finding hot loads

oldbadger said:
An important point is to NOT assume that the maximum load listed will necessarily be safe to use in your rifle.

Stay inside the lines; loads BELOW the minimum reccommended can sometimes cause weird stuff to happen.
Click to expand...

I have found that when I have loaded to max weird stuff eventually does start to happen. Case life is shortened dramatically. Max loads in a 45/70 and a Siameses mauser give a case life of two to three shots. Back off five percent and the case life increases to over fifteen shots.
Your methods of resizing and the crimp on the bullet can change pressures as well, in fact at a max load, the distance your bullet sits from the lands does make a diference. Changing lot numbers of powder or primers can make a significant change in maximum pressures.

Start at minimum, work up slowly in .5 or .3 grain increments, and drop the increase in powder weight to .1 grain as you approach maximum.
If your chronongraph shows no appreciable increase in velocity for a .2 grain increase in powder, you are approaching maximum for your gun.
If your primers are starting to get loose the brass is flowing and you are over maximum, and if your primers fall out, the brass has failed and the next to eventually fail is the gun.
 
In order to use a micrometer to establish your pressure limits you have to establish a baseline for measuring.
Get a box of factory loads, fire each and measure the case expansion about .20 inches from the end of the case. Record these and do an aveage.
Measure each twice, the second time at 90 degrees.
It is important that the brass you are doing this with is of the same brand and lot number as you are reloading. You can not use these measurements for other lots of brass or other brands.
You can then use these cases to develop a load increasing the powder charge by small increments. When the case head expansion exceeds the baseline you have established with the factory loads, you are very likey exceeding pressure limits for the brass and the gun. Back off your load.

Okay i read all this .. maybe I'm missing something .. If you are using a bolt rifle and after the first time you fire the rounds you have chamber formed brass.. and are only neck sizing .. even if the pressures are higher because your loads are hotter .. I'm thinking the case isn't going to expand any farther
 
Her eis a article that deals with the use of a micrometer to guess pressure. I used to do it sometimes, but nowdays just use a chronograph and my brain to GUESS high pressure, because unless we have pressure tesitng gear, mostly that is all we can do- GUESS.

http://www.reloadingroom.com/page7.html

I'm not about to invest in pressure testing gear any time soon. I may load near the edge for siome rifles, but i don't load near the ragged edge:)

SOme knowledge, some caution and clearly determining your goals, along wiht a chronograph, will get you most bang for the buck.;)
 
BrockPython said:

Okay i read all this .. maybe I'm missing something .. If you are using a bolt rifle and after the first time you fire the rounds you have chamber formed brass.. and are only neck sizing .. even if the pressures are higher because your loads are hotter .. I'm thinking the case isn't going to expand any farther
Click to expand...


Think of the chamber as a circular sping. If the load is hotter the chamber will bounce just a little bit as the pressure pushes the brass out. As the loads get hotter the brass with less springiness bounces back less and eventually rounds start to give "sticky" extraction, or even get stuck in the chamber. The case head expansion at the web will indicate higher pressures long before cases start to stick in the chamber.
There is a point where the cases expand enough for the primer to get loose or even fall out, that is far past the point of too much pressure. The web will also grow slightly over a series of reloads with high pressure loads in the same cases. If you find this to be happening it is time to try the load with .5 grain less powder in a new case of the same lot and measure it and compare it to the factory load measurements.
Keeping clear, concise, and accurate records of your reloads are important as well as keeping track of how many times cases have been reloaded and trimmed.

Just keep in mind that if you hammer a piece of steel hard enough for long enough the grain structure is going to change. The steel will get more brittle and will eventually fail.
 
Another point to ponder is that it really isn't worth going all the way up, the law of diminishing returns cuts in fast and hard. The post that suggested that you have reached maximum when a small increment in powder makes no difference in velocity is right on the money! Experience has taught me that the most accurate, consistent ammunition that i can load is usually a grain or two below maximum. I can "tweak" loads at that point by playing with OAL until I get the best accuracy.

The other comment that I really like is the one about going to a bigger/hotter cartridge. I have run into several guys who pull out hot rod 45-70 loads and wait for cheers. When I pull out my .450 Ackley and offer to show what it does through the chrony, they always seem to lose interest.

Another issue is "killing power". The myth persists that a faster bullet is far better; not so, the best killer is the one that goes where it belongs. I own way too many rifles, but I do my hunting with the ones that I am confident of hitting with. This year I shot my moose at about 100 yd with a 150 gr.308 Winchester out of my Tikka Super Sporter. The moose went less than 20 feet.
If I had shot it with the .450 Ackley, it might have gone only 19 feet, but i don't think it would have been any deader!
 
Most novice reloaders go for the max right off the bat, it is a mistake. Like the old Midas commercial went, "First you get good, then you get fast"
 
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