Opinions to help with tightening groups.

[Pa Pap]

Greetings all,
I am shooting a 22 in Criterion Barrel with an upper that I just put together. I used a box of Federal Fusion 120 grain for the barrel break-in. After that, I used the Hornady black 123 grain to test for accuracy groups.

I shot to 5 shot groups. Both groups we're holding 5/8 in Center to Center. I then put on a vg6 Precision Lambda muzzle brake. This opened my groups 2 about 7/8 of an inch for the next two five shot groups.

I loaded up some rounds using the Hornady brass, CCI BR4 primers, IMR 8208 XBR powder and Sierra 123 grain hpbt match bullets. My overall length was 2.300 inch. This just fits in my mag.

My test loads were 27 grain, 27.3 grain, 27.6 grain, 27.9 grain, 28.2 grain and 28.5 grain. The 27.3 grain was about an inch and an eighth group. The 28.5 grain what's about 1 inch group. These were my best two groups. The 28.2 + 28.5 groups were showing pressure signs on the head stamp. The worst group was with 27.6 grains at 2 and 1/4 inches.

I have been reloading for quite a few years, but just for bolt-action rifles mainly. This is my first AR loading for accuracy. Do you think I should seat the bullet back a little further? I'm also contemplating taking the muzzle brake off.

Another thought would be to try the CFE 223 powder with this bullet. Have any of you had this drastic of a change when reloading compared to factory?

Thanks in advance for any and all suggestions.

[A5BLASTER]

Take the brake off and retime it with a accuwasher and lil to no torque.

Don't go over 28.3 with xbr. Cfe223 or leverevolution is the better 2 powders for 123 grain or higher weight bullets, should max out close to or a bit over 30 grains with either.

Try 5 shots each backing your seating depth shorter by .005 till your .025 shorter.

Did you measure you contact to lands with that bullet in your chamber?

[Pa Pap]

I don't have a guage to test seating depth, but I put a loaded round in and manually closed the bcg with my thumb. When I removed the case, there was no marks on the bullet from the lands.
The lambda muzzle brake has it's own system to time the device. It comes with a nut to tighten once the brake is lined up. Not sure how a crush washer would work on this.

[A5BLASTER]

I don't have a guage to test seating depth, but I put a loaded round in and manually closed the bcg with my thumb. When I removed the case, there was no marks on the bullet from the lands.
The lambda muzzle brake has it's own system to time the device. It comes with a nut to tighten once the brake is lined up. Not sure how a crush washer would work on this.

I would get the hornady measuring tools.

And the accuwasher system isn't a crush washer. The idea is to time the muzzle device so it's held in place with locktite and 5 pounds or less of torque.

If it shoot tighter groups without the brake then they opened once you installed it you have your answer the torque used to time and install it is throwing off your barrel harmonics.

[Pa Pap]

I would get the hornady measuring tools.

And the accuwasher system isn't a crush washer. The idea is to time the muzzle device so it's held in place with locktite and 5 pounds or less of torque.

If it shoot tighter groups without the brake then they opened once you installed it you have your answer the torque used to time and install it is throwing off your barrel harmonics.

I do need to get the Hornady tool. I had an older one, but it broke off at the threads.
I figured as much that adding the muzzle brake would throw off the harmonics, just wasn't expecting it to be this much. POI changed about 3".
Thought I could find a load to work.
Oh well, just need to keep trying. I will try your suggestion and start setting the bullet back bit by bit.
Darn! More shooting needed. Lol.

[grayfox]

In my approach the accuracy node you're looking for in a steel barrel is mostly related to 2 things: barrel length and exit MV. (As this is based upon the physical-material properties of steel, I don't know how a carbon fiber or composite barrel would behave.)
This is based upon the work by Chris Long.
So you need a chrony.
Coal is a minor tweak for pressure-wave timing, once you have the node identified.
Accuracy then follows those basic steps.
Some guys don't use this approach so I understand, but this has worked for myseld and a few others I have corresponded with...
With a criterion barrel and the 123's, your node is probably somewhere in the 2550 ft/s range give or take. But every barrel has its unique signature, that's why you need to chrono all your groups. "Book" MV for a given powder/load will not guarantee your barrel shoots that MV.
A corollary: if you're not within the node range and anything, repeat, anything, changes you could see accuracy suffer.
My $0.02.

[Klem]

Pa Pap,

I would not be jumping to conclusions based on firing a few shots. Plus you are playing with too many variables to again, come to conclusions.

The idea that something is wrong because your first two 5-rd groups blew out from 5/8 to 7/8 with the muzzle brake is just part of determining that the gun shoots 6/8", on average. That's excellent accuracy for a gas gun. Way too few groups and too small a deterioration of group size to infer that the muzzle device has something to do with it. If you want to be sure take it off and shoot 100rds without, and another 100rds with it on.

I also wouldn't put too much stock in the barrel tuning concept, especially in a light-weight action like an AR. The one time I saw someone with a proper barrel tuner he could not get it to improve anything, and this was over months of trying different settings and ammo using an 8kg F-Class bolt gun. By all means play around with it but don't expect it will be doing anything that is not swamped by other more influential variables. Back to your first post...Firing only one group for each change in powder and then coming to conclusions is fraught with the possibility that the result could be due to some other variable. If however you graph your optimum load sequence and there is an obvious correlation across all the loads then I would hone in on the area of best groups closest to max peak pressure.

[LRRPF52]

If I have a rifle that consistently shoots several groups sub MOA, I don't waste anymore time shooting paper with it and just take it out on steel.

If your purpose is to chase groups on paper, fire away. Some people enjoy that.

I like hearing impacts on steel, but everyone has their own purposes, so I won't assume that mine are the same.

[snarkscarbine]

I would get the hornady measuring tools.

And the accuwasher system isn't a crush washer. The idea is to time the muzzle device so it's held in place with locktite and 5 pounds or less of torque.

If it shoot tighter groups without the brake then they opened once you installed it you have your answer the torque used to time and install it is throwing off your barrel harmonics.

Far more likely that the directional force from the brake (or even the weight) itself is changing harmonics than the torque used to apply it. In terms of harmonics more torque will help rather than hurt.

[Pa Pap]

I bought some CFE223 and loaded some up to shoot right before it got dark today. The gun seems to like this powder better. I started with 29.5 grains and incrementally went to 31 grains. Got a 5/8" group with the 29.5 load, then every .3 grains opened the groups up until I hit 30.7 and it reduced down to 7/8" before going back to over 1-1/4" at 31 grains.
I'm going to load some 29.3 and 29.7 grain loads and also try 30.5 and 30.8 grain loads. The western Pa weather isn't good enough for taking the chrony out, so I will see what direction works better and work with bullet depth from there.
At least I know that the muzzle brake won't be a paperweight. It really makes a difference in what little recoil there is with this gun.

[grayfox]

I personally like MB's, what extra control it gives me is a benefit and wearing ear protection, I don't mind doing that.
I'm well past 60 also, frankly every bit of help I can get, I'm willing to try! As for the VG6 ones, the Vg6 gamma 6.5 is one of my favorites for the 6.5-ers. jam nut instead of crush washer makes easy to time, a little loctite blue and I'm ready to rock.

[Pa Pap]

I personally like MB's, what extra control it gives me is a benefit and wearing ear protection, I don't mind doing that.
I'm well past 60 also, frankly every bit of help I can get, I'm willing to try! As for the VG6 ones, the Vg6 gamma 6.5 is one of my favorites for the 6.5-ers. jam nut instead of crush washer makes easy to time, a little loctite blue and I'm ready to rock.

The Vg6 Lambda has the jam nut also. I watched a couple videos of this and liked how it keeps the muzzle jump controlled. Plus, it looked simple....I like simple. LOL

[A5BLASTER]

Far more likely that the directional force from the brake (or even the weight) itself is changing harmonics than the torque used to apply it. In terms of harmonics more torque will help rather than hurt.

Ok.

[Mark611]

I have a question or 2 LOL!! are u turning your case necks? and how are u crimping ur necks? the reason I ask because semiautos tend to have a longer jump to the rifling in the throat area, if your case necks are out of round by more then a thou or 2 this will not give very good accuracy, turning ur necks allows even case neck tension so the bullet releases straighter into the lands, IMO handing loading for a semiauto requires a little more detailed work then a bolt gun to achieve better accuracy

[LR1955]

I have a question or 2 LOL!! are u turning your case necks? and how are u crimping ur necks? the reason I ask because semiautos tend to have a longer jump to the rifling in the throat area, if your case necks are out of round by more then a thou or 2 this will not give very good accuracy, turning ur necks allows even case neck tension so the bullet releases straighter into the lands, IMO handing loading for a semiauto requires a little more detailed work then a bolt gun to achieve better accuracy

MK616:

OK -- how much will your accuracy degrade if you don't turn your necks or crimp? You can give it in percent of a group, inches, minutes -- what ever unit of measure you wish.

Oh yes, would love to see your test and statistic too.

LR55