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Rifles, Reloading, Optics, Equipment
Gunsmithing
.6.5 MM X 284 Build?
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<blockquote data-quote="NesikaChad" data-source="post: 428723" data-attributes="member: 7449"><p>I build quite a few 6.5's for folks. Long actions definitely make life easier and better facilitate the "lawn dart" 140+ grain bullets.</p><p></p><p>Great cartridge, great accuracy, easy to load, reasonably good barrel life, and easy on the shooter's shoulder. Your going to get between 1200 and 1500 rounds out of your barrel. You may be able to stretch this out a bit if its a hunting gun as the accuracy requirement isn't as critical as it would be in a full effort target gun. Dont' expect much past 1500 though. The throat in the barrel takes a lickin. Anything that has to deal with exposure to 50+ thousand pounds and flash temperatures of over 6000F isn't going to tolerate it forever. One has to appreciate that powder is abrasive also.</p><p></p><p>If your a shooter (I mean a REAL shooter) then you've already accepted that barrels are consumables. They are no different than tires on a race car. Increases in performance mean something has to give somewhere else. In this case its the barrel. If it costs 500 a year to shoot a gun capable of the performance a 6.5/284 can deliver I personally think it's acceptable. It's 42 bucks a month. . . (300 barrel and 200 to chamber it)</p><p></p><p>To put it in perspective I own a 300-338 Lapua Magnum set up to shoot 125 grain Nosler ballistic tips. 4375fps is my muzzle velocity on a 34" barrel with a 12 twist. I don't shoot the gun often but I don't expect the barrel to last beyond about 700 rounds. It costs money to play hard. . .</p><p></p><p>I still think its great choice. </p><p></p><p>Regarding your question:</p><p></p><p>With a long action you have some room to enjoy the benefits this cartridge offers. For anything less than a dedicated bench/F class gun I think it best that a guy minimizes the drama at the reloading bench. That being said if at all possible you build the gun around the cartridge. The whole point of a 6.5 is to use a bullet with a .6+ BC in most instances. This means 140+ grain bullets which are quite long. Taking advantage of the 284 case capacity means having the bullet's boat tail/bearing surface intersection set just above the neck/shoulder junction. This maximizes the powder charge and avoids the added task of having to potentially deal with (meaning ream out) the "doughnut" that's common at the base of the neck in a lot of cartridges. (Meaning the ID of the neck decreases slightly due to how the brass is made)</p><p></p><p>If the tooling (chambering reamer) is made accordingly it'll time everything up so that the ogive/bearing surface tangent on the bullet is at the appropriate distance (whether it be in or out slightly from the lead in chamber) to promote good accuracy and good overall function of the gun. (I don't encourage jamming a bullet deep in the lands in a working gun as I've seen in too many instances that if the neck tension isn't sufficient the bullet has a nasty habit of staying put and making a real mess out of the gun with powder going everywhere when the case is extracted)</p><p></p><p>Basically, use the long action, load the bullet so that the boat tail stays just above the base of the neck and get to shooting. Target velocity out of a 28" barrel will hover around 3100fps with 140's. Any faster with thin jacket hunting/target bullets will often result in jackets going one way and bullet cores going another. One has to remember RPM is a function of velocity and twist rate. With this cartridge the bullet is spinning at 279,000 rpm when it leaves the barrel (at 3100fps) That seems to be the threshold from my experience.</p><p></p><p>In some instances it is possible to slow the twist down and make up the difference with velocity to get the rpm back up so that it'll stabilize to get good accuracy, but then things become a bit more "moody" and the reloading practice has to be diligent and careful.</p><p></p><p>8 ROT to 8.5 ROT is typically most popular for the heavy 6.5 bullets.</p><p></p><p>Another opinion held by some is to shy away from a single point cut rifle barrel as sometimes the geometry inside the bore is invasive on the jacket. A polygonal, R-5, or other variant may work better as it'll "nibble" on the jacket rather than "bite" and avoid the potential stress point along the jacket that may encourage a bullet to disembowel itself. I personally haven't seen this but it doesn't mean it isn't viable. The last two I did were both on cut barrels (Mark Chanlynn and a Kreiger) and both shoot exceptional. I however didn't try pushing the velocity so who knows?</p><p></p><p>A good starting load:</p><p></p><p>140 grain Lapua, Sierra, or Berger</p><p>55 grains of 4831 SC</p><p>Federal 210 primer</p><p>Lapua case</p><p></p><p></p><p>Good luck on your project.</p><p></p><p>C</p></blockquote><p></p>
[QUOTE="NesikaChad, post: 428723, member: 7449"] I build quite a few 6.5's for folks. Long actions definitely make life easier and better facilitate the "lawn dart" 140+ grain bullets. Great cartridge, great accuracy, easy to load, reasonably good barrel life, and easy on the shooter's shoulder. Your going to get between 1200 and 1500 rounds out of your barrel. You may be able to stretch this out a bit if its a hunting gun as the accuracy requirement isn't as critical as it would be in a full effort target gun. Dont' expect much past 1500 though. The throat in the barrel takes a lickin. Anything that has to deal with exposure to 50+ thousand pounds and flash temperatures of over 6000F isn't going to tolerate it forever. One has to appreciate that powder is abrasive also. If your a shooter (I mean a REAL shooter) then you've already accepted that barrels are consumables. They are no different than tires on a race car. Increases in performance mean something has to give somewhere else. In this case its the barrel. If it costs 500 a year to shoot a gun capable of the performance a 6.5/284 can deliver I personally think it's acceptable. It's 42 bucks a month. . . (300 barrel and 200 to chamber it) To put it in perspective I own a 300-338 Lapua Magnum set up to shoot 125 grain Nosler ballistic tips. 4375fps is my muzzle velocity on a 34" barrel with a 12 twist. I don't shoot the gun often but I don't expect the barrel to last beyond about 700 rounds. It costs money to play hard. . . I still think its great choice. Regarding your question: With a long action you have some room to enjoy the benefits this cartridge offers. For anything less than a dedicated bench/F class gun I think it best that a guy minimizes the drama at the reloading bench. That being said if at all possible you build the gun around the cartridge. The whole point of a 6.5 is to use a bullet with a .6+ BC in most instances. This means 140+ grain bullets which are quite long. Taking advantage of the 284 case capacity means having the bullet's boat tail/bearing surface intersection set just above the neck/shoulder junction. This maximizes the powder charge and avoids the added task of having to potentially deal with (meaning ream out) the "doughnut" that's common at the base of the neck in a lot of cartridges. (Meaning the ID of the neck decreases slightly due to how the brass is made) If the tooling (chambering reamer) is made accordingly it'll time everything up so that the ogive/bearing surface tangent on the bullet is at the appropriate distance (whether it be in or out slightly from the lead in chamber) to promote good accuracy and good overall function of the gun. (I don't encourage jamming a bullet deep in the lands in a working gun as I've seen in too many instances that if the neck tension isn't sufficient the bullet has a nasty habit of staying put and making a real mess out of the gun with powder going everywhere when the case is extracted) Basically, use the long action, load the bullet so that the boat tail stays just above the base of the neck and get to shooting. Target velocity out of a 28" barrel will hover around 3100fps with 140's. Any faster with thin jacket hunting/target bullets will often result in jackets going one way and bullet cores going another. One has to remember RPM is a function of velocity and twist rate. With this cartridge the bullet is spinning at 279,000 rpm when it leaves the barrel (at 3100fps) That seems to be the threshold from my experience. In some instances it is possible to slow the twist down and make up the difference with velocity to get the rpm back up so that it'll stabilize to get good accuracy, but then things become a bit more "moody" and the reloading practice has to be diligent and careful. 8 ROT to 8.5 ROT is typically most popular for the heavy 6.5 bullets. Another opinion held by some is to shy away from a single point cut rifle barrel as sometimes the geometry inside the bore is invasive on the jacket. A polygonal, R-5, or other variant may work better as it'll "nibble" on the jacket rather than "bite" and avoid the potential stress point along the jacket that may encourage a bullet to disembowel itself. I personally haven't seen this but it doesn't mean it isn't viable. The last two I did were both on cut barrels (Mark Chanlynn and a Kreiger) and both shoot exceptional. I however didn't try pushing the velocity so who knows? A good starting load: 140 grain Lapua, Sierra, or Berger 55 grains of 4831 SC Federal 210 primer Lapua case Good luck on your project. C [/QUOTE]
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