I need to form some 17 mach iv 'improved', cases out of some 222rem brass.
Now i realize you are thinking, why not use the 221 case, well i have but, there is a over sight on my part!
I know i need to give as much detail as possible,
Many years back i bought a second hand mach iv barrel and fitted it for some varmint shooting, well after a short time the bore was gone. I really liked the case and its performance, so i decided to get a reamer from DK, fitted a Lilja barrel and fire formed my old '221' come 'mach iv' cases to the new improved version.
My improved version has minimum case taper and 40 deg shoulder, sort of like a 'AI' version i guess. The problem was that after many years of fire forming AI cases of all sorts of cases, i wanted to achieve consistently formed case. Maintain case uniformity and wall thickness. I have found that when forming a big blow out like a 220 AI and even my little mach iv case, the cases stick first at the mouth, then blow back along the case to the base, stretching and thinning the wall in varying amounts, also the case length will vary hugely by up to .040", depending on how they stick and hold. Once trimmed this will give miss uniformity of the case.
I have found the only reliable way, to form the case, with minimum case length variation is with some hornady butter on the case, to prevent it from sticking at the mouth as it is formed. This gives results of only a few thousanths variation in length. I have also found that when using the 221 case as a donor that the case neck length is greatly reduced as the blow out is large enough to absorb the length.
Now hear is the problem, in achieving a new case i need more length at the finished case, so i have opted to use the longer 222 rem case.
So how do i reduce the case shoulder length?
I have found with using either neck forming dies or FLS die, that the case just crushes or squashes, rather than reduces in size.
I am starting to think that i need a series of larger diameter forming dies that will reduce the case diameter from the shoulder back to my desired shoulder height, in the same way a neck forming die works.
Does any one know how the brass is made from new, and how they achieve the desired shoulder and neck?
The experimental Mach IV imp. has been a huge success and really shoots well, and achieves 4180 fps with the 20 vmax, it is fantastic out to 450 yds on varmints.
I have put off making new brass for some time, so really want to get this done.
I also have the worn barrel re chambered to the improved case, with an extra .100" in the neck length, so i can cut the new cases long and then fire form and trim.
All suggestions appreciated!
Jim
Now i realize you are thinking, why not use the 221 case, well i have but, there is a over sight on my part!
I know i need to give as much detail as possible,
Many years back i bought a second hand mach iv barrel and fitted it for some varmint shooting, well after a short time the bore was gone. I really liked the case and its performance, so i decided to get a reamer from DK, fitted a Lilja barrel and fire formed my old '221' come 'mach iv' cases to the new improved version.
My improved version has minimum case taper and 40 deg shoulder, sort of like a 'AI' version i guess. The problem was that after many years of fire forming AI cases of all sorts of cases, i wanted to achieve consistently formed case. Maintain case uniformity and wall thickness. I have found that when forming a big blow out like a 220 AI and even my little mach iv case, the cases stick first at the mouth, then blow back along the case to the base, stretching and thinning the wall in varying amounts, also the case length will vary hugely by up to .040", depending on how they stick and hold. Once trimmed this will give miss uniformity of the case.
I have found the only reliable way, to form the case, with minimum case length variation is with some hornady butter on the case, to prevent it from sticking at the mouth as it is formed. This gives results of only a few thousanths variation in length. I have also found that when using the 221 case as a donor that the case neck length is greatly reduced as the blow out is large enough to absorb the length.
Now hear is the problem, in achieving a new case i need more length at the finished case, so i have opted to use the longer 222 rem case.
So how do i reduce the case shoulder length?
I have found with using either neck forming dies or FLS die, that the case just crushes or squashes, rather than reduces in size.
I am starting to think that i need a series of larger diameter forming dies that will reduce the case diameter from the shoulder back to my desired shoulder height, in the same way a neck forming die works.
Does any one know how the brass is made from new, and how they achieve the desired shoulder and neck?
The experimental Mach IV imp. has been a huge success and really shoots well, and achieves 4180 fps with the 20 vmax, it is fantastic out to 450 yds on varmints.
I have put off making new brass for some time, so really want to get this done.
I also have the worn barrel re chambered to the improved case, with an extra .100" in the neck length, so i can cut the new cases long and then fire form and trim.
All suggestions appreciated!
Jim