I'll start by giving the components I've tried so far. Mind you, I haven't tried every combination,
but what I did try with many helped me to figure out what my combination liked.
BRASS: Lapua and Norma.
Primers: CCI benchrest, CCI std, Winchester LR, and Federal 210
Powders: IMR 4064, Hodgdon Varget, Hodgdon H4895
Bullets (150gr): Nosler BT, Combined Tech silvertips, Barnes "X" Triple Shock, Hornady SST, Speer SPFB in .311, Sierra SPFB in .311
Bullets (168gr): Berger HPBT, Barnes "X" Triple Shock
For case preparation I fully resize my brass. The primer pockets are trued up using my RCBS motorized case prep station, and the flash holes are deburred also using the same machine. The cases are chamfered with an inside cut of 22 degrees, while the outside of the neck is turned with a standard (45 degrees I believe) attachment. All of this work takes a lot of time the first time around, but if you are careful with your brass subsequent loadings aren't nearly as time consuming.
As far as brass preference, I've found that the Lapua cases seem to be more consistant and yield a slightly higher velocity all other factors being equal. The Norma brass is fine, and it's thicker to boot, but my rifle seems to prefer the Lapua.
To date, most of my loads have been with the .308 diameter bullets since I've been told that they shoot just fine (even though all the soviet stuff you find is typically .311). I have managed a few good groups, and out of the .308s in 150gr, the Hornady SSTs fly the best. Nosler and Combined Techs really haven't fared too well, and the Barnes are a close second to the Hornadys.
Shortly after getting this project underway, 7N1 became available and I bought a quantity of it. With an issue bipod, I managed a 10 shot group just over .5 MOA, so I knew the accuracy potential of the rifle was there. I began to look at the 7N1 and realized that the COAL was a whopping 3.017" thanks to the use of steel rather than lead. I reasoned that the overly long bullet must practically be touching the lands which promoted better accuracy, so I purchased some Barnes "X" bullets because their solid copper construction yeilded a longer profile than traditional jacketed lead cores. I loaded up several, and found that mimicking the 7N1's OAL didn't help me at all in the accuracy department. In fact, after I obtained a Stoney Point chamber gauge, I found that the lead (throat) of the Tiger was so long that I simply couldn't touch lands and still load from the magazine. By that time, however, I had also bought some 168 Barnes, and then some Berger BTHP also hoping to find better accuracy with a heavier bullet like my NDM in NATO caliber likes. I had fair results, but nothing sub MOA like I was looking for.
As far as powders are concerned, I couldn't find a single load where my rifle liked the IMR 4064 much at all. The Varget did okay, but as soon as I started using the H4895 my groups shrunk. And because it is from Hogdgon's "Extreme" line, it is one of the least temperature sensitive powders out there.
After all of this experimentation I've come to the conclusion that my rifle prefers Lapua cases, H4895 powder, Federal primers, and Sierra .311 diameter bullets. I'm going to stay in the 150gr weight area since that's what these rifles were designed to take all day long, and I'm working to get the velocity up to around 2750-2800. Currently, my best group has been a 5 shot group measuring .66 including a flyer. The particulars of the load are included in the notes on the picture below. On a side note, every single load I've tried with H4895 and Sierra 150s, has come in under and inch for 5 shots, so I'm pretty sure I've found the right component combination at least. Now I just need to do the final tweaking with COAL and charge weight.
Seeing as how I'm using flat based bullets for this load, I'm limiting my performance to around 300 yards, but realistically I'm not likely to take a shot further than that in the first place. And just for grins I'm going to try the Speer .311s again with this powder, but past performance have suggested that they simply are not as consistant as the Sierras, and considering the minimal price difference, I wouldn't recommend them.
One important safety tip if you're
going to try and duplicate that load.
FEDERAL PRIMERS ARE ON THE SOFT SIDE
My rifle has been upgraded with a spring loaded firing pin, so I felt comfortable using the Federals, but bear in mind that it was the Federal Gold Medal Match that was notorious for the blown up pre-recall .308 NDM-86s. Soft primers combined with floating pins were cited as the cause so before you try Federal in your Romak, Tiger, or 54R NDM-86, get a good spring loaded firing pin set-up.
|Brass: Laupa||Length 2.087|
|Bullet 0.311||Sierra 150 Pro Hunter|