how much should loads be reduced for mi-spec/magnum primers?

[skyugo]

i'm considering switching to a mil spec CCI primer. i've been using the CCI 400 small rifle primers until now. i use ramshot tac.
as i understand the magnum and mil spec primers are hotter, so loads should be reduced to keep pressure in check.
any decent guidelines?
all the .223 load data i've found so far always specifies a small rifle primer.

[ralph]

My understanding is that Mil-spec primers are harder to reduce the possibilty of slam fires, I'm not sure they're any hotter than a standard rifle primer. Magnum primers ARE hotter, usually you reduce your charge by 1gr when running close to a max load. If you're using military brass, you also want to reduce your charge by at least 1gr when running close to a max charge, Military brass is thicker than commerical brass is, so you can't get as much powder in a Mil-spec case, and this is why the charge reduction is needed. Another thing to think about, if you're using a ball powder, you want to be careful, as a rule, ball powders burn hotter than a extruded powder will, with a hotter primer and a near max load this could cause problems, Ball powders are also temp. sensitive, loads worked up last fall when it was nice and cool might be a problem now that summer and it's higher temps are here.

Frankly, I don't use or have'nt really seen the need for using Mil-spec, or Magnum primers, for a .223/5.56 and I don't use them, I haven't had any problems

[markm]

Military brass is thicker than commerical brass is, so you can't get as much powder in a Mil-spec case, and this is why the charge reduction is needed.


This has been proven false. Specifically for 5.56/.223 brass. It may be the case for 7.62X51, but a water volume test was done to dismiss this myth. Mil 5.56 brass had the same or greater volume than commercial.


Frankly, I don't use or have'nt really seen the need for using Mil-spec, or Magnum primers, for a .223/5.56 and I don't use them, I haven't had any problems

I agree completely.

[Kurt Reifert]

CCI #41 primers are equal to a magnum primer and they have harder cups.
I can't give you answer on how much to reduce your loads.
I generally use Rem 71/2 primers in .223

[HolyRoller]

What's wrong with the primers you've been using? Since published .223/5.56 loads call for regular small rifle primers, maybe that's what you should stick with. Should you have to reduce the charge to use magnum primers, doesn't that mean less velocity?

If you insist on changing to magnum primers anyway, it's best to look this sort of stuff up in a reloading manual. I wouldn't try to give a rule of thumb as to how much a load should be reduced when primers change.

[rockm4]

i'm considering switching to a mil spec CCI primer. i've been using the CCI 400 small rifle primers until now. i use ramshot tac.
as i understand the magnum and mil spec primers are hotter, so loads should be reduced to keep pressure in check.
any decent guidelines?
all the .223 load data i've found so far always specifies a small rifle primer.

The old Lyman book that i've got has a footnote at the bottom of the page that advise you to drop charge weight by 10% anytime that a change is made. then work back up to the minim. working loads checking c.u.p. pressures as you go. In 35 years of reloading I've used every primer out there and have had good success out of all brands but I prefer CCI to the rest. now with the War on Terrorism its hard to find CCI at local gun shops and gun shows , at least around here.