I have wanted to update on my Impact for some time so I'm going to start with the magazine. I had once posted about how I used a Dremel tool to route out the bottom of a Side Shot mag in an attempt to be able to increase the length of my slugs for maximum weight. The main reason I wanted maximum weight besides the knock down power was to try and keep the fps around 1100 to avoid the sonic crack. After the power tune performed by Ernest any hopes of keeping the fps at 1100 have been blown out of the water. (Pun intended). Preliminary tests with my routed out mag with a 43.5g BT/HP were 1,365 fps, and that was on power level 4 so there is still potential for more. This is of course on helium, not air. For those of you going straight to your calculator it comes in at 180ft/lbs. Then I got the notion to print the base and cover with a groove to gain maximum length. After many hours spent in CAD measuring, printing and correcting some measurements, sometimes by as little as 3-4 thousandths and having a box of rejects to show for it I finally have a magazine that so far seems to be functioning reliably. I also printed what I refer to as the wheel, the rotating device that moves the slugs which also allowed me to add a count window. I did this because I am shooting a .247 slug, not a .250. I will explain this further in another update on my re barrel job that was more than 2 years in the making. And no, they can't be purchased from Nielsen or anyone else for that matter, at least not without paying major custom die fee's. So, I bought my own press and had a .247 die made for my one off rifle.
So now as you can hopefully see in this photo, with my new magazine with deep grooves I have the capacity to load slugs with a length of .485".
Earlier tests with the previous magazine and trying flat base, small cup base and rebated boat tail showed the RBT to be the most accurate. This definition of RBT is from Corbins Web Site: "A RBT or Rebated Boattail base is an advanced form of the conventional boattail base, which adds a 90-degree step or shoulder between the angled base and the shank of the bullet, to act as a "spoiler" and break up muzzle gas flow, provide a better seal in the bore, and cause a more rapid and concentric transition from the muzzle to free flight than a boattail angle emerging from the barrel." I could get more weight using a flat or cup base than the RBT but accuracy trumped max weight on this decision. Hollow point even though it is hollowed out is actually heavier than a round point. This is because the round point added length at a very narrow diameter, with the HP the narrowest diameter is clipped leaving a wider and heavier section, even when hollowed out.
These slugs now tip the scales at 50.6g. So the next test I'm guessing should approach if not exceed 200 ft/lbs. I will drop in fps with the heavier slug but I also have one more power setting to un-leash the full power of this beast.
I printed the 3 main parts of the magazine and used the hardware from the original Side Shot magazine. I'm sure I forgot something so if there are any questions I will respond ASAP.
