Pressure Spikes With H335?

[us920669]

This is a powder I only recently got involved with, recommended for a variety of cartridges from small bottleneck varmint calibers to large straight wall boomers. I first used it in 458 WM with outstanding results - plenty of zip and no problems - and declared it "Final" for the 440 gr LBT bullet, which I suspected gave a bit more resistance than a jacketed bullet when it hit the rifling. Next I used it in 9.3X62, right in the middle of Hodgdon data, and noticed it was acting a little peaky. In fact one case ironed its primer very noticeably, although the crono reading was not far out of line at all. More testing will take place once the ground dries out, but I happened to be thumbing through the Lyman 45 manual (c.1950s) when what should I see but an entrance for H335 about how "pressures tend to take large jumps suddenly" with some guns being "extremely erratic". I intend to continue using the powder in my next project, 416 Ruger, which has relatively little shoulder, but I wonder if I should call a halt to further use in 9.3X62, which has a more pronounced bottleneck. Has anyone else noticed anything like this?

 

[Mobuck]

The only thing I've used H335 for is .223. Works fine AFAIK.

 

[603Country]

I'm using H335 behind most bullet weights in my 223. I don't use it in any other calibers.

You can get a lot of info from the internet regarding secondary pressure spikes.

 

[Jimro]

Lemme guess, you used magnum primers in the 458 Win Mag, and standard large rifle in the 9.3x62?

Jimro

 

[us920669]

Yes that's correct on primers.

 

[Jimro]

I would change out to magnum primers on the 9.3x62 and do another load workup to see if that doesn't fix the problem.

H335 isn't as easy to touch off as IMR stick powders, so what I expect you are seeing is a delayed secondary pressure spike. The large rifle primer goes off and pushes the bullet out of the neck and into the bore where it gets stuck, but weak ignition on the powder means that there isn't enough pressure from the powder yet to keep the bullet moving. When the powder catches up as enough of it has ignited, now it has to clear a stuck bore which causes excess pressure.

The magnum primer should light off more of the powder right away, and push the bullet further down the bore so that the powder has more time to build pressure to keep the bullet going before it gets stuck.

Anyways, that's my advice, and I hope it fixes your problem.

Jimro

 

[us920669]

Yes, thank you so much. I pictured it yesterday from the way you asked the question. The 9.3 case is a bit larger than 30-06. It's been called secondary explosive effect and it sends people to ERs and lets their non-reloading friends say "told you so".

 

[Unclenick]

In 1989, CCI reformulated their magnum primers specifically for the spherical powders available at the time. These would include H335 and BL-C(2) and H380 and H414 and any Winchester equivalents, where is one. Today, Ramshot powders have more modern coatings that don't require the extra fire, but H335 (canister grade WC844), I was told by Hodgdon, is the exact same original formula it was in the 1960's, so it needs the extra effort.

 

[us920669]

Thank you for finding that. I probably should take that magazine, that and a few others as well. What I really need to do is to get some new primers. All my rifle primers have been around an awfully long time, just like me.