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Rifles, Reloading, Optics, Equipment
AR15/10 Rifles
Over pressure? but i don't understand this!
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<blockquote data-quote="CaptnC" data-source="post: 1603955" data-attributes="member: 101755"><p>Quick little back ground, fell head over heals for the 6.5 Grendel last year and I can't stop!</p><p></p><p>Just bought another barrel and complete side charge receiver. This time 24"...my goal is to have a 400yd 6.5 Grendel AR.</p><p></p><p>I seen a video of a guy shooting a bolt Grendel using Benchmark powder. He was over max without issue with great velocities! I have some Benchmark so I figured...long range...a little faster velocity...sounds like we might have something here.</p><p></p><p>So I loaded up a 50 count of ammo. While nothing scientific I normally drop back 1 grain from max for 107 SMK group, then another add .3 for the next group of 107 SMK. Still well below Hornady max (thier book is very conservative). I also loaded a small sample of heavier bullets 120gr Pro Hunters the same way.</p><p></p><p>I was not do a normal break in because I'm too lazy to break the side charge down after every shot. I planed to shoot 5 and then clean.</p><p></p><p>Well the bolt will not open on shot 5. My bad I never looked at the brass in the brass catcher on shots 1 to 4. With a caming style bolt I was a bit lost as to how to get it out. So I tore the whole gun down on the shooting bench. </p><p></p><p>I didn't have my armorers wrench, but I managed to get everything apart.. I finally got the case out. Primer was blown...a little separation at the web...post firing...you could tell I pulled it apart. </p><p></p><p>Check the 4 in the shell catcher...2 blown primers in there! Put the gun back together and put the magnetospeed chronograph on barrel. It confirmed my load was not up to max book velocity but well below it at 2490fps.</p><p></p><p>After another 107gr SMK stuck case I moved to 120gr PH...</p><p></p><p>Ok now for the weird part! Life was back to normal...no more blown primers, no more marks on the case head. And the weirdest part, velocity was 27fps faster with nearly a grain less powder, with 13 grain heavier bullet! </p><p></p><p>NO PRESSURE SIGNS!</p><p></p><p>I even tried some hot loads (123 SST with H335) that I use in my 18" and 20" guns...again no pressure signs and velocity was where it should have been.</p><p></p><p>So why did the gun have suchad issues with the 107 Sierra MK. I've shot them out of both my other AR Grendel's without issue....</p><p></p><p>Oh...here is a little gun pronounced for those who didn't mind wading through everything! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>[ATTACH=full]128045[/ATTACH]</p></blockquote><p></p>
[QUOTE="CaptnC, post: 1603955, member: 101755"] Quick little back ground, fell head over heals for the 6.5 Grendel last year and I can't stop! Just bought another barrel and complete side charge receiver. This time 24"...my goal is to have a 400yd 6.5 Grendel AR. I seen a video of a guy shooting a bolt Grendel using Benchmark powder. He was over max without issue with great velocities! I have some Benchmark so I figured...long range...a little faster velocity...sounds like we might have something here. So I loaded up a 50 count of ammo. While nothing scientific I normally drop back 1 grain from max for 107 SMK group, then another add .3 for the next group of 107 SMK. Still well below Hornady max (thier book is very conservative). I also loaded a small sample of heavier bullets 120gr Pro Hunters the same way. I was not do a normal break in because I'm too lazy to break the side charge down after every shot. I planed to shoot 5 and then clean. Well the bolt will not open on shot 5. My bad I never looked at the brass in the brass catcher on shots 1 to 4. With a caming style bolt I was a bit lost as to how to get it out. So I tore the whole gun down on the shooting bench. I didn't have my armorers wrench, but I managed to get everything apart.. I finally got the case out. Primer was blown...a little separation at the web...post firing...you could tell I pulled it apart. Check the 4 in the shell catcher...2 blown primers in there! Put the gun back together and put the magnetospeed chronograph on barrel. It confirmed my load was not up to max book velocity but well below it at 2490fps. After another 107gr SMK stuck case I moved to 120gr PH... Ok now for the weird part! Life was back to normal...no more blown primers, no more marks on the case head. And the weirdest part, velocity was 27fps faster with nearly a grain less powder, with 13 grain heavier bullet! NO PRESSURE SIGNS! I even tried some hot loads (123 SST with H335) that I use in my 18" and 20" guns...again no pressure signs and velocity was where it should have been. So why did the gun have suchad issues with the 107 Sierra MK. I've shot them out of both my other AR Grendel's without issue.... Oh...here is a little gun pronounced for those who didn't mind wading through everything! :) [ATTACH=full]128045[/ATTACH] [/QUOTE]
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AR15/10 Rifles
Over pressure? but i don't understand this!
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