6.5 Grendel - Ideal Barrel Twist Rate

[nn8734]

Hello All,

I am strongly considering a 6.5 Grendel build on an LMT Lower that I have laying around and was hoping to get some insight as to ideal twist rates. I will be shooting 123 grain Sierra Match King and/or 123 grain Lapua Scenar. The rifle will be used for distance shooting out to 800 yards or so; I may also use it to hunt white tail deer and coyotes.

I am not as familiar with the Grendel platform as I am with the .308 and 6.8 SPC, however the cartridge's downrange ballistics and compatibility with the AR-15 platform appeal to me. The predominant twist rates that I have come across in my research are 1:8 and 1:9; I will be looking to run an 18-20" barrel. I reload and will be developing max loads (safe loads at max velocity).

Thanks in advance for your responses!

 

[dragbag]

1-8 works well and I wouldn't go shorter then 20".

 

[FCS]

I second dragbag's recommendation.

6.5 Grendel, I'd go Berger 120 Match BT or Sierra 120 MK.
264 LBC with shorter freebore is a better match to the 123 (SMK, Scenar, A-max)

2550-2600 is reasonable expectation for velocity from a 20" bbl with accuracy, can push bullet faster but accuracy is down and brass takes a beating.

 

[bjay]

I got a 26" satern 1:8.75 only tried amax 123 and smk 120.. i shot them to 300 so far cant tell the diff bet the two.maybe 600 plus will show.8208xbr

 

[LRRPF52]

The shorter barrels require faster twist to stabilize long pills, while the longer barrels don't. There isn't a huge advantage to a 24" over a 16" when talking 6.5 Grendel. If you are pushing the velocity with hand loads, your gas system length will be the bigger factor, combined with barrel length. There is no statistical difference between a 20" and 24" gun when looking at velocities, as long as they both use the Rifle-Length Gas System.

Same for the 16" and 18" Mid-Length Gas guns. I really like the handiness and portability of my lightweight 16" gun, and it will hold MOA or better at distance from hasty support, so I can't complain. Bucks the wind extremely well, allowing novice shooters to make 1st-round hits like it's cool in full-value 10-15mph winds.

For your common hunting distances out to 300yds, a 14.5" Grendel is hard to beat. A 20" is the longest I would go with for a target gun, unless I was going to go with an extended length gas system on a 24" gun. This is why I really like the 16" Grendel. It does it all.

 

[nn8734]

Great, thanks everyone! Sounds like 1:9 @ 20 inches should be the way to go.

 

[Jon A]

Personally I'd lean toward 1:8 no matter the length in case you want to shoot 140's. Mine's a 1:8 and it really, really likes 140's. It shoots 123's very well as well so I don't see a downside unless you want to shoot really light bullets. If you want to shoot 105's and 107's I'd suggest getting a 6mm instead.

 

[bobaguilar]

I shoot a 1:9 Black Hole Weaponary 18" 264lbc. It works great out to 800 yards with a 123 amax.

 

[nn8734]

Personally I'd lean toward 1:8 no matter the length in case you want to shoot 140's. Mine's a 1:8 and it really, really likes 140's. It shoots 123's very well as well so I don't see a downside unless you want to shoot really light bullets. If you want to shoot 105's and 107's I'd suggest getting a 6mm instead.

To your point, shooting the lighter rounds essentially defeats the purpose of selecting the Grendel. I will be focusing on the 120 SMK and 123 Lapua Scenar/123 Hornady AMAX. I actually selected an entire upper from Alexander Arms with a Shilen Barrel and 1/9 twist...Worst case scenario, i simply switch to a 1:8 if the 1:9 proves ineffective or if I decide to transition to 130-140 grain bullets.

 

[LRRPF52]

To your point, shooting the lighter rounds essentially defeats the purpose of selecting the Grendel. I will be focusing on the 120 SMK and 123 Lapua Scenar/123 Hornady AMAX. I actually selected an entire upper from Alexander Arms with a Shilen Barrel and 1/9 twist...Worst case scenario, i simply switch to a 1:8 if the 1:9 proves ineffective or if I decide to transition to 130-140 grain bullets.

The 107 SMK and 108 Scenar are some of the best target bullets in the Grendel. For hunting, the 100gr Barnes TTSX and 100gr Nosler Ballistic Tip are great bullets. Here's the partial list of 100-108gr 6.5mm pills:

100gr Cutting Edge ESP Raptor .250 BC (with Talon Tip)
100gr Lapua FMJ .250 BC
100gr Lapua FMJ Cutting Edge .250 BC
100gr Sierra Varminter .259 BC
100gr Nosler Partition Flat-Base .326 BC

100gr Lapua Scenar .424 G1/.212 G7
100gr Hornady AMAX .390 BC
100gr Hornady SP .358 BC
100gr Berger BTHP .370 G1/.193 G7
100gr Lapua Scenar-L (new)

100gr Nosler Ballistic Tip .350 BC
100gr Barnes TTSX .359 BC
100gr Barnes Tipped TAC-TX BC not listed

107gr SMK .406 BC
108gr Scenar .465 G1/.231 G7

The 107gr SMK and 108gr Scenar are like the 155gr Scenar for .308: Run them fast, and you will smoke the heavier bullets for trajectory, just like I do with the 130gr VLD out of my .260 Rem, versus the 140gr class.

The Grendel is fun to shoot with varmint-weight pills of the 85gr-95gr class, 100gr target and hunting pills, as well as 120-130gr class. Some people even enjoy shooting the 140gr class pills for silhouette shooting. There aren't a lot of cartridges of its size that handle such a wide range of projectiles and applications, with such inherent accuracy. Just when I think I've found something I really like, such as the 123gr AMAX and Scenar factory ammo, I develop loads for something else that is just great in its own right.

You definitely don't need a long barrel with the Grendel though. That myth doesn't seem to want to die, but if you run the numbers and shoot a 14.5" or 16" gun compared to 20" and 24", you'll probably opt to the shorter blasters. Even the 10.5" and 12.5" do really well.

 

[bobke]

I have 1:8x18" AA, 1:8.5x20" Bartlein and 1:8.75x24" Satern and they all have their merits. I'd take the Bartlein heavy 20" as my first choice, with the exception that it was cut with very long freebore, but still shoot lights out, especially with newer 123SST and CFE. All reach 500yds without issue. I shoot, as above, with everything from 100 Noslers(very accurate bullet) to 123SST and Amax's, 123 Nosler CC's or Sierra's and the 107/108's in between, each with a sweet spot, depending on barrel. Grendel and the similar chamberings have a lot of flexibility and range well. Make sure you instruct your choice of smith on how you'd like to see chamber cut-if done again, I'd say cut to max mag length minus .020 for ogive of bullet of your choice. But that's just my preference-your's may vary.

 

[nn8734]

I have 1:8x18" AA, 1:8.5x20" Bartlein and 1:8.75x24" Satern and they all have their merits. I'd take the Bartlein heavy 20" as my first choice, with the exception that it was cut with very long freebore, but still shoot lights out, especially with newer 123SST and CFE. All reach 500yds without issue. I shoot, as above, with everything from 100 Noslers(very accurate bullet) to 123SST and Amax's, 123 Nosler CC's or Sierra's and the 107/108's in between, each with a sweet spot, depending on barrel. Grendel and the similar chamberings have a lot of flexibility and range well. Make sure you instruct your choice of smith on how you'd like to see chamber cut-if done again, I'd say cut to max mag length minus .020 for ogive of bullet of your choice. But that's just my preference-your's may vary.

Thanks for the tip on the oal and freebore. I actually ended up purchasing a complete Alexander Arms upper with a 1:9 Shilen barrel and also ordered a modified 6.5 Grendel case for my Hornady oal gauge so will be measuring for seating depth.

LRRPF52 - thank you for posting the information on some of those lighter rounds. I previously had not considered them but will pick up a box of 108 scenars to experiment with.

 

[Tacsnipe73]

There is no statistical difference between a 20" and 24" gun

WTF!..... No statistical difference..... Dude, you could use a course in statistics, cause my stats say this: Out of my 20'' GDMR I get a five shot average of 2483 fps. Out of my 24'' sabre defense I get a five shot average of 2578. Both Rifles were tested using Hornardy 123 gr factory ammo.

Yea..... No difference.

 

[dragbag]

Try cutting that down to a 16" or 14.5" as he stated and there is a big handicap. I will stick to a minimum of 20" on the Grendal platform. If I need a 16" or sub there are better headstamps for that.

 

[Tacsnipe73]

Try cutting that down to a 16" or 14.5" as he stated and there is a big handicap.

True, but there are uses for a shorter grendal, such as the 14.5" that I use for short range pigs and coyotes, it just comes with a price: velocity. It just bugged me that LRRPF52 was saying there was no significant gain in the longer barrels.

 

[fx77]

As stated by LRRPF52
Go to Alexander Arms page for specs and they recommend 7.5"-9"...twist.

 

[dragbag]

True, but there are uses for a shorter grendal, such as the 14.5" that I use for short range pigs and coyotes, it just comes with a price: velocity. It just bugged me that LRRPF52 was saying there was no significant gain in the longer barrels.

At that point I would go to 6.8 or .300

 

[BLDTYLRY]

I have a 1:8 Twist 18" 5R and I shoot 123gr A-Max to 1/2 moa at 100yds easily. One thing to consider if shooting heavies and longer Ogive bullets is Internal Mag Length. You'll be stuck loading to the Mag's COAL before you hit the ideal jump.

AR-Stoner mags are limiting me to 2.28" so running 123gr A-Max is more accurate than 123gr SMKs. I have PRI 6.8 Mags in the mail and should get me to 2.30-2.34"

 

[Unknown]

20 inches is the sweet spot length for Grendel type rounds. You get enough velocity without having an unwieldy barrel that is difficult to transition fast between targets due to it's length. Shorter is handier, but velocity begins to suffer. One of the cartridge's "founders" (Mr. Bill Alexander) thinks the 20 inch barrel is the best "all around" barrel length.

 

[ugadeer]

i shoot a sabre and a satern both of which are 18" and each shoot extremely well to 800 (haven't tried further)........both bbls are 8 twist

the sabre likes the 120 barnes and the satern likes the 129 sst..........(i like to shoot hunting rounds even at paper b/c i don't like to switch loads)

 

[LRRPF52]

True, but there are uses for a shorter grendal, such as the 14.5" that I use for short range pigs and coyotes, it just comes with a price: velocity. It just bugged me that LRRPF52 was saying there was no significant gain in the longer barrels.

Alexander Arms has stated that across a large pool of various 20" and 24" guns, you can't tell the difference if you only look at velocity data. Using velocity data alone will not help you identify which is which, and a lot of it is just the variation of one barrel's characteristics over another.

I have a 16" gun that has chrono'd 123gr Moly Scenars from a factory load from Precision Firearms at 2583fps. That is normally 24" gun territory. It is true that you can milk more velocity from a 24" if you use an adjustable gas block, certain powders, and use heavy weight in your recoil system. What is important is downrange performance. Compare a 24" gun velocity to a 16" gun velocity to see what I mean:

24" 6.5 Grendel, 6600ft ASL(I shoot at 6600ft ASL regularly.), 67F, 100yd zero, 2.5" Scope Height

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2630        1889           0.00         0.0000         0.00
        100      2494        1699          -0.0         0.1171        -0.2
        200      2362        1524          -0.4         0.2407        -0.3
        300      2235        1364          -1.2         0.3712        -0.5
        400      2111        1217          -2.0         0.5093        -0.7
        500      1992        1083          -2.9         0.6556        -0.8
        600      1876         961          -4.0         0.8108        -1.0
        700      1766         851          -5.1         0.9756        -1.2
        800      1660         752          -6.3         1.1509        -1.5

16" 6.5 Grendel, 6600ft ASL, 67F, 100yd zero, 2.5" Scope Height

        Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2450        1639           0.00         0.0000         0.00
        100      2320        1470           0.0         0.1258        -0.2
        200      2193        1314          -0.6         0.2588        -0.3
        300      2071        1171          -1.4         0.3995        -0.5
        400      1953        1041          -2.4         0.5487        -0.7
        500      1839         924          -3.5         0.7070        -0.9
        600      1730         817          -4.7         0.8752        -1.2
        700      1626         722          -6.0         1.0541        -1.4
        800      1527         637          -7.5         1.2445        -1.6

At this point, I would ask: Is that extra 8" of barrel length worth 1.2 Mils less drop, and .1 Mil less wind drift at 800yds? For some people, that answer might be "yes". For me, it is not. With that said, I know a guy who runs a 24" Grendel with 130gr Norma Golden Targets at 2700fps, using CFE, certain 7.62x39 brass, and a long COL closer to 2.300".

For a lightweight hunting carbine, that you can also ring steel with out to 800yds+, the 16" gun is hard to beat.

 

[MNMan]

My Precision Firearms 1-8 twists out of a 24" Lilja bbl shoots 123 gr scenars with amazing accuracy. A dime covers 5 shots at 100 yards. My second one from Mark and they were both that accurate. My favorite out of many including my bolts.

 

[nn8734]

Sweet MNMan-Glad to hear you are getting that type of accuracy out of your Grendel...My 6.5 should be ready to go by end of next week and will be hitting the range...I will be shooting (at least initially) AA 123g Scenars as i have acquired a lot of 10 boxes of those to get me started..I will be reloading the cases w/SMK 120g match kings and will look to try rounds from Hornady and Barnes...I'll post pics and a range report sometime next weekend...

My Precision Firearms 1-8 twists out of a 24" Lilja bbl shoots 123 gr scenars with amazing accuracy. A dime covers 5 shots at 100 yards. My second one from Mark and they were both that accurate. My favorite out of many including my bolts.

 

[bobke]

Go to www.65Grendel.com, do a quick search for 'Google CSE' and everything of any import you might have interest in is laid out at your fingertips. LRRPF52 is a regular there and most helpful with real world data, many others as well. Bwild97 had an extensive thread with pics and chrono data that is an excellent bookmark for any Grendel shooter.

 

[MNMan]

I can get you a my load data if you like later nn.

 

[nn8734]

MNMan - Sure, I would appreciate that, if you have some extra time...I have a few reloading manuals that have loads for the 6.5 so will also be leveraging their content as well...I will be using the AA 123g Scenar as a baseline insofar as performance is concerned and have picked up a box of 6.5mm 120 grain SMKs and have Benchmark, H335, Varget, etc...

Bobke - Thanks for the link - that site is great!

I can get you a my load data if you like later nn.

 

[LRRPF52]

We have a 6.5 Grendel Reloading Handbook out as well, with manufacturer-supplied, pressure-tested load data from AA, Lapua/Vihtavuori, Hodgdon's, and Western Powders (Ramshot, Accurate). There are 166 different loads from these manufacturers in the 6.5 Grendel Reloading Handbook. http://ar15buildbox.com/Home_Page.html

Additionally, Hornady's 8th Edition has 14.5" barrel load data, and their new 9th Edition has 18" barrel load data, to include CFE, which produced 2500fps for them with the 123gr bullets. The new 123gr SST has the same published BC of the 123gr A-MAX, which is .510, and the Hornady Factory 123gr A-MAX load is very accurate in everyone's rifles/carbines that were made by a known source. I can't think of anyone who has reported bad accuracy with that load yet. With my little 16" Grendel, it shoots from 1.69" - 2.18" at 200yds, and that's from a button-rifled economy AA Barrel/Bolt combo off a hasty rest.

 

[MNMan]

Lapua Brass...27.0 gr H-4895...2.26OAL...CCI 450 primers...123 gr Scenars... Can try going up from there to 27.5gr

 

[LRRPF52]

Lapua Brass...27.0 gr H-4895...2.26OAL...CCI 450 primers...123 gr Scenars... Can try going up from there to 27.5gr

That's basically the same as AA's data for the 123gr Scenar with H4895:

CCI 450...Lapua Brass...123gr Scenar...COAL: 2.265"
Start load: 27.0gr....2423fps
Max load: 27.7gr.....2450fps

That's one of the slower loads for the 123gr Scenar. Accurate 2520 produces much faster velocities:

A2520
27.3gr start load
30.7gr max load: 2630fps from a 24" barrel

The 6.5 Grendel Reloading Handbook will give you a bunch of different loads where you can see what powder does better than others for a certain bullet weight/shank profile.

 

[MNMan]

Yes it is. I tried many loads and this one was m pet. Sounds like 8028 may be the one to try also. Good luck to you..

 

[kuhnskaos]

8208 XBR is quickly becoming one of my go to powders for my Grendel 22" 1/8.25 twist Proof Research carbon wrapped barrel. Currently I have loaded for 95 gr V-max, 100 gr TTSX and 120 gr SMK with great results, in fact I am hitting published velocity for a 24" barrel 1-9 twist while still well under the max load and with great accuracy and I have had Standard Deviations around 3 for several loads I've tried. I will have more precise data after my next trip to the range either tomorrow if time permits or in about two weeks.

8208 has also worked wonders for me in a 24" 22-250 and a 18" 338 RCM. Seems to be pretty temp stable as well looking back at my Winter/Summer results.

 

[LRRPF52]

Yes, 8208 XBR is very temp-stable since it's a fine extruded powder, but it will spike on you around max published loads if you exceed them. Great powder in the .223 as well. I'm enjoying CFE right now.

I took my 16" Grendel out to 1200yds a few weeks ago, and I will probably never build a 20" Grendel after what I saw happen. I figured the little carbine was good to 800yds, but at 4400ft ASL in 80 F temp, I'm still supersonic and at least MOA out to 1200yds in no wind. I've only shot it out to 700yds before that.

 

[svxwilson]

My Precision Firearms 1-8 twists out of a 24" Lilja bbl shoots 123 gr scenars with amazing accuracy. A dime covers 5 shots at 100 yards. My second one from Mark and they were both that accurate. My favorite out of many including my bolts.

I ordered from Mark Feb 1st this year. I am waiting for the Neptune 5 with a Bartlein barrel. I was jus reading a thread slamming him. Glad to hear you have had good results from them. It was a large purchase for me to buy that upper. I paid extra to get a expedited order.