Magnum primers for .270 Win

[WillyG]

I will run short on large rifle primers in a few months, but I have plenty of magnums. I've searched threads for the .270 and found a few loads with a mag primer, but I am skeptical. I need more feedback for using it with Hornady 130, 140 and 150 grain bullets. I've heard to use a couple or 3 less grains. I would not chance it for my .308 or 6.5 CM. Getting a little bit nervous, but I am hoping things settle down. Any thoughts for those rifles? I have the magnum primers for a 7mm RM. Thanks for your help! Appreciate it.

 

[NWcityguy2]

The first thing to remember is that there is no standard on what constitutes a magnum or non-magnum primer across multiple companies.

Magnum primers work in rifle loads which don't call for them. Generally, they are not recommended when (and because) they don't benefit the load.

I have used them before in 308/6.5 CM based on need and seen no ill effects for hunting/casual target shooting loads. About the only complaints I have heard is that in some loads there are larger velocity swings. Occasionally someone will say that velocities have decreased.

 

[WillyG]

Thanks a lot! I appreciate the feedback!!

 

[FLIGHT762]

Use your magnum primers. You will likely find there will not be a big difference. I've shot a lot of 308 ammo with magnum primers. You should drop your normal powder charge by 1-2 grains and then see if your velocity changes from your normal primer load. The one primer that does have a stouter brisance than most al other magnum primers is the the Federal 215. Your 270 will work fine with a magnum primer.

You're getting too anxious over something that can be used safely.

 

[WillyG]

I will follow the advice and take it to the range. I was pretty sure the .270 would be ok, but I wasn’t sure about the .308 and the lighter loads. You guys and your reassurance helped ease my mind!! Thanks.

 

[horsemen61]

My .270 load only uses magnum primers

 

[DocRock]

Work up a load from low in the published data for the bullet/powder combination watch for classic pressure signs as you work up and as soon as you get good accuracy, but before you get flattened primers, heavy bolt lift, difficult extraction, or significant case head expansion, call it good.

As I understand it, the issue is not that Mag primers themselves increase pressure but that they more deeply penetrate a powder column on ignition, leading to earlier peak chamber pressures and potentially higher peaks. With the slow powders that work best in 270 win, this may be only a minor issue, but better to be safe then sorry. You could always use an over primer wad (thin roundel of newsprint), a not uncommon primer retardant in the mystical world of BPCR, but I have never heard of this being done with smokeless powder and cannot therefore recommend it, only point to the theory behind it.

Good luck.

 

[WillyG]

I’ll pay close attention to pressure signs and a tight bolt. Most of my brass is is twice or 3 times fired. It’s good to know magnum primers are used in a go to load. Thanks!

 

[Blue68f100]

Mag Large Rifle primers are about 0.009" taller than std. Make sure they will seat flush, if so they will work. SR are the same as SRM.

 

[Mr. Zorg]

Mag Large Rifle primers are about 0.009" taller than std. Make sure they will seat flush, if so they will work. SR are the same as SRM.

Has something drastically changed in dimensions if large rifle primers and large rifle magnum primers?

The chart from 1995 at this link doesn't show difference of 0.009" between large rifle primers and large rifle magnum primers, and has data by primer brand.

https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/

Now, there's certainly a primer height difference between large rifle primers and large pistol primers, but I don't think any use of large pistol primers, magnum or otherwise, would be adviseable in a 270 Winchester rifle cartridge.

https://en.m.wikipedia.org/wiki/Centerfire_ammunition#Boxer_primer

"0.210" (5.33 mm) diameter large rifle primers, and a thinner or softer metal cup large pistol version for use with lower pressure loadings in weapons with light firing pin impact. Large rifle primers are also 0.008" taller than large pistol primers.[10][11]"

 

[jmr40]

Magnum primers MIGHT increase pressure slightly and you MIGHT see 20-30 fps more velocity compared to the same loads when you were using standard primers. Then again it might not change anything. If the current load you're using is right at book max, or slightly over, then the small difference could push you into an over pressure situation but even that is unlikely.

A lot of guys use magnum primers instead of large rifle primers in standard cartridges and many report better accuracy when doing so. I've experimented with the concept a little and it never made any difference at all with my loads. I'd drop down about 1 gr below where you are and work back up. Chances are good you can use the same load you've been using.

 

[WillyG]

I just measured Winchester WLR and WLRM primers and found they are identical in size. I'll reduce my loads a grain or 2 lighter to begin. I appreciate all the input and feedback.