My experience: Sabatti Evo 308 Win. with multi radial rifling and PC cast bullets

[Luke-299]

Hello,

I recently bought a Sabatti Evo bolt action rifle. It features a special type of rifling, namely the multi radial rifling (like polygon rifling). See this link: https://www.thefirearmblog.com/blog/...-1-660x266.jpg
It has a 28" long and 28mm diameter heavy bull barrel and a 1:11 twist.
I wanted to try out if this rifle works with cast bullets and to share my experience here.

I began with some NOE 155gr SP BO1 cast bullets I cast and coated about a year ago. I used Tiger Drylac translucent which worked great. (You can't get TGIC Powder in europe)
With maximum OAL in my rifle the case mouth was exactly at the end of the driving bands. Great!
To illustrate the different OALs with the bullets used in this test, I took a few pictures with a cut 308 case.
NOE 150 SP BO1:

MP Hunter 160gr and NOE 225gr Taco mould

Lee 160gr with GC:


I sized some of them to .309 and some of them to .311 as slugging the barrel was "inconclusive".
I then loaded them with 15,5gr Vihtavuori N110.

The .309 sized load was more or less a shotgun pattern. Aside from that, I think it was way too fast for a plain based boolit (around 520m/s or 1700fps):


The .311 sized load was way better, even faster at 540m/s or 1770fps but still not good.


What to do next? I tried reducing the charge to 14,0 and 14,5gr and kept sizing the plain base bullets to .311.

Here is the whole target:


With 14,5gr N110: quite a lot of horizontal stringing but overall a better group than the 15.5gr load.:


With 14.0gr of N110 groups got a little bigger (488m/s or 1600 FPS)
The first 4 of 5 shots with 14,0 were promisinig. One flyer...

but the 10 shot group showed the truth.



Next I tried a fast pistol powder: Vihtavuori N320. Found some load data published in finnish magazine in the 80s.
I tried 8gr N320 behind the MP Molds 160gr Hunter plain base boolit.

This group was even better than the previous groups, speed a lot slower at 370m/s or 1230 FPS:


As the Lee 160gr RN is the only GC mould I own that fits the short throat of the rifle I decided to try it, even though the bases are really bad, thanks to a slightly bent sprue plate. I hoped the GC would compensate for that. I try to fix the plate in the future. For now groups shrinked a little compared to the plain based boolits.
The same 8gr N320 load:

When removing the first fouling shot the group looks OK


And just for the fun of it I tried NOE 225gr Taco mould with GCs. 1:11 is too slow for the heavy boolits with subsonic speeds (308m/s or 1010 FPS) Once again shotgun patterns from my rifle.



Next time I want to try:
* higher charges of N320 to see if groups improve.
* .309 vs. .311 with lower speeds than my first load.
* more GC moulds are on the way. Ranch dog design and the XCB from NOE


To be continued...