short barrels and long range

[LR1955]

Hi I'm new here but have an AR and hopefully soon a Grendel and I am glad to hear this. If I get a Grendel I'd really like an 18 inch, with a collapsible stock. I love how portable short Ar's are. I usually shoot only to 300 yards but if I buy a Grendel id really like to be able to get to 600. It seems there would be a lot of weight difference between 80 smk and 123 amax. Is there a twist rate that shoots both these well? As I research I'd like to find out. I generally like heavier bullets but I know Grendel has limited case capacity. What do ya think a good length is for a portable truck gun and barrel twist for Grendel you may wanna jump out n pop a coyote at 500 yard on farm or hit 600 on paper? Would a 20 be better?

HT:

Since your truck is carrying the rifle, a 20 or 24 inch barrel will be better than a shorter barrel.

There was a discussion on truck rifles here a couple of weeks ago. Run a search and I think you will find the right thread. It was pretty informative.

I am sure you can 'get to' 600 with any Grendel load. Just depends on how good you are at range estimation and wind doping. Nothing wrong with trying some 140 grain SMKs with about 27 grains of TAC or a similar powder. Very slow but good performance at 600. Maybe a better bet is a 120 SMK as they tend to shoot well out of anything. 600 should not be a huge issue unless you can't stay on top of the winds. Either will kill a coyote.

What is up with the twist rate thing? Grendels come basically with 8 to 9 turn twists. Either or any will be fine with any reasonable bullet weight. The 140's may be on the edge with a 9 turn twist. If you use a very short barrel, most likely something faster than 1 turn in 8 to get a longer bullet spinning fast enough from a short barrel.

You won't have much of a choice as twist rates with these AR blasters are as much dependent on barrel length and function of the gas system as they are in stabilizing the bullet. And in answer to your next question -- no -- there is not one ideal twist rate outside of the laboratory.

LR55

[hydrotech]

ahh ok that makes more sense, thank you! i was assuming both shot in grendel.

[hydrotech]

thanks, thats informative

[JASmith]

That's impressive shooting!

It also reminds us that the AR15 magazine length indeed puts limits on long range performance.

I am mildly curious about why folks haven't tried the WSSM variants for long range competition. (Let me hasten to add that we should start a fresh thread if folks want to beat this horse!)

[bwaites]

That's impressive shooting!

It also reminds us that the AR15 magazine length indeed puts limits on long range performance.

I am mildly curious about why folks haven't tried the WSSM variants for long range competition. (Let me hasten to add that we should start a fresh thread if folks want to beat this horse!)

In two words. cost and recoil. As I understand it, they haven't been shown to be significantly better at the mid ranges than what is available, while offering substantially more recoil. You end up basically shooting the same bullets, but driving them faster, with more powder and significantly more expensive brass. Theoretically, the extra speed should be an advantage, but evidently not as much as you would expect with that extra recoil.

At long ranges, the WSM's and full size cartridges have even more powder capacity, and offer the advantage of driving heavier, higher BC bullets faster. (From bolt guns, of course.) I've seen guys playing with the WSSM's at F Class matches, but they don't seem to be winning. The winners in F Open almost always are shooting 6.5-284, .284's of some stripe, or 7mm WSM's.

[JASmith]

Good info. Thanks!