Dave,
Have NO fear. Decap those case. Go with a single-stage press and go very slowly - as long as you don't slam-bang the rounds through the decapping die, they will only very rarely go off. (My average was just under 2 per 100 that went off.) When they do go off, they just kind of sizzle/pop and are not a danger.
Now, as far as the brass, I strongly recommend you do some additional processing. Brass softens with heat (annealling) and hardens with age. since that brass is 70 years old, it could use some additional pampering. I'm betting it is filthy too.
I just processed 1000 1955 arsenal 30-06 brass, and am VERY happy with the results. First step after you get the primers out, is to clean and passivate the brass. (Google Passivate brass, and you'll see what it accomplishes.)
- This is done by boiling some water, and putting about two heaping Tablespoons of citric acid (I use Lemi-Shine from the dishwasher aisle at the store - cheap and pure) in a plastic bucket along with about a gallon of the near-boiling water. Use a non-metallic spoon to measure the citric acid and stir it into the hot water until it's dissolved.
- Then, put in as much brass as possible, until the water is full of brass, with none of the brass sticking up out of the water. Let it sit for about 30 minutes.
- Then, agitate (again something non-metallic - you can just shake/jostle the bucket around), and make sure the brass is all covered by the water again, and let it sit another 20-30 minutes.
- Drain off the water (citric acid is 100% safe for drains - not toxic waste), and rinse the brass with more hot water (just use a collander and hot tap water) until you feel that it's rinsed well.
- Then, dry the brass. Guys have put it on towels out in the sun in the yard in the Summer, but this time of year, I've baked the brass in a very low oven (200 degrees or lower, if your oven goes lower - don't go over 220) to get it dry.
Now, the brass should be CLEAN (but not necessarily shiney). Throw it into your tumbler to polish it, however you normally polish your brass. Because the citric acid cleaned it, this won't take very long. I ran mine about half the time I normally run range brass.
Now the brass is clean AND shiney -- looking really good.
Lastly, remember that brass is hard. Correctly annealed brass will have a hard base, a medium middle, and a medium-soft mouth and shoulder. Chances are, with 70 year old brass, you have hard-hard-medium/hard... This means you will need to anneal.
I made an ultra-cheap, fairly fast annealing set-up. Take a variable-speed drill, chuck in a 3/8" socket connector and buy a deep-well socket (I think mine is a 1/2" deep-well, but it might be a 9/16"). Now get a propane torch (I bought the fat-tank model, because it sits up very nicely on the workbench, keeping the flame at about a 60-degree angle pointed up) and set it up on the bench, so the nozzle is pointing the flame up at an angle. Drop a case, base-down, into the deep-well socket. Notice how 2/3-3/4 of the case is protected by the socket? That helps keep the anneal from going too far down the case. With the case in the socket, turn on the drill motor real slow -- like you can walk faster with crutches and a walker slow -- and hold the case in the flame so that the brighter blue point of the flame is hitting right where the neck-shoulder joint of the case is. The darker blue flame will lap around the mouth and shoulder of the case as the socket rotates. You may note some orange flame coming from the mouth of the case -- that is the tar sealant burning off. (The military seals their ammo with tar sealant in the neck around the bullet for water-proofing.) AS SOON AS you see the mouth/shoulder of the case turn blue or purple, take the case out of the flame. If the case just begins to turn orange, you haven't ruined anything yet, but you are darn close, and it's unnecessary to go this far. I used the same collander I rinsed the cases in after passivating to catch the hot cases after being annealed. (There is NO need to quench the cases in water. The anneal happens from heating them - quenching does NOTHING to the brass, so why add another drying step?)
Here's the three steps my brass went through (dirty, passivated, and polished and annealed):
Happiness (can you tell this brass is 57 years old?):
The next step is I'm going to run a .32" bronze bore brush on the electric motor into the case necks to get rid of the rest of the tar in the case necks.
Then, I'm running all the cases through my Dillon Rapid Trim, to the trim-to length for my RCBS X-Die. I'm reloading all of my Ball / Match / AP / Hunting 30-06 ammo with full-length resizing, because I'm feeding 2 Springfields, 3 Garands, and hopefully-soon an M-1918A3 semi-auto BAR, so I want all the ammo to fit any gun and be safe and reliable. (Therefore, it's all loaded to M-1 Garand gas system specs.)
As far as your powder, I would use it. I'm not telling you to use yours, but if it were mine, I'd load it. I would step the load down to 49.0 grs. The M-1 gas system is designed to use the VOLUME of gas that is developed between 45.0 and 50.0grs of powder. The military loaded to pressure and velocity within a certain window of grains of powder for that volume. (Yes, that 50.5grs is within the military's window.) Myself, I'd load down just a little bit, but it appears your powder is on the slow side of 4895, AND, being 70 years old, it may have degraded slightly (but usually if storage is good, it won't degrade much). If you load 48-49grs of that powder with 147-155gr bullets, I bet you'll get reliable functioning and lower-than specification (but still respectable) velocity... Again, this is what I'd do (and have done), but you are on your own, since I'm not there and can't guide you in person in your loading endeavors.
