MDT TAC 21 Chassis Stock by Chris Parkin
It’s all in the detail
So we now have a gun - a bipod was simply fastened on to the stud fitted to the underside of the stock’s fore-end and all that remains is to mount the scope. The action section of the TAC21 features a full-length 1913 spec. Picatinny rail with a built-in 20 MOA incline. This Picatinny rail continues all the way to the tip of the fore-end BUT, there is a joint in its centre due to the two-part stock AND the fore-end section does not share the 20 MOA incline and therefore does not ‘flow’ through. You won’t visually notice it but beware – whatever you fit to it will not optically or mechanically align precisely with your scope.
The whole chassis is hard-anodised to Mil. Spec. type 3 standards and this does leave the Pic. rail a little oversized and hence tight for a slide-over ring like a Burris Signature Z but not a problem for a clamp-type Weaver or Picatinny ring. Due to the straight-line design, you will need high rings as the scope’s objective lens does not of course fall above an exposed swamped barrel.
I fitted some Badger 34mm extra high rings to hold my Schmidt Bender PMII and even they offered only half a millimetre of clearance - so no lens cap could be fitted. A replacement barrel of up to 1.35 inches in diameter - the diameter of the action itself - could be fitted and remain fully free-floating in the fore-end but be aware, the recoil-lug pocket machined into the chassis is profiled to fit standard Remington recoil-lugs and a thicker lug, often used by custom gun builders, may require the pocket to be enlarged.
Stay on Target
Of course, the whole point to a chassis like this - or any similarly profiled `tube gun` - is that the recoil forces within the gun, as well as being ergonomically correctly fitted to you, are directed far more in-line with the shoulder and centre of the recoil pad. On a butt-system such as the Magpul, supplied with the TAC 21, the height adjustable cheekpiece allows a precise cheek-weld if you wish.
When shooting a relatively ‘snappy’ calibre - like a short barrelled 308 - recoil, although not at all problematic, is sufficient to disturb your point of aim and consequent return to target and repeat firing time. The joy found with the MDS is that with the moderator or brake fitted - or even with nothing up front - the gun, although still with felt recoil, did not jump around or lift the muzzle - it came straight back into the shoulder.
One downside, for cleaning and bolt removal in a gun such as this, is the need for a quick-release butt. The lateral QR locking pin works well and a small rubber packer next to it prevents any play at what is effectively a pivot point but keep your eye on this as you don’t want it to pop out or work loose. Again, the Magpul systems shows a butt-hook profile and, as it is parallel, offers no vertical movement during aiming other than bag squeezing although this is a personal matter. The underside will slide freely on a back- bag and the cover can be removed to expose further picatinny rail, perhaps to add a monopod?
Does a V-block work? During testing, for various reasons, I had needed to
remove and replace the barrelled-action a couple of times and, other than the trigger, the process was simple enough. The point I found was that by using a torque wrench on all bolts and fasteners, ‘zero’ on the scope was maintained and this is a fair sign that the v-block bedding system was reliably supporting the action stress-free and repeatably.
Not that it matters as they stay hidden anyway, two easily visible lines were now clearly visible in the parkerised finish of the underside of the action, clearly showing the bedding-block was bearing along these two longitudinal contact points, usefully adding some stiffness to the action and thus offering good support for the barrel.
Unlike some tube gun chassis systems, where the action is be bonded-in permanently, there remains a slight air gap around the action and some may doubt both this and the fact the scope is attached to what is effectively a tube surrounding a tube but, I found no cause for concern and again, my unnecessary rebuild of the gun reassured me that the system was working exactly as it should.
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