Magnum vs standard primers revisited

[mmb617]

I didn't want to revive a zombie thread and the newest my search turned up was 5 years old, so is there any new information on this subject I should know about?

At the present time standard primers seem to be in much shorter supply than magnums. Is there any compelling reason not to substitute a magnum primer for a standard one?

I presently only load .223 with H335 and 9mm and .45 acp presently with CFE but will be switching to Titegroup later as that's all I could get the last time I ordered pistol powder. All are done with near minimum loads for range use.

I've read some opinions that I should reduce starting load by 10% with the magnum primers but since I'm already near the minimum loads I don't think I'd really have to change. But I don't know for sure.

I have ordered a chronograph and will do some testing to fine tune but I just want to hear if anybody can give me a reason I shouldn't make the substitution before I buy a bunch of magnum primers.

Pretty much all the online vendors I normally use are out of standard SPP, LPP, and SRP, but all have those same primers in magnums.

 

[WR Moore]

If they're available, Remington 7 1/2 bench rest primers can be used without any changes. I gave them a try long ago and they reduced 200 yard groups by 1/4 of an inch with my particular load.

There's a more recent thread on this same subject. At the time of my post, it's 14 posts below yours on the same page in the reloading section.

 

[OKFC05]

For what its worth, competitors chronoed Titegroup loads in 9mm, .40 S&W, and .45 ACP using USPSA required power level, and then compared to using magnum primers for the same loads during a previous primer shortage.
The results were insignificant, well within normal loading variation and meeting power and safety requirements.
For the people loading Major power 9mm in OPEN Division, the loads were already unsafe and unreliable in normal production pistols, and should only be used in custom OPEN pistols with any primer.
It still depends on the specific load being substituted with mangum primers, but USPSA loads for Divisions other than OPEN are generally similar to available commercial ammunition.

 

[Rule3]

For ARs there is no issue, may change pistol loads a little but not worth being concerned about.
Go forth. load and shoot.

 

[reddog81]

Unless you're loads are operating at the bleeding edge of being unsafe already you won't notice any difference. I certainly wouldn't drop a powder charge 10%. I might drop a charge .1 or .2 grains if near max loads.

 

[DWalt]

I once did some tests on Magnum vs Standard LR primers for .270 Win reloads, otherwise identical. Net results for average MV difference? Zero. Grouping was slightly better with plain LR primers. Some sources indicate that Magnum primers are preferred for use with the slower propellants used in the .270, but my tests indicate no reason for that.

For many years I have treated SP and SR primers as interchangeable for handgun loads. No noticeable difference in MV or grouping. Handguns with weaker springs may produce misfires when using SR primers as primer cups are thicker metal. Absolutely no need to change powder charges.

SP Magnum primers are essentially identical to SR primers.

Bench rest primers are no different from regular primers, except for tighter quality control for better consistency.

 

[rockquarry]

Depending on your accuracy requirements, primers are worth testing. Most of the time, there may be little or no difference, but sometimes the difference is significant enough to merit changing primers. It's incorrect to make an all-inclusive statement regarding primers. Testing in your gun will show what works best.

 

[Funflyer]

I did some testing in both 9mm and 45 using mag primers vs standard. My results are spot on with what reddog81 said, velocity difference in 9mm was equivalent to just about 2 tenths of a grain, 45 about 1 tenth.

 

[Turn4811]

It is powder dependent for pistol. For 10mm using HS-6 the difference on minimum load is not that much, less than 15 fps. By the time you are midway through the range it is 45 fps and climbed rapidly for every 0.2gr increase until I stopped the testing when I reached the FPS of the max recommended load. I was 0.6gr less than the max load but I went all the way up with standard primers where I was 20fps less than the published results.

 

[Eddietruett]

I went to Magnum Primers totally last time I couldn't find any Federal SPP. I have yet to tell a difference even in the 2.7gr Bullseye Target Load. Before my chronograph got stolen, the velocity was not enough difference to hardly notice, but I did say that using magnum primers the spread of high and low velocities did shrink somewhat but not enough to be a science. Its magnum all the way for me on handgun as well as small rifle. Don't load any large rifle, so I can't make any statement

 

[mmb617]

Thanks to all who took the time to respond. I'm pretty new to reloading and just wanted verification of what I had read elsewhere.

Since I am using nowhere near maximum loads it seems I will be able to use the magnum primers without problems. That will make resupply a lot easier.

 

[fredj338]

Whether a mag primer affects tpyour load or not is 100% based on what powders you use. With faster pistol powders, I have found very little diff going to, magnum primer. Slower powders will show a greater change in vel, thus pressures. So yes, if I worked a max load up with std primers, I would drop about 5% & work up.
A chrono will give you a good map to see the direction your load is going. There are few free lunches when it comes to vel. If you swap a component & vel increases, your pressures are increasing.

 

[Qc Pistolero]

Since you are near minimum charges,I wouldn't be too concerned about it.
My experiments are with vintage cartridge(38-55,45-70,30-30)with lead bullets when shot at temp between 10*F to 90*F.What I've found with H and IMR 4198 in such hulls is that when temp goes down below 40*F,my groups won't open up as much vertically when I use a Mag primer.
So yes,a Mag primer does have an impact but I'd qualify it as marginal in small hulls(pistol and .223)with quick burning powders.