5.56 projectile trajectory...

**Mity2** · December 5th, 2012, 12:36 AM

So when you shoot M855, which is 62gr steel penetrator tip over a tungsten-composite core, and shoot M193, with its 55-grain ball out of SAME gun which has a 14.5" barrel with 1:9 rifling, and aimed at exactly the same spot, would the bullet drop @100yard between above mentioned 2 be noticable enough to be needing to re-sight the 4MOA red dot?

**ar15jules** · December 5th, 2012, 12:41 AM

At 200 it is going to be about six inches. If you are looking to be "minute of man", then I would say, "No", don't fiddle with your scope. You should be pretty close at 100.
Jules

**Mity2** · December 5th, 2012, 12:49 AM

I bought 250rds of M855, because it was cheap. I didn't realise that the its 62gr.

I shoot M193 almost exclusively through my AR at the range, and my 2000rds or so of SHTF stock pile is also mostly X193. So naturally my AimPoint is sighted with 55gr ammo. So I was wondering...

**cmcgowan** · December 5th, 2012, 07:43 AM

I'd shoot some to see where the poi is. It may surprise you.

**harold63** · December 5th, 2012, 12:57 PM

It is not going to be very far off, at all. Consider that the powder charges are the same, or close, or not too close; that is going to affect the trajectory more than bullet weight. You are talking about 7 grains of rice at a relatively short distance of 100 yds. The .223/5.56 isn't even breathing hard yet at that distance.

**harold63** · December 5th, 2012, 03:56 PM

Going through some of my notes, Federal 55 gr. produced groups an average of .4" higher than hand loads with 69 gr Nosler BTHP. This from a 16" Bushy. Out of a 24" Stag Varmint upper, the groups averaged about a .6" difference with the Federals being higher, but both groups were almost 3/4" higher, overall. With not shooting both of these rifles at the same time for some time, what I do remember is being able to make a styrofoam cup dance at 100 yds with both bullet weights and no scope adjustments. No, they will not cut holes, but if you are using your red dot to kill pigs with at that range, then you probably don't need to make any adjustments at all.

**ithinkimamedic** · December 6th, 2012, 12:46 AM

If it's that much of an issue I'd be happy to trade out the M855 for some M193. Let me know if you're interested, I generally shoot the 62 stuff out of my 1/7 shorty.

**Blak1508** · December 6th, 2012, 11:52 AM

With a 1:7 twist on a 16 inch I'd say no not at all, I know because I have done this, but on a shorter barrel with a 1:9 twist I am not sure. If anything it will be a very small difference... Go shoot it and find out.. Keep a small range book. I do. I write down ammo changes ,tempture, wind, weather,distance, sight corrections, etc. This will help you in case it does change a bit and then you go back to your M193, and its just an all around good practice. I promise it will help you at some point in the future.

**Mity2** · December 6th, 2012, 12:15 PM

Ya I went shot it yasterday.

With my less then perfect eye sight, and with 4MOA non-magnified optic, shoot it off of bench, most difference I got was M855 grouped about an 1" lower then M193 @ 100yard.

I would imagin group would be less, if I had magnified optics, and i did my part better.

So I guess I'm not going to worry about it.
I don't think zombie cares if I put one through his forehead, or through his face...