We just got a shipment of a variety of AR-15 bolts from Toolcraft and the bolts were all mixed up in the box and unlabeled. So I got a crash course in sorting bolts by the bolt face size. I figure this might happen to one of ya'll so I'm sharing what I learned. You'll need some calipers or super precise ruler to measure.
I also did a bunch of googling and identified the (in)compatibilities between bolts for different rounds. This can be quite important to know if you're shooting grendel, if you mix up a Type II Grendel bolt with a Type I Grendel barrel, the bolt will close but the headspace will be 11 thou too loose and you're gonna have a bad time.
(dimensions are approximate, but precise enough to differentiate)
the 308 bolt is easy to pick out because it's massive.
###y bolt pic. The one on the left is nickel-boron. we have this option for most sizes at the time of writing this. Click the pic for the product
I also did a bunch of googling and identified the (in)compatibilities between bolts for different rounds. This can be quite important to know if you're shooting grendel, if you mix up a Type II Grendel bolt with a Type I Grendel barrel, the bolt will close but the headspace will be 11 thou too loose and you're gonna have a bad time.
| Cartridge | Bolt Face width | Bolt Face depth | Also used by |
| 5.56x45 | 0.380" | 0.125" | .223 Rem, .204 Ruger, 6x45, .300 AAC Blackout, .277 Wolverine |
| 6.8 SPC | 0.425" | 0.125" | .224 Valkyrie |
| 6.5 Grendel Type II (SAAMI) | 0.450" | 0.136" | 50 Beowulf / 12.7x50 |
| .458 SOCOM | 0.475" | 0.125" | .375 SOCOM, .450 Bushmaster |
| 7.62x39 | 0.450" | 0.125" | 6.5 Grendel Type I (rare) |
the 308 bolt is easy to pick out because it's massive.
###y bolt pic. The one on the left is nickel-boron. we have this option for most sizes at the time of writing this. Click the pic for the product
