Using magnum primers

[TexMex247]

After a decade and a half of reloading I've read many a warning about reducing powder charges when changing to a magnum primer. I've always heeded it but time after time I've found an fps difference of about 25-50 fps in rifles and a similar difference in pistols. In many cases there was almost no difference at all, more so in pistol rounds. In 1 instance with the 357 magnum, mag primers were slower with 2 different powders throughout a range of charges.

So I decided to stop wasting powder and just go for it when loading under max. Call me crazy but I just can't justify down loading every time for no good reason. If anything I've learned that just about every old timer I know has a personal hunting load at or a half grain or better over max published charges. There's probably a bigger pressure situation from changing brass versus primers in most cases. Anyhow, comments welcomed.

 

[Moonpie]

Like you I followed the recommendation of charge reduction when using mag primers.
These days I load mostly lower end plinking ammo. I also have a large supply of small pistol magnum primers. So I did a little testing using the SMPP on light loads. Not much of a difference at all. So I’ve steadily been using up the SMPP.
Another unconventional trick I do is to use rifle primers in my handgun rounds.
You can use rifle primers in pistol rounds but never use pistol primers in rifle rounds. The rifle load pressures are too high and you can experience primer piercing and blowback. Using rifle primers in pistol rounds you might have ignition problems when firing them in a firearm that doesn’t strike the primer hard enough such as a D/A revolver. Since I fire them in S/A SAA guns they work fine. Maybe 1 in 100 might need to be struck twice. Of course I would not recommend this for anything but range use.
Remember to always test a few rounds when you change from the established load data.

 

[sparkyv]

I 100% agree to use magnum primers

when loading under max.

 

[db_tanker]

I've read this several times in all my manuals and never really had to worry about it since I've only ever really maxed out loads in one rifle - a 308.

Up until the recent primer drought I've concentrated on only carrying mag primers across the board.

After the drought I've been experimenting - not much deviation on accuracy or velocity?

I do have one load though that I am curious as I haven't tried it yet - I bought a brick of 1500 fiocchi spp that I used in conjunction with some 223 loads that are running about 10 gr of blue dot. I've ran the load before and sounds like I'm shooting something a tiny bit hotter than 22 shorts in my Ruger. I'll be curious how these play out this weekend (fingers crossed I can get my chores done first).

 

[Dermako]

Right before COVID in my haste I ordered magnum spp and srp without realizing it until they arrived.
My findings pretty much mirror Moonpie’s.
I am sure different powders will react differently but in my case with Titegroup and W748 at upper mid-range it was a negligible difference on multiple runs using a magnetospeed.
These are all loaded for plinking and/or varmit loads and not power factor for competition.

 

[TexMex247]

I bought some CCI sp magnum from a commercial reloader who had intermittently used them in rifle loads. I've also used some old stock Winchester sr in some 9mm loads and they matched regular primer velocity and had slightly lower SDs across some 10 shot strings. Since I'm well stocked across the board, I don't need to use rifle in pistol and vice versa but I know in a pinch I could.

As far as the magnum primers I have discovered some combinations that favor a standard primer but I'm done downloading 10%. Glad I'm not alone in this approach. Changing over brass, specifically in the 308 is a different story. Feel like I've already burned plenty of components and I've only learned it was generally a waste of resources. It's also rare for me to work up loads in winter but I do pay attention with temp sensitive powders.

 

[popper]

I thought the title said USED magnum primers. Got to put my glasses on. Shot some full power BO 145gr cast yesterday, mixed normal and magnum primers. Target couldn't tell the difference.

 

[srab]

I've always operated on the presumption that if I change anything at all (powder lot, brass lot, primer, bullet selection), when trying to reproduce a previously verified load, that I need to drop my powder charge back down a bit and work upwards again.

That, however, is assuming that the previous load was near, or at, what I considered a maximum charge for that particular firearm. I really don't worry too much about getting into trouble when switching lots while shooting loads a good bit "under max," but loading at least a single cartridge at a 5-10% lower charge, and comparing MV with a previously recorded velocity at that same charge, is still a good idea.

 

[db_tanker]

I thought the title said USED magnum primers. Got to put my glasses on. Shot some full power BO 145gr cast yesterday, mixed normal and magnum primers. Target couldn't tell the difference.

funny you should mention that...not trying to advertise for anyone but there is a place called GI Brass that had pull down PRIMERS - #41's - for pretty cheap compared to other places not having ANY.

Yeah I got a brick lol

I'm going to use em but likely in my bolt guns or contenders.

times were hard lol
D

 

[contender buff]

To me it’s a waist of time and powder. The only time I reduce is when i run out of powder and open a new can if the lot is different. Ever since I started buying larger quantities of the same lot of powder , no problem .

 

[robertc1024]

I'd forgotten about this thread. I loaded up some 6.5 Grendel, some with CCI magnum primers, some with regular CCI. Shot them over my Magnetospeed - no discernable difference.

 

[Texasjack]

A lot of testing was done when primers became more scarce than honest men in Washington. With pistol primers, the difference is too small to be significant. If you have magnum primers, you can use them in place of regular primers without changing the amount of powder. With rifle rounds, magnum primers still don't make much of a difference, but it's still a good idea to reduce the powder a bit.

 

[S13]

Using mag primers in normal loads is fine.

Where you might get issues is when you use normal primers in magnum cartridges. It can cause inconsistent and/or slower ignition.of powder and a greater variation in velocity.

 

[robertc1024]

Using mag primers in normal loads is fine.

Where you might get issues is when you use normal primers in magnum cartridges. It can cause inconsistent and/or slower ignition.of powder and a greater variation in velocity.

I've heard that too. Do you know of any empirical evidence? Maybe I should load up some .357's with H110 and try both primers. I would have to fire them out of my lever gun, or see if I can strap my magnetospeed on a pistol - that might get me some looks at the range.

 

[S13]

I've never personally done it, but I've read about it.

You would need to load some .357 or .44 mag with and without mag primers and chronograph them to see the difference.

I bet it wouldn't make any practical difference for plinking, but I bet non mag primers would affect accuracy enough you wouldn't want to do it for hunting or competition.