Magnum primers with Win 760

[wayno945]

I'm about to load up some test rounds for my new 257 Roberts with Win 760 powder. I read somewhere online that magnum primers should be used with this powder. Anybody have any experience with this?

 

[DrMike]

Ball powders are somewhat more difficult to fully ignite. Consequently, the general recommendation is to use magnum primers to ensure complete ignition. As temperatures go down, the requirement for magnum primers will be greater still.

 

[Wincheringen]

Not all ball powders are created equal. The Winchester line of ball powders have a greater amount of deterrent on them and do ignite better with magnum primers. Ramshot/AA ball powders do not have as much of the deterrent and don't require magnum primers.

 

[wayno945]

Thanks guys! What would the symptoms look like? Complete misfires, delayed ignition, or just unburnt powder/residue?

 

[Oldtrader3]

When I shot Hodgdon H380 (ball powder) in my rifles without a magnum primer, I get lower velocities and more unburned powder and trash in my barrel.

 

[Guest]

You'll also see more variation in your velocities (wider ES, larger SD). I use mag primers in my 30-30WCF with Win748, even. It's recommended in the manual from which I base the load.

 

[PJGunner]

I've been using W760 for almost 30 years now and have just used the standard Winchester primers. I also use Winchester's discontinued WMR powder in a .270 Win. and .300 Win. Mag. with the standard Winchester primers. I haven't had any problems with erratic velocity, extreme ES or SD and accuracy has been excellent not only with the cartridges mentioned but the .243 Win., 7x57 and recent experiments with the 190 gr. Hornady SPBT in a 30-06.
I do have quite a few Winchester magnum primers on had but have never seen the need. Of course, down here in Arizona, even furing a November deer hunt up in the Kaibab or the White Mountains I've never seen it get really cold. The coldest I've ever seen on one of those hunts was 28 degrees above zero. I would imagine if I lived way up north like Montana that might be a whole different ball game. My .300 Win. Mag. with a max load of WMR does 2930 FPS with a 200 gr. Nosler Partition or 200 gr. Speer Hot Core and both load run slightly less than one inch at 100 yards, usually in the area of .75". I guess it's a case of YMMV. :wink: My .270 does the same thing, sub-MOA and excellent velocity with the 150 gr. Sierra Game King.
I have to load up some .300 mags so maybe I'll give them a try but I don't know if it'll do any better than what I've been getting so far. Maybe I'll do a few .270s as well.
Paul B.

 

[Antelope_Sniper]

Often magnum primers will cut your groups in half with ball powders, especially the old Winchester powders.

I never load them without either a Magnum or benchrest primer.

 

[DrMike]

Both Charlie and dubyam give you a good summary of problems one may encounter when primers that are too "cold" are used.

 

[wayno945]

Thanks for the input guys, I appreciate it.

 

[JD338]

The magnum primer will give you a more complete burn. Just remember to start low and work up.

JD338

 

[257 Ackley]

I use the Hodgen branded version of 760 (H414) for the 257 bob AI and have never used a magnum primer. I have never noticed more barrel fouling or unburned powder using standard 210M primers over a magnum primer. Magnum primers or standard primers with a harder "cup" may help if you are planning on pushing the envelop and getting near the top of your pressure curve with this caliber.

I would try both and see where your best accuracy and velocities come from.