My 9,3x74R FN o/u shoots both bbls. in the same hole at 50 m with its pet load consisting of :
286 Norma / H 4831 / 68.0 (heavily compressed) / Norma LR primer.

Having run out of Norma primers, I switched to the WLR std, same load in the very same cases. Imagine my surprise when I found out that now the bbls crossed and shot 8 cm (3.15 ") apart in the same conditions !?!

I had not expected such a change for a mere primer switch. I started re-developing a load, lowering the powder charge, hence velocity, to compensate for the crossing (proof of too much velocity).

The rifle reacted immediately and both bbls. started shooting together. I stopped at 65.0, having reached the same groups and zero than with the original load.

Still, I'm intrigued it took a full 3.0 g. of powder to balance a load between two std. primers. Or maybe the WLR std. primers are much hotter than I thought ?

The primer has a much greater impact on "barrel time" than most shooter's realize AND I've also found that switching primers without lowering the amount of powder used can lead to potentially serious pressure problems.

Andre - I used standard primers (mostly CCI) for my initial development work with H4831 in my Chapuis 9.3 X 74R. I got some strange results one day at the range and in one case had a load with substantially lower velocity. After mulling it over for a bit I came to the conclusion that the lonngggg powder column in the 9.3 X 74R really merited a magnum primer. I went to a Rem 9 1/2 M (that's primarily what I had on hand in Magnum LR primers at that time) and all of the strangeness in the loads went away. JJ re-regulated my rifle for my load and that load is 69.5 gr. H4831, Rem 9 1/2 M primer, Nosler 286 Partition (or Hornady 286 as it turns out).

For those who are using a different powder in their 9.3's, the reason I decided to use the H4831 was four fold. First, it gave maximum velocities in the 9.3 X 74R (make sure it regulates in YOUR rifle). Second, it was a 100% density load which I prefer whenever possible for ignition uniformity. Third, H4831 is fairly insensitive to powder increases (e.g predictable unlike some powders, principally ball powders) which made the likelihood of an over pressure load unlikely during load developent, and finally, H4831 is relatively insensitive to temperature variations. This latter item makes it more better for Africa's higher temeratures (or anywhere else for that matter) as your load isn't likely to go out of regulation with temerature increases, and it's highly unlikely you will see overpressure loads unless you are right up against the upper pressure limits in the first place. The latter situation is never a good idea whatever flavor of rifle you are using. Will H4831 result ih higher recoil? Sure. More powder = more recoil. Is the difference worth it? IMO, yes, for the above reasons. Agreed, the recoil is stout in a 7 1/2 pound rifle, but not sufficiently nasty to cause a problem if you practice with it a bit. FWIW DuaneB

Primers are critical. Norma use Winchester LRM for the 30-378, .338-378 and the big NE rounds because they are the only ones that give reliable ignition of that huge powder charge at low temps. They used to use Federal but gave up on them and moved to Winchester. For standard "magnum" rounds they use their own primers.

So yes, winchester probably do have either a hotter flame or a longer flame duration

Butch Searcy recommends Federal 215M primers when reloading for the 500 NE and 470 NE. To date I have not tried the Win primers, but now I must do so.

I have used CCI primers (BR2 and magnum ones) for my 265 gr GSFN loads in 9,3x74R with R903 powder:

- with BR2 and 61 gr load I got 2380 fps
- with BR2 and 60 gr load I got 2330 fps

- with MAG primers and 61 load I got 2300 fps

Recoil when using MAG primers was noticeably lower - certanly lower than what to expect for a deviation of 80 fps.

I have discussed it with Gerard and according to him:

"if you use a magnum primer the pressure from the primer igniting will move the powder charge and the bullet forwards so that, when the powder ignites, the bullet is already engaged in the rifling a bigger case was artificially created . As we know, the same charge in a bigger case lowers pressure.

This whole principle works best when the selection of powder is such that the bullet sits tight on top of the charge. The principle is almost unnoticable if a very fast powder is used with low charge levels and there is a lot of air space in the case. Air is compressed and the bullet does not move under primer ignition alone."

Always drop your loads back and work up when you change primers. It's easy to end up with a face full of hot gas. Some of these old DR's have dog tooth hammers and/or firing pins that don't have any gas control and will blow out the stock disaterous results if you happen to pierce a primer!! Don't ask me how I know. Again PLEASE always drop your loads back and work up.

I'm very surprised to see some negative comments above re the Federal 215M primer. I have always found it to be a very consistent performer. That is the primer that I use to light off 94.0 grains of Reloader 15 in my .450 #2 NE, with 2 grains of Dacron fibre over the powder. It works perfectly and standard deviation in the velocities generated is very low.

I had this article on burn rates of powder and PRIMERS take for what its worth

http://www.reloadingroom.com/index_files/Burn%20Rates.htm