reg primers vs mag primers

[yotesmoker]

Wanted to load up some 357 ammo for my new marlin rifle.The reloading books show that small magnum pistol primers are to be used.Since it is almost impossible to locate primers now ,what would be the harm in useing regular small pistol primers that I have a supply of?

[gypsyman]

I did that by mistake. Loaded 50 rds. with some 296, and it wasn't till I was back on the reloading bench that I noticed that I had loaded with std. primers. I had shot 40 rds. and didn't have a problem, so shot the last 10 at a later date. Since I was loading for a revolver, I had put a heavy crimp on the bullet. This might have been the reason I didn't have a problem. If at all possible, I wouldn't try it. I have read in a Seirra manual that to go from std. to magnum can be done, just start at the bottom load suggested. If you do try it, be very careful of squibb loads, as you might not be able to ignite the powder and get a complete burn. gypsyman

[helotaxi]

The most current Speer manual only lists mag primers for a few .357 loads (all heavy loads with spherical powders) and calls for regular primers for most loads.  I very seriously doubt that you'd get a squib but rather would have a low velocity load as some of the powder would leave the barrel unburned.

[LaOtto222]

I am OK on primers for now, so I can use what ever I want. I developed a load for a 22 Hornet using CCI 500 small pistol primers using W296, they shot well and I was not getting any signs of over pressure and the chronograph said I was right were I was supposed to be. Curiosity took over and I loaded up a few small pistol mag primers (WSPM) with the same load. I got over pressure right away - those Hornets are touchy. I say that you would be OK with regular small pistol primers, but you more than likely will get lower velocity along with lower pressures with them over Mag primers. You can only try them and see how it works out for you. Good Luck and Good Shooting

[yotesmoker]

OK,now I'm really confused.While checking out other forums I found that someone used Rem SR benchrest primers to load 357"s.Is this possible?

[Jacko]

I understand that benchrest primers are selected for the cups and anvils exceptional uniformity and the primer mix is metered into the cup with more precision than standard primers which all means they ignite more uniformally across a batch than standard primers .

I'm new to reloading in the course of developing a load for my Rossi .357 discovered that standard Federal 100 SP primers did not produce best accuracy and found groups nearly halved when I switched to Winchester SR magnum primers . I have loaded up some CCI SP 450 primers to see if they produce similar results to the Winchester primers . Lots of folks have told me you don't need magnum primers for the .357 but my results show different , don't know about benchrest primers but they do have the same priming compound in them as standard primers so should ignite the powder the same a standard SP primers

regards Jacko

[gypsyman]

yotesmoker, double check on what you read about Rem 71/2 primers. Years back, there were quite a few silhouette shooters using the Rem 71/2 BR primers in their .357 super mags. The extra flash would help get all the powder burned up in that case. Most were shot in Dan Wesson's, that had a harder hammer strike than most revolvers, which you needed to get rifle primers to ignite. I would definetly stay away from any rifle primers in a handgun. In all likely hood, they might work, but I'm betting you would get some that wouldn't have a hammer strike hard enough to fire it off. Then you'll be wondering if it's a hang fire, or it just plain won't go off. gypsyman

[LaOtto222]

Yotesoker - I thought all you had were reg small pistol primers. Use them, but check you loads just to make sure you are OK. Do not use a ball powder unless you can't help it. I do not think you will find much difference, but if you do, I suspect they will yield lower pressures for the same load. The purpose of small rifle primers is to handle higher pressures. You should not need them, even if you do shoot them in a rifle. If you are needed them because of pressure - you are way over where you should be. There are some "pistol" rounds that call for small rifle primers, but this is due to higher pressures seen - the 357 is not one of them. Be Safe and Good Shooting