Fireforming while working up load?

[ZeroJunk]

I am new to this forum and look forward to catching up on the hobby.I have a 280 improved on a pre 64 model 70 action that I haven't shot in years.Brass has been reloaded many times and I am going to discard it and start over.All my data is on 140 and 150 grain bullets.I want to take it Elk hunting and work up some 160 grain loads.Is blowing the case out going to make enough difference that I can't creep up on a load while fireforming new brass?Be very surprised if I use more than the 60 grains the standard case will hold. Kill to birds with one stone.Will be using Reloader 22 and stop when I see the primer start to flatten any.Not trying to make it a 7Mag.

[amamnn]

You can fireform and work up a load however you want to do it, as long as you do it safely. I don't think I would be working up to flattening primers. For one thing, it is one sign of overpressure most shooters do not interpet correctly. I'd stick with powder or bullet makers' recommended loads keeping in mind the hottest load is not often the most accurate.
Assuming you will be using a neck die to size after the initial loading, one or two medium to medium hot loadings should do the trick as far as expanding your brass. Also assuming the chamber and bore of your rifle are fairly concentric, some care taken to assure your cartridges are also would go a ways toward improving accuracy. Also controlling start pressure with a light uniform from round to round crimp can help as well.

[ZeroJunk]

I don't know where to find any loads for 280 improved other than PO Ackley.Don't trust those.For instance,he said you could use 63 grains 4350 with a 140 grain bullet.I used 60 grains and was shooting a 140 grain bullet 3250 through a chronograph and stretching the case head.Couple of reloadings and the primer was loose.Difference in guns.Is there new published data for 280 improved?

[Unclenick]

Reducing the load from 60 grains to 56.9 grains will give the same pressure with a similar-shape bullet of 160 grain weight that 60 grains of 4350 did with the 140 grain version of the same bullet. I get this is from QuickLOAD calculations, and they probably are pretty close since the difference is relative performance with a given powder.

The picky loaders want all cases fireformed with the maximum load they will see in use. Pressure peaks occur based on expansion into the chamber, so it should be OK to do what you propose.

Nick

[ZeroJunk]

Thanks for the input.Attached is what I mean by starting to flatten.It is a Hornady Light Magnum factory load.

[Scorch]

A lot of the old PO Ackley loads were HOT to say the least. PO Ackley claimed his improved cases gave 10-20% velocity gains, but everything I've read by folks testing his old loads says they were dangerously over pressure. When brought back into normal SAAMI operating pressure parameters, improved cartridges gave about 5-10% velocity gains, hardly enough to justify the trouble. But they do extend brass life, especially with hot loads.

While I am not the ultimate authority on this, I used to fire-form first, then work up loads after reworking the fireformed brass (inspect, trim, neck turn, prime, etc). I would start out with regular cartridge reloading manual information, then work up from there in .5 gr increments until I found a good load, then fine tune it. Good load is defined as good accuracy, no pressure signs, good velocity, and very low standard deviation. I had a 30-06 AI.

[Buckythebrewer]

Just don't do any unsafe loads(too hot!!)to fire form.The one thing you benefit from in fire forming is reducing the possibility head-case seperation(re-sizing your brass too much can lead to this).I would recommend using a Lee factory crimp die and seating near BUT not into the lands when you are UPPING the charge.Just watch your head on the case and for blown primers or whatever..Get a chrono if your going to push your charges,That way you will really know when you are achieving what your after.JMIO

[amamnn]

The latest Sierra manual has info for the 280 AI. You might be better served in keeping track of pressures by measuring head expansion, as certain primer manufacturers are using softer metals in recent years making primers harder to read. It's something of a pain, but worth doing if you know you're going to load hot. When I used to fireform I used that method and it worked well as a definite warning that needs no interpetation like reading primers.
Be sure to measure just above the extractor groove with your micrometer on every case after loading but before firing. Measure again after firing. Any expansion is cause for concern. If you get odd marks embossed by the bolt face on the head itself, you've entered the danger zone. Remember, in fireforming the object is to reduce the free space between the bolt face and the shoulder.

[ZeroJunk]

Great.I just ordered a Sierra manual.Every one I had was dated 1982 or 1983.Will certainly save me a lot of testing.Who knows,I may want to try one of these new short magnums.