Need some help, TAC and 2520...

[Grendelshooter]

[A5BLASTER]

Maybe your barrels are trying to tell you something.

A. They don't like those bullets.

B. They don't like those powders.

C. They don't like your primers

D. All of the above

Try diffrent seating depths. "Mag length" is not an answer, it's an excuse. Some mags allow 2.300 some only 2.260.

Did you do anything to help the accuracy when you put the rifles together? Is the barrel beded? Reciver lapped? Any gas leaks? How's the ejection pattern? Good trigger? Good scope? Good scope mount?

What kind of torque on the barrel nut and muzzle device? What's the gas length?

So many questions we need answered if we are to beable to try and help you sir.

[Grendelshooter]

Maybe your barrels are trying to tell you something.

A. They don't like those bullets.

B. They don't like those powders.

C. They don't like your primers

D. All of the above

Try diffrent seating depths. "Mag length" is not an answer, it's an excuse. Some mags allow 2.300 some only 2.260.

Did you do anything to help the accuracy when you put the rifles together? Is the barrel beded? Reciver lapped? Any gas leaks? How's the ejection pattern? Good trigger? Good scope? Good scope mount?

What kind of torque on the barrel nut and muzzle device? What's the gas length?

So many questions we need answered if we are to beable to try and help you sir.

All that kinda goes without saying so I didn’t bother, but yes uppers lapped, barrels bedded, no gas leaks.
Barrel nut threads moly lubed and did the standard tighten thrice and come to a final torque at about 45 ft/lbs iirc. Barrel nut does not impede the gas tube, both RLGS, JP thread protectors,

Large MBT-2 trigger, SWFA SS 12X, Larue SPR scope mount.

BTOL with 123ELDM of 1.670, gives me between 2.245 and 2.255 COAL. No room to really go longer in my mags due to meplat/tip differences.

If the guns don’t like CCI#41 primers I’ll turn the barrels into tomato stakes and use the uppers for more 5.56 rifles or try a 22 Grendel. They’ve been nothing but gold in my 5.56 guns.

If they don’t like Sierra, Hornady, or Nosler then I’m pretty much SOL regardless.

TAC and 2520 were pretty popular with the Grendel at one point so that’s why I wanted to see what others were shooting them with.

I don’t know if the 100-108gr bullets would do well with these powders, but it’s about all I haven’t tried at this point.

I’m just sitting here going WTF, over?

[Mad Charlie]

You just might have to "dip in" to a little of your ARC, and maybe even buy a pound of 8208. Personally, I think it would be a good thing to have one powder that works well in 5.56 and 6.5G. I don't have any luck with Tac in anything either.

Sounds like a good build.

[Grendelshooter]

You just might have to "dip in" to a little of your ARC, and maybe even buy a pound of 8208. Personally, I think it would be a good thing to have one powder that works well in 5.56 and 6.5G. I don't have any luck with Tac in anything either.

Sounds like a good build.

Man I tried to get 8208 to work but gave up, AR Comp did everything so much better.
If I recall the best I could do with 8208 was about 1” at 100. Not bad but not great.

Your probably right. I just know, deep in my bones, that 26-27 grains of ARC will give me a great performing round, but I need to find something to do with my TAC and 2520 lol

[Popeye212]

Didn't have good results with Tac or CFE223 haven't tried 2520. Yours should shoot with either or ARC or 8208 with those bullets. Sierra 123 didn't work with me but the 120 is GTG.

[Kswhitetails]

How do they shoot with factory rounds? Black and Federal 120 AE are where you should know.

Search LR55 and the 120 SMK. If that won’t shoot, you’ve got issues.

[Nordy55]

What is the twist of the barrels? I’d have to say tac and cfe223 are easy powders to work with..or at least seem good to go with my loads.. 120 nosler b.t. 28.0 grs of tac shoots clover leafs at 100.. but I have 3 300 b.o. 2 same maker and 2 shoot same bullet Hornady sst great the 3rd one likes nosler b.t. And shoots the Hornady 2” groups all day and mow with the nosler.. I’d try new pills..might be all is needed

[Grendelshooter]

How do they shoot with factory rounds? Black and Federal 120 AE are where you should know.

Search LR55 and the 120 SMK. If that won’t shoot, you’ve got issues.

I have a box of the Federal 120gr SMK loads (red box) but haven’t shot them. I just discount factory ammo out of hand these days but I’ll give them a shot next weekend.
The 123gr Hornady black is way over pressure in my Monster group buy barrel, but that barrel has been...disappointing. Have not tried them in my ARP barrel.

I’ll have to try the 120SMK. Didn’t Bill Alexander day the ideal weight was in the 115gr range?

[Grendelshooter]

What is the twist of the barrels? I’d have to say tac and cfe223 are easy powders to work with..or at least seem good to go with my loads.. 120 nosler b.t. 28.0 grs of tac shoots clover leafs at 100.. but I have 3 300 b.o. 2 same maker and 2 shoot same bullet Hornady sst great the 3rd one likes nosler b.t. And shoots the Hornady 2” groups all day and mow with the nosler.. I’d try new pills..might be all is needed

I’ll add the 120 Nosler to my list along with tha 120 SMK.
ARP is 1:8 3r hybrid, can’t recall the monster group buy barre twist off the top of my head but I think it was 1:8.

[Kswhitetails]

If you don't have a baseline, you don't know what to compare it to. It could be other issues beyond build and recipe compatibility.

If that 120 won't shoot, then I'd start looking hard at your hardware for alignment issues, or your barrel for other flaws.

[Kswhitetails]

Did you ever polish or send your barrel to BFT to polish the chamber? If it's a short throat issue, he fixes that too. My GB barrels all shoot black extraordinarily well.

[lazyengineer]

Just my own experience, but in general I find it difficult to get the 6.5 Grendel to shoot as well as 5.56. I'm not sure why, and it could be my components and systems, though I have tried more than one barrel.

As to TAC, I've found that it prefers to be run a touch mild with the TNT 90's - at 31.0 gr. And with 129 gr SST bullets, it seems to do pretty decent for me at 27.8 gr. By by decent, I mean 1 MOA on a good day on a good string. I can't get Grendel to really do any better then that, and most of the time with most of my test loads, I'm pushing closer to 2 MOA.

With 123 gr HPBT, my spec is 28.6 gr of TAC; though I only am able to get 1.5 MOA at that.

I know other people get better performance in their Grendels then I do - so maybe someone else has some sweeter loads they can share.

[grayfox]

I didn't see any chrono data from the barrels.
But, as said already,
1. 120 SMK and Lr55 comments.
2. Hdy Black
3. Federal 120 AE

Add in the chrony data and then we've got something to work with in suggesting what you ought to do.
Without this data you're shootin' in the dark.

btw I found Arp barrels to be pretty finicky altho I could get some good loads in the 123 class...
but I need to know what your rifle is doing MV-wise... this is the over-riding comment from my POV.

[A5BLASTER]

Is it a chance it's the guy driving the gun?