Ultimate Liteweight Precision Grendel Build

[StoneHendge]

If it is not to much trouble, could you give an updated itemized build list of what you ended up with.

Not a problem - I've got the spreadsheet in the office for when it's done.i think with the Faxon CF handguard it was just a tad over 5.4 lbs. And that's with using a buffer tube and Hogue stock I have lying around so I can see how well it balances before I do anything lighter.

[StoneHendge]

Well, the last part was ordered today (had to wait for a business day to call Rainier to use a gift card and be assured that "Standard Shipping" was sent via UPS and not USPS). That was the V Seven Furion Compensator so even if that doesn't make it for the weekend, everything else should.

Final Specs

Ultimate Lightweight Precision Race Carbine.pdf

-Weight could come out of the LPK but the little titanium or lightweight aluminum pieces are pricey! Nonetheless, I did do the V Seven Ultralight Aluminum Castle Nut and Endplate (which are lighter than Ti) and they feel like almost nothing.

- I'm using a carbine buffer tube I had lying around. The 2A lightweight tube would be 0.5 oz lighter for $50

- I'm using a Hogue Carbine Stock I had lying around which weighs 8.7 oz. I really like the Houge stock I have on my 18' Grendel and know it rides a bag well. My choice otherwise would have been the Rogers Super Stoc from Wilson Combat at 7.3 oz which looks like it should also ride a bag well. Smoke Composites is a much lighter option, but riding a bag is a concern for me. We'll see if I change this. I want to make sure the balance is nice so its easiest to use parts I had to check the balance first. The 2A tube and Rogers stock would put it right at 5.25 lbs and just below 6.5 lbs scoped.

- The scope took a lot of soul searching. Ideally, I'd just go with the Nightforce NX8 and be done with it, but I don't have the cash for that now. Everything else is a compromise looking for a 1x low magnification (some are 1.5x), max power of 8x, adjustable turrets, weight and a decent reticle. The Burris XTR II's cover everything but the 1x and weight (they're pigs at 23.5 oz). I stopped at Sportsmans Warehouse Friday and they had the new 1-8x Strike Eagle with the BDC2 reticle (which has 5 & 10 mph marks out to 600) in stock for $399. Since I know I wasn't going to find everything I want for under $1700, I decided the turrets and reticle to 600 only would be the compromise and gave my business to a brick and mortar retailer.

- I'm giving the relatively new Geissele Single Stage Precision M4 Trigger a try. Haven't heard anyone talk about it. But I wanted a single stage for this build, I love my SSA-E's and this has a 3.5 lb pull just like the total on the SSA-E's. Plus I ordered it direct at the start of the Memorial Day Sale which means I get another hat. I already have a black one and a tan one. I wonder if they'll send me a camo hat

If Rainier gets the comp out today, I should have everything by the weekend. That of course assumes that they USPS doesn't lose the package with the handguard and LPK that I ordered from Brownells 11 days ago. It finally made it to the local PO this afternoon, but this is where it gets tough for them.

[StoneHendge]

I don't think I'd be going out on a limb stating that BSF makes a pretty accurate barrel! Still waiting on the compensator so these were shot with a thread protector hand tightened on 2 crush washers (without crushing). I checked it a number of times this afternoon and had to retighten it a few times. Scope is the new Vortex 1-8 Strike Eagle with AR BDC2 reticle. The 1 MOA center dot and no cross hairs don't make it the best for shooting groups.

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Load below was developed for my 20" 1:9 BHW barrel: 55 gr NBTV over 24.6 gr Benchmark in a Norma case with GM205MAR. Shot off of Stu Bag in front and Baseline bag in rear at 100 yards at 8x. I stopped the first one after 3 shots so as to not namesake it. 2nd group is 5 shots.


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The first measurements tad over 0.3" and the second a tad over 0.75". The MOA center dot in the reticle is bigger than the 2nd group. Wacky thing is 5 shot average velocity was 3075 with sd 7 es 18. Right about what I get out of the 20" BHW. Looks like i've got a short range / varminting / defense load already worked up! Should also be an interesting exercise in twist rates seeing how the accuracy holds up at range (it holds 1/2 MOA out to 550 in the BHW). Also going to print up some targets with a 1 MOA center circle.

Also shot two five shot groups with factory 40 gr Nosler BTV ammo and they were both right around MOA.

So BSF gets a thumbs up in the accuracy department. Some heat testing is also on the agenda in the near future.

[StoneHendge]

The UPSperson commenth bearing titanium muzzle brake and behold!

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About 5.25 lbs unscoped, 6.6 as pictured. The tactical scope probably isn't going to work on it for me and I probably will go in the direction of swapping between a 1x and the 16 oz 2.5-10x32 Vortex HS LR with XLR reticle that currently resides on my 20" BHW (that will probably get a little more magnification). Next range session (hopefully tomorrow) will include dismounting and remounting (rinse and repeat) the Vortex Venom red dot on my 300 BLK and seeing if the zero holds. The sight and mount weigh in around 3.3 oz. Otherwise I might look into the Trijicon MRO on a Geissele Super Precision Mount.

Now this could easily be an under 5lb Grendel:

- The CMC LPK actually weighed in 1/2 oz lighter than estimated and I used anti walk pins instead of anti-rotation pins. Using V Seven Ultralight Mag Release, pivot pins, bolt catch and safety selector would save an ounce. So there's 1.5 oz.

- 1/2 oz with 2A Arms buffer tube; 1.5 oz with Rogers stock from Wilson Combat. If one wanted to sacrifice rear bag support, a couple more oz could be found with a CF stock.

- Substitute one of the 18" BSF Grendel barrels that Rainier is blowing out the door for $299 and there's another oz (6.5mm tube iso 5.56).

Wallah! Under 5 lbs unscoped and thoroughly capable of going the distance.

But what's thoroughly crazy is that you can get a 25.9 oz fluted 18" Grrrrrr barrel direct from BSF for 600 clams. I think those are 0.875 at the gas block which opens some lighter weight GB options. But that's 4.2 oz lighter than my 223 barrel, so adding the 3.5 oz above, it would be at about 4.75 lbs. Add the Vortex 2.5-10x32 on the Aero Ultralight mounts and it's a 6 lb 1000 yard pluser. Who knows - that may happen down the road as I have a 556 blasting carbine that's quality parts that could provide a home for this 223 barrel..........

As a side note, my guess is BSF is blowing out the grendel barrels because BSF is moving to 0.875 vs 0.936. There aren't any lightweight non CF lightweight handguard options that would allow a covered .936 AGB. The set screw GB I'm using just barely fits under the Faxon rail since, although it has a 1.7" ID, the barrel is higher on the handguards axis, so there is more room below the barrel than above. There is room for a clamp on non adjustable if I find one (along with the motivation to install a gas tube roll pin and align a new block).

[Sticks]

Nice work.

[fixin]

Very nice!! The photo looks awesome and it is nice knowing the .223 barrel is shooting well. I am loving how everything turned out on your build. How has the strike eagle 1-8 been working out? Aside from the dot being a little large. I am getting a wild hair to possibly attempt another BSF build but with an emphasis on hunting application rather than a do-it-all gun. I know I could go with a 16in barrel from another company, however at this rate why bother. My somewhat local gunshop (local being 2 1/2 hours away) just became a licensed dealer for BSF, so now I have a physical place to order from/go to for the barrels . Which makes my life that much more difficult, because as y'all say, grendels multiply fast.

[StoneHendge]

Fixin, the jury's still out on the Strike Eagle. I'm between swapping between a Vortex Venom 3 MOA red dot on a Samson QR mount and the 2.5-10 Vortex HS LR on Geissele mounts, keeping it or saving up for an upgrade (but even the $1700 Nightforce NX8 has its shortcomings). There simply isn't an optic that can do it all (or at least as much as this build can). Once I have a load together, I'll see how the reticle does with it at range. I have a Venom on my 300 BLK carbine and did a test yesterday to see if dismounting and remounting (which is real easy with their brilliant design). Shot a group of 5, then dismounted and remounted 5 times. This is no magnification at 50 yards. I think its pretty safe to say it gets close enough - its hard to get see through the bad shots (not easy supporting a MFT Minimalist rear stock and front with full pistol grip with flashlight). The zero is a tad low and a tad left - adjustments are in MOA increments so that's as close as I could get it and the low helps a 50/200 zero a bit and I chose left to account for spin drift. It's hard to see, but the middle target on the bottom has three through one hole right where it was zero'd

Venom Return to Zero.jpg

After those, I dismounted and remounted and managed to get 4 of 5 on a life size steel coyote at 200 yards. It sure is light at 3.8 oz including the mount and fits easily in a front pocket if removed. The Geissele Super Precision mount has two 1/2" nuts that hold it down, so a simple combination wrench can do the trick (maybe I can get a Ti one if I ever have a spare C Note lying around ). It will also hold zero if its handtightened on, so a switch really would be fast and easy.

Did a ladder of 77 gr NCCs and XBR yesterday. Like my Proof CF barrel, there was nothing that was really bad, so the CF is definitely doing its dampening job. Since this will be a high volume shooter, I did the development with a CM drop only (trickled onto the CM as opposed to weighing a charge light on the CM and then trickling onto a balance beam). The below had velocity of 2674 (about as fast as you could hope for with a 77 in an 18"), SD 4 and ES 13. The outlier was not a StoneHendge. I was shooting my other 223 with an SSA-E on it just prior to this group and I totally jerked the first shot forgetting I was switching to a single stage.

Rubin 77 NCC XBR.jpg

I made 50 up last night and hope to test them tomorrow. If it works, the load isn't starting to transition until past 900 in my parts. I also didn't realize until I got home last night that I could turn on the optic and have the 1 MOA center dot be red which would allow me to center it a little better on the 1 MOA center dot on the target.

My initial thoughts on a few of the pieces in the build I haven't seen anyone talk about:

V Seven Furion Ti Compensator (1.6 oz). This is a very good if not excellent comp. I shot the rifle with just a thread protector before I got it and it does its job. Not as good with recoil or muzzle movement as a VG6 Epsilon, but there really aren't any options for a bull barrel comp that weigh under a quarter pound. If the barrel was a 0.750, I'd probably "spend" the ounce for an Epsilon (or hope they do another special run of Ti Epsilons), but I'm satisfied so far. The Furion does seem to minimize muzzle movement more than recoil. Its an excellent choice if you have a bull barrel and don't want to screw 4-8 ounces onto the end of it.

Geissele SSP M4. "Single Stage Precision" with 3.5 lb pull. This will take some mental adjustment (see above!), but I wanted this to be a single stage, I love my SSA-Es and this has the same total pull. Incredibly short reset. I have a 3.5 lb Timney on my 300 BLK carbine and a 3.5-4 lb CMC on my 300 BLK pistol and although I like those, they aren't in the same league. I won't mention what it makes annoying on a Timney or CMC because if it doesn't annoy you now, it will if I point it out. Like anything Geissele, they're expensive, but like fine Burgundy, they're worth it. Luckily they go on sale a few times a year.

Taccom Carbine Buffers (1.1 oz) and TTI Ulitmate Lightweight Carbine Buffer Spring (10% reduced power). This set up with the Ti BCG rocks. The Taccom light rifle buffer and spring rocks on my other 223, but its Sproing City on that build which has a full mass BCG. Most of the sproing on the other rifle comes after return to battery, so I think the force of the return with a full mass carrier results in the spring/buffers bouncing around in the tube after the return. With the 6 oz Ti carrier, the set up makes nary a peep. Although Taccom makes a point to say they have not "tested" the system with Ti carriers on their website, once I got the gas set, I haven't had a feeding or ejection problem that wasn't carrier induced (see below) after at least 150 rounds. I probably have close to 500 on the rifle set up on my other 223 with nary a problem.

2A Arms Adjustable Ti Carrier. Works great except for one potentially major detail. The lock screw that holds down the rotating (hence adjusting) gate has come loose twice. As a result, the gate rotates and will ultimately end up in a spot with too little gas. The little torx wrench that came with it (and which fits very nicely in a grip with storage) might be a little stripped and that could be the problem. I'm going to try a different wrench before calling them, but I'm starting to question how they would expect the screw to stay tight given the movement of a BCG. There may be a semi permanent solution using something to bond it down once I have my load dialed in, but I would want to make sure I can get an extra gate and screw from them before going that route. The little gate and screw get exposed to a lot of heat, so I really don't know what would work.

[StoneHendge]

How could I forget the Faxon 15" 8 oz carbon fiber handguard!

So far so good. Comes with and uses standard GI barrel nut and you can shave about 1/2 oz off if you want to splurge on a Ti nut. Easy to install and remove and put back on after you misalign your gas block. My non adjustable 0.936 block just clears it; my guess is at least the Odin 0.936" ABG would fit. It's a "normal" diameter, so if you don't have hands like a basketball player, it's easy to hold offhand, hold with your sling wrapped around your wrist and also steady with your left hand on barriers, etc. It also isn't round - a whole bunch of little flat areas which could help shooting off of flat barriers.

The only downside is probably endemic to most cf handguards. CF is an insulator, so the carbon fiber does insulate around the barrel nut. This sends heat back into the receivers and presumably down the barrel. Rapid fire might end up wearing out your barrels throat a little faster and I guess it might heat up ammo in the chamber a bit more. I certainly don't plan on doing a lot of gratuitous mag dumps with this build so it's not a huge deal, but worth noting since mag dumps might get it pretty toasty in the chamber/throat area.

[Sticks]

Leopold or Nikon makes a 1-? variable firedot that has a daylight visible illuminated reticle. Gets a lot of high praises.

Glad to see your project is working as planned.

[StoneHendge]

Bad day for StoneHendge. Being all excited to zero his new Leupold VX6-HD 2-12, he arrives at the range only to see he grabbed 6x45 ammo instead of the 223 he made last night (yes, he grabbed the wrong box even though uses different colored ammo boxes for 223 and 6x45). No worries, take the S'more to 900 and 1k reliably on the first calm wind day in a month (only 10-15 mph but steady). Get back on the saddle of the 6mm Grrrrrr after 2 months only to have it blow up in your face for the second time. Roll with it, drive home and mentally allocate salvageable parts along the way, walk the dog, have lunch, grab the ammo and head back down.

Two shots at 25, one at 50 and the 3rd shot at 100 has the windage perfect and 1/4" high. Start shooting groups and things get wonky. I'm pretty much convinced I either have a mount problem or a scope problem. Shots are moving around considerably. Chasing the zero with adjustments helps and then doesn't. I'm getting ready to pack up and start thinking about which mount to use next trip down to isolate the issue. I share my targets with the caretaker and he noticed the pattern. The barrel has cooled off and i decide to load up a ten round mag and quickly shoot 2 groups. These were done pretty quickly to try and keep the pace up. After groups 1&2 I decided to keep the barrel warm, quickly loaded another mag and shot at the center line 3" above the bullseye for groups 3&4. As you can see, group 2 moved low and then as things really started to get warm, there was a significant shift low and left. The last 2 shots of group 4 were off the paper.

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I let the barrel cool, had some fun with my 6x45, put up 5 targets and loaded up a 30 round mag. These were shot as quickly as possible but I did have a solid and stable position for each shot. The zero was back where it belonged for the first group.

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Things really started to go south after 7 shots. Shots 16-20 didn't even get on paper (aside from the one shot that got on group 3's target!).

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For group 5 , I shot at the upper right hand corner.

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Yes folks, 5 shots grouped over 8" from zero at 100 yards. How 3 were touching, I'll never know! Maybe it wasn't possible to get the chamber/barrel any hotter.

I'm really hoping this is the cf handguard insulating the barrel nut and chamber at work. I find it hard to believe that a barrel company dedicated to ARs could last even a week if this is how their product performs under rapid fire. I also hope it's the handguard since I bought it from Brownells so I can easily just ship it back! And I'm going to have to eat a lot of crow for prior praiseif it is the barrel.

In the meantime, I withdraw any comments I might have made about BSF barrels until further notice. Next step is to put the handguard on another rifle and put an aluminum handguard on the BSF and see how it goes.

This also explains why I was having a hard time with the Strike Eagle 1-8 BDC 2 reticle. Kind of hard to find your holdover spots when your zero moves over 8 MOA as things heat up! When I shoot steel at 350-550 I use 10 round mags, but use a quick pace. 8 MOA is almost 4 feet at 550. On a positive note, I'm liking the Leupold.

[Sticks]

Might be that the CF barrel is strictly for slow precision fire.

How hard have you run your Smore? Wondering of Proof CF barrels have the same issue.

[bj139]

My recent Howa thread with American Gunner showed the same shift with heating although not as severe.

How about a thermometer on your barrel and a POI shift table?

[StoneHendge]

Might be that the CF barrel is strictly for slow precision fire.

How hard have you run your Smore? Wondering of Proof CF barrels have the same issue.

Ive run 10 round mags pretty fast. Proof's don't have an issue and they actually cool faster than my JP Grendel with radiator fins. Had it out in the morning and had no issues and never have. Christenson's do experience thermal drift, but nothing close the > 8 MOA.

It's got to be the handguard. All of this insulation pressed up against and torqued down onto the barrel nut. Instead of chamber heat passing through the barrel nut into an aluminum handguard where it can be dissipated, the heat has no where to go. Some will travel into the upper receiver but most will likely try to escape by going up the barrel.

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I may just send it back. I don't see any wisdom in proving my theory by overheating and scorching the throat of another barrel...... After the 25 shots above, the handguard on top of the barrel nut was barely warm.

[Sticks]

Ive run 10 round mags pretty fast. Proof's don't have an issue and they actually cool faster than my JP Grendel with radiator fins. Had it out in the morning and had no issues and never have. Christenson's do experience thermal drift, but nothing close the > 8 MOA.

It's got to be the handguard. All of this insulation pressed up against and torqued down onto the barrel nut. Instead of chamber heat passing through the barrel nut into an aluminum handguard where it can be dissipated, the heat has no where to go. Some will travel into the upper receiver but most will likely try to escape by going up the barrel.

[ATTACH=CONFIG]12088[/ATTACH]

I may just send it back. I don't see any wisdom in proving my theory by overheating and scorching the throat of another barrel...... After the 25 shots above, the handguard on top of the barrel nut was barely warm.

Wanna trade? I have a 12" Centurion C4 rail on my middy.

[StoneHendge]

Wanna trade? I have a 12" Centurion C4 rail on my middy.

I think I'm going to give one of the V Sevens a whirl. Brownells has some in stock so I could do a wash with sending the Faxon back and probably get one or 2 of the parts I need for the pistol. But you don't want it. U can even see above that the center for the second 3 shots moved down from the first 5. Don't be melting a Bartlein or Lilja!