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Postal Bob

Magnum vs Regular primers in 38 special loads

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I was recently given 1,800 Win small magnum primers. Though I will load some 357 mag loads, I certainly won't load and shoot 1,800. So I was wondering what may be the effect of using them in my light 38 special loads. I currently load extra light IDPA loads of 2.8 gr Titegroup with a 158 gr coated bullet. I know that magnum primers burn hotter, and in some loads may raise pressures. But my loads are about 110-115 pf, and if there is any increase in pressure,  it would hardly approach maximum. If anything, with my extra small volume of powder, I may even get better, more consistant, burning of the powder.

Anyone have any experience substituting magnum primers for regular primers in their loads? And what effect did they have, if any?

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You may get 10 FPS when shot over the chrono...other than that, no difference. During the great primer shortage, Winchester SPMP is all a

I used, and since then, whenever I see them on sale, I buy.

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I've used magnum primers in 9mm (Minor and Major) and .45.

 

Saw no noticeable difference     :) 

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1 hour ago, GrumpyOne said:

You may get 10 FPS when shot over the chrono...other than that, no difference. During the great primer shortage, Winchester SPMP is all a

I used, and since then, whenever I see them on sale, I buy.

^^^^this

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As said a slight increase in velocity with the same powder charge is about the only change because of the larger volume of primer compound in a mag primer vs a standard one. But the magnum primer has a harder cup by design to resist blowout from the higher pressures traditional of magnum loads. So in a factory set action its no problem, but if you have a worked action and depending on the degree of that work relative to the double action reduction you could have FTF with a magnum primer vs softer standard primers. Load 'em up and if they go bang everytime...run em without worry. 

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1 hour ago, BallisticianX said:

As said a slight increase in velocity with the same powder charge is about the only change because of the larger volume of primer compound in a mag primer vs a standard one. But the magnum primer has a harder cup by design to resist blowout from the higher pressures traditional of magnum loads. So in a factory set action its no problem, but if you have a worked action and depending on the degree of that work relative to the double action reduction you could have FTF with a magnum primer vs softer standard primers. Load 'em up and if they go bang everytime...run em without worry. 

The part about the harder cup is not true all the way through all primers. While some may have a harder cup, many do not. Winchester primers use the same cup in small pistol magnum primers as the small pistol primers, and many other manufacturers do as well. 

 

 

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Posted (edited)
2 hours ago, GrumpyOne said:

The part about the harder cup is not true all the way through all primers. While some may have a harder cup, many do not. Winchester primers use the same cup in small pistol magnum primers as the small pistol primers, and many other manufacturers do as well. 

 

 

 

In hardness let me specify, the material may not necessarily be harder now nor may it be just a bit thicker cup, but all the major Manufacturers (Fed, CCI, WIN) at one time varied those design points on magnum primers. It was to minimize primer piercing/blowout on elevated magnum pressures. Im sure with the levels of engineering technology and mellaurgy that has gone through various changes. But I can tell you the require "strike to ignite Sp vs SPM still does differ based on real world testing. I have many revolvers Ive worked in various levels of mainspring reduction. Using a Smith at a 7lb DA pull as a test medium I have fired loads of the same powder/bullet/case with all three brands of standard and magnum SP primers to determine suitable alternatives during the primer crunch a few years back. All the "magnums" had significant FTF whereas Fed SP & Win SP were 100% and CCI SP had a 16-32% failure rate (based on 6 shot cylinder). Fed SPM had less FTF then Win followed by CCI. I have noticed over the years Win & CCI seem to flip flop with what impact levels they need to set off. CCI has become easier in the last 10 or so years. I have some 15 year old CCI's that need some major energy to ignite. 

(Edited for fat finger spelling errors)

Edited by BallisticianX

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Possible difference in hardness of the magnum primers is someting I'll definitely have to test before loading up hundreds of rounds. I'm using a Ruger GP100 with the Wolff spring kit using the lightest springs in the kit. So far it's been 100% reliable through almost 1,000 rounds in temps ranging from 25° and up. And there are very solid strikes on the primers, so I'm guessing the magnum primers should be no problem. But a test of about 100 rounds with magnum primers, would be prudent before using them in a match.

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Posted (edited)
1 hour ago, Postal Bob said:

Possible difference in hardness of the magnum primers is someting I'll definitely have to test before loading up hundreds of rounds. I'm using a Ruger GP100 with the Wolff spring kit using the lightest springs in the kit. So far it's been 100% reliable through almost 1,000 rounds in temps ranging from 25° and up. And there are very solid strikes on the primers, so I'm guessing the magnum primers should be no problem. But a test of about 100 rounds with magnum primers, would be prudent before using them in a match.

Testing any load changes are prudent before a match....the match environment will certainly expose any issues for sure! The amount of energy applied to a primer vs the DA pull weight has many variables of drag and spring tuning. Speaking in reference to a Smithy: (I have not spent extensive time on Rugers to know there nuances) In a untouched factory spec'd action you can tune just the mainspring down to achieve a 8.5-9 lb DA pull to set anything off. If you have an action job eliminating all drag points to a minimum and a reduced power 12 lb rebound spring can tune the mainspring to 8lbs DA and set just about anything off. With a worked revolver and spring tuning to get south of 8lbs down to 7lbs, in my opinion your limited to SP standard primers from Fed or WIn (CCI is questionable but possible) Below 7lbs your into FED SP standard exclusively for uncompromised ignition reliability. These are my general findings but of course there is always that one unicorn gun that is an exception. I work over everything part interaction, 11lb rebound springs, Wolff Type 2 mainspring re-arched, and debur & polish every working surface and easily run my DA at my preferred 6lbs with Fed SP. Ive had them run at 5lbs reliably but I lose the feel in staging the trigger for longer shots and it gets ify in colder weather. So choose your primer based on what your gun is tuned to (in your case trial and error for whatever makes it go bang everytime). Good luck and enjoy that Wheel Gun! 

Edited by BallisticianX

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Posted (edited)

My revolver has a SA pull weight < 2lbs, with a DA pull weight in the 6.5lb range.  I'm using a 9lb mainspring, and an 8lb trigger return spring. Normally they say this combo will only work with Federal primers. But it has no problem setting off Winchester primers in all weather. I did polish every part in the action that makes any kind of contact, which I'm sure that's why it's so reliable. Along with the fact that the competition model I have, uses shims in the hammer to also smooth out, and lighten the action.

Edited by Postal Bob

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