Magnum Primer/mid range loads

[gemini1]

I'm still on the developing stage on reloading 55 and 77 grain pills, using Benchmark & Varget with regular Tula primers.
I have a couple of boxes of Tula magnum rifle primers than I may end up using when I run out of the regular ones. I have read that when using magnum primers, loads should be reduced by 10%.
Bur it does not seem to make sense to me. The Benchmark load data for 55 grain SP pills min/max is 24./25.6 grains.
So at max load of 25.6 grains, 10% less brings it down to 23.04 grains, lower than the minimum recommended charge?

Can someone educate me on this?
Thanks

[highpower790]

What type of rifle are you loading for?

[gemini1]

Its an AR with 16" barrel. And just to add, I do have loads that are over max for testing both accuracy and velocity for both 55 and 77 grain pills, using regular primers. But for plinking loads I only go at mid level loads.

[highpower790]

I cant speak about the use of Benchmark and 55 projectiles,but I can tell you that I do use Varget and bullets of 75-82gr in weight with Wolf magnum and Rem 7 1/2 primers.
With Wolf magnum and Rem 7 1/2 I load 24.5gr of Varget.I see no negative effects of high pressure.
As a responsible reloader,Im sure that a load will be worked up.

[pacrat]

As a responsible reloader,Im sure that a load will be worked up.

Always sage advice.

[Metal God]

With those two powders you should not need to go to magnum primers . Why do you feel the need ?

Magnum primers are best when loading hard to ignite ball powders like H335 and the like . Even more so in larger cases like 308 and above do to the amount of powder needing ignition . In fact using magnum primers can actually give you less consistent results in velocity and ES/SD .

I did some test with CCI #400 & #450 using 55gr FMJ and H-335 in my 16" 1-7 AR . Other then the magnums being a little less consistent in velocity there was no noticeable difference that I remember . If you like I can post the results but if memory serves . The velocities were about the same but the magnums had slightly higher ES/SD .

Now I did reduce the starting charge by .5 or 1gr with the magnum primers and stopped .5 or 1gr short of max . This resulted in 3 or 4 charges that overlapped using the #400 & #450 . In those charges that overlapped there was not a discernible difference except for the slight difference in ES/SD .

The above is not to say standard and magnum primers are interchangeable . It's just what I experienced with the very specific set of components I used at the time . You should always work up your loads from minimum .

[jericho89]

If i recall corectly Tuna magnum primers are no different than regular, just a harder cup. Double check their web site, but I seem to remember that ney recommend their magnum primers to prevent slam fires in the semi automatic rifles

[Enfield47]

I use CCI No. 41 primers with 24 gr Benchmark and 55 gr FMJBT with good results in my ARs and Mini 14. You shouldn't have any issues with the Tula magnum primers with either powder.

[gemini1]

@ Metal God, its the only one available when my regular ones were running low.

So I guess my best bet is to chrono the same mid level loads, using both regular and magnum. And if there's not a big difference in velocity, then I can use the magnum primers on my over max loads, instead of working back up again(?)

[Metal God]

then I can use the magnum primers on my over max loads, instead of working back up again(?)

NO because velocity is not equal to pressure . Just because you're at or around the same velocity with a mid charge using magnum primers does not mean you're good to go with any charge you previously work up with standard primes . I was using CCI primers with a very specific set of other components . Tula primers are not the same as CCI . How are they different ? Other then a totally different brand , I have no idea because I've never used them but that's a good enough reason for me to disregard my CCI test if I were using Tula primers . I was using a hard to ignite powder , you are using very easy to ignite powders with a different primer . Your load comb is quite different then what I was using .

The reason magnum primers can and often do give poor ES/SD results is there inconsistency of flash . This will cause some rounds to produce slightly different pressures causing inconsistent velocity . Now if you're at a max charge when using a standard primer . Introducing a magnum primer even though most of the rounds shoot fine . That magnum prime can push that max charge over the top .... Past proof loads ? Not likely .... Blow up your gun pressures ? Not likely .... Blowing primers out and sticking cases to the chamber wall ? Maybe .

I can't stress this enough , if you are at max pressure with a load . I would never recommend changing any component of that load with out dropping the charge and working back up .

Case in point about primers , Winchester LP primers are good for standard or magnum loads . That sounds like they are Magnum primers right ? If they can be used in magnum loads they must be . That sounds reasonable but CCI LP magnum primers are more powerful then the Winchester primers . I don't know all the different primers and how they compare to one another but they all act differently then one another .

Just look at the difference in flash comparing the Fed small rifle primer and the Rem small rifle primer in the link below .

http://www.6mmbr.com/primerpix.html

[gemini1]

Gotcha Metal God, thanks. Maybe I'll just use those mag primers when I start developing new loads/powder, I do have a couple lbs of Ramshot Tac.

[LynnJr]

The 6BR and 6 Dasher have won more trophies at 600/1000 yards than most cartridges and they do it using CCI 450 Magnum primers and Tula Small Rifle Magnums.
Primers are a tuning aid that get used when developing your load.
When your extreme spread is in the double digits it is time to swap out your primers looking for a lower extreme spread.
The chronograph should decide your primer choice not emotions.