16” 6.5 creedmoor?

[Earnhardt]

Does an AR10/LR308 upper have a max psi rating?

Thanks

 

[Gtscotty]

Because others might try it too. If you drive a 6.5 creed to 80k psi it will once again handily whip the flying pig.

I'm talking about those two loads he cited as normal .308 loads, not the 80ksi loads. He hints that they are book loads or a half grain under, but he's getting 150fps - 200fps more than most folks and won't just come out and say what the actual load is.

 

[JR1200W3]

Here is a 16" 308 vs 16" 6.4crees. 308 running 175smk at 2497 and 6.5 running 140smk at 2542 . You can get a but better performance out of say a 169smk/178bthp/185jugg etc and a 142smk for the 6.5 but the 140/175 are in my opinion equally anemic in terms of bc for their calibers.

You can see the 308 doesn't even stay super to 1k. Only .1 mil different at 1k for a 3mph wind and a significant drop difference.

6.5creed
View attachment 8542301

308 win
View attachment 8542302

You're comparing the wrong bullet. The 175SMK is a really old bullet and everyone knows the BC is shit. The 140 SMK isn't equivalent in that comparison. Even tho it's old, with poor BC, compared to other 6.5mm projectiles it's still not as DOS/ AOL dialup as the 175SMK.

I haven't been able to find a realistic 308 bullet/ load combo that beats a 6.5 in short barreled ARs but there are combos that narrow the gap to the point you have to ask what the point a 14.5" or 16" 6.5CM serves. The 308 will produce more velocity, relatively, due to the bore size. And there are several 155gr bullets that have BC's over .500. So if you wanted to offer a fair comparison you should be comparing a 155 with a BC of .53 at 2750 compared to whatever you want in a 6.5CM. Clearly beats the 140SMK. Go bigger in the 6.5mm bullet and lose case capacity for powder and slow the velocity down even more. Go lighter to pick up case capacity and MV but you start to equal the 155 BC and still won't close the gap in the MV.

And even in your comparison, you only pick up .2mrad of wind at 950. Turn that .2 into windage "danger space" for a 3mph wind miscall and see that it barely picks up any meaningful horizontal error budget on target. Run the numbers with a 155 G1 of .525 and then run the same elevation and windage danger space comparisons.

I definitely think the 6.5CM is the cartridge of choice in a LFAR for long distance shooting over a 308. But when you cut that barrel back to 16" the margins become so razor thin that it starts to not matter that much.

 

[45-90]

Why not include the actual information here, what are your loads for these, powder and charge?

The powder& charge information is in the picture on the 16" AR 10 308 2756 fps 168 eldm with the 1/2" 5 shot group,... if you just look.

 

[Earnhardt]

The powder& charge information is in the picture on the 16" AR 10 308 2756 fps 168 eldm with the 1/2" 5 shot group,... if you just look.

I can’t read it, since you have the hand writing skills of a 3 year old…

50.0 of what?

 

[joetuono]

I can’t read it, since you have the hand writing skills of a 3 year old…

50.0 of what?

2000 MR