asmo
01-03-2014, 16:51
I am working on developing a load for both my and my friends AR platform DM/SPR guns.. Based on a bunch of stuff I chose to start with IMR XBR 8208 powder under Nosler Custom Competition 69gn - with CCI #400's. Again this was a start and will play from here. On Dec 21st I went to the range with my rifle and 10 groups of test loads (5 shots each) ranging from 21.0gn up to 22.8gn of powder. Based on those groups, we worked up some loads between 21.1gn and 21.9gn and ran them through both of our guns to see if we could find a sweet spot that would match both.
Below is the results of the follow-on testing for both guns. Each of the weights had 10 shots from each rifle (20 shots total). All of the brass was once fired LC '02 - shot from different guns (our M4s). All of the brass was trimmed to 1.750" on a Wilson Micrometer Hand Trimmer and checked with our hand-held calipers. Each weight, for each shooter, also had the brass weighed and sorted into .2gn batches.
Rifle 1: Bushmaster A3 type HBAR with 24" 1:9 fluted barrel - chromed lined.
Rifle 2: Colt A3 HBAR Elite with 24" 1:9 crowned barrel - stainless steel.
Both rifles have between 3-5k rounds through their barrels - and have been run hard and put away wet more times than I can count.
We shot at 50m because the wind was gusting between 12-18mph and we didn't want to have to deal with wind calls while trying to group. All of these shots were taken over a 2 hour period on 12/31/2013 at GGC - with temps around 36-38F.
Here are the results:
Rifle/Shooter 1:
38859
38861
38863
Rifle/Shooter 2:
38865
38867
In a couple of the groups there is an un-recorded shot. Those were specifically called shots where the shooter knew he yanked/flubbed it, and immediately called it to the spotter.
I am thinking of going with 21.7gn for the load - knowing that in the future we wont be sorting brass like the above, nor will we be as uber-particular about the trim/weights.
Thoughts?
Below is the results of the follow-on testing for both guns. Each of the weights had 10 shots from each rifle (20 shots total). All of the brass was once fired LC '02 - shot from different guns (our M4s). All of the brass was trimmed to 1.750" on a Wilson Micrometer Hand Trimmer and checked with our hand-held calipers. Each weight, for each shooter, also had the brass weighed and sorted into .2gn batches.
Rifle 1: Bushmaster A3 type HBAR with 24" 1:9 fluted barrel - chromed lined.
Rifle 2: Colt A3 HBAR Elite with 24" 1:9 crowned barrel - stainless steel.
Both rifles have between 3-5k rounds through their barrels - and have been run hard and put away wet more times than I can count.
We shot at 50m because the wind was gusting between 12-18mph and we didn't want to have to deal with wind calls while trying to group. All of these shots were taken over a 2 hour period on 12/31/2013 at GGC - with temps around 36-38F.
Here are the results:
Rifle/Shooter 1:
38859
38861
38863
Rifle/Shooter 2:
38865
38867
In a couple of the groups there is an un-recorded shot. Those were specifically called shots where the shooter knew he yanked/flubbed it, and immediately called it to the spotter.
I am thinking of going with 21.7gn for the load - knowing that in the future we wont be sorting brass like the above, nor will we be as uber-particular about the trim/weights.
Thoughts?