The Firing Line Forums - View Single Post - Ar15 with shielen barrel loosing velocity

ffffg · March 4, 2012, 07:08 PM

loading proceedure.
comming home from the range i dry the cases on the stove. Lots of snow here

then size
then tumble
clean out media
run a .80 drill bit thru flash hole
check for split cases
check oal, re trim if over .0005 over lenght throw away if under .0005 in lenght... keep cases to .0005 of 1.750 so crimps will be uniform.
if case is trimmed, I outside bevel and lightly inside bevel with long angle bevel tool
primer pocket clean
prime
weigh cases and sepparate into groups of .003 grains or less
add power
seat with redding target seater adjust to .001, and coalate to 1.766 lenght, ( that is the lenght to the rifling DIAMETER of the bullet.. this is measured
with a sinclair tool..
crimp..

Im not able to do much with neck tension becouse if i turn the necks i wouldnt get much of a hold on the bullets for semi auto feeding.. i want all the tension i can get.. I could turn down the expander if you think it would help.

today i tried my 4 best loads close to home at 66 yards, slightly breezy.. i went out to chrono them but chrono was not working may need a new one.

so i shot them at paper two strung down two did not, so maybe im jumping at conclusions, but on other days chrono shows about a 75fps drop between ist and third bullet, could just be poor poweder loads, neck tenson, etc, etc..

first group was 1/4 inch, 66 yds, all rounds hand loaded into chamber and let button close action, then push assist. action was cleaned and lubricated, barrel was not cleaned becouse i was going to go home load some more and clean barrel
number one and two were on top number 3 was 1/4 inch low. sierra 69 grn hpbt, 24.5 re 15

I willhave to start shooting 5 shot groups i can see by the last target and will have more information.. and the dropping velocity could be ulnlucky random odds.
several chronographed events tho showed about a 75 fps drop from the first to third round..
I wish the chrono worked today it would have cleared up some things..

, I got a new target barrel, by evolution to replace factory barrel that wasnt too bad,, the evolution had burrs in the chamber one came out one wouldnt, brownells traded me for a shielen that had a fitted bolt... I was out the install tho on the 2nd barrel...

the barrel seems to shoot well with the 69 grainers probably becouse of the 1 8 twist, but i dont understand the wide velocity variations, ... 25 fps variation at 1000 yards is 7 inches with my .243.. 75 fps would be 21 inches at 1000 yards with that gun.. i think i could shoot 500-600 yards with this gun, so im trying to find out whats causing the velocity variations .. i can see fouling at the front end of the gas tube, could this be opening up when the barrel heats up and streaches? Is 75 fps variation in loads common in the ar15?

I know very little about semi auto rifles, obviosly. thanks dave

March 4, 2012, 07:08 PM	#5
ffffg Member Join Date: October 4, 2008 Posts: 59	loading proceedure. comming home from the range i dry the cases on the stove. Lots of snow here then size then tumble clean out media run a .80 drill bit thru flash hole check for split cases check oal, re trim if over .0005 over lenght throw away if under .0005 in lenght... keep cases to .0005 of 1.750 so crimps will be uniform. if case is trimmed, I outside bevel and lightly inside bevel with long angle bevel tool primer pocket clean prime weigh cases and sepparate into groups of .003 grains or less add power seat with redding target seater adjust to .001, and coalate to 1.766 lenght, ( that is the lenght to the rifling DIAMETER of the bullet.. this is measured with a sinclair tool.. crimp.. Im not able to do much with neck tension becouse if i turn the necks i wouldnt get much of a hold on the bullets for semi auto feeding.. i want all the tension i can get.. I could turn down the expander if you think it would help. today i tried my 4 best loads close to home at 66 yards, slightly breezy.. i went out to chrono them but chrono was not working may need a new one. so i shot them at paper two strung down two did not, so maybe im jumping at conclusions, but on other days chrono shows about a 75fps drop between ist and third bullet, could just be poor poweder loads, neck tenson, etc, etc.. first group was 1/4 inch, 66 yds, all rounds hand loaded into chamber and let button close action, then push assist. action was cleaned and lubricated, barrel was not cleaned becouse i was going to go home load some more and clean barrel number one and two were on top number 3 was 1/4 inch low. sierra 69 grn hpbt, 24.5 re 15 I willhave to start shooting 5 shot groups i can see by the last target and will have more information.. and the dropping velocity could be ulnlucky random odds. several chronographed events tho showed about a 75 fps drop from the first to third round.. I wish the chrono worked today it would have cleared up some things.. , I got a new target barrel, by evolution to replace factory barrel that wasnt too bad,, the evolution had burrs in the chamber one came out one wouldnt, brownells traded me for a shielen that had a fitted bolt... I was out the install tho on the 2nd barrel... the barrel seems to shoot well with the 69 grainers probably becouse of the 1 8 twist, but i dont understand the wide velocity variations, ... 25 fps variation at 1000 yards is 7 inches with my .243.. 75 fps would be 21 inches at 1000 yards with that gun.. i think i could shoot 500-600 yards with this gun, so im trying to find out whats causing the velocity variations .. i can see fouling at the front end of the gas tube, could this be opening up when the barrel heats up and streaches? Is 75 fps variation in loads common in the ar15? I know very little about semi auto rifles, obviosly. thanks dave Last edited by ffffg; March 4, 2012 at 07:18 PM.