Case Preparation

In short range group Benchrest, the cartridge of choice is the 6PPC. You might find the odd 6BR or some version of the two but it’s the 6PPC in first place and daylight second. To form the 6PPC we use a Lapua 220 Russian case, expand the neck to 6mm and fireform it using various techniques. Some use the hydroforming method but I don’t have any experience with this and won’t comment here. The other option is to buy Norma 6PPC cases. I have never tried them but have heard that maximum loaded neck size that can be achieved with these cases is 0.266″ (which would suit a .268″ nd chamber for a no turn option) due to the thinner neck wall thickness.

Note: It is near impossible to buy any of the suitable cases in Australia at the moment. That is even more reason to prepare and size cases properly and look after the ones you have. There is however a new option and that is the Alpha Munitions 6PPC case. At the time of writing this article, they were yet to become available in Australia although there are some encouraging reports from the US.

Fireforming cases with a 6mm bullet:

1. Expand the necks of the Lapua 220 Russian cases with 6mm expander die (use a carbide mandrel if possible)
2. Neck turn down to desired neck wall thickness
3. Size the cases with your full length sizing die and appropriate neck bushing
4. Make sure that your chamber length, bolt face to case mouth, is big enough to take a non trimmed Lapua 220 Russian case which is about 1.516” long. If your chamber is shorter then that, you will need to trim your brass to suit but only enough to fit for initial fire forming as the case will shrink in length after that.
5. Prime cases and load with BM2 or similar powder.
   Please refer to powder manufacturers recommendations for amount of powder to use if you are new to this procedure.
6. Seat 6mm bullets similar size to which you will use in your barrel, meaning not a 105 gr VLD but something in the 60 to 70 grain range
7. Shoot the bullets, taking care to place grease on your bolt lugs before each bullet as the head space may be tight on the unfired brass.
8. Size the cases again, clean your primer pockets, load and repeat the process.
9. After the second firing, size the cases again, clean your primer pockets and now trim cases to appropriate length. I have a 1.517” long chamber and trim my cases to 1.495”
10. Deburr the outside and inside of your necks with a deburring tool after trimming
11. Wash the cases in Shellite or similar, air dry them and your cases are now ready for a match

Fireforming with a .222 bullet:

1. Size the case with your normal 6PPC full length die
2. As in the first method, make sure your chamber length can accommodate the 22 Russian case or trim if required
3. Prime the case and load with BM2, again taking care of the amount of powder you use
4. Seat a .222 bullet, 45 to 55 grain weight range.
5. Shoot the bullets in your 6mm chambered barrel. This should be a barrel you don’t intend on using in a match, a designated fire forming barrel. Make sure you are using a good wide backstop at a distance of no more than about 50 meters making sure your bullets are hitting the backstop as these rounds will not be “accurate”
6. Your case necks will have expanded to your chamber dimension, but because the necks have not been turned to correct wall thickness, you now need to expand them further with an expanding mandrel.
7. After expanding, you clean and neck turn your cases to desired wall thickness, checking your loaded round and making sure the neck is about 0.002” smaller than your chamber neck.
8. Prime the cases and load a full load as recommended by powder manufacturer.
9. Seat a 6mm bullet and fire.
10. After the second firing, clean and size the cases, trim to length, deburr and wash them in Shellite.

The advantage of this method is that you put a lot less stress on the necks when expanding with the mandrel as they have already expanded during firing the 22 bullet thus giving you better concentricity over all.

Recently I have been looking into the IDOD neck turning machine made by F Class Products in the US. It is completely different to neck turning using a mandrel type neck turner like the PMA, K&M or Pumpkin brands. The concept involves cutting the outside and inside of the necks simultaneously with twin cutters. The case is held in a “Wilson” type shell holder which in turn is held by a collet chuck in the machine. The cutters are adjustable for neck wall thickness and to adjust for calibre you simply move the cross slide similar to a lathe. This method gives you virtual zero run out on the neck in relation to the body of the case and exact wall thickness all around. There are no issues of deforming the necks concentricity while expanding as there is no expanding required. You would turn down the necks in virgin brass, load a .222 bullet and fire in a 6mm barrel as explained above.

The downside of the IDOD is the price tag. The cost is about $3000 USD and you will get hit with GST at customs as well.

Here are some video links about the IDOD.

Please note:

You must have an appropriate sizing die to suit the reamer with which your barrels are chambered. Otherwise, your accuracy will suffer and your cases will have a shorter lifespan. Ensure that your loaded round measures at least 0.002” less at the neck then your barrel chamber neck diameter. As an example, if your chamber ND is 0.268” your loaded round should be no more then 0.266” and no less then 0.265” in diameter. Having said that, there are some very experienced shooters who advocate a tighter tolerance, somewhere between 0.001” and 0.0015”.

When sizing your case you need to bump the shoulder of your case. There is some conjecture as to how much to bump but as a general rule if your bumping too much, you are work hardening your cases and if you don’t bump the shoulder enough, you will feel too much resistance when closing the bolt on a loaded round. I bump my cases close to 0.002” which when closing the bolt I don’t feel any resistance until the very end of the stroke. To test this, remove the firing pin from the bolt, close the bolt on a sized case and it should only have very slight resistance at the end of the stroke. If the bolt just drops to the bottom with no resistance, you are bumping the shoulder too much.