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I recently used a MagnetoSpeed chrono and (from 5 rounds) got an ES of 5 and SD of 1... 2669-2668-2665-2668-2670...using factory match ammo.

The gun is a Rem 700 SPS Varmint (308) and ammo is Federal GMM 168.

My question is...is that consistency due entirely to the ammo itself or does the barrel play a role as well?
 

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A bit of both although the Fed. 168GMM ammo is recommended by several custom builders as the standard for thier rifles accuracy potential. It sounds like you got a good barrel to or it is broken in nicely. Does the barrel foul much while shooting?
 

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A bit of both although the Fed. 168GMM ammo is recommended by several custom builders as the standard for thier rifles accuracy potential. It sounds like you got a good barrel to or it is broken in nicely. Does the barrel foul much while shooting?
Yes, I think I got very lucky with that particular rifle...it shoots damn close to 1/2" groups too. I did follow a break-in procedure that someone recommended to me...although I can't remember exactly what it was. As far as fouling I really can't say for sure...last time I cleaned it it certainly was dirty-ish...but not any more than I was expecting...although I only give it a "proper" cleaning once in a long while...I generally just run a bore snake through it before and after I shoot it. Also, it shoots much better with the 168's than the 175's.
 

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I have the exact same rifle modified a bit but the same action and barrel. Mine loves the 178 AMAX with both AR-COMP and Varget.
 

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I recently used a MagnetoSpeed chrono and (from 5 rounds) got an ES of 5 and SD of 1... 2669-2668-2665-2668-2670...using factory match ammo.

The gun is a Rem 700 SPS Varmint (308) and ammo is Federal GMM 168.

My question is...is that consistency due entirely to the ammo itself or does the barrel play a role as well?
Unless the barrel is misshapen somehow, it has nothing to do with the internal ballistics of the cartridge. You've just got some unusually consistent factory ammo. Where the barrel comes into play is POI vs POA, which is affected by harmonics at the time of firing, and to some extent how well made the barrel is (bore smoothness, etc). The more consistent the load, the more consistent the harmonics, and thus the point of impact.
 
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