Magnum primer with 4451?

hifiwasabi

hifiwasabi

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I finally got out to shoot my initial handloads for my .243 X Bolt on Sunday. I'm using New Winchester brass with CCI 200 primers and charges up to 41.0 grains of IMR 4451 pushing Sierra 85 grain BTHP's. The charge is max according to a Nosler manual substituting 85 grain partitions up to 3133 fps. I was getting some promising looking groups at 40.5 grains, but my velocity and SD numbers are...less than hoped for. Think ranging from 2730-2850 fps at the same charge weight. My first step will be to replace the battery in the chronograph, but I was wondering if I should maybe try magnum or benchrest primers and add a light crimp? At 41.0 grains, the primers still looked like they had no pressure deformation and bolt lift was light, is Nosler known for being super conservative with their charge weights and liberal with their velocities?
 
I have burned quite a bit of IMR 4451 in the 7x57, the 6.5 Creedmoor and the
7-08 Remington. Never used a magnum primer yet. Accuracy is great and speeds
are close to where they should be. Dave.
 
I never graphed any 4451 loads at very low temps [<-25ºC] but the velocity loss
over a 32 degree spread averaged only c.25 fps. [+22º to -10º] Dave.
 
When I start loading for my 243 I will be using the magnum primers, but mainly because I have no regular ones over Varget.

I would push the limit and find the max load for your rifle. If you are at book max, continue up, and watch for max pressure signs. You might find another node closer to max pressure.

Using magnum primers, you will want to adjust powder weight down, and work up. I don't think a light crimp will do much for you, unless the bullet has a crimp groove. I have tried on my berger's in a 6.5 PRC with no enhancement, yet seeing improvement on another bullet with the groove. The 124 HH improved in that same 6.5 PRC with a crimp.

I'm holding out for some new brass for the 243 and then start loading. I just have some older brass, and don't know how many firings it has, so want to start fresh on it.
 
I have been loading IMR 4451 for 270 Win and 30-06. Very accurate powder with great velocities. If you don't have specific data for IMR 4451 and a specific bullet, try to get H4350 data for that bullet and start 0.5 to 1 grain lower with IMR 4451. I have only used CCI LR for IMR 4451. I have also found that the fastest way for finding a good load is to do a ladder test in order to obtain a velocity node, followed if needed by tweaking the COL. Let me know if you need more info about this method.

By the way, the most accurate load for your bullet is Vit 140 at 37.3 grains in Sierra's book. Unfortunately there is no data for IMR 4451 or H4350 in their book.
 
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