I am in the process of having my Rem 700 7mm/08 rechambered to 7mm/08 Improved. Redding dies are on their way. What I would appreciate help on is fireforming the brass. Should I start with new brass? my existing brass is on its 2nd firing. Can you fireform without a bullet? What is the recommended way. Thanks

The beauty of the Improved cartridges is you can make up a load using un-fireformed brass and shoot and have fireformed cases.Usually the rounds are accurate enough for general purposes.

And yes you can fireform without a bullet. I did it with a much larger case and my data would not be applicable to you. So somebody else can jump in with a charge weight for you.

Don't expect blazing results above the standard 7-08, 200+ fps is about all you can ask for. But your brass will last longer and you won't have to trim as often.

Best wishes, Bill

quote:

Don't expect blazing results above the standard 7-08, 200+ fps

A friend of mine had his 7mm-08 improved and he got less than 100fps.

Hardly worth it in my oppinion, so thats one of the reasons why I had mine reamed to 284 win, not that I really needed the extra performance.

speed increase depends on the taper of the parent case. A heavily tapered case will increase greatly,..but parent cases (like yours) that have a minimal taper will gain maybe the 100fps.

They will make brass last longer, and allow the use of slower powders for a greater load density and therefore more consistency at extended ranges.

I take a heavy bullet (or whatever you have) and set it to be jammed into the rifling by about .010" so as to push the case firmly against the boltface so as to get the growth of material for the expanded body and shoulder from the neck area of the case rather than stretching the casehead area to form the new case. Use a medium to non-max load of fast to medium burn powder for that case, and light it up. Your cases will form perfectly on the first firing.

You could probably anneal those 2x fired cases and form them just fine.

Just make sure your gunsmith sets the barrel back one thread when he chambers for the improved chamber, and you won't have to worry about jamming bullets into the lands. The standard and improved cases should both headspace on the same datum line. Contrary to popular belief, jamming bullets into the lands will NOT prevent the firing pin from shoving the case forward during firing anyway.

You can fireform without using bullets by loading a few grains of Bullseye under Cream of Wheat with a tissue or wax plug. I use my 7-08AI as my primary deer rifle and only fire 2-3 shots during a typical hunting season. The majority of my shooting is at the range or just plinking, so I simply load up 100gr Sierra's over 45.5gr of IMR3031 to fireform. Although some of the energy is spent fireforming the case to the slightly larger Ackley configuration, it is a very accurate load in my rifle, so I use it for coyotes and general plinking. I fireform cases in this manner so I can actually enjoy it. That beats fireforming at the range any day. It will be a long time before I wear out my barrel, so I don't worry about fireforming with bullets.

With 140gr Nosler Partitions or Ballistic Tips, I use 50.0gr of H380, or a similar amount of IMR 4831 or IMR4350. With H414, I have chronographed 3075fps from my 22" #2 Shilen without stiff bolt lift, flattened primers, or loose primer pockets, but my most accurate load clocks in just under 3000fps with IMR4831. I hope this helps.

I once read somewhere that there is little to be gained from improving any cartridge based on either the .308 Win or the 30-06 Sprg.

If your smith did the rechamber correctly and set the barrel back a turn then simply load 7-08 rounds and use them while you fireform. No reason to form without a bullet. Why waste the primer and powder. If he didn't set the barrel back check the factory cases you might need to form a false shoulder. Still just load and fire. I would never start with used cases for forming. Brass is cheap.

As to the AI gain I have played with plenty of AI and other improved cases over the last 30 years. Many with pressure testing. Loaded to the same pressure the 308 case will give you around 1% velocity for each 5% capacity increase. The 06 will be around 1 for 4 and the 7x57 based case due to the long taper will be closer to 1 for 3%. For rule of thumb I always use 1 for 4. Claims other than that are usually due to pressure.

I'm shooting a .260ai, IMO, you have to push the snot out of a 308 based AI to get much more than 100fps. Still, cases last forever & fireforming isn't really a big deal.

the firing pin can not push the case forward in a properly chambered AI chamber while using the parent ammo. The .002"-.003" of shoulder crush will firmly hold the casehead against the boltface during firing. The jamm seat allows pressure to build slightly more quickly, thus the case blows out very nicely when forming.

This is how it works on all 3 of my Ackley's anyway. YMMV