.223 ballistic mystery...

[00tec]

How would a faster twist rate (1:7) vs., say, 1:12, affect the grouping?

A 62gr will keyhole at about 10 yards out of a 1:12.
Been there, done that.

My 1:12 loves 40gr, but anything over 55 is a disaster.

[Grant H.]

How would a faster twist rate (1:7) vs., say, 1:12, affect the grouping?

The object of the rifling is to spin the bullet and create a gyroscopic stabilization of it that allows for significantly greater consistency in flight paths.

As the bullets weight, shape, and cross-sectional density change, the rate of twist that is ideal for that particular bullet changes.

Lighter bullets generally prefer a slower rate of twist (1:12)
Heavier bullets generally prefer a faster rate of twist (1:7)

Generally the bullet manufacturer can/will provide a recommended barrel twist and velocity for "ideal" functionality of that specific bullet.

ETA:

The less stable the bullet is leaving the barrel, the less consistent the flight path will be.

Shooting for groups is often considered "accuracy", but that's not really correct. That is consistency. The smaller the group you can create with your rifle, the more consistent the rifle, load, and shooter are.

Accuracy is more often talked about in terms of "POA vs. POI" (point of aim vs point of impact).

Having the wrong weight of bullet for the twist of your barrel will cause poor consistency and large groups, or in extreme cases like 00tec mentioned, it will cause complete loss of accurate flight within very short distances.

[bellavite1]

62gr is pretty light for a 1:7, which may be a good chunk of your 3-4MOA grouping.

The 69gr that you mentioned buying should help, but even up into the 7Xgr will stabilize better, and should help to tighten groups up.

FYI, this thread shows a guy having really poor luck with velocity and accuracy out of very similar load and rifle configuration. https://www.thehighroad.org/index.ph...d-dots.864212/

If it were me, I would ignore the ballistics "anomaly" until you get a load that the rifle likes, and then re-run your tests.

Update:
Swapped upper with a 20" Palmetto.
Same trigger and scope as before, same 62gr loads ammo.
...Same results...2-3MOA groups.
The good news are that my barrel may not be the culprit after all, I am more leaning towards the load.
So I am going to try some 75gr loads with some Hornady Match bullets I have laying around.
I will start with 24.4 of CFE223 and see where it takes me (Hogdon shows a max load of 25gr).
TBC

[Duman]

Update:..Same results...2-3MOA groups.

Are you sure you're not shooting an AK? ...

[bellavite1]

Are you sure you're not shooting an AK? ...

[Grant H.]

Update:
Swapped upper with a 20" Palmetto.
Same trigger and scope as before, same 62gr loads ammo.
...Same results...2-3MOA groups.
The good news are that my barrel may not be the culprit after all, I am more leaning towards the load.
So I am going to try some 75gr loads with some Hornady Match bullets I have laying around.
I will start with 24.4 of CFE223 and see where it takes me (Hogdon shows a max load of 25gr).
TBC

Is the PSA 20" also 1:7? For my own edification.

I have stumbled onto my own versions of loads that just simply will not shoot, so you may be onto something.

I know it has been talked about, but you might want to inspect rings/caps very closely. A buddy of mine was shooting one of my .17HMR's and it was continually changing groups, POI, etc (worse case than you are seeing), and it turned out that when I bought the scope, the front ring cap was put on backwards. Even though it was torqued, it never behaved. Only changed the front ring cap 180?, re-torqued, re-zero'd, and has been perfect from 25yds to 250 since. Baffled the hell out of me how a scope ring cap could cause that much heartache, but there was a small bevel at the edge of one side of the ring that didn't exist on the other, and they were mismatched.

Just another thought to look at, given the same results with the same scope, although this seems far more consistent than that .17 ever was with the ring installed wrong.

[bellavite1]

Is the PSA 20" also 1:7? For my own edification.

I have stumbled onto my own versions of loads that just simply will not shoot, so you may be onto something.

I know it has been talked about, but you might want to inspect rings/caps very closely. A buddy of mine was shooting one of my .17HMR's and it was continually changing groups, POI, etc (worse case than you are seeing), and it turned out that when I bought the scope, the front ring cap was put on backwards. Even though it was torqued, it never behaved. Only changed the front ring cap 180?, re-torqued, re-zero'd, and has been perfect from 25yds to 250 since. Baffled the hell out of me how a scope ring cap could cause that much heartache, but there was a small bevel at the edge of one side of the ring that didn't exist on the other, and they were mismatched.

Just another thought to look at, given the same results with the same scope, although this seems far more consistent than that .17 ever was with the ring installed wrong.

Yup, 1:7 as well, just to confirm that my hardware is still in good shape.
Same twist, same results.
In fact, I even had a keyhole...
No issue with the rings, thankfully, because of the shape there is no way it can be backwards.
BTW, I have these 500 Sierra Match King 69 gr coming, which I will probably be returning to Midway if the 75gr load is halfway decent, unless somebody is looking to trade or buy them, that is...
Any takers?

[Grant H.]

Yup, 1:7 as well, just to confirm that my hardware is still in good shape.
Same twist, same results.
In fact, I even had a keyhole...
No issue with the rings, thankfully, because of the shape there is no way it can be backwards.
BTW, I have these 500 Sierra Match King 69 gr coming, which I will probably be returning to Midway if the 75gr load is halfway decent, unless somebody is looking to trade or buy them, that is...
Any takers?

Well, at least there is consistency... Helps keep one sane when chasing something like this.

You might consider keeping the 69's and loading them over a different powder. You may find a good load for them.

Beyond that, I will send you a PM. I'm never opposed to having another box of bullets.

[Duman]

Updates?

[bellavite1]

Slow burning powder giving low velocities with extreme spread over 100 fps.
Grant H link was spot on.
2427fps to 2592 fps out of a 16".

75 gr bullets vs 62 gr bullets did not help.

Then again, in the past, 26" gr of varget over 62gr bullets was still over 1"...