Testing the 135gr Afterburner
Got my 135gr .308" Afterburners in today. So here starts the testing on them. Follow along.
I'll be starting the testing in a 24" 1:10 twist 308win and the intent is to test them close range first on whitetail this November.
First thing was first, I wanted to see how consistent these bullets are out of the box. So I weighed all 50 on my
AnD FX120i and then measured all 50 with my Sorteez digital indicator. The results are pictured below, in the notebook.
The extreme spread for weight was .9gr with the average coming in at 134.85gr. The extreme spread for base to ogive was .0065" but the majority were within .0025"
I did some initial comparing in QuickLoad to determine which powder combo would likely be best. My go-to powders in 308 (albeit with heavier/longer bullets), being Varget and RL-15.5 look to be too slow burning, and thus fill the case up way too fast. Both are showing compressed already at starting loads, and way compressed at max loads. Not a big surprise, but nice to know ahead of time.
IMR 8208 XBR looks the the most promising temp stable option, with a potential node possibly being around 2922fps. This of course will change once I start testing it, but it gives me an idea of what to maybe expect. I'm still hopeful I can get 3000fps.
I've decided to use small rifle primer Peterson brass, as I really like the consistency I get from them, as well as I have more SRPs on hand lol.
COAL looks to be around 2.810" based on as far as I can seat them out without the bore rider and crimp groove negatively interfering and potentially producing issues with runout.
The next step is to load up a few rounds each at 3 different charge weights so I can go shoot them and record velocities. I'll then use that to calibrate QuickLoad to my actual results. That'll allow me to get much more accurate node estimates from it. Then I'll be able to load up some more to confirm where the node actually is. If that goes well, I may or may not need to do a seating depth node test, then I should be set for deer season with bullets to spare.
The ballistic chart below shows the potential at my altitude for this bullet with a MV of 2922fps. For this initial test, it’s unlikely I’ll take a shot further than 300 yards.
Got the initial rounds shot today. The following below is the data gathered from those rounds:
135gr Afterburner
42.0gr
1- 2953
2- 2953
3- 2962
Avg- 2956
SD- 5
ES- 9
42.5gr
1- 3004
2- 3011
3- 2993
Avg- 3002
SD-9
ES- 18
43.0gr
1- 3003
2- 2996
3- 3017
Avg- 3005
SD- 10
ES- 21
So that’s exciting and means it is faster like we thought and capable of the 3000fps mark. So with all that data plugged in to QuickLoad and with it now calibrated the estimated OBT node is 42.8gr with an estimated MV of 2996fps.
So next, I will load up some more rounds below, at, and above that estimated charge weight and then go shoot those and confirm where the actual node is.