IMR 4198 in a .308 Winchester Bolt Gun
Hello to The Reloaders Network!
I thought I would try something different in my 308 target rifle. It started as a Savage 11VT that was found to be a little unsafe with the original barrel (short throat with rifling at 0.307″ would pop primers on factory loads occasionally and was almost always a hard bolt close due to jam), and so I replaced it with a Shilen Varmint taper barrel. I was shooting 178gr ELD-X bullets at 2700 fps. I ordered a 24″ barrel (the original was a 26″). All of a sudden it seemed to lose the handle on my reloads and a replacement Criterion 28″ bull was ordered. It was found, once the barrel was in hand, that the bullets were at fault. I had several bad boxes that were all of a sudden 4 MOA. The last box of 100, which was loaded in a lot of 200 pieces of brass at the same time as another, was magically back at 3/4 MOA and awesome, but alas, the new barrel was here and I installed it. It wears a Bell & Carlson M40 stock and Harris Bi-pod with either a 10×42 Mil-Quad SWFA SS scope or a Primary Arms 4-14×44 308 HUD.
I initially did a work up of 155 Lapua Scenars and Lapua brass replacing my Hornady 308 Match brass. The workup did pretty dang good with Shooter’s World Propellants Precision Rifle Powder. All brass was match prepped. Annealed, trimmed, chamfered, deburred, flash holes uniformed and primer pockets uniformed.
All loads at 2.886″ which is 0.005″ from the lands.
However after receiving my copy of QuickLOAD and looking into other odd stuff, I came across the IMR-4198 in a 308 as a possible load with a maximum load of just over 38gr of powder behind a 155 Scenar.
So I went to the range and shot them and results are as follows….
PC Velocity SD ES
35 2633 23 54
35.5 2722 18 45
36 2745 5 12
36.5 2749 16 43
37 2807 14 34
37.5 2851 16 39
38 2865 11 39
Those are the seven groups I shot left to right with left two reversed. 35.5, 36.5, & 37.5 where the good groups.
However I did shoot 15 of the 35 in the end into a nicer group than the first group of 2.05″.
So clearly that first group was too much time off the rifle!!!!
At this time I also did a proof load group of 45.3 gr of SWP Precision Rifle and shot this…
This is at 2897 fps. SD 11. Little higher than last time out at 8. hmmm… Still easily good enough for a 308 to 1000 yards though.
In the end the brass showed no indication of pressure from the primers and was as clean as when it went in but was a little sticky coming out. This was a common problem all through the charge weights. I guess in the end I would not recommend the loads.