This has been a topic I have been playing with and struggling with since the day I first shouldered a big bore air rifle. Should you preload your bipod or let it freely slide during the recoil of your shot cycle? I have tried everything and used many different options as part of the shooting platform. In my testing I've found some pretty consistent findings I'd like to share.
As part of this journey of discovery and experimentation, I realized that when you start pushing PCPs up into higher pressures and higher FPE slinging heavy for caliber slugs, that peaceful little pellet pusher can turn into a bucking bronco. It's not like shouldering a 12 gauge shotgun or even close to that kind of violent recoil, but you start getting this frustrating amount of movement that you don't get with pushing pellets in that typical 850-900 FPS range.
That additional shot cycle movement is caused by a few different things, but all of it put together can mean the difference between fantastic or horrible shot groups. So let's first talk about what we do know about magnum power slug slinging PCPs.
For the sake of this conversation, I define magnum slug slinging PCPs to include small bore (.177-.30) and big bore PCPs (.35 and higher) set up to shoot heavy for caliber (high BC) slugs which typically includes longer barrels in that 27-34 inch range and shooting at 2400-3600 PSI.
An important part of this conversation also includes everything that happens the second you pull that trigger to the time the slug leaves the barrel. It might seem like it is an instantaneous moment in time, but there is A LOT going on during that shot cycle.
To add to the complexity of this shot cycle, there is a multiple recoil event occurring. This is common knowledge with break barrel springer, but I don't think it gets talked about enough when it comes to big bore airguns and small bore airguns that are starting to get hot rodded into magnum power levels. As we get up into higher powered airguns, that multiple recoil event is something that needs to be considered for maximum accuracy.
With a big bore airgun or magnum slug airgun there is an exponential amount of movement in the shot cycle as compared to the tamer shot cycle in a more mild tune for pellets. This movement includes everything from the moment that you pull the trigger that releases the trigger sear which then - releases the hammer - under spring tension moves towards the valve face - hammer impacts the valve opening the valve - air is released sending air through a transfer port or top hat - hitting the back of the slug moving it through the barrel and if set up correctly the valve slamming shut before the slug leaves the barrel. All of these micro events are called "lock time".
These lock time micro events occur no matter if you're shooting a sub 12 FPE airgun in .177 cal or an air belching 800 FPE Deer slaying big bore .50 cal airgun. The difference though is the magnitude of these micro events that are found in magnum slug slingers. Those factors include a heavier hammer weight, increased spring tension, heavier valve impact, and the size of your slug and the force of propelling it forward and the resulting forces imparted on the platform.
All of these things put together can really mess up your shot groups if you don't learn what your rifle likes or does not like in controlling these forces. The resulting forces can be easily described by Newton's Third Law of Motion. That law states for every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.
So think about Newton's Third Law of Motion as it pertains to our airgun shooting platforms. When you start using heavier springs and hammers to open valves that are under increased air pressure in order to get them to open enough to push your projectile - you are gonna get an equal amount of movement in the opposite direction. When you push a heavy for caliber projectile, the resulting amount of recoil from pushing heavier ammo will have an equal and opposite reaction. That is A TON of increased movement when shooting slugs from a magnum powered PCP as compared to a peaceful pellet puffer.
The other factor we need to consider is in which direction are these forces being exerted and how many times these micro events occur during the shot cycle causing these multiple recoil events. In PCP airguns, when the trigger sear is released the spring is throwing the mass of the hammer rearward (first recoil movement event) to strike a valve (second recoil movement event) which causes the valve to open to propel the slug forward (third recoil movement event). So using Newton's Third Law of Motion, think about how many back and forth movements are going on during the shot cycle.
Do you think this is all a bunch of malarkey? Well consider this..... In extreme situations with Magnum Springer Break Barrel rifles when that motion is so abrupt and going in opposite directions so quickly and violently causing a double recoil and in opposite directions - it can destroy a low quality scope in just a matter of a few shots.
In PCP airguns, multiple recoil isn't as violent going in opposite directions, but it does exist especially with heavier hammers and springs shooting at higher pressures propelling heavier ammo. So if these forces can destroy a scope in a springer, we would be greatly mistaken to think they can't affect the accuracy of your shot groups in a magnum powered PCP.
I had a conversation with Joe Iturralde from Predator Pellets (The Lord of Lead himself) and we both agreed that if you want to learn how to shoot big bore airguns with precision - go buy a Magnum Break Barrel Springer and shoot as much as you possibly can. Why? Learning the art of recoil management and mastering the artillery hold will serve you well when it comes to slinging slugs with airguns.
So how do we control these forces to tighten up our shot groups? I have found the more you try to control them, the worse your shot groups get. I have tried many different hold techniques and bipod / support options to see the differing results. These include using different bipod feet to either use a "preload" or "slide" approach.
I have found that wrestling with your rifle to try and bear hug or push it into submission will result in poor accuracy. The more and more I shoot various big bore airguns and now I'm getting into the magnum slug slinging small bore calibers with the FX Impact M3 in .22 cal shooting over 80 FPE, just letting it move naturally is the much better approach for maximum precision and accuracy. So what can we do with our equipment to achieve this natural state of recoil zen?
To test differing bipod options I set up two of my Atlas Bipods with extreme examples on the spectrum of sticking the bipod in place or letting it slide back and forth. In this 75 yard test I used the Atlas Spike Feet with the BT65 Gen. 2 CAL Atlas Bipod and the Ski Feet for the BT35-LW17 5-H Atlas Bipod.
One HUGE improvement was the addition of the Saber Tactical Arca Swiss Rail to push the bipod out much further. This gets rid of that "teeter-totter" effect of having the bipod mounted behind the bottle closer to the trigger. This is a MUST HAVE accessory.
In the rear I am using a canvas shooting bag which also needs further testing as I have a theory on the use of a bag vs. a monopod in how it affects recoil management, but for the sake of single variable testing, I am just using a rear bag for now.
I tried the spike feet first by preloading the bipod with heavy shoulder pressure and pushing the rifle forward which resulted in the worst groups of all. I also tried it with little shoulder pressure with no preload. The groups were better than preloading, but not nearly as good as letting the rifle freely recoil. I have found similar results shooting the AirForce Texans big bore airguns with a similar set up, especially with my .257 Texan.
I also found that shooting on a slick surface also helped with accuracy. For the sake of testing and in the name of science, I used my wife's vegetable cutting board as it gave me a very stable and slick surface for the ski feet to glide on. She doesn't typically read these posts, so she will never know her germ free sanitized vegetable cutting board was sitting on the ground which is most likely covered in Deer pee and Turkey poop. Meh - she will be fine. It's all organic.
There is more testing needed, but I am very much learning into the "let it slide" on a slick surface as far as recoil management for maximum precision and accuracy. I think it has a lot to do with all the different recoil motions and resulting counter motions going on in the shot cycle. I am no scientist, but when it comes to studying empirical evidence, I am frickin obsessed. So in conclusion, give this ski feet bipod option a try and learn to master your hold to really tighten up those groups!
