over-pressure, signs/formulas

[prodigalson]

First off, Merry Christmas to all!

I am a novice reloader and have a question. I apologize if this question has been posted before, however i am too lazy to search for an answer. But, when reloading, what are some signs to look for when one over pressurizes a load? Also, is there a somewhat simple mathematical equation, of Some sort, to use to determine chamber pressure BEFORE, you begin seeing signs on the brass?

Any help will go a long way in educating and helping me and others stay safe. Thank You.

 

[Graham]

Re: over-pressure, signs/formulas

The only true answer to any non-trivial question is: It depends.

With a .223 in an AR you sometimes don't see any pressure signs until you start blowing primers. And you sometimes won't see any in a .50 either:
http://www.thehighroad.org/archive/index.php/t-524760.html

 

[eagernoskill]

Re: over-pressure, signs/formulas

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ProdigalSon</div><div class="ubbcode-body">First off, Merry Christmas to all!

I ......., however i am too lazy to search for an answer. But, when reloading,

what are some signs to look for when one over pressurizes a load? Also, is there a somewhat simple mathematical equation, of Some sort, to use to determine chamber pressure BEFORE, you begin seeing signs on the brass?

Any help will go a long way in educating and helping me and others stay safe. Thank You. </div></div>

<span style="font-weight: bold">POINT 1 The Process</span>
There is no short cuts when you dealing with 50,000 PSI plus - well actually its a short cut to monetary and physical damage.

<span style="font-weight: bold">POINT 2 Reloading knowledge </span>
Part of the reloading process is learning the rules and developing the insight into the combinations that work safely in your gun.
"Any help will go a long way in educating" .. well then start by reading at least the LYMAN and SIERRA reloading manuals - otherwise our advice will not have a framework to hook onto and add value and you cannot develop your insight or even assess the validity or correctness of advice.

<span style="font-weight: bold">POINT 3 Pressure Formula </span>
"Also, is there a somewhat simple mathematical equation, of Some sort, to use to determine chamber pressure BEFORE, you begin seeing signs on the brass?"
<span style="font-weight: bold">YES AND NO</span>.
There are fundamentals and principals you must understand and then you can safely develop the recipe for combinations.
A excellent programme called QUICKLOAD may give you an estimation but it is not an absolute statement - it is that a clever estimation.

<span style="font-weight: bold">SUMMARY </span>There is some crucial basic work you <span style="font-weight: bold">must </span>do to develop the framework for your own knowledge to develop from and the advice to make sense.

 

[aloreman]

Re: over-pressure, signs/formulas

measure your case heads and if they grow back off

 

[Graham]

Re: over-pressure, signs/formulas

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: aloreman</div><div class="ubbcode-body">measure your case heads and if they grow back off </div></div>If your case heads have to grow back, you're doing it wrong.

 

[rem300wm]

Re: over-pressure, signs/formulas

You state that you are a novice reloader. My advice is to purchase at least one reloading manual from a reputable source like Sierra, Nosler etc. The loads published within these manuals list starting and maximum loads.

All of this data you have paid your hard earned money for has been tested extensively to make sure it is safe. If you start with one of the lighter charges listed and work up to something less than the maximum load, it seems very unlikely to me that you will exceed safe pressures.

If you want to develop your own data on pressure, my advice is to purchase the same equipment as companies like Sierra and Nosler have at their disposal and to immerse yourself in the studies of physics, metallurgy and internal ballistics.

 

[insight3b]

Re: over-pressure, signs/formulas

Until you get more experience the safest thing to do is follow Sierra's 5th edition loads to the number. Its real easy to get into dangerous territory quickly. One classic sign of over-pressure is flattened primers and its a sign that applies to any action type. You can also get into over-pressure well within the realm of published safe powder data by changing just primer or brass type used. Also easy to get into over-pressure if you develop a load in the cooler months and shoot the same load in the heat of summer.

 

[Niles Coyote]

Re: over-pressure, signs/formulas

As has been said you first must educate yourself, buy a reloading book or two and read it. Hodgdon and others have good load data free on the web however not helpful info for new loaders other than the raw load data.

Pressure:
I watch for pressure by noting the primer condition, case head condition, the amount of pressure needed to lift the bolt and extract the case. But my most preferred method is to use new brass and take a few measurements on the case head/web and just forward of it and watch the growth upon firing. Most all will grow on the first firing but when you notice more growth than the others it’s a good indication that you’re very near or at max pressure. Continued firings at this level will lead to shorter brass life... but some continue to push till they see ejector swipes on the head stamp. If you get there you are most certainly WAY over pressure.

One thing to note:
Many times you will hear people say or post “primer cratering” as a sure sign for pressure but... On Remington rifles at least(and maybe some others)it is normal to see firing pin cratering around the firing pin strike unless your bolt has been modified with a sleeved firing pin or maybe in some untouched older rifles. All of mine are 1990's-on and they all exhibit this at even starting or minimum loads. By the time you see the radius flatten or start to squire on the primers’ edge you most likely are also seeing light ejector swipes on the head stanmp area. So watching primer condition alone is not a great indicator of pressure.