Executive summaryThis is conceptually a Jeff Cooper Scout Rifle airgun for convenient personal training. The objective is to get as close to the Scout concept as possible with existing components, and test it to see if the idea is sound. (If it is, the idea could be refined.)
The base gun would be a wood-stocked Benjamin Marauder rifle in .177, with a shortened length of pull, Ching Sling installed, and Leupold Scout Scope (or equivalent) mounted.
Who is this for?Not to be flip, but this would be a valuable tool for anyone who wants to learn the mechanics of general-purpose riflery. As described in Jeff Cooper's indispensable The Art of the Rifle, expertise gained on a Scout platform is of use to everyone: the woods hunter, the action competitor, the precision varminter, the soldier, the plinker, or the uppity peasant.
Look at it this way. This would be a valuable tool for the rifleman who wants to maintain his skills for, say, the hunting fields, but cannot afford lots of live practice at a distant range. Many people have recourse to a safe range environment either at home or close to home, and could certainly benefit from more "live-fire" practice on both precision and speed targets. A few well-placed steel spinners and/or "field-target" type challenges can make practice possible daily instead of weekly or monthly.
The detailsThe Benjamin Marauder (aka "M-Rod") is already known as a high-quality, (comparably) affordable precision airgun with a good trigger and built-in sound suppression. Importantly it is a repeater, using a detachable 10-shot rotary pellet magazine along with a manual turnbolt that can be reversed for left-handers.
The stock is too long, the way most people seem to like them, but that problem can easily be fixed by shortening it to a LOP of around 12.5 inches, and rounding the rubber buttpad for mounting. The wood stock should also permit whatever slimming and weight-reducing might be desirable, and should support mounting the three anchors for a proper Ching Sling, whether in leather form or the nylon variant from The Wilderness. With a stock shaped to support snapshots and sporting a Ching Sling to lock the rifleman to the rifle, we go a long way toward what Col. Cooper was on about. In short, one could really learn on this platform. Train on this platform.
Mounting a proper Scout scope may prove tricky, but someone should be able to figure it out, and the M-Rod is a good enough rifle to justify the cost of doing so. Maybe it's as simple as a cantilevered rail going forward off the receiver's 11mm dovetail (11mm is the de facto airgun standard); maybe it's more complicated than that. It doesn't have to look fancy, it just has to work, putting the intermediate eye relief glass (the Leupold M8 2.5x has long been the standard) at the right distance and as low as possible over the bore.
For training, the trick to keeping it as practical as possible will be to develop targets of the proper size and perspective. While there is ultimately no complete substitute for shooting at a 300 yard steel plate with a .308 Scout, one can certainly approximate the challenge with an airgun at 50 yards by applying just a bit of attention. Using the rough approximation for "minute of angle" that most of us grew up on in reverse, if your goal is to hit a 12" plate at 300, then use a 2" plate at 50 for the airgun. For the same 12" plate at 200, use 3" at 50, or maybe 1.5" at 25, for the airgun. For the 12" plate at 100 offhand challenge, perhaps use 3" at 25. Use your imagination: if you are limited to a fixed range distance you can calibrate all your targets simply based on size; if you have the luxury of using various distances, you could use the same size target everywhere. If you've done your arithmetic correctly, the perspective should be the same through the glass, so you should be able to practice things such as range estimation off the reticle, holding over and under at various distances, etc., in a pretty conventional way.
One thing I would want to do if I started working at this would be to spend some time carefully learning trajectory behavior of diabolo pellets. Ideally, I'd want to find the right balance between actual trajectory, scaled target size and placed distance. The Marauder should be capable of half-inch groups or less at 50 yards, and better than that closer in. But if the trajectory curve of the pellet over that distance describes an arc proportionally like a .45/70 rather than a .308, I might consider scaling everything to 25 yards instead of 50 to make the curve closer. Obviously the closer in I get, the less I can train my eyes to see things at the "true distance", but in general I think there may be a lot of value in this "perspective foreshortening".
What is the value?Some benefits of this idea are self-evident. The use of .177 pellets instead of centerfire rifle ammunition is a fairly staggering cost savings. It permits many more range options because of its significantly reduced power. It's quiet: even loud airguns are quiet compared to firearms (even .22s), and the .177 Marauder is renowned for its sound suppression. You can refill the Marauder either with a hand pump (it's like a bicycle pump on steroids) or from a SCUBA tank.
Other values start to sink in more slowly. The ability to construct a suitable, personal "walking range", with targets placed at various distances that come into and disappear from view while walking a path, is an extremely significant selling point for training. Constructing such a range for .308 rifle requires resources most of us don't have, but doing so for a sub-1000fps, 8-grain .177 pellet is quite possible and very worthwhile.
And the convenience is hard to overstate, especially as it may translate into more actual practice. To be able to run through a few magazines every day, in different light and weather, with little or no commute and no need for hearing protection, potentially means a far more experienced and confident rifleman. The value of a durable, quality precision rifle, equipped with good trigger, ergonomic stock, effective shooting sling, and general-purpose sights, seems hard to overstate.
Of course there are downsides. The most significant is probably the safety lever, which from an ergonomics standpoint is just terrible. It operates like a Garand safety (which is hardly ideal itself), but when engaged offers no room at all; your finger might well literally be on the trigger if you're riding the safety in Standard Ready. It may be worth custom work to remedy this, just so that one can train properly.
The bolt-throw is obviously going to be different than for a centerfire rifle. If nothing else it will be significantly shorter. Now, whether or not this is a big deal is a bit open to question; if one trains to work the bolt to its limit each time, then it won't matter whether the bolt needs to load a .177 pellet, a .22 rimfire, a .308, or a .375. But, nonetheless a bolt throw that would approximate a .308 rifle would be better. Also, although the M-Rod has a reputation for durability and quality, it remains at least a bit to be seen how robust the bolt action truly is; to train properly for bolt work, one is not gentle.
A precharged pneumatic (PCP) airgun will not have any recoil. Again, whether or not this is significant is arguable, but it is there to consider, and all other things being equal, having at least enough recoil to disturb the sight picture between shots would be preferable to calm.
The Marauder does not come with iron sights. One could easily mount a rear ghost-ring aperture on the 11mm dovetail, but the front sight would require custom mounting of some sort. This is another thing that is more "nice to have" than "essential" in a trainer, although Jeff Cooper did consider reserve irons to be critical to back up the glass--at least on "the real thing".
That's about it, though. I don't know how the piece might or might not "make weight", but for a trainer, this would seem to be a reasonably minor consideration, in light of all the other advantages.
Are there other ways to do this?
Theoretically, there are other guns and optics that could serve this purpose. The best option in firearms is to go to the rimfire. Gunsmoke Guns in Denver has long produced what they call the "Cub Scout", which is a custom Ruger M77/22 with Leupold scout scope and Ching Sling. It's a fantastic idea, and if .22 ammo were plentiful again, it is very faithful to the Scout concept, with a vastly superior safety, and gives up only noise and backstop concerns to the airgun.
There are other PCP repeaters, but most of those are much more expensive than the Marauder. The AirForce airguns are marvelous machines and well-suited to a few useful things (e.g., mounting a scout scope, adjusting LOP), they are single-shots, and training for a repeating rifle really should involve a repeater. Other airgun powerplants are problematic. CO2 is fussy about temperature, and most guns running other powerplants (than PCP) are too far away from the action operation you'd want in a boltgun trainer.
Scout scopes have been around a while now, and there are alternatives to the Leupold, but all at some cost or other. The Burris unit is the best alternative, but it gives up objective diameter and thus a little light. I have been impressed with the quality of the Leapers 2-7x variable with 30mm tube and huge objective, but great balls of fire, that thing is huge and heavy. The Leupold is much more compact, one third the weight, and it gets the job done. Somewhat to my surprise, having now shot both the Leapers and the Leupold, I can conclude personally that the Leapers' extra field of view (which is significant) is not needed when using a scout scope binocularly. It's noticeable when you're using the scope as a viewing device--and the glass is beautiful--but it's not noticeable in practice when using it as a sighting tool. With both eyes open, you just don't notice it--and you don't need it.
There are alternatives to the Ching Sling, but they are all compromises. The "Safari Ching Sling" does get more out of a two-point mount than a standard "hasty", but it is not the same as a true three-point Ching Sling; anyone who tells you it is simply does not fully understand the latter. There is also the Giles sling system, which seems to work well for truly "wearing" a carbine, but it too gives up the precision that a Ching Sling can bring out of a rifle. (To be clear: one can also get a solid sling lockup from a standard military loop sling, but not nearly as fast.)
Suggestions for custom work or manufacturer refinement
Stock. The ideal stock would be as light weight as possible, slim and compact, and would feature either a short LOP (12.5" ideal) or an adjustment range suitable for kids through adults (say 9.5" to 13"). It would house three flush-fitting sling studs for a proper Ching Sling. It would be nearly perfect if it also incorporated a flush-fitting bipod as on the Mannlicher (Steyr) Scout.
Power adjustment. The Marauder already features a degree of power adjustment; here we would simply wish to refine or extend that. We don't need all the M-Rod's power for a trainer; ideally what we want is 1) enough accuracy, 2) a trajectory as close as possible to the scaled curve of a .308 rifle bullet over at least 300 yards of travel, and then 3) as many shots per fill at that ideal velocity as we can get. What might be really nice, even ideal, is if we could dial the valve so far both ways that we could accommodate a) absolute max shots per fill on minimum acceptable velocity, b) max shots per fill for a trajectory-optimized velocity, and c) max power, if we decided to take the rifle afield. Here, I'm new enough to airgunnery that I can't even really conjecture on whether such a thing could be done, much less how to do it. :-)
Safety. In looking briefly at the part diagram for the trigger/safety group on the Marauder, it seems hard to believe that one couldn't find a way to redirect the safety lever (perhaps just doglegging around the trigger/safety group) back toward the tang, for either a true tang safety or even a M700-style rocker switch. It would be worth a custom price to do this for the ergonomics!
Scope mounting. This is just a matter of how to securely get a rail space out far enough forward of the receiver to mount a Scout scope both low and forward. Other than the general principle that lighter is better, it wouldn't much matter how this was done; clearly the Benjamin Armada has such a rail-space, but we don't need plumbing fixtures everywhere, just on top. What would be really nice would be a rail that permits both conventional and Scout scope mounting, and which incorporates a reserve ghost-ring rear aperture sight, a la the XS shotgun sight/rail.
Bolt throw. This would require some ingenuity, but I think it could be done. The ideal end result is a bolt that behaves exactly like a .308 length boltgun, in terms of bolt lift and throw. How to do this? Well, it is already evident that Crosman/Benjamin understand enough about their rotary magazine to have developed both a turnbolt system (Marauder, Armada), and also an AR charging handle system (MAR177) that manipulate it. I would imagine that one could create a replica rifle bolt that cams the rotary magazine slowly over its travel, easing wear on the magazine itself while still allowing the rifleman to run the bolt vigorously at full speed.
Well, there it is.
Got the idea out of the brain; now I can attack it and possibly start asking around. :-)