I was developing a load for a 300 wby vanguard and could not find a load that would give me better than 1 1/2 inch groups at 100 yards. I tried many powders, bullets and ladder tested them with little succes using cci large magnum primers. I finally tried federal large magnum primers and my groups shrunk to under 1/2". I did not expect primers to make that much differance. Has any one else experienced this. My final load I went with for big game hunting was 185 gr Berger vld with 85 gr retumbo and federal 215 primers average velocity of 3140 fps. I have taken 3 elk and 2 mulies and love this load.

Tuck,

Welcome to the Forum. Your experience is not surprising. Primers will have a greater effect than most would guess. The Federal 215 was developed specifically for Weatherby cartridges and is a hotter primer than most. Retumbo is a slow powder and needs lot of spark. It all has to do with the combinations of course but good to hear that you found a good load and your success on game is proof. I found the same type of effects on accuracy as you have but was using Remington primers at the time. I subsequently switched to the 215’s for all my heavy magnum cartridges.
Paul

The Federal 218 primer was developed for the 300 Weatherby magnum. Your results are not suprising. I have used the Federal 215 primer for loads in the 300, 340 and 378 Weatherbys with good results.

I load for three .300 Roys. I've had best accuracy with WLRs. Mine do not do as well with Fed 215s, but I use IMR 4350 behind 180s for around 2950 fps.

Sam

I use the Federal 215's in my 300 Weatherby and have had good results for accuracy with IMR 4350 and the 180 grain TTSX. I had the same experience that you did switching primers on my 7 Mag from the 215's to the WLR with no other changes it dramatically shrank the groups. As others have stated it is the entire combination of components and methods that make the difference. It certainly doesn't seem like a primer should make that big a difference but sometimes they do.

I had the same results in my .340 Weatherby, which is essentially a necked-up .300. The CCIs resulted in poor accuracy, but the same loads with Federal 215s tightened up groups from 1 3/4-2 1/2 inches to just 0.75". Yet in smaller cases--a .257 Weatherby, .300 Winchester and .350 Remington--the CCIs do very well.

In all of the reloading books that I've seen, the books reccomend the 215 primers. I use the 215 match grade primers and my 300 Wby Vanguard shoots great! Here's the photo of my Utah moose that I shot with my 300.