barnbwt
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- Joined
- Aug 14, 2011
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Whoever made that chart is also riding the hairy edge safety-wise, because I don't think you can get 2650 on that 123gr SMK bullet without exceeding the bolt thrust of a 5.56 at 62KPSI.
I dunno man, take it up with Wikipedia or Bill Alexander or SAAMI or whatever, since 123 @ 2650 seems to show up in a lot of places. Seems like a standard (if not 'the' standard) load from what I can tell. Maybe it's causing all those bolt failures, who knows (btw; wasn't the new M855A1 causing bolt failures or something, which was ultimately handwaved away with more intensive maintenance procedures, or something? Why, it's almost as though the gun itself is trying to tell everyone something...). At any rate, it doesn't appear to be a serious source of concern for the folks actually running these guns, meanwhile I still hear about the occasional 223 broken bolt, admittedly with a much higher frequency-bias than Grendel (a failure, btw, that simply doesn't seem to happen in ANY other platform but the AR15; why, it's almost as though the gun itself is trying to tell everyone something...)
And what about putting bullets through an autoloader that are so long they are practically falling out the inside of the case neck? Is it even possible to do a 6x45 with a 105gr VLD inside an AR mag OAL? I thought 6x45 typically ran closer to 70-80gr bullets. I'm also curious what kind of spin-stability issues you might be running into with such extreme lengths, as well as performance consistency; not saying it doesn't work, but you're talking radically longer bullets & I'm curious how well a standard rig can handle both. Especially with the bullet necessarily so far back from the lands inside the case (that Grendel II chamber thing has a similar issue with all the extra freebore they added being a detriment to ultimate accuracy, though it did reduce peak pressures)
6x45 also has 27gr capacity vs 35gr H2O for the Grendel case, likely more of that going towards lead volume vs powder when the bullets start getting heavy (not great for either, of course, but Grendel has a shoulder that's farther back so more of the ogive can stick out the front before sucking up cartridge volume, not to mention more powder along side the bullet due the wider case)
I get what you're saying, that the narrower case allows for higher pressures that can partially compensate for the reduced volume. Just as with automobiles, though, more volume ultimately triumphs over higher pressure, even when talking the same basic engine block (the AR15). At any rate, you have to admit these rounds are a heck of a lot more similar than they are different, so getting this passionate about one or the other is kind of silly. If Grendel is 'the worst cartridge evar' I'm afraid that means your pet 6x45 (seriously, I'm good on Google searching stuff, but it does not appear this chambering is at all common even compared to the fairly obscure Grendel) is the second or third worst cartridge ever conceived, itself
For sure I can't easily find trajectory data on the 6x45, but I have a hard time believing it could possibly be significantly different (compared to the factors a shooter can compensate for at various ranges, I mean) considering the rounds are in a similar size class, at a similar velocity, with the Grendel generally having a slight edge in BC but both higher than average. I'd be especially surprised if one abruptly pulls away from the other at some point before 800yds the was Grendel does from PPC at around 600 or so.
At any rate, the purpose of those charts was to show the effect of BC and long range drop & windage; it's a horse race until about 500yds, then the BCs take over regardless. Also that 5.56 simply doesn't do great past 400/500yds (who'd a thunk it?) which is why these ~6mm things came into being vs 7.62 NATO. I'd love to see a chart showing how the 6mm diameter between 5.56 and 6.5 leapfrogs to the front with similar BC bullets, though (that's the closest we can get to an apples/apples comparison, though as I said initially, the realities of such long bullets strongly favor short/stubby case geometry)
TCB
*I've read numerous times in my only-recent research into Grendel that Quickload is notoriously inaccurate for the Grendel cartridge. I recall the same being true for 5.7x28 to a massive extent before updates. Their algorithm seems to overestimate pressures for short, stubby cartridges with high BC bullets for whatever reason (I'll bet the WSSMs have similar issues with QL)