Thought i would share my latest build the .257 Bobcat. it is my first crack at designing and building my own wildcat.
Intro: The .257 Bobcat is based on the 270AR made by AR15Performance. the 270AR is a 6.5x47 lapua shortened .120 and necked up to .277. It uses AR15performace's 800 series bolt and extension so it can run at 60,000 psi.
I wanted a flat shooting quarter bore so i necked down my 270AR cases to .257
My performance goals are 85gn bullets 3300-3400, 100 grain bullets at 3200 fps and the 115 bergers at 3000 fps that will make it a very flat shooter
.257 Bobcat quickload predicted velocities with 24” barrel
100 sierra pro hunter sp 3050-3200 fps
100 sierra game king bt 3100-3250 fps
100 nosler partition 3050-3200 fps
100 nosler ballistic tip 3100-3250 fps
100 barnes ttsx 3050-3150 fps
110 nosler accubond 2850-3000 fps
115 berger hunting vld 2825-2950 fps
115 nosler partition 2850-2975 fps
117 sierra pro hunter sp 2800-2950 fps
117 hornady sst 2800-2925 fps
117 hornady sp 2850-2975 fps
120 nosler partition 2750-2875 fps
120 hornady interlock sp 2800-2900 fps
120 speer grand slam 2800-2900 fps
here are some dummy rounds for mock up
100gn nosler ballistic tip, sierra 100gn sp bt, 85gn nosler ballistic tip
I have been testing the rifle now for a month and a half and it has reach all the performance goals i had set for it.
here is a little of the data i have collected.
here are the pressure traces and primers, the 8208 didn't lock back with any of the loads with any of the bullets. cfe locked back and cycled fine. gas port seems a little small -- better to start too small.
and the 100 nbt with cfe
here is velocity from the bergers. neither one is at max but again cfe cycled the action and locked back with 1 fail to feed and the h4895 wouldn't pick up rounds or lock back.I opened up the gas port from .082-.086 and now the guy is cycling better than ever. some slight feed issues but have isolated the problem to the chamfer/blend on the chamber opening -- was the first ar barrel my smith had made. going to take it off and have it messaged a little.
i tested leverevolution to compare to cfe and was pleasantly surprized it pushes the 100 speer spbt faster than cfe here is the chrono data i stopped with 2 shots left because i got a faint ejector swipe.
Intro: The .257 Bobcat is based on the 270AR made by AR15Performance. the 270AR is a 6.5x47 lapua shortened .120 and necked up to .277. It uses AR15performace's 800 series bolt and extension so it can run at 60,000 psi.
I wanted a flat shooting quarter bore so i necked down my 270AR cases to .257
My performance goals are 85gn bullets 3300-3400, 100 grain bullets at 3200 fps and the 115 bergers at 3000 fps that will make it a very flat shooter
.257 Bobcat quickload predicted velocities with 24” barrel
100 sierra pro hunter sp 3050-3200 fps
100 sierra game king bt 3100-3250 fps
100 nosler partition 3050-3200 fps
100 nosler ballistic tip 3100-3250 fps
100 barnes ttsx 3050-3150 fps
110 nosler accubond 2850-3000 fps
115 berger hunting vld 2825-2950 fps
115 nosler partition 2850-2975 fps
117 sierra pro hunter sp 2800-2950 fps
117 hornady sst 2800-2925 fps
117 hornady sp 2850-2975 fps
120 nosler partition 2750-2875 fps
120 hornady interlock sp 2800-2900 fps
120 speer grand slam 2800-2900 fps
here are some dummy rounds for mock up
100gn nosler ballistic tip, sierra 100gn sp bt, 85gn nosler ballistic tip
I have been testing the rifle now for a month and a half and it has reach all the performance goals i had set for it.
here is a little of the data i have collected.
here are the pressure traces and primers, the 8208 didn't lock back with any of the loads with any of the bullets. cfe locked back and cycled fine. gas port seems a little small -- better to start too small.
and the 100 nbt with cfe
here is velocity from the bergers. neither one is at max but again cfe cycled the action and locked back with 1 fail to feed and the h4895 wouldn't pick up rounds or lock back.I opened up the gas port from .082-.086 and now the guy is cycling better than ever. some slight feed issues but have isolated the problem to the chamfer/blend on the chamber opening -- was the first ar barrel my smith had made. going to take it off and have it messaged a little.
i tested leverevolution to compare to cfe and was pleasantly surprized it pushes the 100 speer spbt faster than cfe here is the chrono data i stopped with 2 shots left because i got a faint ejector swipe.