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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Big Seven Case Capacities
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<blockquote data-quote="Austin" data-source="post: 29893" data-attributes="member: 1956"><p>One thing I noticed you had mentioned earlier about neck-turning. You didn't have experience? It's pretty easy and something you may want to consider. At this time, I use a .313 Titanium Nit. neck die for this case. The neck tolerance runs at .003 (neck of chamber dia. = .3195 and I have to turn the neck down to an even .316 OD after bullet seating. I also have a full-length set which is built from the same reamer used to cut the chamber. This has been a big plus also and i'm glad I invested the money in it. The reamer used to cut this chamber at this present time is yielding a .321 chamber neck which gives you more room to play with your bullet pull. I've found that what helps more in this rifle is to leave about .010 of the neck unsized at the base to better help in cartridge alignment and to seat the bullet right up to the lands. At this point, neck turning is much less of an issue as far as accuracy goes. Many a benchrest shooter I know would have to call me on this one! But, for my needs, and for all of my purposes, I have never really seen neck turning to make that big of a diff unless the reamer you are using is one which is set to cut a match-tolerance neck. Now, I HAVE seen neck sizing help some in the smaller 6mm bore in my 6PPC, but the only reason I turned the necks is because that chamber neck so danged tight! I had to shave .002 - .003 of the brass just to be able to chamber the things, but that is part of the territory with those match chambers. It was a good learning experience though and I DID learn where neck-turning is appropriate and necessary. It seems so far that the cartridge generates quite a considerable amount of pressure even with the slow burners like H870. I have been keeping bullet pull VERY low and seated WAY OUT in the lands. As I said, on some bullets, I have only been seating them about .191" into the case. That's very little and bullet pull is low, but it seems to keep pressures down. So, neck turning will not likely help here even though the chamber is fairly tight. That's why I said that I am learning more and more about the importance of the chamber neck and designing a barrel and action around a certain weight bullet. The next time I undertake this cartridge, it will be from a different reamer with a neck suited especially for the weight of bullet I am looking to shoot. As it stands, this reamer was built for a the larger bullets (168 and 175gr), thus, the neck is a little longer to accomadate these bullets without having too much seated into the case. It was also designed with a 1:12 twist bbl in mind. Though, it has been used succesfully with a gain twist bbl. in the past and has seen velocities exceeding 3600fps with these larger bullets. Given these details, it seems logical to pressume that one could run the 130 and 140 grainers at around the 4000 fps mark in a bbl of this length and twist rate. Just my two cents for what it's worth!</p></blockquote><p></p>
[QUOTE="Austin, post: 29893, member: 1956"] One thing I noticed you had mentioned earlier about neck-turning. You didn't have experience? It's pretty easy and something you may want to consider. At this time, I use a .313 Titanium Nit. neck die for this case. The neck tolerance runs at .003 (neck of chamber dia. = .3195 and I have to turn the neck down to an even .316 OD after bullet seating. I also have a full-length set which is built from the same reamer used to cut the chamber. This has been a big plus also and i'm glad I invested the money in it. The reamer used to cut this chamber at this present time is yielding a .321 chamber neck which gives you more room to play with your bullet pull. I've found that what helps more in this rifle is to leave about .010 of the neck unsized at the base to better help in cartridge alignment and to seat the bullet right up to the lands. At this point, neck turning is much less of an issue as far as accuracy goes. Many a benchrest shooter I know would have to call me on this one! But, for my needs, and for all of my purposes, I have never really seen neck turning to make that big of a diff unless the reamer you are using is one which is set to cut a match-tolerance neck. Now, I HAVE seen neck sizing help some in the smaller 6mm bore in my 6PPC, but the only reason I turned the necks is because that chamber neck so danged tight! I had to shave .002 - .003 of the brass just to be able to chamber the things, but that is part of the territory with those match chambers. It was a good learning experience though and I DID learn where neck-turning is appropriate and necessary. It seems so far that the cartridge generates quite a considerable amount of pressure even with the slow burners like H870. I have been keeping bullet pull VERY low and seated WAY OUT in the lands. As I said, on some bullets, I have only been seating them about .191" into the case. That's very little and bullet pull is low, but it seems to keep pressures down. So, neck turning will not likely help here even though the chamber is fairly tight. That's why I said that I am learning more and more about the importance of the chamber neck and designing a barrel and action around a certain weight bullet. The next time I undertake this cartridge, it will be from a different reamer with a neck suited especially for the weight of bullet I am looking to shoot. As it stands, this reamer was built for a the larger bullets (168 and 175gr), thus, the neck is a little longer to accomadate these bullets without having too much seated into the case. It was also designed with a 1:12 twist bbl in mind. Though, it has been used succesfully with a gain twist bbl. in the past and has seen velocities exceeding 3600fps with these larger bullets. Given these details, it seems logical to pressume that one could run the 130 and 140 grainers at around the 4000 fps mark in a bbl of this length and twist rate. Just my two cents for what it's worth! [/QUOTE]
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