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It has something to do with the over-bore of the cartridge, and maybe the length of the powder column, but medium powders like Varget are too fast for most 243 loads, leastwise at speeds I'd like. I do have (I think) an H4350 load for one 95sst load, but in general when I look up loads for the 95-100 gr class it is like H4831, H1000, 7977, etc etc. I have a great load for my 100 gr GK in H4821 but when you go to the 6 Cm, since the case is a tad shorter (and more efficient I think) seems like a bit faster of powder class is allowed. I can do Varget, H4350, 8208, RL 17, etc... and I do like the more temp-stable ones. Anyway, that's what led to my comment earlier, may not be the case, but I hope so.
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Sigh...
Just when I was finally content with my assortment of ARs.
Dammit.
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No rest for ornery!!! 
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Interesting that they've basically diminished dimensions of the 6mmAR *just enough* on this one. I suspect this would make it necessary to buy 6mm ARC dies rather than go with a 6.5 Grendel bushing die with a .268" bushing for resizing.
Clever.
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I use a Redding 6.5 Grendel sizing die with busing to size my 6 mm Grendel. It works great no issues whatsoever. I have 2 243lbc/6G rifles 24" xcaliber bull barrel and a 20" BHW Polygonal rifled barrel that is an absolute tack driver. My 6es are quite a bit more accurate than my 6.5s
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grayfox Wrote:It has something to do with the over-bore of the cartridge, and maybe the length of the powder column, but medium powders like Varget are too fast for most 243 loads, leastwise at speeds I'd like. I do have (I think) an H4350 load for one 95sst load, but in general when I look up loads for the 95-100 gr class it is like H4831, H1000, 7977, etc etc. I have a great load for my 100 gr GK in H4821 but when you go to the 6 Cm, since the case is a tad shorter (and more efficient I think) seems like a bit faster of powder class is allowed. I can do Varget, H4350, 8208, RL 17, etc... and I do like the more temp-stable ones. Anyway, that's what led to my comment earlier, may not be the case, but I hope so.
The two most common powders I see used for 6CM is H4350 and H4831SC. Hodgdon stops recommending Varget for bullets over 95gr. I use H4831SC for 115gr DTAC and it works well. I think H4350 is too fast for even 105gr VLD but people still flock to it. I've done work ups using H4831/SC, H4350, RE16, RE22, and RE26. RE26 made the most velocity, H4350 had the widest node, and H4831SC had the best accuracy.
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03-14-2020, 08:33 PM
(This post was last modified: 03-14-2020, 08:53 PM by Harpoon1.)
RiverRider Wrote:Interesting that they've basically diminished dimensions of the 6mmAR *just enough* on this one. I suspect this would make it necessary to buy 6mm ARC dies rather than go with a 6.5 Grendel bushing die with a .268" bushing for resizing.
Clever.
Could be but, I wonder if it wasnt simply just a legal/safety issue to keep the Grendel from being able to also fit in the chamber?
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Harpoon1 Wrote:Could be but, I wonder if it wasnt simply just a legal/safety issue to keep the Grendel from being able to also fit in the chamber?
Or a legality to change it enough that it didn't infringe in the Grendel design. IE like the 300whisper/300blackout piddling contest.
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LtDan Wrote:I use a Redding 6.5 Grendel sizing die with busing to size my 6 mm Grendel. It works great no issues whatsoever. I have 2 243lbc/6G rifles 24" xcaliber bull barrel and a 20" BHW Polygonal rifled barrel that is an absolute tack driver. My 6es are quite a bit more accurate than my 6.5s
My two are BHW barreled also, but I opted for 20" barrels.
Leverevolution with Hornady 105 HPBTs works really well.
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Ive long thought of getting a custom barrel for my Howa Mini and having the perfect little deer rifle here where .243 is the minimum legal diameter. Would be easier/more cost effective if they just came factory. Especially if Hornady is gonna offer ammo. Wonder how fast 87 grain VMaxes, 85 grain Interbonds, or 90 grain ELDs might go...
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My guess-timates are, for each 10 grs lower wt you get ~100 ft/s more MV.
So, if their standard is 2800 ft/s for a 108, an 87 or 90 gr should be able to (and I say, SHOULD) maybe ~3000 ft/s.
But that of course would be under ideal, 24" barrel, conditions.
I guess.
That doesn't mean you would find a node at that MV, either...
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Reminds me of the 250/3000. First center fire rifle I shot was a take down Model 99. One in 6mm Grendel would be nice now
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What sort of barrel life are the 6mm Grendel Wildcats getting with nitrided barrels?
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hill37 Wrote:Reminds me of the 250/3000. First center fire rifle I shot was a take down Model 99. One in 6mm Grendel would be nice now
While the Creedmoors are essentially a 250/3000 improved, a 6.5 Grendel in a bolt gun with 22 or more of barrel and handloads can nearly match a 250/3000 with 100 grain bullets. AND the 6.5 Barnes and Nosler 100s are only about .01 shy on G1 BC when compared to the .257 100s, according to my Litz manual. Pretty neat.
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grayfox Wrote:My guess-timates are, for each 10 grs lower wt you get ~100 ft/s more MV.
So, if their standard is 2800 ft/s for a 108, an 87 or 90 gr should be able to (and I say, SHOULD) maybe ~3000 ft/s.
But that of course would be under ideal, 24" barrel, conditions.
I guess.
That doesn't mean you would find a node at that MV, either...
From what I recall, book loads for the 108 ELD are about the same as 95 SST/ 100 BTSP velocity. So I would suspect that the 85gr IB would top out around 2800 (again, about 300 FPS below max in a .243). I cant shoot over 100gr in my .243 anyways, so I cant confirm actual velocity between the bullets.
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I load my 100 gr SBT in 243 to 2815 ft/s, maybe not top end but it's a tack driver and blooded this year w/ a doe.
Any time I can find a 2800-ish node in these smaller centerfires of mine for 100 class, I'm a happy hunter.
Am waiting to see the roll out of this 6Arc, could be a nice AR package. Bolt-style too.
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Mit, the other thing we don't have ability to figure into the equation, is the perhaps better efficiency of the fatter Grr-style case. All we have to go on right now is the "book" figures on the Saami drawing, 108 gr bullet, 2800 ft/s. But with the 0.020-30 setback of the shoulder vice the 6-Grendel "proper", we're looking at a slightly smaller case capacity. Maybe 0.5-1.0 grs? just a guess, again. When Hornady did the Creedmoor, they took a "308-like" 30-Rem cartridge, thus essentially bumping the case shoulder back a bit so a smaller volume but I think, more efficient. I could be wrong on that though.
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If it can run within a few hundred FPS of a .243 I can see it doing well. If it isnt a flop I can see one finding it's way into my safe.
The 6.5cm runs a higher pressure than .260, which runs a higher pressure than 6.5x55. Unless this cartridge can be a lot more efficient, it will have to run a lot more pressure that .243 to match it.
One thing I like about my 6.5 G is that it can match velocities with my 6.5x55 running M96 pressures.
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Harpoon1 Wrote:Could be but, I wonder if it wasnt simply just a legal/safety issue to keep the Grendel from being able to also fit in the chamber?
I agree that this is the reason.
A 6mm Grendel case should actually be longer, about 1.590 if I recall whereas the 6.5 Grendel is 1.520, to get more powder in for the lighter and shorter weights of 6mm bullets.
But, if this is geared to longer 6mm bullets, then it looks like a Hornady design where they are planning on the boattail ending and the bearing surface starting at the neck/shoulder junction.
This has been begging to be a factory round for a LONG time. it was inevitable and congrats to whoever did this (be surprised if it's not Hornady).
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What I'm wondering is this. Might the headspace of this 6mm ARC be close enough to fire factory ammo in a 6mmar chambered barrel?
Basicly fireforming it to the 6mmar chamber.
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