6.5 Grendel Build

[fj40cody]

This is my first time posting and just joined snipers hide. I have just built my first 6.5 Grendel that is pretty much franken-gunned together. I am getting inconsistent accuracy from it. (go figure lol) The barrel was a used barrel that I found. I didn't strip the copper out of it I just cleaned the fouling out before shooting. I shot my 1st 40 rounds today. The groups ranged from apx 2" to two groups being 3/8" (3 shots) I seem to have 2 shots very close and 1 flyer in every group except the two best ones. Could the difference be in the bolt locking to the rear? As I usually only load 3 per mag. however I did load some with more. The gun cycled 100% and function was perfect. These are the parts that I had laying around or could find. And I would have went with some different parts but I have an extremely tight budget. Any thoughts would be a great help

Surplus Arms & Ammo lower
DPMS slick side upper
unknown barrel (most likely J&T / Double star?) 20" 1-9 twist 1/2x36 thread vortex f/h
Bolt from a shop that actually had bolts! Type 2 .136 recess
Rock River bolt carrier
Rock River match trigger
DPMS buffer/tube/spring
Magpul PRS
Weaver 20moa riser & tactical rings
Sightmark 8.5x25x50
free float hand guard
Hornady 123gr SST

 

[user]

Welcome! Lotta good folks here. You'll enjoy it here.
Nice 6.5 G. I experienced the same issue with a really expensive barrel in 6.5 G. Never could get it worked out, so I sold it.

I wish you the best in your quest for accuracy. Take care

 

[fj40cody]

Thank you for your welcome to the Hide!

 

[Strykervet]

Assuming it is the weapon and not the shooter or glass (both of whom I'm not familiar with):

If you don't know which barrel you have, you could be slightly off in the headspacing. There are three ways I know of: unmodified x39 bolts, modified type 1 and modified type 2. What is your twist rate? From my analysis, 120-130gr. bullets are ideal for 1-8.75 twist where 95gr. (VMAX in particular) works best with a 1-12 or 1-13 even. With that said, my best group ever was .33MOA at 100m using 100gr. AMAX handloads, so experimentation is in order to say the least.

Now the last time I talked with Bill (back when arms dealers answered phones, remember that?) he said that in those 1-8.75's he was having the best results using Berger 120's (Pretty sure he said 120).

Also, sort of like with the 6.8SPC, there were a few early chamberings for the Grendel, some better than others? I'm not sure, I've always dealt directly with Bill Alexander and Mr. Satern since '03 or so.

Your best bet is to take that rifle to a gunsmith and just have him measure it out and give it a once over to rule out any measurement issues (headspace, chamber/throat, etc.) since you used unknown parts. Could be nothing, could be .002 off somewhere, but a good smith will find it. Unlike 5.56, nothing is milspec (or any common spec) for the Grendel. So keeping a tight tab on where the parts come from on a build is a good idea when putting together a non-milspec weapon.

Take a closer look at the barrel. Most quality barrels mark 'em. I've never seen a good Grendel barrel unmarked. If you have one of those, it could just be the barrel. It is the most important part of that build by far. If it suffers, well, need I say more?

Good luck, my Grendel turned out to be my favorite AR and my favorite rifle by far. Oh yeah, and welcome!

 

[fj40cody]

Thank you. I sent the barrel out and had it checked for the correct bolt. Also I did tear it apart already and decided to use the best parts that I have. Switched the upper and lower out to rock river now all parts in the upper and lower are rock river except barrel and bolt. I also ordered the Vortex PTS 6-24x50 FFP Mrad today. Very excited to get it in a few days. I was also considering the Sightron SIII 8-32x56 moa2 but went with the pst due to some of the better features. And I really wanted the ffp. Some of it is also me shooting, a good friend of mine was watching me and was correcting my body position behind the rifle and it showed down range for sure. I also have on oreder for a few months now a bolt from A.A. So if and when it shows up Ill eventually get a top notch barrel as well in the future.

 

[meyersa88]

Call up les baer custom and they'll get you a bolt within a week for $87 shipped.

 

[LRRPF52]

Welcome. The thread pattern you listed is an oddball. I'm drawing a blank on who uses 1/2x36.

There are several accuracy-enhancing techniques common to hi-power shooters that work well with the Grendel, mainly loc-titing the gas block with Red Loc-tite, and bedding the barrel extension with Blue Loc-tite.

If your barrel has no markings, it's probably not a SAAMI 6.5 Grendel chamber.

I didn't catch what trigger you are using either. A good trigger will often tighten-up your groups, or at least make it easier to exploit the accuracy potential of your system.

 

[Unknown]

If you assembled the rifle like LRRPF52 suggests, and everything like headspace, scope, rings, mounting, shooter and ammo are squared away, I would suspect the barrel has accuracy issues. If finances permit, gunsmiths like short action customs, or AR15performance can get you squared away. If you are going to buy a new barrel, you could have Les Baer, or Alexander arms, or one of the other fine companies install it for you, thereby removing most doubt about the barrel or it's installation.

 

[Shotplacement]

I was quite interested in this set up to. Good write up though

 

[Strykervet]

Call up les baer custom and they'll get you a bolt within a week for $87 shipped.

I called 'em and they said make sure that the headspace won't be an issue if you use an LBC bolt in a Grendel barrel. There could be a .002 difference and that could or could not make a difference in your barrel I'm told. A set of go, no-go gauges would be nice.

I want to say my bolt that came with the Satern barrel was .136, but I can't remember for certain. This was a couple of years ago at least, just before the LBC when Satern quit making them for awhile. I think the Beowulf I have from '03 is the same.

They did say the extractor should work fine, and those are in production right now and will be ready end of month, middle next month he said. I'll be getting a few of those. Regular AR extractors can work, but they are hell on the brass. I guess some modify them, file them, but I never have.

I've had bolts and extractors only on backorder with AA for six months now, you can't get ahold of them and I guess they are just slammed. They kind of got popular here recently too, and that doesn't help.

 

[meyersa88]

Well I'm making a true .264 LBC with black hole weaponry barrel so that's what worked for me. Although I'm sure a gunsmith could help with that headspace issue on the bolt. I also had an AA bolt on order but gave up after I called LBC and they told me they had them in stock. Works for me because I have an LBC bolt carrier so no at least I can say that matches... Haha

 

[yetigoode2]

Thanks for the write up

 

[PhOnEpHrEaK]

Any idea where to grab a set of go/ no go gauges?