Bullet keyhole / tumbling problem...BHW barrel???

[Tailgate]

Folks, I'm very frustrated with my Grendel build. Finished building it in February of this year, but haven't had a lot of time to shoot it. Range trips have been somewhat disappointing due to horrible groups, which culminated in today's trip, in which the bullets were keyholing into the target. Now, I'm no master AR builder, but I'm also not a novice at gun work. I made sure everything, especially the handguard was torqued to spec. And now I'm beginning to wonder if it's the barrel itself.

Here are the upper specs:

Upper DPMS heavy / competition low profile
Black Hole Weaponry 16” mid length 264LBC barrel, 1:9 twist
Vortex flash suppressor (did have an A2 at one point)
Spike’s Tactical BCG
Les Baer Bolt assembly (264LBC)
Clark Custom Free Float tube - carbon fiber
DPMS mid length gas tube
JP Enterprises SS railed gas block adj. (clamp, not set screws)

Total rounds so far have been 68. Here's the timeline of events:

Trip #1: First 20 rounds were Wolf Gold 120gr Copper MPT, in which I was adjusting the gas block and sighting in the scope, no flash hider on it. Was also doing a barrel break-in procedure of cleaning after every round. Best 5-round group was maybe 3 inches at 100 yds. Not good. But, bullets were going in normally.

Trip #2: Next 20 rounds (21-40) were also Wolf Gold 120gr MPT, but had put on a A2 flash hider. Groups were very inconsistent, and rounds were scattered in random 5-7 inch groups at 100 yds.

Trip #3: Next 20 rounds (41-60) again Wolf Gold 120gr MPT, but I replaced the A2 with a Vortex flash hider, thinking that maybe the A2 was binding on the barrel in a weird way, whereas the Vortex you just hand-tighten on. No better shots, scattered groups. Again, all Wolf ammo had gone into the targets "normally."

Now I'm thinking, "Man, this Wolf ammo sure is crap, even though the Gold 120 MPT are supposed to be decent according to the guys at 6.5 Grendel Forums ," and I switched over to Alexander Arms 123 gr. ammo with the Lapua brass, etc. The first 3 rounds (61-63) were scattered, and in retrospect, they were keyholing. The reason why I didn't pay as much attention to the keyholing at that time was because I starting thinking it may be scope I was using, and I was ticked-off at the way the rifle was shooting. It was an older Leupold 3x9 that had recently been completely rebuilt by Leupold including all but rear lens and replacement of all internals (why they didn't REPLACE the scope altogether, I'll never know, since pretty much all of it was replaced with new stuff plus labor...but I digress).

Trip #4: Today's 5 rounds (64 - 68) I put on a different "known" scope, torqued to spec, and put the target at 50 yards. Put in the AA 123 gr. ammo, and the group was approx 3 inches at 50 yards. They went in sideways, no doubt about it.

So, as you can see...I'm quite frustrated. What do you think it is? In summation, the groups were never that great regardless of flashiders (none, A2, or Vortex), two different scopes, two different decently-rated factory ammos. Could there be something wrong with the gas block? I wouldn't think so, it's clamped on and adjusted well. The handguard is on very tight, and should be keeping that barrel rock-solid. The gas tube is not touching anything unnecessarily on it's journey to the BCG. I have not seen any indication that the bullets are striking the flash suppressors, and in fact, they are all .30 cal flash suppressors, so there's a bit extra room.

Is it possible it's my barrel? I would think the Blackhole Weaponry 1:9 barrel would be much, much better than this performance, and I don't think the twist rate is out-of-spec for the grain bullets I'm shooting. I don't want to accuse the BHW barrel if there is something else causing this, so I'd rather troubleshoot other potential causes first.

Help me!!!!

[ricsmall]

you might have the land/groove dimensions checked by a gunsmith to be sure the bore is right. I know its a long shot, but that would be the first thing I checked. Hope you get it worked out.

Richard

[LR1955]

Folks, I'm very frustrated with my Grendel build. Finished building it in February of this year, but haven't had a lot of time to shoot it. Range trips have been somewhat disappointing due to horrible groups, which culminated in today's trip, in which the bullets were keyholing into the target. Now, I'm no master AR builder, but I'm also not a novice at gun work. I made sure everything, especially the handguard was torqued to spec. And now I'm beginning to wonder if it's the barrel itself.

Here are the upper specs:

Upper DPMS heavy / competition low profile
Black Hole Weaponry 16” mid length 264LBC barrel, 1:9 twist
Vortex flash suppressor (did have an A2 at one point)
Spike’s Tactical BCG
Les Baer Bolt assembly (264LBC)
Clark Custom Free Float tube - carbon fiber
DPMS mid length gas tube
JP Enterprises SS railed gas block adj. (clamp, not set screws)

Total rounds so far have been 68. Here's the timeline of events:

Trip #1: First 20 rounds were Wolf Gold 120gr Copper MPT, in which I was adjusting the gas block and sighting in the scope, no flash hider on it. Best 5-round group was maybe 3 inches at 100 yds. Not good. But, bullets were going in normally.

Trip #2: Next 20 rounds (21-40) were also Wolf Gold 120gr MPT, but had put on a A2 flash hider. Groups were very inconsistent, and rounds were scattered in random 5-7 inch groups at 100 yds.

Trip #3: Next 20 rounds (41-60) again Wolf Gold 120gr MPT, but I replaced the A2 with a Vortex flash hider, thinking that maybe the A2 was binding on the barrel in a weird way, whereas the Vortex you just hand-tighten on. No better shots, scattered groups. Again, all Wolf ammo had gone into the targets "normally."

Now I'm thinking, "Man, this Wolf ammo sure is crap, even though the Gold 120 MPT are supposed to be decent according to the guys at 6.5 Grendel Forums ," and I switched over to Alexander Arms 123 gr. ammo with the Lapua brass, etc. The first 3 rounds (61-63) were scattered, and in retrospect, they were keyholing. The reason why I didn't pay as much attention to the keyholing at that time was because I starting thinking it may be scope I was using, and I was ticked-off at the way the rifle was shooting. It was an older Leupold 3x9 that had recently been completely rebuilt by Leupold including all but rear lens and replacement of all internals (why they didn't REPLACE the scope altogether, I'll never know, since pretty much all of it was replaced with new stuff plus labor...but I digress).

Trip #4: Today's 5 rounds (64 - 68) I put on a different "known" scope, torqued to spec, and put the target at 50 yards. Put in the AA 123 gr. ammo, and the group was approx 3 inches at 50 yards. They went in sideways, no doubt about it.

So, as you can see...I'm quite frustrated. What do you think it is? In summation, the groups were never that great regardless of flashiders (none, A2, or Vortex), two different scopes, two different decently-rated factory ammos. Could there be something wrong with the gas block? I wouldn't think so, it's clamped on and adjusted well. The handguard is on very tight, and should be keeping that barrel rock-solid. The gas tube is not touching anything unnecessarily on it's journey to the BCG. I have not seen any indication that the bullets are striking the flash suppressors, and in fact, they are all .30 cal flash suppressors, so there's a bit extra room.

Is it possible it's my barrel? I would think the Blackhole Weaponry 1:9 barrel would be much, much better than this performance, and I don't think the twist rate is out-of-spec for the grain bullets I'm shooting. I don't want to accuse the BHW barrel if there is something else causing this, so I'd rather troubleshoot other potential causes first.

Help me!!!!

TG:

Everything indicates something is wrong with the barrel. They may have given you something much slower.

Hopefully they will take the barrel back and test it for twist rate.

LR1955

[Drifter]

Was bolt matched to barrel? I think BHW has made barrels headspaced two different ways: standard (Type 1), and Grendel-type recessed (Type 2).

Did you clean the barrel after the first 60 rounds of Wolf?

FWIW, I had a BHW 1:9 barrel that shot very well. You might also try measuring the twist with a cleaning rod and patch to verify that the twist is indeed 1:9. Seems like your bullets are unstable.

[txgunner00]

Have you looked at the crown? A ding in it could case some accuracy problems. Problem as bad as as you are describing are usually either incorrect twist rate or bore as Rick & LR1955 said.

[Tailgate]

Was bolt matched to barrel? I think BHW has made barrels headspaced two different ways: standard (Type 1), and Grendel-type recessed (Type 2).

Did you clean the barrel after the first 60 rounds of Wolf?

FWIW, I had a BHW 1:9 barrel that shot very well. You might also try measuring the twist with a cleaning rod and patch to verify that the twist is indeed 1:9. Seems like your bullets are unstable.

As for cleaning, I did after every round for first 20, then after every 5 rounds for the remaining 48 rounds.

As for the crown, I've not noticed any dings...and just checked it with a flashlight (again, my flash hider is .30, so a bit larger than the muzzle crown edge), looks sharp and clean all around.

UPDATE: Well, after looking at my invoices, there is no indication if either the barrel or the bolt was a "Type 1" or "Type 2," and frankly, now I can't remember. I want to say they were both Type 2, but at this point, I'm not sure.

The "good news" is that the barrel is indeed 1:9 when I tested it with a patch and rod. Right on the money, in fact. So, "now what???"

[Lead Chucker]

Iv read on other forums that BHW barrels are kinda hit & miss weather you get a shooter or a tomato stake. I would contact them & let them know what the barrel is doing & see what they say. Hopefully they will help you & make it right. I dont believe everything i read on the net, but i read alot of it. It does sound like a bad barrel to me, just my opinion. Anyway, good luck.

[LRRPF52]

I think this is the first time I've heard of a new barrel grouping like that and key-holing on this forum. That barrel is whacked. Maybe it's a .277" bore? I also noticed the thread started out with:

Folks, I'm very frustrated with my Grendel build.

I think it would be a good idea to be specific about what type of barrel it is right off the bat to help out more, which you clarified later on in the post. I have seen a lot of trouble-shooting and problem threads start out described as a "Grendel", only to later learn that the chamber is of unknown dimensions, unknown maker, and of course not a Grendel.

At least we have an identifiable company who will take care of this, as they seem to be responsive to problems in the past.

[LR1955]

As for cleaning, I did after every round for first 20, then after every 5 rounds for the remaining 48 rounds.

As for the crown, I've not noticed any dings...and just checked it with a flashlight (again, my flash hider is .30, so a bit larger than the muzzle crown edge), looks sharp and clean all around.

UPDATE: Well, after looking at my invoices, there is no indication if either the barrel or the bolt was a "Type 1" or "Type 2," and frankly, now I can't remember. I want to say they were both Type 2, but at this point, I'm not sure.

The "good news" is that the barrel is indeed 1:9 when I tested it with a patch and rod. Right on the money, in fact. So, "now what???"

TG:

That is because there is no such thing as 'Type 1' or 'Type 2'. You can find two types of Grendel chambers because one is cut for a 7.62 X 39 bolt and the other is cut based on a 7.62 X 39 bolt with the bolt face recessed another .011 (?) inches. The only difference is the depth of the chamber, not anything else. And, brass fired out of one, when resized using a decent sizing die, will shoot just fine out of the other. And, if the barrel / bolt combination is called a 'Grendel', it uses the deeper bolt face. The only company I know of that will use a chamber cut for the 7.62 X 39 bolt is Lothar Walther if the customer wants one. And, if such a bolt is used, LW is very clear that he is using a 7.62 X 39 bolt and a chamber cut a bit deeper than for a Grendel bolt.

If you had a true 7.62 X 39 bolt but with a chamber cut for the 'Grendel' (deeper) bolt face, your brass would not chamber. Or if you had a true 'Grendel' bolt, and used a chamber cut for the 7.62 X 39 bolt face, the brass would chamber and shoot but it would be stretched on the shoulder rather dramatically. Enough for you to tell the difference. However, that would have nothing to do with keyholing.

LRP52 may be on to something with his .277 bore hypothesis.

Either way, you won't get it to shoot by cleaning it. If it is keyholing, cleaning it won't do anything but waste your time and money.

Too bad because now you will most likely go through a huge problem.

LR1955

[kamrr4437]

Definately would be a barrel problem. Its not stabalizing the bullet and for it to be only at 50 yards thats just horrible. I would disassemble and send it back, and wouldnt take no for an answer. barrel exchange or money back. would be a fix in my eyes. Theres no reason a 1 and 9 twist shouldnt be stabalizing those rounds. Mine is a 1 and 8.75 twist. Its not your build man its your barrel.

[txgunner00]

I think this is the first time I've heard of a new barrel grouping like that and key-holing on this forum. That barrel is whacked. Maybe it's a .277" bore? I ...st.

That was my initial thought. A new barrel of the proper bore shouldn't be keyholeing unless there are obvious flaws in the machining.

[Drifter]

...there is no such thing as 'Type 1' or 'Type 2'. You can find two types of Grendel chambers because one is cut for a 7.62 X 39 bolt and the other is cut based on a 7.62 X 39 bolt with the bolt face recessed another .011 (?) inches. The only difference is the depth of the chamber, not anything else.

BHW has cut 264 LBC chambers two different ways, just as you describe. Whether correctly or not, BHW refers to the bolts as Type 1 and Type 2.

Here's a vid posted by BHW:

http://www.youtube.com/watch?v=DZncepUMgBg

It seemed worth mentioning since the OP has a BHW barrel, but I agree that the bolt is likely unrelated to the keyhole results.

[bugboy]

Talk to BHW tomorrow. My experience is that they will make it right.

[just_john]

Might also look to see if the bore of the A2 is concentric with the barrel bore. That would give the described results.

[Tailgate]

Quick Update:

I removed the flash suppressor and confirmed the muzzle / crown is still perfect. I then mic'd a round to confirm it was .266, and stuck in gently into the muzzle to make sure it didn't slip in (i.e. a .277 bore)...it was tight, and wouldn't get close to going in.

I also double-checked the bolt assembly / chamber fit. I took out the BCG, and removed firing pin and bolt assembly. I inserted a factory round into the chamber, then placed the bolt assembly on top. It locked-in solidly, with no wiggle room, no spinning, etc. Therefore, I think everything's good to go there. I haven't had any functioning problems apart from getting the gas block adjusted properly at first to eject rounds reliably.

So, hopefully I'll get an email response from BHW tomorrow (doubt I'll have time to call them tomorrow). I hate taking this thing apart because of the way the handguard is designed...but, I'm 99% convinced it's the barrel.