I've just finished reaming out the chamber of my first wildcat - an 8mm-06 AI - in a Czech 98/22 Mauser that had a touch too much headspace at the start. I can't hardly seat a bullet out long enough to touch the lands in this rifle, even after the rechambering was completed. I might be able to seat my Hornady 220 gr bullets out that far, but I don't want to waste those bullets, since Hornady has discontinued them. I've resized a number of 30/06 cases and prepped them for fireforming. I'm looking for the best way to fireform.

I'll soon be replacing the trigger and the stock, so the rifle will be ready for action soon. I like the COW (Cream of Wheat) method, but I don't have any Unique, Bullseye, or Red Dot (I use Green Dot in my 20 ga loads).

Any tips?

TXLoader

The best way to fireform, as you already know, is to seat a bullet out far enough to engage the lands. This keeps the case head up against the boltface controlling headspace. Load a moderate charge of IMR 4895 and the fired case should become perfectly fireformed to your chamber. Ever consider casting a long lead bullet? Lee lists a 175 grain GC that might work.

The next best way is to use some inert substance poured over the powder charge. My only experience is with cornmeal because that's what my gunsmith, R.W. Hart suggested I use for my 338-06AI. Checking the relative burning rate of green dot puts it in between red dot\bullseye and unique so it should work OK. I'd say any fast burning powder will do. My recipe is 10 grains Bullseye, fill the case with cornmeal then add a little tissue paper in the neck to keep everything together but don't pack tightly. Point the muzzle skyward and fire. This method will not produce perfectly sharp-shaped shoulders but will be close enough that they won't be sloppy when you next load real bullets. Hope this is of some help. Good luck.

Now for the right way:

Expand your cases to the next size up using something like a .338 or .358 expander ball (or better yet, start with .35 Whelen cases). Then, run them into your FL 8mm-06 AI die ONLY far enough for the bolt to close on them with just a bit of resistance. This will create a "false" shoulder where the fatter part at the base of the neck bears against your chamber shoulder for perfect headspacing. This method will allow no case stretching and will provide you with cartridges that can be fired with full-power loads and good accuracy.

Only God knows what kind of mess you're going to make with baby breakfast cereal and what kind of case stretching or headspace it would result in (the cartridge is still going to be slamed foward by the force of the firing pin, then stretch rearward when gas pressures increase). I hate to think of trying to clean gummy, half-burned rice or wheat out of my barrel. The "cram the bullet into the riflings" method is okay for case forming, but you can't generally use ammunition so loaded for regular, or even casual, hunting because the cartridge usually can't be removed from the chamber without actually firing it. Besides, with the bullet crammed into the riflings you always run the risk of unanticipated pressure spiking, so you have to cut your loads back to somewhat less than normal power.

Good luck with your 8mm AI; it should be a great cartridge with a lot of power compared to its parents.

Did you set the barrel back any or simply ream the already too long chamber? A properly reamed AI chamber will provide a slight crush fit on the parent brass and negates the need to expand the neck to a larger size to create a false shoulder. That tip is appropriate for cartridges whose shoulder is farther forward than the parent brass like the 9.3x62 made from .30-06 brass.

z1r,

All I did was simply reamed out an already too long chamber. The action originally swallowed a 8mm Mauser field gauge and had room to spare...not going to fire that kind of chamber!

As I'm just cutting my teeth on gun projects, this looked like just the ticket for a first wildcat project, for I've wanted an 8mm-06 AI for awhile now.

Since I have no lathe (and don't know of anyone locally with the time and equipment to walk me through it), I reamed it by hand.

I continually checked the chamber with a go gauge, and reamed until I close the bolt smoothly with a go gauge, would not close on a no-go gauge, and closed on a necked-up 30/06 case with just a bit of resistance.

'Loader

Sorry guys, my bad. I misread and thought you said 8x57 AI. The proper way to chamber for any AI cartridge is to chamber so that the headspace is .004" shorter than that of the parent cartridge. Chambered in this way you wouldn't need to use need to use Stonecreek's method. However, since the chamber is now a tad long, his method would be a way of compensating.

Sorry for the misread.

TXLoader: You don't need a .338-06 die. All you need is a .338 or .358 (or even a .355-9mm) expander button which you screw onto your decapping stem. Run the '06 cases into the die just far enough to expand the necks, but not far enough to size them back down. After neck expanding, replace your standard 8mm expander button and resize partially as described earlier.

Thanks, Stonecreek...expanders balls are easily obtainable for my RCBS dies....

'Loader