I am puzzled by this one.

[sammy]

Hello all,

I have a head scratcher here you might be able to help me sort out. First of all I know light .223 bullets in a 1/7 twist can cause jacket separation. After doing some research and in need of something to feed my AR I ordered Hornday 50g. V-max bullets to try.

The rifle is a new BCM 16" midlength. Test loads are as listed:

24.9g. 335=2780 fps.
25.2g. 335=2820 fps.
25.5g. 335=2830 fps
25.8g. 335=2860 fps
25.1g. 335=2910 fps.


In this pict I fired 10 shots at 100 yards benched. The results are poor and the rifle is zeroed using Montana Gold 55g. bullets which the rifle gets 1-1/2" 10 shot groups on a good day. Starting from the top left being the lightest the bottom left is the max load. As you can see the max load only has 6 on paper. The 6th is the one far right that keyholed.

My question is why did the max load start going wild while all the others are fairly consistent? What is it about the extra 50fps of velocity that caused the bullets to keyhole?

Thanks for looking, Sammy

 

[armoredman]

You pushed the bullets to a velocity where they started stripping the rifling, riding right over the lands/grooves and ripping out the bore tumbling sideways. Too fast, back it down. That first group is stellar. You just need to ask yourself - what do I want to do with this load? Light game? Go for a wee bit more punch, like just below when it starts to go wild. Paper punching? Group one looks like a good one to branch off with COAl and other minor tweaks, if you want, or sit on it as is.
Dumb question - scoped?

 

[Rollis R. Karvellis]

Can't give you an exact answer, but this is a great example of how a max load does not equal the most accurate. I, guess the last 50 fps was all it took to make the round unstable in your rifle.

 

[sammy]

These were fired using a 4x optic. My shooting was poor. Short on time and rushed the groups. Shooting from a bench is not my thing but they needed to be tested as the results show. This ammo will only be used for punching paper and old eggs.

Thanks for the response armoredman!

Sammy

 

[ArchAngelCD]

Since you're only looking to kill paper it looks like the 25.2gr and 25.5gr loads did the best. That's what I would stick with after a little tweaking. (Maybe 25.3gr or 25.4gr will be just a little better) For 10 round groups you might have rushed that doesn't look all that bad.

 

[beatledog7]

Every bullet has a its linear and angular velocity limits--you just proved it. "Max" loads are those at which SAAMI pressure range tops out, not at which the bullet works best.

Based on those groupings I'd load that bullet to 25 grains even. Easy to remember and to read, as accurate as anything you tested. Whatever you hit at 2800fps won't know the +/- 20fps difference.

That said, if you're trying for maximum punch at the target try some bullets in the 62-65 grain range then some in the 68-72 grain range. They'll be a little slower but with a fast twist should group very well at 100 yards and will carry as good or better energy.

But as I was typing several people chimed in. Based on your target selection, stick to the light bullets (they're less expensive, generally) and 25 grains. Honestly, if you shot another set of groups at the powder charges from 24.9 to 25.2, I bet you wouldn't able to tell the difference, as you really can't now. Your scale variance is likely about .2 grains anyway (which is <1% of the charge).

 

[Searcher4851]

I don't recall ever having a max load shoot well in any of my rifles, particularly with light bullets for the caliber. I start low and work up until groups start to open up, then back it off to best group shot. That's my load for that bullet in that rifle. In my ripe old age, I no longer seek the fastest speeds. I'm more accuracy inclined. I'd rather hit something slower than miss something really fast.

 

[Walkalong]

1 in 7 twist is a bit fast for a lightly constructed varmint bullet. They may not be handling it well. As suggested, back off the powder charge a bit and retry them. I agree with ArchAngelCD that 25.2 would be a good place to try and perhaps a bit more. Actually, I think I would load some at an even 25.0 and test them out.