Ive been working on this new cartridge for the last year or so, when i had time between customer rifles. The 408 case has been very fun to work with, so many posibilities wildcatting it. I wanted to design a new case larger than the 408cheytac, i looked real hard at the 50cal spotter case (short 50BMG) as a possible choice. I also looked at the 416 Barrett round, but didnt want to get into the hassels of the BMG class of actions and barrels. I wanted a round that can be used for hunting in a reasonable carry type rifle if needed. I had several conversations with my brass maker and told him what i was contenplating, he came up with several possible choices of brass he allready has dies for. He sent me several samples to check over and i cut them apart to check the web area as this new round will be a high pressure case. He also mentioned that he had a customer that had done somthing similar that i was looking to achieve. I contacted the gunsmith in New Zealand to get his story on what he had done and if it has worked out to his liking. We exchanged emails and thoughts on what he had done and what i was attempting to do.
His case was not as improved as mine is on the drawings i provided to him, he was tring to develope a new gun for thier military and had to keep it simple for feeding and extraction.
His test rifles were getting 3200fps using 400grain bullets out of a 28" pacnor barrel, 416 cal. Accuracy was very good at 1500yds, sub MOA groups he stated.
The case has a head size of .682 vs the 408 cheytac at .635 The new case is the exact same length as a 408 case which makes it nice as you dont need a very long action. I did however design a new action just for this case, i increased the bolt body from .750 to .800 in dia. this gives the rim of the bolt face more thickness.
I pushed the shoulder forward .090 over his case design, i did not remove any body taper as its allready very minimal. I added the 35deg shoulder as all of my SnipeTac cases have. With the 416 cal, the neck length is .400 long. I have a 510cal in the works for the same case, but that is a story for later on.
The fire formed case holds just shy of 190 grains of water, vs the 408chey tac case that holds 157grains of water.
There might be a 375cal version later on, but i dont think the jacketed bullets we have would be capable of handling the added velocity this case is capable of producing, lathe turned solids would be the best choice.
I'm calling this new round the "416 Viersco Mag"
I did a prelim test fire to check the chamber and case forming, i used a standard 408cheytac powder load behind a 400grn barnes X bullet, the load was so light it
was a semi hang fire. 125grns of Re25, the case was only about 3/4 filled. 150grns+ is what the guy in NewZealand is using. I added a 32" ABS carbon wrapped barrel with a
Benchmark barrel for the liner, cut rifling 12.6" twist. The barrel is 1.450 breech, tapered
to 1.200 at the muzzle, barrel weighed in at 6#
The new action is my "Black Diamond" model, 1.625" dia x 10.5" long .800 bolt body, 1.187x16 TPI barrel tennon. 4340 Chrom-Moly material, 17-4 stainless steel bolt body with
4340 moly bolt lugs.
The stock is special made from Joel Russo in his A5L with thumbwheel comb adjuster. It is single shot for test purposes, later on it will be converted to a repeater version with detach magazine system.
Here is a comparison of the 416 VM and a 308 Win
Picture of the "Black Diamond" action and the parent case vs the necked down
pre-fire formed case.
The test rifle in my messy Lathe room.
Picture of the A5L Russo stock and thumbwheel cheek adjuster. Nightforce 5.5-22 sits on top with a 40MOA scope base.
The test rifle as seen with out scope is 15#
I still have to make the muzzle brake, Titanium is the material being used. The end nut
on the carbon barrel is also made from Titanium.
I am hoping for velocitys around the 3250-3300 fps range with 400gn bullets, with the longer barrel set up we will be testing with slower burning powders vs the faster powder that was being used in New Zealand. My case design has more capacity than the original
Lehigh has sent me some new test bullets, BC has been calculated in the high .9's
Once i get my dies back from the heat treater i can start forming brass and hit the range for initial testing. The rifle is in the finishing stage, the action is a matte black KG GunKote finish with the engraving done after the finish was applied. The stock will be hand rubbed in some sort of stock finish oil for a matte look. Its been a long process from getting the brass, drawing up the case, reamers, building the action and the carbon barrel.
I will update the story when testing has started and and the rifle is completely finished.