primer question in .357 magnum with H110

[JEB]

i have just started working up a .357 magnum load with H110 and a 158gr hornady XTP. right now im at 16.3gr of H110 and accuracy is very good, but i am finding small amounts of unburned powder after firing. i am already using a medium-heavy crimp so i wouldnt think that that is the issue. if i were to step up from a standard sp primer to a spm primer i am thinking that that may get me the better burn i need to eliminate the unburned powder issue, but i am concerned about causing too much pressure. according to my lee manual this is not a max charge, but not far from it. is it safe to keep the same load and just swap the standard primer for the magnum, or should i back off the charge (maybe 15.8gr?) and then try the mag primer?

this will be from a 3" barrel with no specific goal in mind; just to make my .357 all that it can be.

 

[ArchAngelCD]

Some don't agree but I always use magnum primers with hard to ignite ball powders like H110/W296, HS-6 and HS-7. I find I get much lower SD numbers and more complete powder burn. I highly recommend using a magnum primer with your H110 loads...

 

[murf]

+1 on mag primers with h110.

murf

 

[ssyoumans]

Unburnt powder is just part of using slower powders. The slower powders still deliver higher velocities though.

Per quickload, 16.3gr of H110 or W296 with a 158gr bullet out of a 3" revolver - only 58.2% of the powder burnt. By comparison, 6" nets 73.4%, 20" gets 87.6%. You just aren't going to burn all of the powder, but you can't back off the load either. Use a Magnum primer.

In order to get a complete burn you would have to go to a powder as fast as Unique or faster. Unique shows 100% burn, but will probably lose some velocity and the muzzle flash.

 

[JEB]

so should i back the charge off a tad when i add the mag primer or is it safe to use the mag primer with my current load?

 

[rcmodel]

Yes, it is safe.

Hodgdon shows a max charge of H-110 with the 158 Hornady XTP to be 16.7 grains.
They also show that a Mag primer was used.

SO, you are a 0.4 grain below max and should be fine with a mag primer.

rc

 

[Funshooter45]

You're probably safe. But I would back off to 15.9 gr or so anyway to be even more safe when switching primers. You might even find that you like the results better with that lower charge. I always use magnum primers for H-110. Always.

 

[gamestalker]

I had the exact same issue when I used a standard small pistol primer with H110 and 296. I was out of magnum primers and thought I could cheat with the standard primers. I think the those magnum powders are so dense that only a magnum primer will deliver enough flash to efficiently ignite.
On another note, don't you just love the 158 XTPs over the 125 grainer's? I get a lot less recoil with them, and accuracy is deffinitely better as well.

 

[mahansm]

I've used standard small pistol primers with 296 and 125 grain jacketed bullets in .357 mag.
About 1 of 6 did not light the powder. (Winchester primers). They all light with magnum primers.

 

[gamestalker]

It isn't recomended to go below minimum listed charges with either H110 or 296. And magnum primers are the recomended primer for those powders and is what the data is developed with. It's perfectly safe to use magnum primers. To reiterate, do not reduce your powder charge below minimum listed data or your pressures can go up. Look at Hogdon's loading site. They show H110 to be used with magnum primers, and also state to not reduce the minimum charge. These slow burning powders act very different than faster burning powders when the charge gets reduced below minimum, and can cause an excessive pressure spike.
I load exclusively with H110 and 296 for all my revolvers, two S&W 66s, a Taurus 608, and a Ruger SP101. My S&W 66s are snubbies and handle the data as listed just fine.
Your crimp will not have any effect on the powder burn, but a good firm cimp is important to prevent the bullets from jumping up, the result of high recoil with these full magnum loads.

 

[ArchAngelCD]

I agree, with the charge you're using there's no reason to drop back the charge at all. Like said above, your charge of 16.3gr is .4gr below the Max of 16.7gr suggested by Hodgdon and .7gr below the 17.0gr Max suggested buy Lyman.

 

[sniper5]

H110 is a unique bird. The powder likes it hot, heavy, and tight. Heavy bullets, hot primers and tight crimps. People tend to get in trouble by going too light. You can get away with standard primers in warm weather although it is not advised. When it gets cold you will start having fizzles. Everyone I know recommends magnum primers in their recipes.

 

[JEB]

just double checked my manual (modern reloading 2nd edition by lee) and there is no mention of magnum primers that i can find. i'll make up a few with the magnum primers and try to post the results. odd that a magnum primer would be used in load development but not be mentioned anywhere in the data. looks like i am going to have to get a couple more manuals to cross-reference my loads.

 

[murf]

the hornady manual shows 15.6 grains as maximum for the 158gn xtp. they show the wspm primer for all 357 magnum loads. you may want to reduce and work up.

murf

 

[JEB]

well i loaded up a few rounds with my same charge of 16.3gr of H110 but used a mag primer. there was much less unburned powder left behind but accuracy seems to have gone to pot. at 10 yards i was only holding about a 5" group, whereas with the same load with a standard primer, all shots were falling into a ~1" group. any ideas as to why the loss of accuracy?

 

[Funshooter45]

Changing the primer led to more of the powder being burned, which led to the pressure changing, which can lead to barrel vibration harmonics being different, thus affecting accuracy. That's why I said you might want to lower the charge weight and try it. For my particular Blackhawk, I got the best accuracy at about 15.9 with no detectable unburned powder. When I went higher than that, the accuracy deteriorated a little bit, but not as much as you saw. But every gun is different.

 

[JEB]

just fired a few more to make sure. looks like the innacuracy was my fault. these went into about a 1.5" group. guess i didnt concentrate enough. might try backing it down a bit

 

[murf]

h110 has a tendency to reach a certain velocity then "level out" when more powder is added. a good burn and good accuracy is right before you reach that point. this is a difficult concept to describe, but if you back off on the powder (using mag primers) and work up, you can hit this "sweet spot".

murf

 

[derek45]

I run 158grXTP, w296 with a SIERRA bookmax load(17.3) and MAGNUM primers, and a FIRM CRIMP.

MAG primers and a FIRM crimp are they key