Pressure spike and velocity

[tacotime]

The question occurs to me, is an unplanned pressure spike (within reason) always accompanied by higher velocity? 
 
And another way, can you have totally normal velocity but dangerously excessive pressure? (just from the load, ruling out obstructions like bullet seated too far, or pinched case neck, etc). 

[MePlat]

This is another question that would best be answered by a ballistician.  People that do ballistic testing probabaly have seen enough patterns on this subject to be able to answer it far more reliably that anyone on a forum that has no pressure gun and or chrony doing both at the same time.
Anyone can give a guess from wag to a swag but it it is what it is.  A guess.

[cwlongshot]

The question occurs to me, is an unplanned pressure spike (within reason) always accompanied by higher velocity? 
 
And another way, can you have totally normal velocity but dangerously excessive pressure? (just from the load, ruling out obstructions like bullet seated too far, or pinched case neck, etc).

NO, higher pressure will not guarantee higher velocity.
 
YES, you can have normal velocity and hi pressure.
 
Are you attempting to judge a calibers given pressure with a chronograph? It's NOT an accurate use of this tool.
 
CW
 
Edit:  I can answer with certanity because the question deals in absolutes. Words lie "always" and "totally" leave zero room for error and there needs to be room for error. Having said that you can new see why its easy to answer with certainty. 

[Flash]

I agree with CW. I was experimenting with with some AA Data 2200 in a 22-250. There wasn't any loading data for that caliber so I thought I'd try to work up some loads. Anyone who reloads will know where a 55 grain load in the 22-250 should be and I was expecting to be getting around 3,400 fps as a starting point. I was barely at 3,000 fps but I ruined the cases with expanded primer pockets. The bolt face was imprinted on the back of the case and the headstamp was flattened. Not to the point it couldn't be read but anyone could tell that the pressure was too damn high for going any further. The recoil wasn't even noticable but the pressure signs gave me cold sweats. Pressure sometimes does and then again,  doesn't correlate with velocity so to be safe, learn how to recognize some signs of high pressure.

[Larry Gibson]

The question occurs to me, is an unplanned pressure spike (within reason) always accompanied by higher velocity? 
 
And another way, can you have totally normal velocity but dangerously excessive pressure? (just from the load, ruling out obstructions like bullet seated too far, or pinched case neck, etc).

I've been measuring the velocities and pressures of numerous cartridges with many handloads and factory loads for several years now.  Based on my experience at such;

is an unplanned pressure spike (within reason) always accompanied by higher velocity

Usually but not always.  I've seen numerous cases where increases in pressure did not correspond to and increase in velocity.  I've also seen a few cases where an increase in velocity gave a lower pressure.

can you have totally normal velocity but dangerously excessive pressure

Most definately.  When developing loads make sure the burning rate of the powder corresponds to the expected velocity.  This is where using loading data from current manuals is highly recommended.  However, as all the manuals state, loads should be worked up.  All to often we find reloaders just use the max load and have at it.

Larry Gibson
 

[tacotime]

Good info, thanks.

[yooper77]

The question occurs to me, is an unplanned pressure spike (within reason) always accompanied by higher velocity? 
 
And another way, can you have totally normal velocity but dangerously excessive pressure? (just from the load, ruling out obstructions like bullet seated too far, or pinched case neck, etc).

I would say higher than normal velocity comes with excessive pressure. You cannot get one without the other, and looking for pressure signs isn't a foolproof way of knowing if you are already over pressure.
 
The normal safe practise is work up loads from the minimum load data as you approach the maximum load, but never ever exceed it and all the time looking for the most accurate load.
 
Speed doesn't mean its better.
 
yooper77

[Flash]

The question occurs to me, is an unplanned pressure spike (within reason) always accompanied by higher velocity? 
 
And another way, can you have totally normal velocity but dangerously excessive pressure? (just from the load, ruling out obstructions like bullet seated too far, or pinched case neck, etc).

I would say higher than normal velocity comes with excessive pressure. You cannot get one without the other, and looking for pressure signs isn't a foolproof way of knowing if you are already over pressure.
 
The normal safe practise is work up loads from the minimum load data as you approach the maximum load, but never ever exceed it and all the time looking for the most accurate load.
 
Speed doesn't mean its better.
 
yooper77

I worked with my 250 extensively and according to many reloading manuals that list pressure, you can have a lower velocity with extremely high pressure. I'll quote Lyman's 47th as an example. A 50 grain bullet in the 22-250 with a 34.3 grain charge of Winchester 748 will give you 3391 fps and a pressure of 36,800.
The same bullet with a  31.8 grain charge of AA2230, which is very close to AA 2200 that I used but faster, will produce a velocity of 3290 fps and a pressure of 40,500
A 30 grain charge of 3031 will give 3181 fps with a pressure of 33,000
A 31.4 grain charge of AA2460 will give a velocity of 3154 fps and a pressure of 37,300.
 
These are just four examples of one caliber and one bullet. My testing with AA2200 was with a 52 grain BTHP and I could only chronograph the load but the pressure signs made me stop immediately.
 

[Catfish]

To get more velocity you need to keep presure on the bullet for a time. If you are useing a fast burnning powder the presure curve will climb faster. For small capicity cases like the 22 hornet great. But, for large cases like the 06 not to good. With the larger cases you need to go to a slower burning powder so you can keep the presure high without going over presure limits.

[wncchester]

Broadly stated, velocity is determined by the area under the time:pressure curve.  The term "spike" isn't well defined so it often gets misunderstood and confused.  Seems a LOT of people think it simply means the peak pressure is too high without regard to its duration.   "Spike's" original use was to explain that a rapid rise and fall of pressure due to a too fast powder could easily reach and exceed max safe peak pressure but be so brief that the velocity would be less than proper. 
 
IF the correct powder burn rate is used for the cartridge and bullet weight the velocity will normally be at or near the  projected velocity so, within rational limits, a chronograph can strongly suggest pressure.  However, small variations from the norm such as actual bore/bullet diameter, the effects of the lands when engraving the jacket, the jacket material and shank length, primer briesance, actual burn rate of the powder lot, which way the ducks are flying, etc. IF a combination of those variables are in  play they can increase the pressure.  What many don't quite understand is the burn rate of a powder is highly dependant on the pressure of combustion; if the pressure goes up the burn rate is faster and they can combine to produce a spike where one should not be!  Thus, a chronograph reading is a valid aid to judging pressure but it sure ain't anything to bet your azz on.
 
I do load development with the ladder method starting low and using small charge increments, usually .2 or .3 grain per step.  I record and plot the increase in speed for each increase in powder as I shoot.  I've easily observed non-linear velosity progressions when charges (and pressures) are too low but they usually become much more linear as the correct pressure is approached.  And, should things go screwy as the charges are increased still further, I at least suspect I'm rapidly approaching the squirrely/spikey pressure range and stop no matter what my manual suggests.