Hey all;
I went to the range today to shoot an XCR-M with both the heavy, and light profile barrels. The heavy barrel had about 200 rounds through it before the trip, while the light was brand spankin' new.
The difference in accuracy was noticeable. My question is whether the significantly worse performance of the light barrel is a barrel weight issue, or a "break-in" issue for a new barrel? In addition to poor accuracy, I had a number of Failures to Extract (FTE) with the newer light barrel, even with the gas turned to max.
I used a Burris 3-9 scope.
To start with, the light barrel:
XCR-M Light Barrel, at 100 yards, at max gas setting, with Winchester Super-X Powerpoint Ammo, 180 grain .308
This was just over 7 MOA. Not impressed. On top of that, the nose of the bullet on three occasions drove itself into the bottom of the chamber, so it didn't load. I also had numerous FTEs.
XCR-M Light Barrel, at 100 yards, at max gas setting, with Remington Core-Lokt ammo, 150 grain .308
This was also over 7 MOA. Again, not impressed. While I didn't get the same number of stoppages with Winchester 180 grain, I did get a number of FTEs.
XCR-M Light Barrel, at 100 yards, at max gas setting, with Chinese mil 7.62mm
Surprisingly better than the expensive stuff - around 5 MOA. A few FTEs, but not as many as the hunting ammo tested earlier.
Now, the Heavy barrel:
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Winchester Super-X Powerpoint Ammo, 180 grain .308
Grouping approx 4.5 MOA. About the minimum I would expect for a battle rifle
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Remington Core-Lokt ammo, 150 grain .308
About a 3.5 MOA grouping. Reasonable, I would be happy with this result consistently. It's a 9 round group, as I had a failure and damaged a round with a double feed. the bottom most round was a flinch on my part, so I think that this ammo could hit 2.5 MOA with a little better shooting on my part.
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Chinese mil 7.62mm
Just under 4 MOA. The top right round may have been a flinch on my part (not sure unfortunately).
Some final observations / questions:
1. The light barrel really hated the heavier bullets. Is it possible that a heavier bullet causes more barrel-whip in a lighter barrel? Still, 7+ MOA sucks.
2. The barrel change on the XCR retained it's zero - sort of. Switching from heavy to light barrel moved my mean point of impact about 8 MOA. So I had to re-zero. But when I switched back to the heavy barrel, I had to reset the scope almost exactly to the original zero. So that tells me that for removing and replacing the same barrel, the mean point of impact won't really change (much)
3. I am starting to question the utility of a light .308 barrel. In essence, if I want a semi-auto "designated marksman" type battle rifle, I would consider weight a second priority after accuracy and MOST IMPORTANTLY reliable action. Is anybody else having trouble with their light barrel, or is this just the break-in period?
I went to the range today to shoot an XCR-M with both the heavy, and light profile barrels. The heavy barrel had about 200 rounds through it before the trip, while the light was brand spankin' new.
The difference in accuracy was noticeable. My question is whether the significantly worse performance of the light barrel is a barrel weight issue, or a "break-in" issue for a new barrel? In addition to poor accuracy, I had a number of Failures to Extract (FTE) with the newer light barrel, even with the gas turned to max.
I used a Burris 3-9 scope.
To start with, the light barrel:
XCR-M Light Barrel, at 100 yards, at max gas setting, with Winchester Super-X Powerpoint Ammo, 180 grain .308
This was just over 7 MOA. Not impressed. On top of that, the nose of the bullet on three occasions drove itself into the bottom of the chamber, so it didn't load. I also had numerous FTEs.
XCR-M Light Barrel, at 100 yards, at max gas setting, with Remington Core-Lokt ammo, 150 grain .308
This was also over 7 MOA. Again, not impressed. While I didn't get the same number of stoppages with Winchester 180 grain, I did get a number of FTEs.
XCR-M Light Barrel, at 100 yards, at max gas setting, with Chinese mil 7.62mm
Surprisingly better than the expensive stuff - around 5 MOA. A few FTEs, but not as many as the hunting ammo tested earlier.
Now, the Heavy barrel:
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Winchester Super-X Powerpoint Ammo, 180 grain .308
Grouping approx 4.5 MOA. About the minimum I would expect for a battle rifle
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Remington Core-Lokt ammo, 150 grain .308
About a 3.5 MOA grouping. Reasonable, I would be happy with this result consistently. It's a 9 round group, as I had a failure and damaged a round with a double feed. the bottom most round was a flinch on my part, so I think that this ammo could hit 2.5 MOA with a little better shooting on my part.
XCR-M Heavy Barrel, at 100 yards, at gas setting 2, with Chinese mil 7.62mm
Just under 4 MOA. The top right round may have been a flinch on my part (not sure unfortunately).
Some final observations / questions:
1. The light barrel really hated the heavier bullets. Is it possible that a heavier bullet causes more barrel-whip in a lighter barrel? Still, 7+ MOA sucks.
2. The barrel change on the XCR retained it's zero - sort of. Switching from heavy to light barrel moved my mean point of impact about 8 MOA. So I had to re-zero. But when I switched back to the heavy barrel, I had to reset the scope almost exactly to the original zero. So that tells me that for removing and replacing the same barrel, the mean point of impact won't really change (much)
3. I am starting to question the utility of a light .308 barrel. In essence, if I want a semi-auto "designated marksman" type battle rifle, I would consider weight a second priority after accuracy and MOST IMPORTANTLY reliable action. Is anybody else having trouble with their light barrel, or is this just the break-in period?
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