With primer availability limited at best, there has been a lot of conversation about substituting magnum for standard primers. Lots of opinion but few hard facts so I decided to test one of my "standard" loads by substituting magnum primers for regular. My load is built around a commercial 200 gr cast lead SWC purchased from Oregon Trail. I seat them to a length of 1.25 and crimp to .467 over 5.8 gr of W231 and use a Winchester WLP primer. Cases used in the test were R-P once fired brass. When developed last year this load was measured at 887 fps with the Chrony at ten feet which equates to a calculated MV of about 925 fps. In the course of development I also measured the same combination with loads of 5.2, 5.4, and 5.7 gr. For this test all specs were identical except that I substituted Wolf large pistol magnum primers.

I first re-measured the "standard 5.8 gr load in order to get an idea of the variances that may be caused by temperature differences compared to last years tests. The load clocked at 886.8 which was almost identical with the results from initial development last year. I then fired ten shot strings of test loads with charges of 5.2 gr through 5.8 gr and magnum primers. Each magnum load was found to have an average of almost 18 fps higher velocity than the equivalent "regular" load except the 5.8 gr load which was measured at almost 7 fps slower!

Also of interest was the comparison of Standard Deviations observed. The SD for the magnum loads was higher than the equivalent non-magnum load in every case with the greatest difference in the lighter loads.

All of the loads performed normally in my PC945 with cases extracted and ejected consistently. I did not compare accuracy as I was pretty much focused on not shooting the Chrony. A visual inspection of the fired cases revealed that the magnum primers appeared to be somewhat flatter than the standard primers. This was true of all of the magnum loads including the lightest ones. As can be seen in this picture the 5.8 gr load appears identical to the 5.2 gr load.



For comparison purposes here is a picture of the cases fired in the test with 5.8 gr and regular primers.



Finally here is a picture of a factory Winchester White Box 230 gr JHP showing similar flattening.



Based on these observations, I would be inclined to think the Wolf primers are generally softer and therefore would be "flatter".

I don't think I have enough data to draw any firm conclusions. My test does seem to confirm that that magnum primers can be substituted in loads that are less than maximum. Regardless of these results any such substitution should be approached cautiously and starting loads should be reduced by at least 10%.

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sona si latine loqueris .

With primer availability limited at best, there has been a lot of conversation about substituting magnum for standard primers. Lots of opinion but few hard facts so I decided to test one of my "standard" loads by substituting magnum primers for regular. My load is built around a commercial 200 gr cast lead SWC purchased from Oregon Trail. I seat them to a length of 1.25 and crimp to .467 over 5.8 gr of W231 and use a Winchester WLP primer. Cases used in the test were R-P once fired brass. When developed last year this load was measured at 887 fps with the Chrony at ten feet which equates to a calculated MV of about 925 fps. In the course of development I also measured the same combination with loads of 5.2, 5.4, and 5.7 gr. For this test all specs were identical except that I substituted Wolf large pistol magnum primers.

I first re-measured the "standard 5.8 gr load in order to get an idea of the variances that may be caused by temperature differences compared to last years tests. The load clocked at 886.8 which was almost identical with the results from initial development last year. I then fired ten shot strings of test loads with charges of 5.2 gr through 5.8 gr and magnum primers. Each magnum load was found to have an average of almost 18 fps higher velocity than the equivalent "regular" load except the 5.8 gr load which was measured at almost 7 fps slower!

Also of interest was the comparison of Standard Deviations observed. The SD for the magnum loads was higher than the equivalent non-magnum load in every case with the greatest difference in the lighter loads.

All of the loads performed normally in my PC945 with cases extracted and ejected consistently. I did not compare accuracy as I was pretty much focused on not shooting the Chrony. A visual inspection of the fired cases revealed that the magnum primers appeared to be somewhat flatter than the standard primers. This was true of all of the magnum loads including the lightest ones. As can be seen in this picture the 5.8 gr load appears identical to the 5.2 gr load.



For comparison purposes here is a picture of the cases fired in the test with 5.8 gr and regular primers.



Finally here is a picture of a factory Winchester White Box 230 gr JHP showing similar flattening.



Based on these observations, I would be inclined to think the Wolf primers are generally softer and therefore would be "flatter".

I don't think I have enough data to draw any firm conclusions. My test does seem to confirm that that magnum primers can be substituted in loads that are less than maximum. Regardless of these results any such substitution should be approached cautiously and starting loads should be reduced by at least 10%.

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sona si latine loqueris .

What mag primer did you use?
The Winchester Large Pistol is also magnum primer, Winchester only makes 1 large pistol primer, and it can be used in both.
I use Winchester WLP for this reason, because I load 45 ACP witch needs regular primers, and also 44 mag witch in most loads it needs a mag primer.

I went back and read your post again, I see you used Wolf Mag primers for your test.

Again Winchester WLP primers are for mag loads.
I really don't think going to a mag primer with a starting load is going to hurt anything anyway.
Just watch for pressure signs.

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John

I am currently faced with this problem I have 4,000 Magnum Small pistol primers and 500 standard small pistol primers. I want to load 1000 rounds of .38. I am going to start by reducing my standard load by 10% using the magnum primer and see what happens in an N frame Smith. I want to save the small pistol for 9MM. What do you think of using the magnum primer in a .38 with a 10% reduction in powder?

reduce 10% of what load? what powder and what bullet?

I'd load 5 or 6 and give them a try, if alls good, load the rest.

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John

3.5 Grains of Bullseye 158 Lead SWC and yes I planned on loading 6 to start.

If you start your load at 3 or 3.1 you should be safe, work up from there.

Have fun, and be careful.

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John

Here is my prediction, and if we were shooting together I'd place money on it. Using the load you mentioned, 3.5 gn BE with a 158gn bullet in 38 Special cases you will see no practice difference using small pistol Mag primers and standard small pistol primers. Personally I feel you can have a greater variation changing brands of SP primers than going from magnum to standard of the same brand. With a mid range load like you mention there should be no issue.

Tell you what though, I'm willing to help you out. Send me a K of your magnum primers and I'll load them up with 3.5gn of BE and a 158gn bullet. Then I'll test them against my standard 38 Special loads, which right now are Wolf standard SP primers, 3.5gn of BE and a 158gn FP bullet.

If you were loading close to maximum loads the usual warning about reducing 10% would of course apply fully.

I think I agree with that totally Red. We have all noticed how published loads seem to have become milder over time. I believe most of that is due to product liability concerns. If the courts can pay out millions for someone who burns herself with hot coffee can you imagine the payout if someone gets hurt because they used the wrong primer? I think loads have been dumbed down so that something like using the wrong primer will not result in a KB.

Just my opinion.

Frank

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sona si latine loqueris .

walnutred thanks for the offer but I would not want to burden you with all that work. Why not just send me a couple three of your Smith's and I will do the testing here.

Thanks but the FFL transfer fees would be too much of a burden to place on you . Seriously though, if it were not for the onerous hazmat fees I'd offer to trade you a thousand standard primers for a thousand magnum primers. I honestly do not think that with the load mentioned you will see a noticeable change in group size or point of impact substituting magnum primers for standard. Unless your shooting ability and equipment has you competing at the National level. And even then I'm not that sure.

I didnt get into the crony testing but did try some wad cutters with primers and NO powder. I loaded 38spl, With small pistol.small P mag. small rifle and small R mag. The small rifle mag put the slug about 25feet. The rest were about 15feet and could not tell any real difference. I know this is not a great way to do things but I dont load max loads anyway. The large ones dont interchange between rifle and pistol