Was reading an interesting post by Mr. Sisk over on 24 hour about secondary pressure spikes and was just wondering what the consensous was over here on AR concerning the same topic.

He claims that one of the causes is loading a case full of powder. Seems that there is an initial pressure spike that casues the bullet to start down the barrel and then basically stop for an instant before the full buring of the powder catches up, which in turn causes a tremendous pressure spike that can actually ruin barrels.

I guess I was given bad information when I started reloading many moons ago. Back then the theory was to fill the case, which I have been doing all this time and still do. Now I am a little concerned about the whole deal.

What say you?

Did he explain what causes this "pause"? Sounds like a impossiblility to me. Did he have equipment to measure these spikes?
I guess I'm from the same school that sez you should nearly fill your cartridge to ensure proper powder distribution regardless of the shooting attitude.

There is a pressure curve that has to be consistent and repeatable shot to shot in order to be accurate. The shape of the powder column i.e. short & fat case as opposed to long & thin, will have a different time to peak pressure.

Unless the bullet's "basic stop" can be documented, measured or verified (for lack of better/other terms), I'd say it's a theory yet to be proven. Full case loads and compressed loads have been around a long time, this is the first time I've heard that they can ruin a barrel. Providing of course, proper powder and charge weights for the given application.

22WRF,

the phenomenon you describe has been observed when NOT filling the case properly with slower burning powders. It is known as the secondary explosion.

quote:

Seems that there is an initial pressure spike that casues the bullet to start down the barrel and then basically stop for an instant before the full buring of the powder catches up,

I wonder what undiscovered physics is causing this phenomenon . The bullets acceleration rate may change slightly but that's about all I can think of.

Ken....

Actually, it can occur (secondary pressure peak) with certain powders, and the case is filled.

http://hunting.about.com/gi/o....hootingsoftware.com/

Here is a link to an article showing what happens in a 223 with AA2230 26.9 gr and a 40gr Vmax moly.

Low bullet pull/tension lets the primer charge push the bullet out of the case, jamming bullet into the lands/rifling. This causes the pressure spike. When a bullet is seated into the lands/rifling, pressure will rise by 10,000 PSI or more, compaired to the same maximum powder charge with the bullet backed off the rifling and jumbing .010" or more. Any time you seat the bullet into the lands/rifling, pressure always goes up.

I hardly think that the "pressure" from the primer firing starting the bullet moving until it stopped at the leade and then began moving again when the powder ignited would be considered a pressure spike.
Bench shooter often seat their bullets with their fingers (zero neck tension) but routinely jam the bullets into the lands. But then, many of the things bench shooters do have little application to hunting reloading.

Actually Sisk IIRC was useing light for caliber bullets with very dense powders. He not only observed the secondary spikes (not primary spikes) with a Pressure trace but, blew the muzzle brake off 3 barrels. The cartridge was a 300 WSM.
http://www.24hourcampfire.com/...e_testing#Post311958

Well if you look at the dates it is a post from 2004. Somehow someone found it and revived it. Doesn't seem like any other "incidences" showed up.
Now you guys have me a bit worried as I just loaded up some 130ttsx in my 300 wby under 95.0 magpro. Hope I still have a face this weekend....then again...I'm not that pretty and could use some help.

Charlie has done ALOT of work and has pressure testing equipment at his shop. Barsness wrote articles in either rifle or handloader a/b his visit to Sisk shop for testing and developing the 9.3 BS and the effects/differences in case shape--300H&H vs 300wsm. I think you can trust his info.

I certainly didn't mean to be-little Sisks work...just saying that the thread died and I'm wondering if what happened 5 years ago wound up being another phenominon......or something.
Seems like if we had a continuance of the situation we'd be hearing more about it. I'm certainly not seeing a trend by the bullet manufacturers or powder people to curb slow powder under smaller bullets...and smaller tougher bullets seem to be a trend these days.
Certainly willing to listen to more of this....if it's out there.

No, my skepticisum (if that's a word) isn't about someone that has the eq and knowledge to make statements of verifiable facts but too often you read posts where someone talks abut he is getting "pressure spikes" from Winchester store bought ammo that he doesn't get from Hornady, etc.

Here`s a new post from today by Charlie Sisk on his later findings.
http://www.24hourcampfire.com/...E_SPIKES#Post3448617

All in all it is an interesting read if nothing else.