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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Put Together my First Custom Rifle
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<blockquote data-quote="264MHC" data-source="post: 1725360" data-attributes="member: 111161"><p><strong>The Cartridge</strong></p><p>The 264 MHC Cartridge is my version of an improved 6.5x55. I chose to improve the 6.5x55 case because I already had experience with the parent and I feel that the case capacity of the improved version is about the ideal compromise of barrel life and performance in the 6.5 bore. This cartridge has about 5 grains more powder (not water) capacity than the standard Swede, slightly more than 260AI and slightly less than 6.5-284 and PRC. In addition, Lapua 6.5x55 is some of their cheapest, regularly found around $80 per 100. Why did I not go with one of the available designs? Well there are no barrel manufacturers with a reamer for any of them and dies are basically non existent anyway so my cost to chamber and reload for this cartridge was no more than any of the other designs. Getting a custom reamer through Manson is only slightly more expensive than buying one of their standard reamers. Manson does have the original BJAI reamer but it has a .100 Freebore which is too short for my purposes. </p><p></p><p>The .264 MHC has a 35 degree shoulder and .0098 Taper. There were 3 reasons I chose 35 degrees for the shoulder. First is I can use a 270 wsm die to slightly bump the shoulder until my custom Whidden die is in hand. I haven't had to bump the shoulder after 3 firings on a few pieces of brass so this may be a moot point, but I didn't know that would be the case when I designed it. Second, while I'm sure someone has done it before, there are no well known designs with a 35 degree shoulder, and I like to be different. The BJAI and standard AI have 40 degree, and the GWI and PR&T have 30 degree. The 6.5 Addiction has a 37.5 Degree. I also felt that the 35 degree shoulder is the ideal compromise between case growth and feeding, and just looks balanced. I probably don't have enough experience with other shoulder angles to make this claim, but I'm happy with how it turned out. </p><p></p><p>The attached image is my drawing of the chamber design. This is not the exact reamer print but all the measurements are the same.</p><p></p><p>I designed the freebore at .200 to be optimal for the 156 Bergers in Lapua brass. Of course the 156 Bergers had not yet been released when I made my design, so I used 150 Sierras seated .050 above the neck-shoulder junction, just in case the 156 had a longer bearing surface. When I recieved my first two boxes of 156's, and tested CBTO, I found that the design is close to perfect, with the boat tail about .040 above the neck-shoulder junction seated to the lands (2.525 with Hornady Comparator). This freebore is a little long for 140 class bullets but I only plan to shoot 150's and 156's.</p><p></p><p>The only thing I would change about the design would be to shorten the overall chamber length. My Lapua brass measured and average of 2.155 case length, and after fire forming, shrunk to 2.135 and hasn't grown much so far. .035 short of the chamber length is not ideal, but will probably be just fine, and I will likely never have to trim this brass again. Also, the headspace is set to be tight on the virgin Lapua, so my fired brass from my other chamber will not chamber. I did not expect this and was slightly disappointed, but I don't plan on using brass fired in my other chamber anyway.</p><p></p><p><strong>Performance</strong></p><p>Because of my schedule, I have only been able to do some preliminary velocity ladders with several powders behind the 150 Sierras and 156 Bergers, as well as one seating test with the 156's. To set a baseline, I will share some of my data with the standard Swede from a 24" barrel. With 140 Hornady BTHP's and RL23, I maxed out at 46.8 grains for 2840 fps. With the 150 Sierras (Keyholed with the 9 twist), I maxed out at 46 grains for 2731 fps. Both with Fed 215 Primers in Norma Brass. Using this data I worked up a fireform load from 46-48 Grains of RL23 in virgin Lapua with Nosler 140 RDF's. 48 Grains shoots about .75 at 2840 in the new chamber, producing totally formed brass, not bad for a fireform load.</p><p></p><p>With the 150 Sierras in the MHC, I tested RL 23, Ramshot Magnum, and IMR 7977. For RL 23, I maxed out at 50.4 grains for 2916 fps, with a node around 50 Grains for 2898 fps. 49.6 was 2892. Case was full at 52 Grains.</p><p>Ramshot Magnum looks to be a good performer for this cartridge. I maxed out at 56 Grains for 2950 fps, with a node around 55 for 2902. Case was full at 56.</p><p>IMR 7977 Appears to be way too slow. The case was full at 53 grains but that only produced 2789 with no pressure. All of these loads were worked up from 4 grains below max.</p><p></p><p>For the 156 Bergers, I only tested VV N565. I was able to find some last minute so I reserved it for these bullets. This powder is a perfect match for this case. I started at 48 Grains which is listed as max for the standard swede in the Vihtavuori data, and worked up to 55 in .5 Grain increments. 55 is a full case. I saw the first ejector mark at 54.5 but had no flattened or cratered primers, and no hard bolt lift, even at 55. 54.5 was 2989, and 55 was 2993, so probably a node there. However, I chose to work around the 53-53.5 node which both produced the exact same 2870. In my first seating test, I used 53.4 Grains, as the temperature was 81 degrees when these velocities were tested. So far 2.52 CBTO or .005 off the lands is looking the best with a .93" 4 shot group at 200.</p><p></p><p>I've had some interesting observations in my testing so far. The way this case handles pressure is entirely different than the standard swede case. In the standard case, my first sign of pressure was almost always hard bolt lift. I almost never saw flattened primers or ejector swipes. With the MHC, I got ejector marks first but have yet to experience hard bolt lift. There could be several reasons for this. First I feel the low taper/sharp shoulder design is gripping the chamber walls much more effectively. Second, the MHC is in a custom action vs the Swede being in a looser factory action. And third, I am using Lapua brass for the MHC as opposed to the Norma I use for the Swede. I feel all of these factors are coming together to produce a quite significant performance increase over the parent case.</p><p></p><p>Overall I am extremely pleased with the performance and feel the extra effort was worthwhile. I am loving the new rifle and cartridge and can't wait to test it out on a nice whitetail. If anyone has any questions about the rifle or cartridge, feel free to ask. </p><p></p><p>Cole</p></blockquote><p></p>
[QUOTE="264MHC, post: 1725360, member: 111161"] [B]The Cartridge[/B] The 264 MHC Cartridge is my version of an improved 6.5x55. I chose to improve the 6.5x55 case because I already had experience with the parent and I feel that the case capacity of the improved version is about the ideal compromise of barrel life and performance in the 6.5 bore. This cartridge has about 5 grains more powder (not water) capacity than the standard Swede, slightly more than 260AI and slightly less than 6.5-284 and PRC. In addition, Lapua 6.5x55 is some of their cheapest, regularly found around $80 per 100. Why did I not go with one of the available designs? Well there are no barrel manufacturers with a reamer for any of them and dies are basically non existent anyway so my cost to chamber and reload for this cartridge was no more than any of the other designs. Getting a custom reamer through Manson is only slightly more expensive than buying one of their standard reamers. Manson does have the original BJAI reamer but it has a .100 Freebore which is too short for my purposes. The .264 MHC has a 35 degree shoulder and .0098 Taper. There were 3 reasons I chose 35 degrees for the shoulder. First is I can use a 270 wsm die to slightly bump the shoulder until my custom Whidden die is in hand. I haven't had to bump the shoulder after 3 firings on a few pieces of brass so this may be a moot point, but I didn't know that would be the case when I designed it. Second, while I'm sure someone has done it before, there are no well known designs with a 35 degree shoulder, and I like to be different. The BJAI and standard AI have 40 degree, and the GWI and PR&T have 30 degree. The 6.5 Addiction has a 37.5 Degree. I also felt that the 35 degree shoulder is the ideal compromise between case growth and feeding, and just looks balanced. I probably don't have enough experience with other shoulder angles to make this claim, but I'm happy with how it turned out. The attached image is my drawing of the chamber design. This is not the exact reamer print but all the measurements are the same. I designed the freebore at .200 to be optimal for the 156 Bergers in Lapua brass. Of course the 156 Bergers had not yet been released when I made my design, so I used 150 Sierras seated .050 above the neck-shoulder junction, just in case the 156 had a longer bearing surface. When I recieved my first two boxes of 156's, and tested CBTO, I found that the design is close to perfect, with the boat tail about .040 above the neck-shoulder junction seated to the lands (2.525 with Hornady Comparator). This freebore is a little long for 140 class bullets but I only plan to shoot 150's and 156's. The only thing I would change about the design would be to shorten the overall chamber length. My Lapua brass measured and average of 2.155 case length, and after fire forming, shrunk to 2.135 and hasn't grown much so far. .035 short of the chamber length is not ideal, but will probably be just fine, and I will likely never have to trim this brass again. Also, the headspace is set to be tight on the virgin Lapua, so my fired brass from my other chamber will not chamber. I did not expect this and was slightly disappointed, but I don't plan on using brass fired in my other chamber anyway. [B]Performance[/B] Because of my schedule, I have only been able to do some preliminary velocity ladders with several powders behind the 150 Sierras and 156 Bergers, as well as one seating test with the 156's. To set a baseline, I will share some of my data with the standard Swede from a 24" barrel. With 140 Hornady BTHP's and RL23, I maxed out at 46.8 grains for 2840 fps. With the 150 Sierras (Keyholed with the 9 twist), I maxed out at 46 grains for 2731 fps. Both with Fed 215 Primers in Norma Brass. Using this data I worked up a fireform load from 46-48 Grains of RL23 in virgin Lapua with Nosler 140 RDF's. 48 Grains shoots about .75 at 2840 in the new chamber, producing totally formed brass, not bad for a fireform load. With the 150 Sierras in the MHC, I tested RL 23, Ramshot Magnum, and IMR 7977. For RL 23, I maxed out at 50.4 grains for 2916 fps, with a node around 50 Grains for 2898 fps. 49.6 was 2892. Case was full at 52 Grains. Ramshot Magnum looks to be a good performer for this cartridge. I maxed out at 56 Grains for 2950 fps, with a node around 55 for 2902. Case was full at 56. IMR 7977 Appears to be way too slow. The case was full at 53 grains but that only produced 2789 with no pressure. All of these loads were worked up from 4 grains below max. For the 156 Bergers, I only tested VV N565. I was able to find some last minute so I reserved it for these bullets. This powder is a perfect match for this case. I started at 48 Grains which is listed as max for the standard swede in the Vihtavuori data, and worked up to 55 in .5 Grain increments. 55 is a full case. I saw the first ejector mark at 54.5 but had no flattened or cratered primers, and no hard bolt lift, even at 55. 54.5 was 2989, and 55 was 2993, so probably a node there. However, I chose to work around the 53-53.5 node which both produced the exact same 2870. In my first seating test, I used 53.4 Grains, as the temperature was 81 degrees when these velocities were tested. So far 2.52 CBTO or .005 off the lands is looking the best with a .93" 4 shot group at 200. I've had some interesting observations in my testing so far. The way this case handles pressure is entirely different than the standard swede case. In the standard case, my first sign of pressure was almost always hard bolt lift. I almost never saw flattened primers or ejector swipes. With the MHC, I got ejector marks first but have yet to experience hard bolt lift. There could be several reasons for this. First I feel the low taper/sharp shoulder design is gripping the chamber walls much more effectively. Second, the MHC is in a custom action vs the Swede being in a looser factory action. And third, I am using Lapua brass for the MHC as opposed to the Norma I use for the Swede. I feel all of these factors are coming together to produce a quite significant performance increase over the parent case. Overall I am extremely pleased with the performance and feel the extra effort was worthwhile. I am loving the new rifle and cartridge and can't wait to test it out on a nice whitetail. If anyone has any questions about the rifle or cartridge, feel free to ask. Cole [/QUOTE]
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