7-300prc brass prep. experience

bitbythebug

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May 5, 2015
Messages
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I am putting this on the forum to maybe help anyone trying to find any information about how to proceed with making brass for this cartridge. I looked everywhere and found bits and pieces, but no real world experiences developing this brass. The round intrigued me because of the shorter, beltless case with an extra long neck. I also struggled with the 28 Nosler and finally sold the gun with all the reloading dies and all the brass. I wanted to replace my STW velocities with a more modern cartridge. It didn't work for me. Never worked harder at developing an accurate load and never found it, so I gave up and cut my losses. I also wanted to load long and that was not an option with the STW. Loved the gun. I found it to be very accurate with blistering speed with heavy 7mm bullets. I ruined the entire gun(long story) and wanted to replace it with a shorter cased cartridge. While I was developing a load for my 300prc, I thought that necking it down to 7mm would be a tremendous cartridge. It has more powder capacity than the 7mm win mag., doesn't have the belt, has a much longer neck, and the case is shorter. It has about 6-7 gr less powder than the 28, so it should be easier on barrels. I read others experiences with this cartridge, and they all seemed positive. Yet there was little to no info on how they prepared their brass, and there are no commercial dies available.
After much ferreting for any info on brass prep, I finally decide on a Redding Type S-Bushing full-length sizing die #77776 in 300prc. I got the Redding Series A 300prc Seat Die #92776. I then ordered a ,311 bushing(for the 7mm-300prc) and a .334 bushing for the 300prc. I don't, as of this writing, know if the .334 will work, but I think it is close. But, I have tried the .311 for making the 7mm-300. It has worked perfectly so far. I run all the new brass through the 300prc bushing, then swap it out to the .311 bushing, lubricate the necks with the case, and carefully run them up through. I am processing the brass before my rifle is built because the gunsmith has requested a finished round. I have a Manson reamer ordered. The spec's say it is cutting a .319 neck. The brass come out of the die at .312. I have a primer rod ball coming. I then ran the necks over a neck expander for my neck turning cutter. I didn't turn the necks, just expanded them for softer neck tension. I then ran cases into the seat die and left them at 3.62". The loaded necks measured .3145. I don't know if that is enough for proper neck expansion, but I think .0045 is enough or very close to enough. I will discuss it with the gunsmith.
I was afraid that the 300prc necks wouldn't go through the .311 bushing, so I borrowed a 28 Nosler sizing die and run one brass in it. It worked great but, I later found, that it was an unnecessary. I tried pushing a case up and fully expected it to crush the shoulder, It did not. It worked every time for me. By the way, this was all with Hornady brass. I know many people hate this brass. They are far more knowledgeable than me. I am purely a hunter interested in wildcats magnum cartridges.
Please keep in mind that this was my experience. It may not be yours, but if it helps anyone to not be afraid of brass prep for this cartridge, then I'm happy. Thanks
 
What he said ^^^^^^^^^^^^^.

But go for it, I like Wildcats myself and have built something that someone else had already figured out. O - well, I have fun doing it myself.
Thanks for sharing, keep us posted on how it turns out. 👍
You've burdened yourself unnecessarily.
Go to Sherman Wildcats. The 28 Sherman Magnum is the cartridge you're pursuing. They have dies, reamers and brass.
 
I knew about the Sherman and considered it. I think it is a great cartridge, it is just proprietary. If I didn't already have a 300prc being built, where I can use the same dies, I doubt if I would be doing it. It just seemed like a natural extension and fun to figure things out myself. In my research into this cartridge, it seemed like there was quite a bit of interest but little information. Now I have something to keep me interested through the long, cold winter months ahead. Thanks for all input.
 
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Sounds like your well on your way with a very neat project. Is the shoulder on your necked down case going to be longer? Wondering if you will have a donut issue if not inside or outside neck trimming. May not be a problem using a bushing die. With any luck it turns out to be a laser, enjoy!
 
built several of these... very nice round super easy to load for and are real shooters..

One step neck down I use lapua OR ADG brass .313" bushing and use a 284 expander mandrel on the way out after sizing down and its ready to load .. pretty simple just like a 7-300 WM .. same process.
 
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