Barrel lenth and twist for 6.5mm Grendel ?

[jazer]

Just got enough mullah to dump into an AR.

I heard a lot of hype on the 6.5mm Grendel wanted to explore the idea of building a smaller system with a 11.5 to 16 inch barrel.

With it that short what twist would be the best for a mid weight bullet (something like 120gr.) and what gr. has a decent ballistic coefficient and how many fps would I lose with a short barrel? Would it still be super sonic out at 1,000yds?

 

[bohem]

Re: Barrel lenth and twist for 6.5mm Grendel ?

The 16" barrel is where it's at unless you're actually going to make it an SBR. I don't understand why you'd have an 11.5" barrel with a 4.5" weld on flash hider to make the 16" min requirement.

That being said, the Grendel is well suited to 120gr bullets, the 120 Amax has a similar BC to the 155 Scenars do in 308. It should be able to get to 1k if you can get it over 2650 fps at the muzzle. I haven't run the round myself, I'm using the data in JBM.

120 Amax at 59F at sea level hits 1k around 1150 fps.

 

[jazer]

Re: Barrel lenth and twist for 6.5mm Grendel ?

16" barrel is where it's at unless you're actually going to make it an SBR.

Ya I actually didn't know that 16" was the the legal minimum.

I have heard of manufactures designing pistol AR's with 7" or 7 1/2" barrels with no butt stock (just the buffer tube as a shoulder rest is that what you mean by SBR?), but I don't know who makes them.

If it was that short I think it would be too sharp to enjoy shooting at all, though it would have a slight cool factor to it.

 

[Tactical30]

Re: Barrel lenth and twist for 6.5mm Grendel ?

I have built a Grendel myself and am in the process of building another.

The thing is If I were to build such a short barrel setup it would defitnetly not be the 6.5 Grendel. The bullet is made for longer ranges and with the short (SBR) barrels you are going to lose alot of velocity. If your ever on the 65Grendel forum I dont think you will ever see such a short barreled Grendel (in fact I dont think I have ever seen one that short on any website and there is a reason for it). The shortest maybe a 16" in length nothing shorter.

If your going to build such a short setup I would go with a different platform, maybe something like the 6.8SPC, .458SOCOM or the 50 Beowulf. Those calibers are made for shorter distances and would work better in a shorter barrel setup.

A 11.5" 6.5 Grendel sounds kinda pointless to me. I would rather have a 18" barrel at least on it.

The 2 builds I have in 6.5 Grendel is 18" and the build in process is going to be 22".

But its your build so build what you want. Im just giving you some things to think about.

 

[500grains]

Re: Barrel lenth and twist for 6.5mm Grendel ?

It seems to me the whole idea behind a 6.5 Grendel is to push a heavier bullet out to 1K. If you want to hunt with the gun, the 6.5 has more punch than the 6.8 due to case capacity and a little heavier bullet.

So I would go for a 18 inch barrel to enjoy the benefits of the greater case capacity.

If you want a short barreled rifle (SBR), keep in mind that even the small case capacity of the .223 makes it very loud and you lose a lot of velocity. For really close shots it would be fine, but the 6.5 Grendel is designed for long shots.

Just a friendly side note: If you want a rifle with a barrel length of less than 16", you need to fill out forms IN ADVANCE with the BATFE and pay a tax, or you will be committing a federal felony. It would be a shame to get into trouble for a few inches of barrel length.

 

[JSTARSZ]

Re: Barrel lenth and twist for 6.5mm Grendel ?

in my opinion the 6.8mm and the 6.5 are not even close in comparisons. One is for short range and the other for medium to long range. I would have no issue with building a 6.8mm as a SBR - say 11" or so and I would use it for hunting. In fact I would use it over a 223. The 6.8mm has more punch than a 223 by far.

 

[jazer]

Re: Barrel lenth and twist for 6.5mm Grendel ?

Thanks for the comments, I really am interested in the 6.5mm Grendel for the "perfect gun" (and I know there is no such thing).

My brother wants a Springfield SOCOM 2, my pops prefers the M1A. I don't care for either. I like the versatility of the AR platform.

Which leads to another question, does the 6.5mm Grendel and 6.8mm use a AR-15 or AR-10 lower?

If they do y'all convinced me to throw out the short barrel stuff. I'll go shorter on a 6.8mm, but on the 6.5mm 16" or 18" is what I'll do. Thanks for saving me from a big mistake.

 

[Super Bee 950]

Re: Barrel lenth and twist for 6.5mm Grendel ?

One thing about the 6.8 and the 6.5 is the cost of ammo. Dont get either unless you have a lot of money to burn, or you reload.

The 6.8 is best out to 400 yards. The Grendel is good to 1000. At what distance are most of your shots going to be?

Both use the standard AR-15 lower.

 

[jazer]

Re: Barrel lenth and twist for 6.5mm Grendel ?

I do reload. Gunsmithing and AR's are new to me.

I mostly bear hunt in southern Oregon. The furthest I have killed (and retrieved) a bear was 575yds with a 300WSM. My areas that I shoot go into the 800yds range. Beyond that my range finder won't work.

The reason I want it shorter is for the brush. I would like to enter some local long range events too.

Is the 6.5mm comparable to a semi 7.62mm when you get on the trigger, or is it less?

 

[Greg Langelius *]

Re: Barrel lenth and twist for 6.5mm Grendel ?

I like pretty much everything about the 6.5 Grendel <span style="font-style: italic">except</span> the case's base diameter. I'd much rather have something with a .473" diameter.

In this capacity range, there's nothing available commercially, and the .260 Bobcat (a necked up 250 Savage) is the only wildcat I'd be eagerly considering.

Greg

 

[lfagan]

Re: Barrel lenth and twist for 6.5mm Grendel ?

This was done strictly out of morbid curiousity....two years ago I cut down an early Alex-A barrel to 10.5" added a Larue rail, 24x optic, put it on a lower with a good trigger and then shot it at 400 yards. We used factory loaded 123 Lapua and the little barrel was shooting 4.5"-6.00" five shot groups at 400. Believe it or not...
Len

 

[TheGWP]

Re: Barrel lenth and twist for 6.5mm Grendel ?

Maybe you should be building a different rig. Try a 300whisper, it's all kinds of fun! When you'r serious about accurate distance then go for the 6.5 Grendel or 6.5 CSS. There is a lot of expense when you get into 24x scopes but Vortex makes a nice entry level version.

 

[chase102798]

Re: Barrel lenth and twist for 6.5mm Grendel ?

Wannabeninja,

The 18" barrel that LongRange30 has is a fluted Sabre Defence barrel. That might be a nice light weight setup for you for brush hunting and such. LR30 has reported some fantastic groups out of his 18" sabre. Many guys like the 18" barrels for hunting and that would probably want to be your starting point for a hunting gun in the ranges you are talking as to not lose to much velocity. I would try a medium weight contour in 18-20". The 18" satern Spartan barrel would be a winner for your needs too. Some of the high end barrels that are longer than this have pretty stout diameters before the gas block, so that would prolly be out for you since they weigh alot. If you had a collapsible stock on the gun, it would be plenty short for brush hunting for bear. I think you would be happy with the balance and handling for a gun setup like this. Also, if you don't have a need for quad rails, the new troy or Viking Tactics Battlerails (they do have little rails that bolt on here and there) will shave some weight for you too, plus they have a nice slender feel for a hunting gun.

If by "get on the trigger" you mean recoil wise, then IMHO it is quite a bit less recoil that a 308 semi.

 

[jazer]

Re: Barrel lenth and twist for 6.5mm Grendel ?

Hey thanks, that good info.