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7mm TCU fireforming loads
HandgunHTR52
Member Posts: 2,735
Hello all.
Here is the story. I picked up a couple of 7mm TCU barrels for hunting/silouhette shooting. I also was given a bunch of .222 Rem Mag cases. They are new. After necking them up, bumping the shoulder back and A LOT of trimming, I had some TCU cases ready to be fire-formed.
I have a bunch of Hornady 139gr SP bullets that I use with my 7-08 so I figured I would use them for my fireforming loads. I also had some IMR-3031 and H4895. My Hornady manual listed 25.3 grains of H4895 as the starting load. This load filled the case to the shoulder. When I checked Hodgdon's website for loads with IMR4227 (which I also have) I noticed that Hodgdon lists the MAX load with H4895 at 25.0 grains. Why the disparity?
The other question is this. With IMR-3031 one grain above the starting load (25.3 grains) fills the case all the way to the mouth. My manual doesn't list this as a compressed load. From what I saw of the difference between the .222 Rem Mag case and the .223 Remington (the parent case for the 7mmTCU) the only differences that I saw was the overall length and that the shoulder was farther forward on the .222 Rem Mag. So, I guess my question is, is 25.3 grains of 3031 a safe load in this case?
Here is the story. I picked up a couple of 7mm TCU barrels for hunting/silouhette shooting. I also was given a bunch of .222 Rem Mag cases. They are new. After necking them up, bumping the shoulder back and A LOT of trimming, I had some TCU cases ready to be fire-formed.
I have a bunch of Hornady 139gr SP bullets that I use with my 7-08 so I figured I would use them for my fireforming loads. I also had some IMR-3031 and H4895. My Hornady manual listed 25.3 grains of H4895 as the starting load. This load filled the case to the shoulder. When I checked Hodgdon's website for loads with IMR4227 (which I also have) I noticed that Hodgdon lists the MAX load with H4895 at 25.0 grains. Why the disparity?
The other question is this. With IMR-3031 one grain above the starting load (25.3 grains) fills the case all the way to the mouth. My manual doesn't list this as a compressed load. From what I saw of the difference between the .222 Rem Mag case and the .223 Remington (the parent case for the 7mmTCU) the only differences that I saw was the overall length and that the shoulder was farther forward on the .222 Rem Mag. So, I guess my question is, is 25.3 grains of 3031 a safe load in this case?
Comments
I've never formed 7mm TCU brass from .222 Rem Mag before. But, it should be the same as a .223 if you are moving the shoulder back...not forward like on a standard .222 case. I generally use 24 gr. of 4895 to fireform mine. I don't have any manuals out here with me and I'm not going to wake up my other half to get one. 25.3 gr of 4895 seemed to me like it was on the upper end of 139/140 gr. bullets out of the 7mm TCU. But as long as it's within normal 7mm TCU load ranges it will fireform just fine.
Thanks for the reply. 25.3 grains of H4985 was the starting loaded listed in my Hornady manual.
I went to the range and shot them yesterday. Formed very nicely. The IMR 3031 loads were suprisingly accurate. As for forming the TCU brass from .222 Mag, it worked very well. I am sure you know that some T/C barrels tend to have loose chambers. Using .222 brass allows the brass to be formed without shortening the necks too much. When you first run it through the TCU die, it bumps the shoulder back and you get a tiny bulge right below the shoulder, but when you shoot them it blows the brass out nicely.
tcu needs no formimg load, load em and shoot em
They do if you are using .222 Remington Mag brass.