Over the past month I've done a lot of shooting into clay at 50 yards with nearly all of my airguns. I've found that the clay is much easier to work with than ballistics gel as it can be infinitely reused, subject only to having the wound channels be pounded in between shots.
The above picture shows what happens with bullets over expand at high velocity. The bullets on the top are .308 NOE cast 98 grain hp, the bullets on the bottom are .45 NOE cast 218 grain hp Bob's Boattails. The lead allow is random tire weight lead that's been heavily slagged. The left bullets that only have a base left represent muzzle velocities of 940-950fps in the .308 and 900fps in the .45. The bullets on the right represent muzzle velocities of 810fps and 755fps respectively in the .308 and 830fps in the .45. Impact distance on all shots is 50 yards.
I've very encouraged to see my alloy perform so well at lower velocities. Over the past year that I've been casting, I thought my allow was hard and brittle. In fact, I've simply been firing the projectiles too fast for optimal mushrooming. Although in truth there isn't a major difference in the wound channels between the fast bullets that fragment and the slower bullets that mushroom. Both offer almost the same size wound and depth of penetration.
Based on these results, I'd say the maximum killing range of my .308 is much further than I anticipated. 200-250 yards at least if fired at 950fps from the muzzle. I'm even getting good mushrooming at muzzle speeds as low as 650fps, but at that slow there's a noticeable decrease in penetration.
In the below videos I tested various loads both commercial and cast in my .25 Condor (40fpe), .300 Flex carbine (74fpe), .300 Flex long rifle (115fpe), .308 Texan SS (124 and 195fpe), and .45 Texan SS (330fpe).
https://www.youtube.com/watch?v=UUQNAE4X15E
https://www.youtube.com/watch?v=xm5BF3UtCEg
I was using clay for my own knowledge independent of Matt Dubber's videos. I started with playdough and went to clay when my wife had some coupons from Hobby Lobby. But I was inspired by Matt's recent videos to focus on bores larger than .22 for my own video. There was no reason to retread the ground Matt covered in his .22 videos.
That being said, the biggest bang for the buck (in terms of wound channel vs. energy and air expenditure) seems to be .22 Gamo Red Fires. They produce a shallow but big wound channel out of my .22 Urban at the default 23fpe at 50 yards that is very comparable to .25 Polymags at 40fpe. Go figure.
