We are starting to work up some hunting loads with different powders and bullet weights in a new Merkel 9.3x74R. A quick search of the Federal site showed they use 210 LR primers in their factory loaded ammo for this caliber. We have these primers on hand so this is what we are starting with.

I've noticed several of the hand loads a few of the DR guy's have posted for 9.3 use the 215 Magnum primers. Can anyone explain the reason they use Mag primers over LR primers?

Rhodes
DRSS

To ignite the long powder column of sometimes relatively slow burning powder. You will know you need them if you get a click boom. I just always use mag primers in the 9.3 as I don't use any powder faster than 4350. Mostly.

To keep my reloading bench as free from clutter and confusion I use LRM primers in everything. While now I shoot only low pressure double rifle cartridges I did not see any pressure problems when I shot modern magnums. I have not used a LR primer since the '80s.
Cheers,
Cal

I use the standard F210 on the 9.3X74R.

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.

Mandatory:

1. Drive band bullet - The resistance to engraving is about a quarter of that of a smooth bullet.
2. The selection of powder/load is such that the bullet sits tight on top of the charge.

By Gerard - 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 and you have artificially created a bigger case. As we know, the same charge in a bigger case lowers pressure.

FWIW

9.3X74R Federal 210s
450/400 3 inch Federal 215 Magnum Match. I use primarily Norma 203B/aka RL-15. I think you need the extra for the big cases.

Thanks for the responses, some good info there. I was a little concerned about the long case.

For the first lot of testing we are using AR2209 powder and the cases are pretty full so that should help ignition.

I think we'll get some fed 215's for testing as well.

Rhodes
DRSS

Rhodes:

My Hornady Manuel (8th edition) recommends Winchester large rifle magnum primers in the 9,3X74R because of the long powder column. In addition, in Pierre van der Walt's book, African Dangerous Game Cartridges is says that "in tests conducted by and eminent local handloader, magnum primers delivered tighter groups than standard ones on most occassions." I use the Hornady data with the Winchester large rifle magnum primers and they have worked well in my little Chapuis.

Dave

Thanks for your reply. Fed 215's are on the list of things to try.

The batch of loads we just tested used AR2209 powder and FED 210 primers behind 284 grain bullets. The individual barrel groups weren't too bad ranging from 1.1" to 1.9" with horizontal spread between barrels. The spread between barrels was just too wide at ~8". I can't see this coming together with load development alone. This rifle was regulated for the Norma 232gr vulcan load so we may not get it to shoot 280 grainers.

This raises another question. We were getting slight keyholing at lower velocity suggesting there may not have been enough barrel twist to stabilize the longer bullets we were using. Does anyone know if Merkel used a different barrel twist in rifles regulated for the lighter 9.3 bullets?

Rhodes
DRSS

I have also noted that with ball or spherical double based powders magnum primers are frequently used where they might not be called for with single base tubular powders. Maybe the ball powders are harder to consistently ignite and need a hotter primer.

I think a good rule of thumb is a magnum primer once about 60 grains of powder is used.

I use Federal 215 mag primers in all my loads for the 9,3x74R. Mainly like Cal says I only have to stock one type primer for my double rifle loads.