Magnum vs standard rifle primer

Pineman

Beginner
Dec 20, 2021
64
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I've found a couple of excellent loads for my 300WSM but have a question for you guys: Most of the reloading manuals, etc use magnum rifle primers with the 300WSM. I do have a very good load worked up with WLRM primers but also have any excellent load with Fed 210 primers. The velocity difference is less than 50fps in favor of the WLRM. Any reason to use the magnum primer vs the standard rifle primers?
 
Magnum primers help when using slow/ball powders, and in cold weather. If it were me I wouldn’t sweat using a standard primer in your 300WSM with most powders. It has a relatively short powder column. I use CCI200’s in a 7mm Rem Mag load using IMR4831 and 140gr BT’s. No pressure or ignition issues and it gives 3167 fps with a 24” barrel. A nice load really. For powders much slower than the 4831 neighborhood I use MRP’s, but with that being said, 4831’s are about the fastest powders I’ll use in 7RM’s. The 4831’s are better suited to your 300WSM.
 
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Yep to both above. More than 60 grains, slow powder or ball powder at those charge weights, or extreme cold weather. I agree with Joe, that short powder column in the 300 WSM should help and it's not using really slow powders or massive charges........either or should work fine unless you're in COLD hunting conditions.
 
Magnum primers help when using slow/ball powders, and in cold weather. If it were me I wouldn’t sweat using a standard primer in your 300WSM with most powders. It has a relatively short powder column. I use CCI200’s in a 7mm Rem Mag load using IMR4831 and 140gr BT’s. No pressure or ignition issues and it gives 3167 fps with a 24” barrel. A nice load really. For powders much slower than the 4831 neighborhood I use MRP’s, but with that being said, 4831’s are about the fastest powders I’ll use in 7RM’s. The 4831’s are better suited to your 300WSM.
Joec:
Funny you mention 4831. I'm using H4831SC. I know lot's of people say to use RL17, 19,22 and I have a pretty good load with RL17 but my Browning really likes H4831SC.
 
I think you have been given solid advice, but occasionally there are exceptions. I have two different 300WBY rifles that i load with LR primers. One likes 180 Grain noslers (AB, BT) with IMR4350 and Remington 9 1/2 LR primer, the other like 180 TSX and IMR7828SC with CCI200 (LR primer). Could I find loads with LRM? Absolutely, but I have two others I looad with 200 grn AB or PT, RL22 and Fed215. I problably would not hunt with my first two up North in the winter unless I tried them first.
 
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Only one thing to add. You may - may - find a difference in either group size, or point of impact when using regular vs magnum primers. Even if you do, I don't know if it would be enough to matter, but I would suggest doing up a small batch with everything identical but the primer and shoot them side by side.
 
One of my favorite powders for certain cartridges is Winchester Magnum Rifle, short name WMR. It's a cantankerous beoch, working beautifully in some cartridges and total garbage in others. I use it in the .270 Win., .280 Rem. and .300 Win. Mag. with excellent velocity and extremely good accuracy. Note that two cartridges are based on the 30-06 yet WMR it toal crap in that cartridge. Winchester furnished data shows only two loads, one for a 200. bullet and the other for a 220. Both bullets are given the same load as maximum, 55.0 gr. IIRC. I am thinking of trying it for the 200 gr. Speer Hot Cores I have on hand.

I've used CCI200s, Winchester WLR and WLRM with equal results in all three cartridges, in desert heat while working up loads and in temps close to zero on some elk hunts. On one hunt, one of the rifles I took as back up for my ,35 Whelen was my custom .280 Rem. Bullet was the 160 gr. Speer Grand Slam, the older two core version. At the range the day before the hunt while checking my rifles, there ws no chaange in POI andI believe velocity was not affected even though the ammo was in my truck overnight. Temp at the range at 8 AM was 14 above zero. I've seen that same thing with my .270 and .300 Win. mag. when using that powder and one of those three primers.The only other person I know of who has lamented the discontinuance of WMR besides myself was the late gun writer Ken Waters. IIRC, he was working on a Pet Loads article for the .280 Rem. when Big W pulled the plug and he couldn't find more. In my case, no pun intended, I heard early it was being dropped and when talking with a friend in the L.A, area mentioned its being dropped, he told me of a gun store that had a whole bunch. I asked him just how much and he said he'd take a look over the weekend when he went to but some components. He called me on a Saturday night and said the guy had five eight pound cans marked down to $100 a can. Ended up buying all five cans. I arranged to met my friend at Quartzite Arizona to make the exchange. I paid him his costs for buying the powder, gave him one of the canes as a gift and bought lunch. I still have about a can and a half of WMR. A good powder but limited as to use.
Paul B.
 
Several years ago I tested Fed 210 vs Winchester large rifle primers using exact matches in case weight, bullet weight and charges of the same powder with my 300 Weatherby Magnum. My variable was the barrel temperature since I had no way to accurately measure it. The Winchester primers were faster in the first test, then faster by a smaller margin in a second test.
I think the biggest advantage of a magnum primer is a slightly stronger cup. I have not measured this, but it is what I suspect.
 
Several years ago I tested Fed 210 vs Winchester large rifle primers using exact matches in case weight, bullet weight and charges of the same powder with my 300 Weatherby Magnum. My variable was the barrel temperature since I had no way to accurately measure it. The Winchester primers were faster in the first test, then faster by a smaller margin in a second test.
I think the biggest advantage of a magnum primer is a slightly stronger cup. I have not measured this, but it is what I suspect.
Slightly stronger cup is the reason some bench rest shooters use CCI450 in the 6br. I tried it with good results.
 
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