Magnum Primers VS Regular

hemidart

hemidart

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Hi I am reloading a jag of .303 with 180gr. Sierra's I given a bunch of new Winchester magnum Primers is there any problem I might encounter using these versus the regular primers? I will be using IMR 4350 Powder also any Idea what the Min. and Max. powder measure should be? I am building all for a Parker Hale Mk 4.
THANKS TO THE GUYS WHO HAVE GOT ME THIS FAR :)
Pete......
 
Magnum primers are not required for those small charges of 4350 and will only drive up the pressure, not something you want to do in that cal. I would save them for when you reload a mag. cart. or when using ball powders in your .303. As it is you may not notice anything esp. in cold weather, but on a hot summer day everything may come together and leave you sooty faced at best.
 
X2.Use magnum primers for ball powder reloads only.Go to .303british.com for "free" reloading data using IMR 4350. Several of the well known reloading manuals give data for this combination of propellant and bullet in the .303 British.Well worth the investment if you plan to reload for this or any other cartridge.
 
I don't know about 303 Brit but I have used Regular Small/Large Rifle, Match and Magnum primers in .223, 22-250 and 6BR using normal load data with no issues.

When working up a load with any new component, start at the lower end of the scale and work up.
 
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Well the jig is up
First time reloading and I made up 600 casings allready primed with the magnum primers:mad: On the advice of the local gunstore and the help of a local know it all reloader. I went to .303british.com and there is a recipe with magnum primers. The powder they call for is the Win 760. I will change to this powder. Any idea where to buy Win. powder in Canada?????
Thanks for everyones help.
Pete......:)
 
You can also use H414 which is also a ball powder with a similar burn rate to Win 760 (it's said to be the same powder). Hodgdon has published loads for it.
 
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hemidart said:
Hi I am reloading a jag of .303 with 180gr. Sierra's I given a bunch of new Winchester magnum Primers is there any problem I might encounter using these versus the regular primers? I will be using IMR 4350 Powder also any Idea what the Min. and Max. powder measure should be? I am building all for a Parker Hale Mk 4.
THANKS TO THE GUYS WHO HAVE GOT ME THIS FAR :)
Pete......
Click to expand...

Hi Pete,

I would not lose sleep over it or travel across the country to find another powder....

Simply cut one grain off your powder charge and everything will be all right.

Enjoy.

BB
 
There's no way to know what the pressure change will be switching to a mag primer. Sometimes nothing, sometimes as high as 12000 psi. Generally a 5% cutback will be safe, but as noted above you don't need to use them unless they're called for - big charges of slow burning stuff in large capacity cases.
 
Lot more "flap" about the use of magnum primers than they deserve. You can use them in your 303 without any issues, but you should redevelop your load from a bit below, so you don't get any surprises. FWIW, I use W760 a lot in the 303 with excellent results. Regards, Eagleye.
 
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