Shooting slugs from Airguns can be frustrating and a lot of us (to include myself) have deemed different ammo options as a NO-GO out of our rifles! Well... You might be WRONG!
With this slug in particular, I was TOTALLY wrong! This is the NSA 33.5 grain .25 cal slug out of my FX Maverick with 700mm Sniper kit with Superior liner. I can get the 36.2 grain NSA slugs to shoot sub MOA with very little messing around with my factory tune, but I’ve struggled with this one. That is until today!
I've found that with slugs vs. pellets they are MUCH more finicky with the harmonic tune of your rifle. I'm not sure if it has to do much the much larger bearing surface of slugs vs. pellets and / or the spin stabilization of slugs vs. drag stabilization of pellets, but I do know things get magnified BIG TIME while tuning with slugs.
The 3 Step process I’ve been using has changed everything for how I test and tune slug based Airgun ammo.
Step #1 Is the projectile stable in flight?
Step #2 Is my velocity tight? (low SD/ES)
Step #3 Where is the harmonic accuracy node?
I just got the SideShot scope camera installed with a GoPro 7 with custom Back-Bone lens from the guys over at Saber Tactical and holy crap! I’ve got this thing set to 1080 with 240 frames per second and now I can see the stability or lack there of for any given pellet or slug at various velocities.
STILL HORRIBLE GROUP!
With my particular rifle, if I push 33.95 grain pellets over 940 FPS they spiral out of control. So using the SideShot as my first step in tuning to determine stability will save me tons of time and frustration.
We can learn a lot from precision shooters in the powder burner world. I’ve been lurking in the precision firearm shooting forums and FB groups just soaking up information in how they develop custom loads and seating depths with their cartridges to find that sweet spot of tight velocities shot-to-shot and finding that harmonic node with seating depth to find those sub MOA groups. Getting your rifle to shoot any given ammo with as small of velocity deviations as you can get is a NON-NEGOTIABLE!
For us airgunners, we obviously don't have to worry about powder charge or primer combinations, but we have a related variable of finding that sweet spot of regulator pressure / hammer and spring weight combination to give us the smallest velocities variations.
You’ll hear me talk about this more in upcoming videos, but changing these variables also changes the harmonic signature ever so slightly with even the most minor tweaks. With precision shooting in the firearm world, they use seating depth and the jump to the rifle's lands as a way to harmonically tune their loads.
As airgunners, we don’t have the variable of our slugs jump to the lands in our rifles like firearms do, but recently we are seeing pin probe innovations come into our sport to control slug seating depth. This variable can also have a harmonic tuning effect on your rifle.
THERE'S THE SWEET SPOT!
So after shooting quite a few groups changing various things, I finally found that sweet spot for these 33.5 grain NSA slugs and was shocked how much the slightest changes could effect my groups. These groups were just my testing groups at 50 yards, but imagine this at 100 yards. If your ammo is stable and you’ve got tight velocities shot-to-shot, you can find a harmonic accuracy node and shoot great groups. DON’T GIVE UP!