123 Amax accuracy issues

[rabiddawg]

With a gas gun, the bolt locking back after shooting the last round in the mag interrupts the cycle of function and will throw off that round. That is why if your going to shoot 5 rounds, load 6. If your going to shoot 3 rounds load 4.

After some scientific research (Google)I am going to disagree with you.

If I am understanding you correctly you are saying that the bullet is still in the barrel when the bolt carrier locks back on an empty mag. The slow motion videos I just watched shows the bullet is gone from the barrel before the bolt even moves.

[molar]

How good are you at calling your shots?

Also, what did you expect? Guys will write here describing their very best groups and it is easy for someone to believe that the name Grendel alone will result in half minute or less accuracy. Facts are that very few barrels and loads will shoot a Grendel or anything else for that matter out of a gas gun consistently, dependably, and on demand under 3/4 of a minute. I mean 3/4 MOA is the biggest group, not the mean group. If your Grendel consistently holds 3/4 minute, you have a pretty damn good combination of ammo, rifle, sighting system, position, and you since you are the one pointing the barrel and pulling the trigger. If your mean group is 1/2 minute, you got lucky with the barrel, load, gas system, bolt, and who knows what else. Most people can't hold 1/2 minute consistently so don't sweat it just yet.

earl39 has some sound advice that you may want to try before getting rid of a barrel and or chasing your tail. I would go with four each five shot groups, each group shot in no more than 15 seconds with a solid focus on holding the sight picture through every single shot. Or you can go with two each ten shot groups fired with a focus on the same thing. Might as well try. However, if you go into the test thinking that one shot will be out, you will probably put one shot out. Thats why I asked if you could call your shots. If you are real good at that task, when a shot goes out, you know it instantly, dump it instantly, and will be able to get your focus on holding the sight picture through the rest of your shots in that string.

Advice is cheap, ammo isn't. Barrels are even more expensive so be sure before dumping a barrel is my advice.

LR55

Honestly, I would be happy with 3/4 MOA. The barrel in question is a 6.5 ARP. I've seen plenty of 0.5 MOA groups shot with both 6.5 and 6.8 ARP barrels.

Maybe I've been lucky, but all of my other AR barrels seem to shoot better than this one, with the exception of a 458 Socom barrel.

My 20" Shilen 6.5 Grendel will reliably hold 0.5 MOA with factory 123 SST's or AMAX. I gave up on getting the factory hornady rounds to group in the ARP barrel. 2" is about the norm
A 20" Wilson 223 wylde varmint barrel shoots 1/2 moa with 24.0 gr varget and 77 smk and my 16" Sabre defense carbine will shoot 3/4 moa with that same load
A daniel defense 16" CHF 300 blackout barrel I have will hold 3/4 MOA with speer tnt's.

Maybe I have unrealistic expectations for this barrel based on my previous experiences.

I will take it back out in the next few weeks and do more testing with 28.5 8028 and 31.5 CFE 223. I also have some 107 and 120 SMK's on the way. I believe I read here that the 120 SMK was potentially the most accurate bullet for the Grendel and that the 123 AMAX did not shoot well in all chambers due to the ogive design if I remember correctly.

[Klem]

Could be neck tension, permitting bullets to shift forward to the lands from the inertia of being auto-loaded.

The difference between an aggregate group plus one flyer could be either the majority touching lands and one off the lands or the other way round. The solution here is deeper seating and/or tighter neck tension.

To eliminate this possibility you could try seating the rounds deeper. Even though the jump will be longer there's less chance of bullets shifting forward into the lands.

Agree with rabbid', the bullet is long gone before last round lock-back affects anything.

Agree also with 55'. We see more of posters best groups here than we do everyone's average groups. If you summed all the group photos you'd be forgiven for thinking this is a wonder calibre. Let's face it, to post an average group without asking for help risks others thinking less of you. Shooters are tempted to conflate their ability to group with their worth and status as a shooter. 0.75-1MOA for 4rd groups from a bench rest on a still day from this platform is about normal in my experience.

[molar]

Could be neck tension, permitting bullets to shift forward to the lands from the inertia of being auto-loaded.

The difference between an aggregate group plus one flyer could be either the majority touching lands and one off the lands or the other way round. The solution here is deeper seating and/or tighter neck tension.

To eliminate this possibility you could try seating the rounds deeper. Even though the jump will be longer there's less chance of bullets shifting forward into the lands.

Agree with rabbid', the bullet is long gone before last round lock-back affects anything.

Agree also with 55'. We see more of posters best groups here than we do everyone's average groups. If you summed all the group photos you'd be forgiven for thinking this is a wonder calibre. Let's face it, to post an average group without asking for help risks others thinking less of you. Shooters are tempted to conflate their ability to group with their worth and status as a shooter. 0.75-1MOA for 4rd groups from a bench rest on a still day from this platform is about normal in my experience.

Neck tension appears to be good.

My OAL is 2.245, so I should be off the lands a bit. I will measure distance to the lands tonight when I have time

[SG4247]

How do you figure neck tension is good?

[terrywick4]

+1

After some scientific research (Google)I am going to disagree with you.

If I am understanding you correctly you are saying that the bullet is still in the barrel when the bolt carrier locks back on an empty mag. The slow motion videos I just watched shows the bullet is gone from the barrel before the bolt even moves.

[LR1955]

Honestly, I would be happy with 3/4 MOA. The barrel in question is a 6.5 ARP. I've seen plenty of 0.5 MOA groups shot with both 6.5 and 6.8 ARP barrels.

Maybe I've been lucky, but all of my other AR barrels seem to shoot better than this one, with the exception of a 458 Socom barrel.

My 20" Shilen 6.5 Grendel will reliably hold 0.5 MOA with factory 123 SST's or AMAX. I gave up on getting the factory hornady rounds to group in the ARP barrel. 2" is about the norm
A 20" Wilson 223 wylde varmint barrel shoots 1/2 moa with 24.0 gr varget and 77 smk and my 16" Sabre defense carbine will shoot 3/4 moa with that same load
A daniel defense 16" CHF 300 blackout barrel I have will hold 3/4 MOA with speer tnt's.

Maybe I have unrealistic expectations for this barrel based on my previous experiences.

I will take it back out in the next few weeks and do more testing with 28.5 8028 and 31.5 CFE 223. I also have some 107 and 120 SMK's on the way. I believe I read here that the 120 SMK was potentially the most accurate bullet for the Grendel and that the 123 AMAX did not shoot well in all chambers due to the ogive design if I remember correctly.

molar:

Honestly, your groups don't really show any signs the barrel sucks. Not the best in the world but not the worse either. I see something that can probably be tuned.

You didn't say if you could call your shots well. If you can, you would know very quickly if the barrel and or load or both were not going to make it. If I had shot those groups I probably would be skeptical but not yet ready to drop a couple hundred more on a barrel. However, I have no idea who makes an ARP barrel. Doesn't sound like a high end maker but maybe another 'AR Stoner' type of product.

I am the proponent of the 120 Sierra as kind of a test bed for performance. Not only with a Grendel though, with any 6.5. It is not a hybrid, not a VLD, so its numbers are not as impressive as other 'modern' 6.5 bullets. However, it is very forgiving in terms of loads, neck tension, and jump. Seems like about any reasonable load will shoot very well with this bullet. I will not say the same for the 107 Sierra. We have had problems with this bullet in the past and it seems it either shoots very well or not at all with a Grendel.

Good luck with your testing!

LR1955

[molar]

molar:

Honestly, your groups don't really show any signs the barrel sucks. Not the best in the world but not the worse either. I see something that can probably be tuned.

You didn't say if you could call your shots well. If you can, you would know very quickly if the barrel and or load or both were not going to make it. If I had shot those groups I probably would be skeptical but not yet ready to drop a couple hundred more on a barrel. However, I have no idea who makes an ARP barrel. Doesn't sound like a high end maker but maybe another 'AR Stoner' type of product.

I am the proponent of the 120 Sierra as kind of a test bed for performance. Not only with a Grendel though, with any 6.5. It is not a hybrid, not a VLD, so its numbers are not as impressive as other 'modern' 6.5 bullets. However, it is very forgiving in terms of loads, neck tension, and jump. Seems like about any reasonable load will shoot very well with this bullet. I will not say the same for the 107 Sierra. We have had problems with this bullet in the past and it seems it either shoots very well or not at all with a Grendel.

Good luck with your testing!

LR1955

ARP= AR Performance. They have a reputation for being uncannily accurate barrels. In the past, the barrels were turned by Compass Lake Engineering. I really bought the barrel for the matched ARP superbolt. It is one of the strongest 264 LBC/6.5 Grendel bolts available

Yes I can call shots well. In addition, I was using a solid setup. Rock BR front rest and rabbit ear rear. Geissele SSA-E trigger. I can assure you I did not pull any of the shots.

I will do some more testing and report back. I hate to hear that the 107 SMK's may not do well in the Grendel. I plan on trying them with H335.
For the 120 SMK, I have CFE223 and XBR 8028 on hand. I thought about picking up some ARcomp, Leverevolution, and TAC if I can find it locally.

[rabiddawg]

ARP= AR Performance. They have a reputation for being uncannily accurate barrels. In the past, the barrels were turned by Compass Lake Engineering. I really bought the barrel for the matched ARP superbolt. It is one of the strongest 264 LBC/6.5 Grendel bolts .

Hmm, the only thing I ever heard about him was being a nut.

That guy obviously has an axe he is grinding against the 6.5 Grendel.

[molar]

Hmm, the only thing I ever heard about him was being a nut.

That guy obviously has an axe he is grinding against the 6.5 Grendel.

He is different, that is for sure. He isn't grinding his axe against the Grendel as much as he is against a certain mod here. Not sure why. Anyway, his personality aside, he does have a reputation for making accurate barrels. He was actually the one to determine what the issues were with the early 6.8 and SPC II chambers and then solve them with the 6.8 ARP chamber. I have to give him credit for that.

[Hoser1]

Molar, check out this thread ….. http://forum.accurateshooter.com/ind...opic=3814361.0 (long range load development at 100 yards)
Somebody else posted it a couple months ago, I have learned a lot reading all 119 pages, this thread has been going since 2013.
Sit down with some adult beverages and enjoy. I agree with LR1955, maybe we are holding this round on a pedestal thinking that its magic. everybody has flyers…… loaded up some 100gr amax and 26.1gr of 10X, shot the the first 3 in one hole, got excited, and pulled the next, and grouped 3 more in a vertical string all touching, overall the group was .920 minus the flyer. Going to load some more and try again,trying different seating depths, the load does show really great potential. When I started reading about this round I too had high hopes for a tac driver. I think with some time it may or may not be the tac driver I was hoping for, but still be a very versatile round that will do many things very well, from prairie dogs to elk up close and everything in between.

[terrywick4]

maybe he just took offense to having his barrel called low grade? he is looking for input on a solution not to be nut or have his rig called not high end when the person posting admitted he didn't know anything about the barrel.

Hmm, the only thing I ever heard about him was being a nut.

That guy obviously has an axe he is grinding against the 6.5 Grendel.

[LR1955]

ARP= AR Performance. They have a reputation for being uncannily accurate barrels. In the past, the barrels were turned by Compass Lake Engineering. I really bought the barrel for the matched ARP superbolt. It is one of the strongest 264 LBC/6.5 Grendel bolts available

Yes I can call shots well. In addition, I was using a solid setup. Rock BR front rest and rabbit ear rear. Geissele SSA-E trigger. I can assure you I did not pull any of the shots.

I will do some more testing and report back. I hate to hear that the 107 SMK's may not do well in the Grendel. I plan on trying them with H335.
For the 120 SMK, I have CFE223 and XBR 8028 on hand. I thought about picking up some ARcomp, Leverevolution, and TAC if I can find it locally.

molar:

Just hit me after I posted. AR Performance. Don't know much about them so can't really comment.

Normally when someone posts groups I ask if they are good at calling their shots. I trust what they are describing far more if they can tell me their call area and or that they called the shots. You would be amazed at how many guys have no clue what I am talking about,why, or how calling shots fits into the critical thinking process when it comes to marksmanship.

You don't need anything elaborate for the 120 Sierras. We used H 335, TAC, 2520, 8208, and I am sure CFE will do as well as the other powders so you don't need to spend more money on powder for that bullet. I like from 28 1/2 to 30 1/2 grains of 2520; 28 1/2 of TAC; 28 of 8208. Cant remember the load of H 335 but probably 28 grains. About any primer was fine.

The 107's are more particular towards powders from what I have experienced and also particular with jump. When I shot them competitively through a .260, I always had to seat them so they would touch the lands and for 600, I hard seated them. I never had an iota of luck with them with any of six or seven different Grendel barrels of varying lengths and styles over the years so I stopped shooting them. And the guys on the forum for the most part said they either didn't shoot well at all or were marginal. A few never seemed to have a bit of a problem with them no matter how they loaded them. Bill Waites is one of those guys. Of course since you bought some of them, test them since they offer the potential for decent velocities with the Grendel.

About the only thing constructive I may offer is to shoot at 200 or even 300 if possible. 100 just isn't far enough to show if you really have a big problem or not. My opinion only.

LR55

[rabiddawg]

maybe he just took offense to having his barrel called low grade? he is looking for input on a solution not to be nut or have his rig called not high end when the person posting admitted he didn't know anything about the barrel.

I think you misunderstood me. The arp beene ent. guy is who I was referring to not molar.

[molar]

I think you misunderstood me. The arp beene ent. guy is who I was referring to not molar.

LOL. I knew you were talking about Harrison. He has an entire page on his site devoted to LLRP