We had a sneaking hunch that the SHOT Show might change the course of our short/light build, so that is the bad news. The good news is that it didn’t alter a component selection we’d already discussed. Better still, you haven’t run out to get a part we’re now changing.
Sharps Rifle Company ReliaBolt
We’re not sure human anatomy metaphors apply very well to our build, though it would sure be handy if they did: Component X is the “heart,” Y the “lungs,” and Z the “eyes” (though our nifty Leupold from Part 6 comes close). But since we’ll nominate some back-up irons in a week or two, even that partial fit isn’t very satisfactory. Ah well.
That said, it may well be that the bolt carrier group, or BCG, on a Stoner-pattern rifle is as close to a heart as we’ll come. Obviously crucial to nearly every aspect of semi-auto function, it interacts with the charging handle or release, magazine and recoil spring in the beginning of each feeding cycle, and with the feed ramps, lugs and chamber at the end. In between, it shepherds any spent case through a geometrically complex path to ejection, and a new round to the chamber for a subsequent shot. All at literally a couple of hundred miles per hour—fair to say then, that it’s important to have a good one.
Any serious AR/MSR builder will tell you that “good” can be a more subjective quality than it might initially appear. The occasional weekend shooter is likely to be just fine with the “stockest” of stock—Carpenter 158 steel, shot peened, magnetic-particle-inspected and mil-spec finished. No worries.
We have a little more—OK, a lot more—in mind, however; more shooting for sure, and harder (read “dirtier?”) use. You may recall our barrel profile was chosen with this in mind: We gave back a little weight and length to get something that would heat more slowly and preserve accuracy somewhat better in longer shooting sessions.
The analog for this as far as the bolt and BCG are concerned is tougher material, slicker bearing surfaces and a highly innovative bolt design. Luckily, we get this in an enviable “one-stop shop” with the Sharps Rifle Company Xtreme Performance Bolt Carrier group.
The material of the carrier itself is S7; tool steel, in other words. We’ve heard the argument that S7 is actually too hard for this application, but Sharps addresses this with a 24-hour, proprietary, thermal cycle heat treatment that achieves an optimal balance of hardness and resilience. The bolt follows suit, and both are shot peened.
Beautifully made and cutting edge. Nothing else to wish for.
Next comes DLC “Diamond-Like Carbon” coating of the surfaces. This yields remarkable lubricity (.1 coefficient of friction against dry steel) and incredible hardness (Rockwell 90). It’s also a fairly astonishing aid to maintenance: In the samples we saw, even intentional fouling—up to and including deliberate attempts to score the surface—failed. Normal carbon fouling wipes off like talc.
The last (and our favorite) feature is the design of the locking lugs. The back end of these retain all the locking surface of a regular bolt, and keep the chamber closed until pressure falls and the cycling system pressurizes to rotate the bolt, eject the spent case and sweep a new cartridge off the magazine (or lock the bolt open on an empty mag). What’s tougher to appreciate without close inspection is the front of the lugs. In a patented configuration, these are shaped to cut through any massed crud that can slow the bolt in the chambering part of the cycle, leaving you out of battery and “bang” disabled.
A good memory will perhaps have a distant recollection struggling up: We tested the earlier NP3ed version of the ReliaBolt without inducing a failure. We stopped short of sabotage, but it was also the dirtiest rifle we’ve ever run by a long chalk. That bolt is still in our go-to gun, and trouble free.
We can only imagine what the enhanced model will run like. It’s got a spot in our short/light build.