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Stunned by .233 to 5.56….
I see a lot of postings about the difference in dimensions and pressures for .223 and 5.56 but not about
how different they shoot…….read on…..
I shot about 80 rounds of PMC 55gr FMJ .223 at 100 yards with a 4X scope and a bi-pod and sand bags.
Pattern was within 2.5” of center, multiple targets, at a gun range bench with little if any wind blowing.
I let the gun cool off for about 30 minutes and reloaded the same plastic magazines (1 Thermold-30 and 2 Promag 30’s)
with 80 Lake City (LC) XM195 (5.56mm FMJ) rounds. Same range, very little if any wind. All ammunition was new and purchased
within a month of each other. The LC has the 2011 stamp. Everything was the same but the ammo and a half hour of time.
I shot 5 groups of 3 shots and was stunned to see the 5.56 bullets pattern about 6” high and 4” to the right of where the .223 was.
I swapped the magazines and checked the bench set-up, no changes. I fired the rest of the 80 rounds and zeroed the scope to the
5.56 ammo since that is what have now (just a few PMC and Remington .223 left). 5.56 patterned at about the same 2.5” at 100 yards.
The gun is a 581 series tactical stock. Anybody ever experience this? Odd or common?

Trig
 

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I bought a case of the PMC 223 a few years ago my AR. It was loaded pretty weak. It is the only ammo that has caused the AR to fail. There is a difference between 223 and 5.56, but I think the PMC ammo may by partly to blame.
 

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Interesting, but I hope that doesn't happen to me. I bought 1500 rounds of PMC 55gr, and have shot about 500 rounds so far no problem. I also have about 2000 rounds of XM855 62gr 5.56, which I have not tried yet. I'll cross my fingers next range trip.
 

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Interesting, but I hope that doesn't happen to me. I bought 1500 rounds of PMC 55gr, and have shot about 500 rounds so far no problem. I also have about 2000 rounds of XM855 62gr 5.56, which I have not tried yet. I'll cross my fingers next range trip.
Lets see, 55gr PMC .223. XM855 62gr 5.56 NATO penetrator ammo that has bullets that are as long as most normal 69gr .224 slugs. Nope i don't think your POI is going to be the same.
 

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That's really not that uncommon. You could try 2 or 3 different brands of 223 ammo & end up with groups in differing locations like that.
 

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I had an MSAR AUG. I sited it in at 50 yards with an Eotech using 5.56 WWB initially. I then changed it slightly for .223 TAP.

However, I did not get that big of a distance between 5.56 WWB FMJ and .223 Fiochi FMJ in the AUg
 

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Lets see, 55gr PMC .223. XM855 62gr 5.56 NATO penetrator ammo that has bullets that are as long as most normal 69gr .224 slugs. Nope i don't think your POI is going to be the same.
Yeah I know my POI is not going to be the same but at 50 yards I hope its not as extreme at the OPs. I mainly use my Mini 14 with open sights or my Aimpoint red dot so if the POI is 1-2 inches off in either direction not a huge deal.

Shooting with a 3-9 scope I know I'll have to re zero.
 

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The 5.56mm should be a hotter load then the 223, and that might be why your seeing a difference.

A couple of years ago there was an article posted about people that shoot 22 long rifle in competitions - like in the Olympics. Sub-sonic ammo gave better accuracy then super-sonic ammo.

I have also seen buckshot patterns change - with the faster buckshot having a wider spread then buckshot that was traveling at sub-sonic speeds.
 

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there are alot of variables . just because the bullets are the same weight doesnt mean they are the same length , seated to the same depth , use the same powder or crimped different . and the burn rate on the powder. also the lake city will have less case capacity due to thicker walls. all these things can and do make changes on bullet flight
zero for what your shooting and expect a point of impact change when changing ammo manufactures.
 

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Change in POI is routine with any change in powder, bullet, case, etc, let alone temp, elevation, humidity. I mean anything.
 

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Change in POI is routine with any change in powder, bullet, case, etc, let alone temp, elevation, humidity. I mean anything.
what he said...:D

you'll see the same POI shift between ammo manufacturer when using any other caliber round, it's not just .223/5.56.

zero for what you use most - then use that zero as a starting point for adjusting POI between other rounds - take copious notes... and memorize your sight adjustments off zero for your other rounds you commonly use. that way you can do it on the fly if you find you need to shoot something other than your preferred load.
I have a setting for my prefered mini 30 hunting load, (fed. SP) as zero, and I know off the top of my head how many clicks up I need to go at 100 yds to zero my winchester FMJ plinking ammo. (it shoots 2" lower than the federal) = 8 clicks.
 
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