Optimal Pressure?

[Mr Underbridge]

So I got the quickload software and I started playing with it.
Can some one explain the purple line in the pressure chart?
6.5 Lapua is rated for 63k psi and I got about 59k psi with a stout load according to quickload.
Is the 63k number do not exceed number? Is running loads at around 59k psi be safe on a regular basis(taking temperature changes into account)?

 

[savagedasher]

So I got the quickload software and I started playing with it.
Can some one explain the purple line in the pressure chart?
6.5 Lapua is rated for 63k psi and I got about 59k psi with a stout load according to quickload.
Is the 63k number do not exceed number? Is running loads at around 59k psi be safe on a regular basis(taking temperature changes into account)?

Remember whe picking a load Your not jamming the bullet it can add 2 to 5 thousand PSI at the initial start pressure .
Larry

 

[Mr Underbridge]

Did you mean to say if I seat into the rifling it will spike my pressure 2-5k?

 

[savagedasher]

Did you mean to say if I seat into the rifling it will spike my pressure 2-5k?

No I said it could . Read the instructions . Just like coated bullet reduce pressure .
I can say the load I shoot I jump + 20 thousands and my primers stay tight . When I touch I can't get 4 reloads an the primers get loose . Larry

 

[Mr Underbridge]

Thanks. The ones that you only get 4 reloads do you have any idea what the pressure was?

 

[savagedasher]

Thanks. The ones that you only get 4 reloads do you have any idea what the pressure was?

No but it was more then was wanted. Larry

 

[jepp2]

Can some one explain the purple line in the pressure chart?

Which graph do you have selected? I have 4 different graphs labeled pressure available to select.

6.5 Lapua is rated for 63k psi and I got about 59k psi with a stout load according to quickload.

Yes the SAAMI max pressure for the 6.5 Lapua is 63,091 PSI max. But don't necessarily believe that just because QL shows your load is generating 59K, that it really is. Too many differences:
powder lot
maybe bullet used
actual barrel used
primer used
bullet seating depth difference
temperature
barometric pressure
water capacity
and on and on.

So unless you adjust the powder burn rate to match your actual lot, realize you could be a lot higher or lower.

I will include a link that shows a very good listing of potential "pressure signs". I personally believe too many folks rely on primer flattening too much. It can be as much of an indication of excessive headspace as it can be of pressure. And for many of the other signs - difficult bolt lift, excessive brass flow into the ejector, etc., by the time you experience these, you may be in the 80K pressure region.

I always compare my velocity readings with what QL predicts as I am working up my load. So if I am running much higher velocity, I might be running higher pressure as well.

The link: https://www.shootersforum.com/handloading-procedures-practices/58763-pressure-signs.html

 

[mikecr]

Optimum pressure is an attribute providing best load results with a given bore -regardless of what that pressure actually is(nobody can predict this with precision).
Those supposed pressure signs? It's rare when they're actually caused by pressure.
And of course 'problems'(actual), whether coming in with pressure or not, are still problems. They should be fixed for what they are.

 

[Mr Underbridge]

I keep hearing about 6mmBR and how it's made of pixie dust and the Brass lasts forever. Is it because the brass is so good or because it has high pressure rating? Or people so not load it hot?

 

[mikecr]

A lot of it because of Lapua brown box alloy. Good stuff.

http://bulletin.accurateshooter.com/?s=X-Ray+Spectrometry+of+Cartridge+Brass&submit=Search

 

[BoydAllen]

I know that Quickload is fun to play with but IMO the only real use for any "manual" as far as pressure is is concerned is to determine a safe starting load to use for a proper live fire workup. As far as pressure signs not being real, I disagree. If cases have been fired to fit a chamber and then bumped to proper clearance, and the chamber and ammunition is free of any lubricant, I believe what I see. Some case designs show pressure less than others. 40 degree shoulders do not show primer signs to the degree that cases with smaller angles do, but that does not mean that the pressure is not there. Ultimately having a good handle on head expansion is useful as well. I do not generally push my loads to levels where primer pockets become loose, but in the past I have, and I took that as a sign that I should look for another node at less pressure. If I were working close to the edge on a routine basis, I would probably pick up a used blade micrometer on Ebay to measure extractor groove diameters.

 

[mikecr]

Some case designs show pressure less than others. 40 degree shoulders do not show primer signs to the degree that cases with smaller angles do, but that does not mean that the pressure is not there.

This is a good example of cases NOT showing pressure at all. They're showing you their character under pressure.

With what you're saying, and I agree:
Run newly fire formed 6Dasher with a 70Kpsi load, per QL, and observe any changes.
Do the same with a 243win, incrementally, until observing the same changes.
At this point the 243win is not showing you 70Kpsi pressure, if anything it's showing ~58Kpsi(by QL), so the same 'pressure signs' here are way less indicative of actual pressure.

I personally trust QL math, for pressure, over these signs. It's not going to be off so much as to kill me (that takes extra efforts).
I measure the web lines, not to determine over pressure, but because I want my brass to last.
If everything's great, shooting great, cases problem free, extraction ok, but QuickLoad shows I'm 10Kpsi above SAAMI max, or 10Kpsi below, I don't care about that. And if my actual pressure is ~5Kpsi different than QL predicts, why would I care?

On the other hand, if I get popping extraction, it's time to seek a solution, possibly permanent, that includes lower pressure(regardless of actual). That's just something I can't put up with.

 

[BoydAllen]

Some time back there was a discussion in which I shared that the importer had told me that Xterminator and AA2230 are the same powder in different packages. One of the posters said that he would believe QL's difference in powder speeds over that. I rest my case. No one in the industry has sufficient faith in calculations to do away with pressure gun testing. That should tell you something.

 

[dcali]

Some time back there was a discussion in which I shared that the importer had told me that Xterminator and AA2230 are the same powder in different packages. One of the posters said that he would believe QL's difference in powder speeds over that. I rest my case. No one in the industry has sufficient faith in calculations to do away with pressure gun testing. That should tell you something.

Berger does. Before their manual came out, they responded to load data questions with QuickLOAD output. In fact, I'm not sure their manual isn't based on calculations. They're not really specific about it, if I recall correctly. Like any engineering software, it has limits, but it seems pretty good to me, and tends to give me better predictions than manuals based on real tests have.

 

[Laurie]

I've found QL results very variable depending on cartridge and/or powder grade. And that's after doing the basic fine-tuning such that the correct overflow water capacity value is used, COAL just off the lands etc. There are some cartridges I don't trust with the program too much and some powders not at all. On others, I trust it completely and have obtained range test results in MV terms that are very close to those predicted.

So, I'm in the camp that says, yes it's a great tool that can and does save time, barrel wear and component expenditure, but that it is still just a starting point for proper load development / testing.

I'd agree with Boyd's comments except in that on primer condition, that only applies with one make / model of primer. Different primers react very differently to pressure. Here are five models all fired in one rifle with an identical load in a single session, allowing time to cool and restarting with a clean barrel. If primer appearance were reliable, the viewer would regard some loads as much 'hotter' than others. In particular, the copper coloured PMC (Russian Murom standard SR) and Winchester WSR (brass colour on the extreme left of the box) look much higher pressure than the others. Note these are placed in columns, two columns for each primer model, not rows.

 

[Gr8Horses2003]

I know that Quickload is fun to play with but IMO the only real use for any "manual" as far as pressure is is concerned is to determine a safe starting load to use for a proper live fire workup. As far as pressure signs not being real, I disagree. If cases have been fired to fit a chamber and then bumped to proper clearance, and the chamber and ammunition is free of any lubricant, I believe what I see. Some case designs show pressure less than others. 40 degree shoulders do not show primer signs to the degree that cases with smaller angles do, but that does not mean that the pressure is not there. Ultimately having a good handle on head expansion is useful as well. I do not generally push my loads to levels where primer pockets become loose, but in the past I have, and I took that as a sign that I should look for another node at less pressure. If I were working close to the edge on a routine basis, I would probably pick up a used blade micrometer on Ebay to measure extractor groove diameters.

BoydAllen,
I have a 260 AI with 30 degree shoulders. I have been looking for a way to measure pressure reliably and, although I don't "think" I'm close to the edge, have decided to try to objectify it. I agree with your advice and have decided to obtain a blade micrometer. Will you please describe your method for measuring the cases? Thanks, Harry

 

[BoydAllen]

It is not really my method. I said if I were loading near the edge. Blade micrometers that read to .0001 can be used to get down into the bottom of extractor grooves to look at changes in that diameter. http://www.ebay.com/sch/i.html?_fro...icrometer.TRS0&_nkw=blade+micrometer&_sacat=0

https://www.google.com/search?q=blade+micrometer+case+expansion&ie=utf-8&oe=utf-8

 

[mikecr]

No one in the industry has sufficient faith in calculations to do away with pressure gun testing. That should tell you something.

None of us use certified pressure testing barrels. Even when using strain gauges & software, that still stands uncalibrated while on anything but a pressure tested barrel. So no matter how you approach it, there is no load data for us that connects to our individual pressures with high accuracy.
There never will be sight of our actual pressures, until our barrels come with strain gauges installed, and printouts of each barrel's testing.

My point is that a pressure problem, is not, until it's pressure that in itself is unsafe, or until a separate issue interferes with a desire to go higher in pressure.
That separate issue could be cartridge design differences, primer thickness differences, pin or pin clearance, head spacing issues, lack of breech support, excess clearances, burrs on a boltface, rough ejection plunger, or sizing problems. None, telling us what our pressures are, and we chose to fix these things, live with them, or back away from them.
Luckily for us, while following a golden rule to always work up, we hit our issues (barriers) before venturing into unsafe pressures.

 

[BoydAllen]

"...while following a golden rule to always work up..." That was my exact point. Always back off and work up when starting with a new load or when you change a component. My concern is that some shooters will not do this because of all of the praise of Quick load that they read. Back in the day, a friend who was overly concerned with reaching the same chronograph readings that he had read in an article blew the primers out of the cases of a couple of his rifles..twice. At that point I coined a new term (although I did not share it with him) "Chronograph idiot"