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Posted: 3/28/2010 12:11:17 PM EDT
| I sighted in my Vortex Srikefire at 50 yds. with pmc bronze 55 gr. Next I tried some XM 193 55 gr. The XM shot 3-4 inchs low. Why? The rifle is a Spikes lower with a BMC 16" midlength upper. |
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could have to do with the PMC being .223 and the 193 being 5.56mm.. a couple hundred FPS difference could be the reason Even at 100 yards, the difference in the trajectory due to a velocity difference of 250 fps will only alter the point of impact by 0.17". 
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| I loaded two lots of ammo recently, the first with a 55gr softpoint the other with a 55gr hornady FMJ. Both loads where the same except the bullet being used. The 55gr softpoint shot 4 inches left of where the fmjs went. Any time you change ammo you need to check the zero on your rifle for that specific ammo. |
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I loaded two lots of ammo recently, the first with a 55gr softpoint the other with a 55gr hornady FMJ. Both loads where the same except the bullet being used. The 55gr softpoint shot 4 inches left of where the fmjs went. Any time you change ammo you need to check the zero on your rifle for that specific ammo. Something else is up with yer loads, yer shooting, or the conditions you shot in. Up and down deviation is somewhat normal (Within reason) but left to right will not be affected by the ammo. My guess is it was either shooter related, or if you wanna try and save face, enviromental...I.E. the wind. I have shot numerous 55gr loads and they have all shoot within the same relative POI at my 50yd zero. My standard 55gr practice load (55gr FMJ, 24.5gr Tac, Wolf SRM primer), my accuracy load (52gr hornady match, 27.1gr RL-15, Wolf SRM primer), and standard XM193 loads. |
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I loaded two lots of ammo recently, the first with a 55gr softpoint the other with a 55gr hornady FMJ. Both loads where the same except the bullet being used. The 55gr softpoint shot 4 inches left of where the fmjs went. Any time you change ammo you need to check the zero on your rifle for that specific ammo. Up and down deviation is somewhat normal (Within reason) but left to right will not be affected by the ammo. It most certainly can be affected by the ammunition. |
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Barrel harmonics, my man. You Think? just between different brands of ammo. Granted one pmc was.223 and xm was 5.56. I was using sandbag rest. Larue freefloat rail. Well, I'm definately not an expert on the subject, but I've had some major shifts between ammo loadings. These were during the same range sesions, and ammo was the only variable. |
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I loaded two lots of ammo recently, the first with a 55gr softpoint the other with a 55gr hornady FMJ. Both loads where the same except the bullet being used. The 55gr softpoint shot 4 inches left of where the fmjs went. Any time you change ammo you need to check the zero on your rifle for that specific ammo. Up and down deviation is somewhat normal (Within reason) but left to right will not be affected by the ammo. It most certainly can be affected by the ammunition. Interesting....learn something new....I've never seen it happen in all the years of my reloading however. |
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Barrel harmonics, my man. You Think? just between different brands of ammo. Granted one pmc was.223 and xm was 5.56. I was using sandbag rest. Larue freefloat rail. Well, I'm definately not an expert on the subject, but I've had some major shifts between ammo loadings. These were during the same range sesions, and ammo was the only variable. If you want to test the theory, I would do this: 1. Have a friend load 10rds of each, haphazardly into the same mag. 2. Fire all twenty rds at the same poa. 3. See if you have two, distinct ten rd groups. If you do, this should help rule out any equipment / shooter issues. I suspect you have stumbled upon a distinct combination. One load that leaves your barrel at an extreme positive deflection, and one that leaves at an extreme negative deflection. |
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When experimenting with different ammo in the same day I have found out some ammo do not mix.Example I was zeroed for FED XM193 for over a year,I shot Brown bear one day with a clean barrel and then back to Fed XM 193 SAME DAY. The fed had a different zero and was not consistent like it should be. I went home cleaned barrel went back dead on after a couple foul shots with the FED. When I test ammo I do not mix for that day.
Keith |
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