Mag or Std Primers in .223

I have used WIn 748 a lot in my .223 to date and always used mag primers with it. However I am trying some different powders, H-322, RL10x, AA 2015 and IMR-4198. I have/had two bricks of CCI#450 Mag Small Rifle primers and not much else.

I'm not sure this will make a difference one way or the other with the easier to light powders, any pointers, guys?

I'll be ladder loading from start to Max and hopefully the Chrony will work out to capture the velocities. :-)

I'm going to use 50 gr Amax bullets for these. I collet sized and reprimed 100 this morning before it got too hot in the garage. I'll do another 50 rnd lot in the morning.

With starting loads of rifle powder in a high pressure cartridge like .223 and working up, I wouldn’t be the least bit concerned with using magnum primers where the recipe calls for standard.

I have used Large Rifle Magnum primers a lot with cast level on up loads. I've not used SR Magnum primers but I would. Like you said, begin with starting loads and it'll be fine.

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I haven't done it with 223, but I have with LRP's. I bought a brick of what was labeled as large rifle standard primers, when I got them home and went to store them I noticed the individual flats were labeled LRPM. Did the research and loaded some up with these magnum primers at start charge minus .5 grains. I ended up working up loads a little over start charge. (I don't have my notes in front of me.)

Well I'll be using these in a Ruger 77 MKII 20" bore so I'm not worried about over loading it too much. The peak pressures may get there a little sooner than with standard primers though.

With 748, I've used Small Pistol Primers with loads up to 20 grains with a 70ish grain boolit with no issues. As long as you stay under the max charge, all should be fine.

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Originally Posted by Krag 1901

Well I'll be using these in a Ruger 77 MKII 20" bore so I'm not worried about over loading it too much. The peak pressures may get there a little sooner than with standard primers though.

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You will be fine using the 450s with those powders working up using current load data. Any increase in pressure will be slight and well within the MAP for the for either the 223 Rem or the 5.56 Nato for use in your rifle.

I ladder loaded 10 rnd lots of RL10x and A2015 -2.5 gr to Max, in 0.5 gr steps, with 50 gr Amax bullets, this morning before it got hot and am all set to test now. I never have gotten what I consider good accuracy from my Ruger MkII from max charges of 748 so thought I'd try some different powders. I figure two five rnd groups should give me a good test with each charge. I used fire formed brass and collet sized the twice fired cases. Neck tension varied a bit when seating but I doubt that will be a factor at these charges.

I may be unfairly comparing it to my 1885 Low Wall which shoots darn well, under 1 inch, with 748 or 4198. The Ruger does well to stay under 2" at 100 yds. If it can't do better, been thinking about swapping it for a SP101 in 327 Mag, or a Rossi 92 in .44mag.

My bad experiences (hangfires) with double-base, graphite coated powders led me to use only Winchester primers (designed for coated ball powders) with those powders. Your CCI magnum primers should be powerful enough as well. By-the-way, in my 22-250 and 748 powder and a Hornady 50gr bullet, WWLR primers not only gave the tightest groups but almost 150 fps more velocity than CCI non-magnum large rife primers. The speed difference mirrored what Western Powders got with one of their Ramshot powders and the same primers. But they measured the peak chamber pressure and it was 3000psi more with the hotter WW primers.
So the caution is don't work up or reference a max load with standard CCI primers and substitute WW primers without reducing the powder charge. Loading manuals tell which primer was used in their data for a reason.

If you are using less than 30 grains of ball powder, there is no need for a magnum primer. Can you use them, yep and many people find they at times capable of smaller groups than standard primers. I've chronograph .223 loads using ball powder with both mag and standard powders and I find no advantage either in accuracy or velocity.

I made an error and loaded 30-06 ammo using standard primers with 48 grains of ball powder. Firing them, I had a two foot ball of fire out the muzzle and a boom rather than the sharp crack I normally enjoyed. I put substituted magnum primer, using the same powder charge and was rewarded with the sharp crack I normally expected and no retinal burns from the fire ball.

Both of my Ruger Mark II’s (243, 30.06) shoot much smaller groups when bullets are loaded into the lands, or a least as long as the magazine box allows. The 243’s short neck length prevents getting into the lands with lighter bullets on my 243 rifle.

I have used Federal 205 SR primers in bolt action, Ruger Mini 14, and AR platform .223R/5.56 using 748 powder with no problems.