Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
Posted: 1/4/2012 11:55:47 AM EDT
I know we have some ballistic gurus on here. If somone sighted their rifle in using M855 and then shot some Black Hills .223 77 grain BTHP match, does anyone know what the point of impact difference would be at 50, 100, and 200 yards?

You can use 25, and 100 yards as the zero. Just for a comparison. This will be out of 14.5 and 16" barrels.

The reason why I am asking is that I recently bought a new Leupold Patrol VX-R scope that has the SPR reticle. The hash marks correstpond to bullet drop for M855 rounds. I wanted to see how the 77 grain ammo I usually shoot would compare in point of impact. I don't get to use a 100 yard range all buy once a year, and usually shoot 25 yards indoors.

Any help is appreciated.
Link Posted: 1/4/2012 11:57:51 AM EDT
[Last Edit: 1/6/2012 7:04:53 AM EDT by Krinkplinker]
I am by no means any kind of expert, but I doubt there would be any discernible POI difference in 25 yards.
Link Posted: 1/4/2012 12:58:30 PM EDT
I believe Trijicon has a accel sheet on their web page.
RCBS has Point Blank program for free I believe. I like the Point Blank program because you can plug in information and see trajectory. You can also switch screens to see data down to 5 yard increments. You can save text of data for everything to include wind drift info and total drop etc. Great program to compare rounds on paper.
Link Posted: 1/4/2012 1:00:07 PM EDT
I use a cocktail for my defensive ammo mags alternating one IMI M855 62gr with one 75gr Privi HP match round and there is no difference in POA at 15-25 yards which is what i expect zombie combat ranges will be.

MY zero at 100 yards is the center dot on my EOTechs, all 3 of them which translates to 6 O'clock on the outer ring right at 20 yards.
basically at 10-100 yards it is more about me holding than bullet variance in POA.

I have various ranges to work with at our club so it is a matter of staying familiar with my tools


Wulfmann
Link Posted: 1/4/2012 2:54:11 PM EDT
At anything under 200 yards you shouldn't notice any more than a 1-1.5" deviation between the two rounds. At 25 yards you won't be able to tell the difference.
Link Posted: 1/4/2012 9:56:55 PM EDT
Agree with the forum. The calculated trajectories are meaningless when we talk about the real differences between guns.

The particular ammo in any particular rig is potentially a bigger effect than the math can predict for the difference between those trajectories.

Within 200, your rig and my rig are probably more different for the same ammo. let alone the different ammo.
Link Posted: 1/5/2012 5:36:23 AM EDT
[Last Edit: 1/5/2012 5:37:52 AM EDT by FMJ]
I shoot Blacks Hills 77 & 75gr all the time along with M855
M4 & aimpoint 14.5

zero at 50Y with MK262

The M855 the SS109 bullet is long because of the Mild Steel INSERT

Ive found that M855 POA/POI is Almost the same as BH 77


At the most its .5 off

At the Berm 220Y I can hit tins cans using M193,M855,BH 75,BH 77,MK262

So if this carbine is used for SD/HD/SHTF I wouldnt worry about it.
Link Posted: 1/5/2012 3:29:33 PM EDT
There are a couple of things here. First is that what you want to know only has any real meaning in one set of conditions (temp, pressure, humidity). The difference in trajectories is non linear with changes in conditions. Second the differences in trajectory are not the only contributor to a change in point of impact, there is also a jump component. Jump is commonly forgotten because typically it is zeroed out for a single round type and it is variable base in the gun tube in question. When multiple round types are fired without rezeroing the jump difference can be as large or larger than the trajectory differences.
Link Posted: 1/5/2012 3:55:17 PM EDT
Here you go guys

I shot the 855 1st then backed it up with 77s on the next 5. 100yds.

Looks about the same from my house.





Link Posted: 1/5/2012 3:58:54 PM EDT
What is 'jump'? Is it recoil/barrel flip?
I'm sighted at 100 with M855 but I'm changing that rifle to 75 gr because it has a 1:7 twist. I expect to have to make a slight adjustment. I'm using only a 4x combat-type scope so I might not see much difference since my groups will likely be about 3". The slower, heavier 75 gr should be a little lower at 100, then more noticeably lower as the distance increases. But in a combat scenario you would still be getting torso hits out to at least 200 with sights/scope still set for M855.
Link Posted: 1/5/2012 4:01:12 PM EDT
Originally Posted By AMUshooter10:
Here you go guys

I shot the 855 1st then backed it up with 77s on the next 5. 100yds.

Looks about the same from my house.

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2897.jpg

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2898.jpg



Damn! Looks like the 77s are a lot more accurate in that 1:7! I hope mine turns out that good.

Link Posted: 1/5/2012 4:39:57 PM EDT
Originally Posted By 1saxman:
Originally Posted By AMUshooter10:
Here you go guys

I shot the 855 1st then backed it up with 77s on the next 5. 100yds.

Looks about the same from my house.

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2897.jpg

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2898.jpg



Damn! Looks like the 77s are a lot more accurate in that 1:7! I hope mine turns out that good.



For what they cost you would think they could fly around corners though

Link Posted: 1/5/2012 5:01:43 PM EDT
Originally Posted By 1saxman:
What is 'jump'? Is it recoil/barrel flip?


Technically the recoil and barrel whip are a part of the jump however its not the whole thing. Jump is the difference in trajectory from a round that flies perfectly straight out of the barrel. This very rarely occurs but because most people never bore sight (at least not accurately) this is never picked up and the sights are adjusted to account for the jump. The randomness of some of the jump components cause dispersion. The army understands this concept fairly well from the work on tanks. I can try do dig up some reports if anyone is interested. Although they will likely be pretty old if they are releasable to the public.

Jump is likely the most important and most overlooked quantity when talking about projectile launch and flight mechanics
Link Posted: 1/7/2012 5:20:05 PM EDT
Originally Posted By AMUshooter10:
Here you go guys

I shot the 855 1st then backed it up with 77s on the next 5. 100yds.

Looks about the same from my house.

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2897.jpg

http://i40.photobucket.com/albums/e237/amushooter10/IMG_2898.jpg



Thank you for showing how close the 2 loads are

Nothing to worry about if you are using a carbine of SD/HD/SHTF
Top Top