Originally Posted by
alx01
@clint another question: what's the reasoning behind having a 5R 1/8 twist and 5.56 Nato chamber for the lightweight barrel vs 4 groove 1/7 twist with a proprietary chamber? How's 5.56 BRT Chamber different and why would I choose it over 5.56 Nato? Would 5.56 BRT Chamber cause any issues with certain types of ammo or casing?
Does 4 groove barrel have deeper grooves for a better bite? I don't have any experience with 5R barrels, but like the idea of 4-groove AK-like barrel.
Not Clint, but I can offer some thoughts on some of the above. For the twist rate, unless you plan to launch some very heavy or very long projectiles, a 1:8 will handle it all. Outside of the LR benchrest community, there is pretty much no difference when comparing the capability of a 1:7 to a 1:8. In fact, on the lighter end of the spectrum, some will say that a 1:7 won't do as well with 55gr and under bullets. But, in practice, 1:7s have proven to do just fine with the lighter projectiles. Ultimately, there are no "absolutes". What one barrel prefers may be different than another. But, that won't necessarily have anything to do with twist. Now, if we introduce twist rates of 1:9 and higher, then there's a conversation to be had.
Regarding the rifling, some will associate 5r with a greater potential for precision/accuracy. In practice, it's more about who makes the barrel than the number of lands and grooves. The reason some believe that 5r is "better" is the result of a couple things. One, 5r has lands opposing grooves; compared to lands opposing lands with conventional rifling. The argument is that this results in a better gas seal and less jacket deformation. Another reason, which is tied to the last, is that 5r barrels will pick up less fouling and clean up easier. There is some truth to these things. Projectiles going through less "trauma" when traveling down the bore should, in theory, perform more consistently. By that same token, a barrel that fouls less, in theory, should shoot more consistently throughout a range session. Still, while there are some legitimate reasons to desire a 5r over conventionally rifled barrel, it's actual significance may be overstated. Again, whomever is making the barrel will have a far greater impact.
TL;DR - A 1:8 twist with 5r rifling is nothing to be concerned about. If anything, some may find one or both of those specifications to be desirable. For me, the type of rifling or twist rate is highly unlikely to be a dealbreaker. Heck, I don't even mind having a 1:9 twist. To each, his own. YMMV.
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