AR-15 barrel: Version what?
You might have noticed when we discuss our AR-15 barrels we refer to them as version 1, 2, 3, etc. At the time of this writing we are on version 4. We did this because during testing we would find different diminishing returns to incorporate into our barrels, or discover changes we wanted to make. We tried different; barrel twists, contours, gas block diameters and extensions. All DMR AR-15 barrel versions use a rifle-length gas system and Bartlein 5R blank.
The version 1 barrels were our first attempt at a AR-15 barrel. We went with Bartlein 5R blanks because of the excellent performance and consistency they exhibit in our bolt action rifles and pre-fit barrels. The barrels featured;
- Heavy marksman contour
- 0.750″ gas block diameter
- 1-6″ twist
- .223 Wylde chamber
The reason for the 1-6″ twist was because we initially planned on doing .223 Remington, .22 Nosler and .224 Valkyrie but after the initial release decided to focus on .223 Remington. The version 1 barrel would manage 1 MOA accuracy with match ammunition but we were not happy with how they performed overall.
The version 2 barrels maintained the same heavy marksman contour and 1-6″ twist. The defining change that make the barrel a version 2 is;
- 5.56x45mm NATO chamber
The ammunition we shoot in these rifles utilize heavy bullets like the 77 grain SMK. We prefer the 5.56x45mm NATO chamber because of the ogive relation to the rifle lands when restricted by AR-15 magazine length. The version 2 barrels performed very well with an average accuracy of 0.65 MOA. This is based on a sample size of 2 barrels and averaging multiple 5 round 100 yard groups using Federal Gold Medal Match 77 grain ammunition.
The version 3 barrel saw multiple changes including;
- 1-7.7″ twist
- 0.936″ gas block diameter
- “Bull barrel” contour
The initial results were excellent but after adjusting the contour forward of the gas block we were not able to replicate them. The barrel was re-done with a 0.750″ gas block diameter and heavy tapered contour. We currently need to re-test the barrel after the changes but ended up moving on to version 4. I intend to re-test version 3 by building a dedicated upper.
We recently completed version 4 barrels and started testing. The initial results are excellent using Federal Gold Medal 73 & 77 grain ammunition. The changes on the version 4 barrel include;
- 1-7.5″ twist
- Heavy tapered contour
- Enhanced barrel extension
Version 4 we did two barrels with different gas block diameters, 0.750″ & 0.936″. This will allow us to compare the accuracy performance side by side. The outcome will help us finalize the details for the barrels that will be used in our complete uppers and rifles. Our testing has slowed due to the scarcity of ammunition but we will continue as resources permit.