onondaga
03-28-2011, 08:09 PM
My new 7.62X39R Collet Neck Sizing Die and the .303 Brit. mandrel parts came in today. My goal here was to neck size the 7.62X39R for .312" diameter cast gas checked bullets. The standard mandrel with the set miked out at .306", The .303 Brit. mandrel miked .3085".
http://i30.photobucket.com/albums/c338/rhymeswithwhat/X39Mandrel.jpg
You can see the standard mandrel in the box and also the piece I cut from the .303 Brit next to it.
I used a cutting disk with a Dremel type tool to cut the new larger diameter mandrel. I measured the original mandrel and cut the Brit. pin to the same length.
Inside the die is a collet and separate collar that the mandrel fits into. The hole in the collar was too tight for the new mandrel. You can see a wooden dowel in my electric drill chuck. There is sand paper in the slotted dowel end. I oiled the paper and polished out the collar to fit the new Brit. mandrel diameter. This was very easy and took less than one minute. as very little metal had to be removed.
I cleaned, oiled and assembled the modified die and put it on my press. Here is how I set up the die:
I measures the neck OD on some of my loaded ammo that was sized with a full length sizing die that has the larger de-cap/expander pin for .311-.312" bullets. I have good neck tension with that die for seated cast .312" bullets. So I used the outside neck diameter measurement from ammo loaded with that die to adjust the new Collet Die. That outside diameter is .335"
I put the lever down on the press and adjusted the new die to contact the shell holder.
My un-sized neck OD is .341". I started to adjust the die in 1/8 turn adjustments and checking the neck OD each time. After a number of adjustments I got the Neck sized OD to .335" .
I re-adjusted my case mouth flair die while I was in the mood to adjust stuff and set it for a .002" flair. Then I adjusted my Lee factory Crimp die to return the flair to zero after seating bullets. I decided not to really crimp for this caliber anymore as my rifle is a single shot break open Remington Spartan.
I loaded some ammo with the new and modified die and noted that the case capacity has increased with collet neck sizing versus full length sizing. That volume gain is one reason I chose to neck size. Longer brass life is certainly gained with collet neck sizing too.
Hopefully there will be an accuracy gain too with neck sizing and the reset of the crimp die. I am fighting to get less than 1 MOA out of the 7.62X39R for a deer load for my grandson. I was pretty darn close with full length sizing but couldn't get groups less than 1 inch at 50 yards. My hopes are up again with the new collet die and good neck size for my cast bullets.
Gary
http://i30.photobucket.com/albums/c338/rhymeswithwhat/X39Mandrel.jpg
You can see the standard mandrel in the box and also the piece I cut from the .303 Brit next to it.
I used a cutting disk with a Dremel type tool to cut the new larger diameter mandrel. I measured the original mandrel and cut the Brit. pin to the same length.
Inside the die is a collet and separate collar that the mandrel fits into. The hole in the collar was too tight for the new mandrel. You can see a wooden dowel in my electric drill chuck. There is sand paper in the slotted dowel end. I oiled the paper and polished out the collar to fit the new Brit. mandrel diameter. This was very easy and took less than one minute. as very little metal had to be removed.
I cleaned, oiled and assembled the modified die and put it on my press. Here is how I set up the die:
I measures the neck OD on some of my loaded ammo that was sized with a full length sizing die that has the larger de-cap/expander pin for .311-.312" bullets. I have good neck tension with that die for seated cast .312" bullets. So I used the outside neck diameter measurement from ammo loaded with that die to adjust the new Collet Die. That outside diameter is .335"
I put the lever down on the press and adjusted the new die to contact the shell holder.
My un-sized neck OD is .341". I started to adjust the die in 1/8 turn adjustments and checking the neck OD each time. After a number of adjustments I got the Neck sized OD to .335" .
I re-adjusted my case mouth flair die while I was in the mood to adjust stuff and set it for a .002" flair. Then I adjusted my Lee factory Crimp die to return the flair to zero after seating bullets. I decided not to really crimp for this caliber anymore as my rifle is a single shot break open Remington Spartan.
I loaded some ammo with the new and modified die and noted that the case capacity has increased with collet neck sizing versus full length sizing. That volume gain is one reason I chose to neck size. Longer brass life is certainly gained with collet neck sizing too.
Hopefully there will be an accuracy gain too with neck sizing and the reset of the crimp die. I am fighting to get less than 1 MOA out of the 7.62X39R for a deer load for my grandson. I was pretty darn close with full length sizing but couldn't get groups less than 1 inch at 50 yards. My hopes are up again with the new collet die and good neck size for my cast bullets.
Gary