I have a Zastava M48 which is essentially a Yugoslavian copy of the kar98k chambered for 8x57 IS. It's a really nice shooter and my existing good known load of Ramshot Big Game with a Privi 198gr makes it capable of knocking Fig11 targets down at 900m on Sennybridge F-range (OK I'll admit I only get 3/5 hits when the weathers good!).
I managed to get hold of some 8mm 200gr Sierra Matchking projectiles at the same price of the Privi bullets (I bought up all the supply and not willing to share the source for obvious reasons!!) so I started up a loading session to maximise the potential gain of this projectile. I also happen to have a MagnetoSpeed sporter so would use that in conjunction with the standard procedure for documenting a good load. The MagnetoSpeed fitted onto the barrel once the cleaning rod was removed. I used the slightly thicker rubber base to try and stabilise it underneath the barrel.
Here's a couple of pics of the ol' gal.
The below is a summary table of the results, including starting load and incremental step. CAUTION: LOAD AT YOUR OWN RISK!! I followed the starting load of Vihtavouri N-140 (which so far has been a good indicator of the above calibres) and found that at a powder mass of 42.7gr with a 200gr Speer SP I should be getting a muzzle velocity of approximately 2169fps. From my data I had an average of 2163fps (5 shots) so I'd say it's a pretty safe starting point, and continued to shoot. Increments were at 1% (0.5gr) loading 5 bullets at each step, but only loaded enough up to 46.2gr to see what the results were like. Shooting distance was 100m and I was seated at a bench using a front and rear sandbag, squeezing the rear ever so slightly to align my front sight perfectly. Sights were set at 200m (the lowest setting) and I was aiming with a 6 o'clock hold on the target. I maintained the same point of aim for every single shot in the series so not to introduce any errors.
This first target are the first 20 shots, 5 shots per powder mass, 4 different groups (42.7gr; 43.2gr; 43.7gr; 44.2gr). The first 15 bullets shot quite low, but you can see the last group loaded at 44.2gr were starting to pick up a wee bit and started to form some level of grouping (where the fifth bullet went, who knows).
This next picture shows the last 20 shots, again, 5 shots per powder mass, 4 different groups (44.7gr; 45.2gr; 45.7gr; 46.2gr). You can now really see the groups forming, and the bullets are impacting exactly where I wanted them to go. One of the groups produced an ES velocity of 4fps across 5 rounds, I could hardly believe it myself. I'll be more convinced once I've managed to repeat this and test against different sensitivities of the MagnetoSpeed! At this point average velocity was approx. 2,307fps so is still quite moderate.
The first chart shows the velocity of each individual shot within a powder mass group. Notice how little spread is at 45.2gr! I added a 6-order polynomial line to show a "line of best fit" of sorts (sorry, only have Excel to work with on my personal computer!) which shows that the velocity change plateau's at 45.2gr-45.7gr, I shall repeat this range to see if any change in powder mass further changes velocity.
The second chart shows the average velocity per powder group (left x-axis) and the standard deviation & extreme spread per powder group (right axis). The data shows two "nodes" of stable velocities; 43.7gr and 45.2gr; such that the velocity spread remains tight at these loadings. Given the good accuracy, point of impact and decent velocity; I shall continue working with 45.2gr-45.7gr and also continue loading higher powder charges until I reach approximately 2,400fps velocity. Just to point out, at this moment in time there is no issue with the cases or primers that are normally associated with "high pressure" loads. All cases were full length sized and the bolt was very easy to open upon shooting. Although these should not be used as a sign of over-pressure loads they do provide comfort for me along with the chrono'd velocities.
I had a great day on Saturday shooting and hope this helps out any shooters who might be looking to using this powder in 8mm Mauser.
EDIT: Whoops, forgot the summary table!
