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Discussion Starter #1
I realize that this question has been asked and debated many times, but I feel like I need to ask this question in a slightly different way that has been asked before. Went looking for small rifle primers and found none to be had. Finally found some small rifle magnums. Counter guy said that they would work for 5.56 but I should reduce my load. My question is that the load that I am currently using is about mid-range on the charts (maybe as much as 1 full grain below max) So................ if switching to magnum primers, should I drop back to a starting load, Drop back maybe 10% from the load I am using or stay at the load that I am using since it is well below maximum? Thanks in advance for your input
 

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I reload pistol ammo only, so I use the small pistol primers. I have also used small pistol magnum primers and absolutely cannot see any difference whether I am loading mild, or loading to +P. This applies to many different powders also. I would say to just use the magnum primers and don't worry about it.
 

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"One full grain below the charts" doesn't mean much. If you were using five grains it would be a 20% reduction, If you were using fifty grains it would be a 2% reduction. When you reduce loads you need to do so as a percentage, not a whole number. Anyway, I use magnum small rifle primers all the time. During times of "shortages" I stock up with what I can get. To be honest, it rarely makes noticeable difference in group size when using different primers. I'd suggest you reduce your load 10% off the max load listed with your powder and look for pressure signs. If they look "OK", you're probably safe to increase it upwards if you're not satisfied with the results.
 

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The Troll Whisperer (Moderator)
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One grain in a 5.56mm is not "well below" maximum. Would suggest you take the 10% of present load reduction and work back up in .2 increments for accuracy. My experience with standard and magnum primers is usually about 2 grain + when using the magnums.
 

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The Shadow (Super Mod)
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I agree with Kdub, that in that little case it will make more of a difference.
But honestly the brand will make a big difference as well.

Some folks' magnum primers just aren't much different in terms of total output, others are.


Cheers
 

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I'm not an expert by any means, but as I understand it, the magnum primers are used to ignite slow burning harder to ignite powders. As such, they burn hotter and possibly with a bigger flame. I can see where this could cause pressure spikes depending on the type of powder they are used with and the amount of free space in the case. If used with a fast burning powder in a case with a low density powder charge, I can see where this problem could become exacerbated and possibly dangerous. Again, I'm not an expert, this is just speculation on my part.
 

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CAUTION: This post discusses loads or load data that equals or exceeds published maximums for the cartridge(s) mentioned. Neither the writer, The Shooter's Forum, nor the staff of The Shooter's Forum assume any liability for damage or injury resulting from using this information. DO NOT ATTEMPT TO DUPLICATE THE DESCRIBED LOADS without first working them up from a published safe starting level charge while watching for pressure signs. If you don't know how to do that, don't try.

In 2006 Charles Petty ran a load of 24 grains of RE 10X under the 55-grain Hornady V-MAX bullet in .223 Rem in his Cooper Phoenix using every primer he could find. The velocity range varied from 3150 to 3300 fps, which corresponds to a 10% increase in average pressure and about a 24% increase in peak pressure in QuickLOAD. With that particular powder, reducing the charge about 5% to 22.7 grains brought the hot primer's load down to the velocity he was getting. Quickload shows about 7% charge reduction to 22.3 grains will bring the peak pressure down to a match to what he was probably getting from the mild primer (that 7% reduction cost 50 fps off of his lower velocity due to the loss of muzzle pressure from using less powder, where his charge weight was constant). I used to recommend the 5% reduction for primer change to people, but 7% is more conservative and is where I would go with a primer change in that cartridge today and figure the peak pressure matched when velocity was down about 1.5%.

It should be noted that Petty's load was a full grain over the Alliant maximum from the git-go, and probably adjusted for his rifle and chamber.
 

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Discussion Starter #9
Thanks everyone. All good information. I am currently using RE 10X and CCI primers. Without going to look my load info, I think I'm using 21 grains with 55 SP in 5.56. I try to always use CCI primers. No reason why, just seem to like them best and they usually are more readily available where I shop. I will have to look at my data (and some in the manuals too) I had in mind of reducing that load by at least 10% and see what happens. As long as I'm getting good accuracy, I really don't bother in trying to shoot max or beyond max anymore. When we get chance, we are going to try to take out some coyotes with our ARs. If we ever find time to try this, I may try to increase the load for this, but I feel like the one that I have is more than enough to take out a yote. It is good and accurate (more accurate than my ability to shoot it)
 

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Alliant max data for 10X in the .223 with a 55-grain bullet is 23.0 grains. Your 21 grain load is already about 10% below that max, but it would still be wise to reduce your load by at least one grain. Without a chrnograph it won’t be possible to know if pressure increased or not, but safety first...



.
 

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When recording differences in the use of standard and magnum small rifle primers in my 223/556 loads I used my chronograph. While a chronograph doesn't tell you anything about pressures you can measure other differences. In my tests using H335 there was very little change in velocity but the extreme spread was reduced by almost 50%. All that tells me is that the ignition process is more consistent. That was all I needed to know. I recorded the same drop in extreme spread with my 257 Roberts and H414 loads and in my 30-06 loads using H414.
I have no way to measure the pressure other than reading the normal signs and watching for primer pockets to loosen up over time. In my experience if primer pockets loosen up in less than 20 loadings then I assume the load is producing too much pressure for my gun and load down accordingly.
 

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Discussion Starter #13
Thanks again. I was already leaning toward reducing my light load by at least 10% but felt I wanted to know what others thought. Also, I have been wanting to break my Chrono out of moth balls because I know that it's use is critical to load development. It would be an interesting experiment to see if magnum or regular primers generate much difference in velocity (assuming I work the magnum primers back up to the same powder charge as I have with the regulars)
 

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Common reloading practice is to reduce the powder charge with any change of components. Some say 10% which isn't a bad idea. I like reloading so there's no reason not to change and do another work up, I'm just having more fun. If there is a reason not to reduce and work up like shortage of components and time for shooting/testing, then you can take your chances with adding Magnum primers to your "mid range" load...
 

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The Shadow (Super Mod)
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In my tests using H335 there was very little change in velocity but the extreme spread was reduced by almost 50%. All that tells me is that the ignition process is more consistent. .
It normally points to that, but there are weird things that happen.

A good example is a light load of CFE in my 204, then also used in MZ5's 204.
The load is spooky accurate, but has wild ES numbers. The ES is over 100fps.

Normally you would think that means that ignition is suspect, but the ignition curve isn't different, no hanging or anything funny. I'm not sure what the culprit is, but with a stable accuracy and burn curve; I don't really think I care.
Cheers
 

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I reload pistol ammo only, so I use the small pistol primers. I have also used small pistol magnum primers and absolutely cannot see any difference whether I am loading mild, or loading to +P. This applies to many different powders also. I would say to just use the magnum primers and don't worry about it.
You experience matches mine reloading pistol ammo and using SP, SR, SP magnum primers. No experience re rifles. Do know a lot of people in PRS and other precision rifle sports are uing magnum primers in cases which normally used SR. Cannot speak for their powder or amount, but do know they are looking for 3,000 fps of faster in 6 mm and 6.5 mm loads with heavy bullets.
 

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I have learned that most of the medium and slow burning double base powders are better with magnum primers.
H110, H335 and H414 all are better with magnum primers in my guns and calibers I shoot.
The fast burning pistol primers do fine with a standard primer. HP-38 and TiteGroup are the powders I use in 38, 9mm and 40.
 

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I have learned that most of the medium and slow burning double base powders are better with magnum primers.
H110, H335 and H414 all are better with magnum primers in my guns and calibers I shoot.
The fast burning pistol primers do fine with a standard primer. HP-38 and TiteGroup are the powders I use in 38, 9mm and 40.
I've always use magnum when reloading with slow burning double based powders. When using single based powders like: IMR-4198, IMR-4064, and H-4350 and other powders I always reduce the load by 10% when using magnum primers. I've found that the medium level loads are about right for either a standard or magnum primer regardless of powder choice.
 

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Elk Whisperer (Super Moderator)
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A good example is a light load of CFE in my 204, then also used in MZ5's 204.
The load is spooky accurate, but has wild ES numbers. The ES is over 100fps.
It comes down to mind over matter Darrker.

If you don't mind, it don't matter.

RJ
 
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