereof on the bench shows in the groups. All of that aside, AR-Comp does show promise with 140gr bullets. Especially considering it is spec'd for -20 to +160 degrees with only a 20fps change. The POI shift in the last two groups may be a function of hitting a poor barrel time as I did not change the scope from the first two groups.
Interestingly, when I reverse analyzed the load results into QL, I had a near perfect match with AA2520. Now you have to take that with a grain of salt as I have never had QL accurately predict resulting velocity and pressure for any load I've tried it with. That is, not without tweaking some of the parameters. That's another story altogether. So, the fact that AR-Comp nails QL's predicted performance of AA2520, doesn't have as much merit since a load worked up with real AA2520 does not match QL's predicted performance for it, without massaging some of its parameters. It is however useful information in case you want to use QL to predict how AR-Comp would behave with your 140gr bullet loads using Remington 7 1/2 primers. All that and a $1.59 will get you a cup of coffee at Starbucks.
PS: In case someone wonders, yes, the 24gr group is 5 shots.
Hoot
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