Heavy, long .224 versus "Std" jacketed bullets in the 223/5.56 cartridge

[roysha]

I'm not sure I'm posting this in the right place but since most of the current crop of AR platform .223/5.56 rifles seem to have 9" twist or tighter I thought it might be appropriate here.

After comparing the 69 grain Sierra Match and the 55 grain Sierra SPT (55 grain being more or less the accepted "Standard" weight) using the Sierra ballistic program, in virtually all categories except wind drift at extended ranges, (400 yards or more), the 55 grain bullet exceeded the performance of the 69 grain bullet. This was using velocity compared to velocity, (ie. both fired from the same length barrel and not comparing a 16" M-4 to a 24" Varmint). I can only imagine what the 70+ and 80 grain bullets give up.

Assuming the accuracy is the same for both bullets, and having shot many rifles with both these bullets I believe that would not be an issue, I am at a loss to understand all the fuss about the longer, heavier bullets. I see nothing but a down side to pretty much anything more than 60 or so grains. Perhaps there is something I am missing here and someone could explain it to me. I am truly curious.

One last thing, before anybody jumps in with their 22-250 or Swift results, please reread the title.

[DCM]

Retained energy and penetration are better with heavy for caliber slugs.
On the other hand if a slug is too long for the twist it will not stabilize.
Big question is what distance are you going to use it at and what purpose? Matches? Vermin(small 4 legged)? Other vermin? Plinking?
Best to match the tool to the job, especially with all of today's choices.

[LynC2]

I can only guess that you have never shot any 600 or 1000 yard competition where the wind drift is of paramount importance!

[Jupiter7]

All I've ever shot in my white oak uppers in service rifle has been the 69gr MK. Weight definitely helps fight wind drift at 600m. But both of them are 7.5" twist, stabilizing is a non issue. Speaking of downrange wounding performance, some of the best rounds are in the 75grn range. Also the military uses 77gr bullets in 1:8 twist 18" barrels in short range "precision" rifles. Google: ar15 SPR. lots of info on the rifles,optics, theory and ammo.

[Larry Gibson]

Lot of AR NMC shooters use 52 - 55 gr match bullets at the 200 & 300 yard lines. The 69 and heavier bullets are used at the 600 yard line. I don't shoot matches with the AR anymore and prefer the 52-55 gr bullets for coyote and other sundry varmints (including 2 legged ones if need be) none of which are signatories of the Hague Accords. Ergo I prefer 12 or 14" twits in ARs which have an affinity for 52 gr Speer HPs or Sierra 55 gr HPBTs, both of which are deadly and do not depend on "tumbling"for any effectiveness. Both are effective to 500 yards (used them that far on coyote and rock chucks) out of 20" barrels but do better out of 24 - 26" barrels. The balistic tips do as well but not really better for the increased cost. The 12" twist is a lot easier to use cast bullets with BTW.

But unfortunately the current fad is 16" barrels with 7-9 twists for use with the 62 - 90 gr bullets which are very seldom used by reloaders for other than match shooting. The predominent bullet weight still used by the military is still the 55 gr M193 because it is a lot cheaper per round than the M855 or the newer bullets.

Larry Gibson

[horsesoldier]

As far as I know the M193 is no longer in service with the army at least, we are starting to make the switch from M855 to the M855A1 now