.223 vs 5.56 (not what you think)

[Bill92869]

Assuming velocity is the only variation (cases, primers, powder and bullet being identical), is there any significant change in POI at 100yards? In other words: If I've sighted my rifle in at 100 yards using 5.56 ammo (M193), then change to shooting commercially reloaded .223 ammo, will the POI be much different. I'm told that the velocity separation between the two is 100 fps. Doesn't seem that would cause a major change in POI at 100 yards, maybe at further yardage. I drove to L.A. to buy bulk 5.56 ammo only to get home and realize I had .223. The store I bought it at says they reload both, but that the POI won't change much at all.

[Bill92869]

Someone on AR15.com had the answer. They supplied a link ot a site that calculates trajectories: http://www.biggameinfo.com/index.asp...2fbalcalc.ascx

BC of an FMJ 55gr boat-tail projectile is .243 and the sight is 2.6" above the bore.

The change of POI is minimal in my opinion, at least for my needs.

[dw1784]

shoot it and see?
I'd be more interested in it's grp size than the difference in POI.

[rksimple]

100 fps shouldn't change 100 yard trajectory too much. If you're shooting at MOA targets, yes, you'll probably miss. If its on steel, you probably won't notice a difference.

[Fjold]

Any change you make will affect the trajectory. Just the fact that they are loaded to different over all lengths will affect it some.

But the question is, How much?

It may move it 1/4" at 100 yards or it may move it 2" at 100 yards. The only way to know for sure is the shoot it.

[RAD-CDPII]

Just for clarification, it's OK to use .223 in a .556, but it is unsafe to use 5.56 in a .223? I believe it has to do something with the taper of the bullet iteslf and where the refeling starts. I have a Mini 14 .223.

[Fjold]

[jess]

Does Dillion make a set of dies that are 5.56 Nato Specific or are the .223rem dies used?

[jess]

Nevermind... I found the answer.