c-g-designs

BARREL BLOCS.

            Our friend Hitman recently asked if I once considered the barrel bloc systen and my reply was ‘yes, but my attempt did not lasted very long’.

            I will then tell my Barrel Bloc venture . Unfortunately, I no longer have my group records . I can only say they were rather disappointing.

            It was around 1977-1978. At this time, we had here in Chambois a testing base on which  it was sufficient to adapt a system  supporting a Barrel Bloc adapted to a suitable  barrel. I had at the time an unlimited access to the necessary mechanical means, therefore, it  as feasible.

            First, an action was needed. As it was not the most important element and, as the Mauser actions were not scarce here , a 1941 made at Steyr was chosen .

            Now, the barrel. The barrel was to have a very long reinforce to bear the Barrel Bloc as it was necessary to be able to move  it to determine best fixing point.

            George Swenson supplied me a 1.125 cylinder barrel, 28 inches long, 10 inches twist . The blank was cylinder ground 2550mm long from the breech, then tapered to end 19mm diameter at the muzzle . Chambered .308W to shoot the 190SMK in a load I was using in my Match Rifle .

The barrel bloc was realised in light metal alloy 7075 T6 ,120mm long with 4 M8 screws each side  screwed directly in the base at a torque of 20Newto/n/metre.It was then bored in 2 half-shells with 0,02mm smaller than the ground diameter of the barrel tp ensure the necessary tightening. Optical black anodised fpr the look.

            Fixed on the base and set to be on target at 200metres, we have first fixed the barreled action with the blooc at 100mm from the action face and we started to shoot groups of 5, using my Match Rifle loads .

            From the first shot , it is noticed a downwards reaction of the action , up to the point to become unpleasant to the index hit by the trigger finger curve.

            At the time, my first Match Rifle was  built on a Mauser action sleeved to allow the  rigidity  and bedding support itw as originally missing (This action is still active and end its career on the Big Bang Junior Philippe and I mentioned  hers sometime ago). This rifle, then equipped with a Schultz-Larsen  10inches twist. Fitted on the same fixed base system, this rifle gave better results than the Barrel Bloc test system.

            I cannot determine exactly the reason why what made the Barrel Bloc system gave results slightly inferior . I would tend to think the primary vibrations hereover mentioned and to the firm fixing impairing the ‘jump’ of the barrel muzzle . Perhaps also because the barrel vibrate in two times ?. I will not conclude..

            We have moved  the bloc at 50mm, then against the action front with no great success, perhaps a slight reduction of the groups (5shots).

            It is to notice the vertical position of the groups varied slightly, moving up together with the move of the bloc to the rear.

            This is the reason why my barrel bloc testing quickly ended..

            The barrel bloc is still on a shelf in my ex-workshop. I had later had it modified to make it bearing ¾ on the barrel and ¼ on the receiver ring, up to the recoil lug . This slightly improved the results, but no better than those obtained with its more  conventional brother.

            I drew the lesson of this test : it is certainly preferable to allow the barrel to live freely  its life, fitted on an action having an exccellent bedding.

            R.G.C

            01/2018