There are a couple reasons I do not like or recommend cream of wheat or any other filler type fire forming. One is simple, walnut shells can be used as a sand blasting media, think about that. Second is how we are forming the case and how the forming differs. When you fire form with a bullet and powder you essentially have a pressure vessel with pressure forcing the case outwards in all directions. This why cases shorten up when formed, they are pulling brass down into the shoulder. This is the correct way to do it IMO. With cow you are compressing a media under high pressure and then forcing it through the neck, pulling the neck forward stretching the shoulder brass. What I want to see in a formed case is 2 things. I want the case to shorten, and I want the oal variation to remain the same as virgin cases or close to it. If new brass has a .003" variation short to long, I want to see .003" variation after ffing as well. If you end up with .010" variation for example, you have not formed cases in a consistent way.
Alex, - C.O.W. is Not Walnut shells (as we all know) - but no doubt there is some "abrasive" effect of C.O.W. - exactly how much is another story, but surely not as much as Walnut Hulls. - Powder does also have an "abrasive effect" as it burns.
- Not saying that a bullet seated to, or into the lands is not a "correct" or effective way to fire-form. (at all).
I've fire-formed brass from .223 to 223 A.I. all the way up to 50 bmg to 50 bmg Imp. and in some instances I've used C.O.W. as a filler & also a wax plug, along with a "false shoulder" turned into the neck.
And the cases
did shorten and it was consistent. - I believe that type / burn-rate of the powder being used and the amount of it has much to do with the out-come when using C.O.W. as a fire-forming method.
- I don't "advocate" C.O.W. fire-forming as a means to all ends or "the best method" ever created. - I do believe that it can be used effectively to form brass "to a partial degree" to where on the next (2nd) firing there isn't headspace concerns in the brass length (case head to datum).
To me what you've stated (in regards to C.O.W. and its use) has some inconclusiveness in it in reference to using C.O.W. as a fire-forming method.
- Also, how do you know where the brass is coming from and where its going to during the fire-forming process when using C.O.W. ??
- And how do you know how much pressure is being built in the process. And if a wax plug is used how much does the pressure differ versus using a bullet seated say 0.010 into the lands ??
Not trying to stir up a hornets nest here, I just believe that there is a "way" to use C.O.W. to fire-form
partially & if done correctly decent results can be obtained, there are other articles on here and on the accurateshooter.com website that substantiate using C.O.W. as a "method" to form brass.
I use it (C.O.W.) when the parent case dimensions in the body length are shorter than the body length dimensions of the finished cartridge. And as a method to get the body length correct.
- On a "true" Ackley Improved cartridge the Ackley versions body / datum to case head dimension is normally 0.004 LESS than the non-improved parent case (chamber dimensions) so in essence that is not normally problematic and a bullet seated at any "reasonable length" works fine, provided the brass being used doesn't have head-space issues from the start. (As the Ackley version is actually 0.004 less - datum to case head)
- Ron -
