mav
NES Member
Took my new Garmin Xero C1 Pro Chronograph to the range Sunday. I wanted to get the actual muzzle velocity for certain ammo out for a couple of rifles. I was somewhat surprised by the results and in each case, MV was low as compared to expected. Looking for some info/validation or if I'm missing something.
Here's the breakdown:
1st rifle
Rifle: custom DPMS LR-308 .308 build with a 20" match barrel.
Ammo: Federal Premium Gold Medal Match 175Grain Sierra Matchking BTHP .308
Average MV over 6 shots (cold): 2472.8, Max 2488.7, Min 2460
Expected (based on box) 2600
I'm assuming barrel length for the Federal box is 24". That much drop off to be expected? Also, looks like the fastest of the 6 shots fired was the first from a cold barrel. The next 3 were each sequentially lower, the 5th and 6th were similar and higher than the 4th, so I assume the barrel had "warmed up" by that point.
2nd rifle
Rifle: HK G36 / SL8 build with an HK 18" barrel
Ammo: Winchester M855 green-tipped 62 grain 5.56
Average MV over 50 shots (cold) 2928, Max: 2974, Min: 2873
Expected: 3000-3050?
I think M855 was tested (and designed for) a 20" barrel. Making an assumption there.
Using the integrated ShotView app, pics below:
Federal Premium Gold Medal Match 175 Grain Sierra Matchking BTHP .308
Winchester M855 Green-tip 62 grain 5.56
Here's the breakdown:
1st rifle
Rifle: custom DPMS LR-308 .308 build with a 20" match barrel.
Ammo: Federal Premium Gold Medal Match 175Grain Sierra Matchking BTHP .308
Average MV over 6 shots (cold): 2472.8, Max 2488.7, Min 2460
Expected (based on box) 2600
I'm assuming barrel length for the Federal box is 24". That much drop off to be expected? Also, looks like the fastest of the 6 shots fired was the first from a cold barrel. The next 3 were each sequentially lower, the 5th and 6th were similar and higher than the 4th, so I assume the barrel had "warmed up" by that point.
2nd rifle
Rifle: HK G36 / SL8 build with an HK 18" barrel
Ammo: Winchester M855 green-tipped 62 grain 5.56
Average MV over 50 shots (cold) 2928, Max: 2974, Min: 2873
Expected: 3000-3050?
I think M855 was tested (and designed for) a 20" barrel. Making an assumption there.
Using the integrated ShotView app, pics below:
Federal Premium Gold Medal Match 175 Grain Sierra Matchking BTHP .308
Winchester M855 Green-tip 62 grain 5.56