19 April 2003, 04:57
SEALDOGGYNewbie, how do you detect pressure signs
Iv'e heard you guys all talk about presure what do I look for, Regards Steve
19 April 2003, 05:11
DigitalDanDifficulty with extraction, cratered primers, blown primers, brass failure, brass extruded into extractor channel, heavy recoil for the weapon in use, stars in your field of vision, stinging sensation in your hands, paramedics saying "can you hear me now?" etc etc. I'm sure I left something out. For the most part these things are grossly unreliable for measuring pressure and in many cases the pressures required to cause them are enormously higher than what your gun is designed for. Many things influence this, so many in fact that without careful evaluation the cause cannot be established. Flattened primers would be one example, resulting from excessive high or low pressure or excessive headspace. These things are warning flags, not goals. If you experience one or more of them, step back and figure out what the problem is before proceeding.
19 April 2003, 07:57
R-WESTWith the advent of reasonably priced, sophisticated electronic pressure measuring devices, it seems the old reliable indicators (I always used the 'degree of primer flattening' method)
shouldn't be used any more. By the time any of those pressure signs show up, we're way over where we should be. So, unless you have an M43, or equivalent, what do you do?
Well, what I do is try to find a reasonable velocity for whatever combo I'm working with (say 2650 - 2700 FPS for a 180 in a 22" barreled 30-06), then use the slowest powder I can that a number of sources show will get me close. Start at least 10% below the max listed, and work toward the velocity goal, keeping an eye on velocity produced with each incremental powder increase; any sudden jumps or dips means potential problems. A chrono is mandatory. So far, that method has produced acceptable results for me.
R-WEST
As the other guys have said,once you experience any of the pressure signs you'r way over,heres a site with pics of primer and case conditions.
Jeff
http://www.reloadingpro.com/20 April 2003, 01:02
Hot CoreHey SEALDOGGY, I prefer good old time proven, 1st hand Pressure info from the case by using Pressure Ring Expansion(PRE). All you need is a set of 0.0001"capable Micrometers and a box of factory ammo to establish a Benchmark.
I also measure Case Head Expansion(CHE), but have found it a bit more difficult for a person just beginning to use this method to understand.
But, use ALL the Pressure Detection Methods available to you and you will do fine. And simply accept your 308Win as an outstanding cartridge at it's normal operating levels.
...
By the way, 0.001" capable Calipers are not accurate enough for PRE and CHE measurements.
20 April 2003, 02:25
R-WESTHot Core -
a box of factory ammo to establish a Benchmark What do you do for non-factory loaded cartridges, like wildcats?
R-WEST
20 April 2003, 03:36
Chuck NelsonSeveral reloading manuals and a chronograph.
Chuck
20 April 2003, 12:36
Hot CoreHey R-WEST, It can be done SAFELY without a Factory cartridge to establish a Benchmark. It becomes
self-evident with experience gained using PRE and CHE.It is a subtle but noticable "trait" that can be easily seen on the micrometer data.
People who have never used PRE or CHE that have Wildcats have tried to get me to divulge this bit of wisdom before, but it is in their best interest not to do that. Because they could "overlook" the indication.
If they were near me I could show them, or they can "learn it" on a regular cartridge, but I won't put it in print for someone unfamiliar with the method since they could miss it.