Pressure: when is too much and why?

[35WhelenAI]

Over pressure loads work brass harder in the chamber, just like a die. Loses "elasticity" and needs more force to size which in turn leads to more working of the brass when sizing.

No brainer solution is knowing how to set up a die and shoot loads that are not over pressure. This is not new nor rocket science, however seems to be news.

 

[TaperPin]

It’s like the public service announcements every year around thanksgiving to not use a turkey frier in the garage, or learning to not run with scissors - you don’t know until you know.

 

[35WhelenAI]

It’s like the public service announcements every year around thanksgiving to not use a turkey frier in the garage, or learning to not run with scissors - you don’t know until you know.

Good one! Yet some folks still do both in the realm of reloading.

 

[HighUintas]

Disregard

 

[A382DWDZQ]

It’s like the public service announcements every year around thanksgiving to not use a turkey frier in the garage, or learning to not run with scissors - you don’t know until you know.

I usually set my frier on top of my wooden powder magazine. I know it’s ill advised but when I cook a turkey like that and the house is still standing, somehow it is just more satisfying.

 

[35WhelenAI]

I usually set my frier on top of my wooden powder magazine. I know it’s ill advised but when I cook a turkey like that and the house is still standing, somehow it is just more satisfying.

And you can post on the forum that you did it and everything was fine.

 

[A382DWDZQ]

And you can post on the forum that you did it and everything was fine.

Stayed tuned for my podcast “Over pressure, doing less with more.”

 

[mt terry d]

Knowing is good. Understanding is better. That’s how I read the OP.

Regarding moisture and its effect on pressure

Gunwerks episode 162 on YouTube. 9:00 mark. Is this guy wrong?

*Im new to this game and don’t know who is and is not credible.

I apologize for not posting a direct link. Dumb guy on not-so-smart phone.

 

[mt terry d]

Correction: episode 142

 

[mt terry d]

 

[Tell]

I watched that when you posted about it before. O forgot exactly but I think he talked about moisture in the barrel acting like a lubricant and causing lower pressure and less velocity on cold bore shots.
My gunsmiths theory on why the first shot is regularly slower on the chrono has to do with the barrel temperature. I’d be interested in more tests

 

[35WhelenAI]

It all comes back to the original post. Are you willing to sacrifice reloading components when those aren't what saves your ass if the action goes boom and let's go? Your choice, your sight, your face, your life. Fools game pushing past SAAMI specs with a case too small to get the velocity needed. Apparently, there is a chicken component to go to a larger case to give velocity safely because recoil is purported to be such a bad thing. For one shot in the field at 99% of the ranges game is engaged, use enough gun and don't run small cases past industry established specs.

 

[Tell]

It all comes back to the original post. Are you willing to sacrifice reloading components when those aren't what saves your ass if the action goes boom and let's go? Your choice, your sight, your face, your life. Fools game pushing past SAAMI specs with a case too small to get the velocity needed. Apparently, there is a chicken component to go to a larger case to give velocity safely because recoil is purported to be such a bad thing. For one shot in the field at 99% of the ranges game is engaged, use enough gun and don't run small cases past industry established specs.

The original post asks what happens when, in what order, and why. The point is to understand it and avoid problems. I don’t think that repeatedly saying to not shoot hot loads has anything to do with the question.

 

[35WhelenAI]

To my eye, the original post has the things I mentioned. Those questions arise in this day and age, particularly on forums, because guys want to push loads to velocities the fan boy cartridge of the day are not meant to do.

"Death and dismemberment" oughta be warning enough, but that's just me.

The first post is how much is too much pressure and why. Simple answer is industry established specifications are the limit. Stick to them using due diligence in comparing different data and working up loads accordingly. Those questions should never need an answer because no one should run in those ranges of pressure if they do that.

Anyone ("Jake" from State Farm/Unknown) saying publicly he doesn't care about pressure and is willing to sacrifice components by running too hot, is giving fools advice from foolish practice and has no credibility other being credible at being self centered to get views.

 

[Runwilderness]

I’ll chime in:

I load for a Tikka 6.5x55. Most load data is fairly anemic due to older actions with low proof ratings.

Vihtavuori does provide load data for 380 MPa rated 6,5 x 55 SE / 6,5 x 55 SKAN, but only for 139 Lapua Scenar…They publish data for 6,5 x 55 Swedish Mauser, which is 2.3 gr lower max for the same 139gr bullet.

Nosler seems hot. Hodgdon is much lower.

What if I’m running different brass and a different COAL for accuracy? Something other than a 139gr Scenar or 140gr Partition?

I’m not trying to blow myself up. I do want to reload safely and that means trying to understand how to assess how my loads are behaving without a laboratory setup.

Ignoring the thoughtful question and simply saying ‘book max’ doesn’t help me. It doesn’t help the guy shooting 6.5CM today but considering barreling a wildcat. And it definitely doesn’t help the guy that is honestly ignorant and starts playing with fire because they found some ‘reliable’ internet load but has never learned the magnitude of the danger they may be playing with.

I learned something from the rain comments in this thread. It makes total sense that adding a non-compressible fluid outside the brass is going to prevent expansion and increase pressures..but it’s not something I had ever thought about or experienced myself, so thank you to this thread for helping me learn some more.

 

[wind gypsy]

Knowing is good. Understanding is better. That’s how I read the OP.

Regarding moisture and its effect on pressure

Gunwerks episode 162 on YouTube. 9:00 mark. Is this guy wrong?

*Im new to this game and don’t know who is and is not credible.

I apologize for not posting a direct link. Dumb guy on not-so-smart phone.

I've not heard that theory before.

It sounds like he's talking about basically undetectable levels of condensation in the barrel from ambient air. Which is not the same as enough water in a chamber that it impacts the volume of the chamber and prevents the brass from adequately gripping the walls.

 

[JGRaider]

I’ll chime in:

I load for a Tikka 6.5x55. Most load data is fairly anemic due to older actions with low proof ratings.

Vihtavuori does provide load data for 380 MPa rated 6,5 x 55 SE / 6,5 x 55 SKAN, but only for 139 Lapua Scenar…They publish data for 6,5 x 55 Swedish Mauser, which is 2.3 gr lower max for the same 139gr bullet.

Nosler seems hot. Hodgdon is much lower.

What if I’m running different brass and a different COAL for accuracy? Something other than a 139gr Scenar or 140gr Partition?

I’m not trying to blow myself up. I do want to reload safely and that means trying to understand how to assess how my loads are behaving without a laboratory setup.

Ignoring the thoughtful question and simply saying ‘book max’ doesn’t help me. It doesn’t help the guy shooting 6.5CM today but considering barreling a wildcat. And it definitely doesn’t help the guy that is honestly ignorant and starts playing with fire because they found some ‘reliable’ internet load but has never learned the magnitude of the danger they may be playing with.

I learned something from the rain comments in this thread. It makes total sense that adding a non-compressible fluid outside the brass is going to prevent expansion and increase pressures..but it’s not something I had ever thought about or experienced myself, so thank you to this thread for helping me learn some more.

Use a chrono during load workup. High velocities always equal high pressure. No better way to know.

 

[mt terry d]

I've not heard that theory before.

It sounds like he's talking about basically undetectable levels of condensation in the barrel from ambient air. Which is not the same as enough water in a chamber that it impacts the volume of the chamber and prevents the brass from adequately gripping the walls.

Agreed.
I’d always assumed the taped barrel was only to prevent snow or dirt getting jammed in by accident. Sounds like another good reason to do it. Especially if it’s raining.

Regarding the water in the chamber causing pressure ( which is something I’d never heard of or know enough about to even consider):
How is that prevented other than reasonable care ? Can that increase pressure in a book-maximum load (which doesn’t show pressure signs) to a dangerous level? Does keeping a round in the chamber prevent that? Hunting with a chambered round I rarely do even when hunting alone. I think I’d rather risk a hopefully less than catastrophic event from water induced overpressure than an accidental discharge.

 

[Shortschaf]

Regarding the water in the chamber causing pressure ( which is something I’d never heard of or know enough about to even consider):
How is that prevented other than reasonable care ?

• cleaning visible moisture off of ammo before chambering
• Taping muzzle
• if you look at your action and see it's wet might be good to wipe it all down, but it does (sort of) seal out moisture from entering chamber if bolt is closed
• For the chamber itself, a bore mop would be the only way to wipe it dry

Can that increase pressure in a book-maximum load (which doesn’t show pressure signs) to a dangerous level?

Yes.
If you are already at a hot load for your rifle, your margin of error is smaller. Adding moisture causes pressure spike bigtime. Maybe not going to shear bolt lugs or firing pin assembly threads, but stuck chamber (ruined hunt) and ruined brass certainly.

The uncontrollability of getting moisture on stuff in the field is (to me) the biggest reason to stay clear of max max loads

Does keeping a round in the chamber prevent that?

Not really. If there's rain coming in your muzzle and down your bore, moisture can get between brass and chamber no problem.
Obviously an empty chamber can collect more, but its a problem either way.
Just make sure you chamber dry rounds

Hunting with a chambered round I rarely do even when hunting alone. I think I’d rather risk a hopefully less than catastrophic event from water induced overpressure than an accidental discharge.

Water on the ammo happens more to me than water collecting in the chamber. Inspect rounds/mag prior to chambering and wipe off moisture if you see it

 

[Harvey_NW]

My gunsmiths theory on why the first shot is regularly slower on the chrono has to do with the barrel temperature. I’d be interested in more tests

I'd be willing to bet that the first "slow" shot would fall within the ES of a large sample size. Shooters are obsessed with theorizing about the dynamics of ballistics and why something did what, the problem is they don't understand statistics and put merit into small data sets. If you repeat a cold bore shot 30x and it falls outside the ES of a subsequent 30 shot string, you probably have something there. But Running 5 shots over the chrono and thinking the cold bore is an outlier because it was 20fps slower than the next 4 is just playing within some serious noise.