Do you re-zero when you change up bullet weights? (60 V-max and 77gr SMK)

[BaileyMoto]

Probably a bit anal to do so I suppose, but do you guys re-zero when you go between rounds? When I return from overseas, I was considering rezeroing from my 77gr to a 60gr V-max since I shoot a lot of varmints. I use a 200 yard zero for all ammo with my m4ergy and I figure the max difference in rise isn't enough between the two to make much difference...especially since any unlikely defensive situation would likely be within 15 yards

How about for those of you who shoot both heavy (75gr+) as well as the much lighter weight varmint rounds, such as the 40gr's?

[Stickman]

Probably a bit anal to do so I suppose, but do you guys re-zero when you go between rounds? When I return from overseas, I was considering rezeroing from my 77gr to a 60gr V-max since I shoot a lot of varmints. I use a 200 yard zero for all ammo with my m4ergy and I figure the max difference in rise isn't enough between the two to make much difference...especially since any unlikely defensive situation would likely be within 15 yards

How about for those of you who shoot both heavy (75gr+) as well as the much lighter weight varmint rounds, such as the 40gr's?


If I plan to use the new load, then yes. If I'm just shooting paper at the range to see how it works, and am then going back to my other ammo, no.

Zero for the ammo you are using.

[BaileyMoto]

If I plan to use the new load, then yes. If I'm just shooting paper at the range to see how it works, and am then going back to my other ammo, no.

Zero for the ammo you are using.

I use a TR-24R on this particular rifle. What do you think about simply marking/remembering the elevation between the 2 rounds and adjusting for it? See any reason not to go that route?

[ST911]

Did this hasty exercise last year to illustrate POI deviations. The point was to show that a troop picking up a mag from a partner with different duty ammo could still be expected to deliver good hits at likely ranges. 40 rounds total, a few of each 52 through 75gr in weight, fired at 50yds, a little faster than 1:sec. IIRC, it was just under 30 seconds. That target zone is ~4" in diameter.

I've also done this several times with various loads at 25yds, where most have little to no discernible deviation from each other.

Optimal choice is always to zero for the load in the gun, verified at all ranges expected. Less optimal, but still acceptable is to data card others and do the adjustments, assuming you have a quality optic with reliable adjustments. If you had to switch without verification, you're likely good at close ranges.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/374a4065.jpg

[arizonaranchman]

The jump from a 60gr to a 77gr bullet is a big change, so point of impact may be significantly off. You say you intend to use it for varmints so accurate point of impact at known ranges is very important when working with such small targets (compared to self defense where you still have a relatively large target area so a couple inches left or right really don't matter much).

Zero for the round/bullet you intend to use and the purpose it's intended - varmints with the 60gr in this case.

For self defense go ahead and use the 77gr and don't worry about re-zeroing cuz you're dealing with a large target and short distances 99% of the time.

[arizonaranchman]

Skintop's response was not posted at the time I began my response above. Excellent demonstration to show the change in impact with bullet weight changes - at 50 yards in this case. Imagine the differences at 100 to 200 yards when varminting and trying to blow up a prarie dog with a 4" chest cavity.

Now in Skintop's case this was a steady fire target at relatively rapid pace unlike a varminter who may have many seconds or no time limit between shots to deliver a good hit. Still the point can be seen in his photograph that if you're dealing with a SMALL target you need to be precisely dialed in with the exact load you'll be using.

[MistWolf]

The only way to find out what sight changes, if any, need to be made when switching between loads, is to go out & shoot them and keep record of your findings

[tuck]

I use a TR-24R on this particular rifle. What do you think about simply marking/remembering the elevation between the 2 rounds and adjusting for it? See any reason not to go that route?

I do this for my .308 when changing between loads. I see no reason not to do it for your AR.

[Belmont31R]

I would zero to the load you are going to use when it counts.




As far as POA/POI with different loads MOST Ive tried are all acceptable in deviation up to a point. You'd probably start noticing around 300 yards. Some more than others.



These were all shot at 100 yards with the same zero, and on different days with different weather:


http://i274.photobucket.com/albums/jj245/BM31R/002356a5.jpg

http://i274.photobucket.com/albums/jj245/BM31R/a68ba35e.jpg

http://i274.photobucket.com/albums/jj245/BM31R/3a553b0a.jpg

http://i274.photobucket.com/albums/jj245/BM31R/7cc39664.jpg


You should, however, do your own testing to see what your particular setup. Its just been my experience most loads are very close to each other at 100 yards. Even a 2" difference at 100 will only be 6" at 300. Still good enough to be making COM hits.

[davidjinks]

Probably a bit anal to do so I suppose, but do you guys re-zero when you go between rounds? When I return from overseas, I was considering rezeroing from my 77gr to a 60gr V-max since I shoot a lot of varmints. I use a 200 yard zero for all ammo with my m4ergy and I figure the max difference in rise isn't enough between the two to make much difference...especially since any unlikely defensive situation would likely be within 15 yards

How about for those of you who shoot both heavy (75gr+) as well as the much lighter weight varmint rounds, such as the 40gr's?


I will re-zero when I switch up my ammunition.

That is if it's a permanent change. If I'm just using a different weight bullet for training, then no.

My main go to ammunition right now is Hornady Tap 75 Gr. (.223). My back up ammunition is MK262 MOD1. I see a difference when shooting at longer range between the two (200 yards or more).

Shorter ranges, I haven't seen a huge difference.

[COVERBUSTER]

For varmints ? Why not rezero ?? Get a data book and keep track of your dope for what you shoot , then you can switch back and forth willy-nilly as you wish .

Only makes sense .

[cacop]

The more intense your accuracy needs the more anal you need to be.

For example one of our SWAT team snipers uses only two loads for his rifle, one for barrier and one for open shots, and he has his data down. Now on his entry gun he zeros with the duty ammo but shoots practice ammo. He considers the POI difference between the two for entry purposes unimportant.

Our pool patrol rifles are zeroed with 75 gr TAP but we practice with 64gr Win Ranger. The difference isn't much for those purposes.

For nailing varmits I would rezero or at least know the difference for POI. If this is a self defence gun only I wouldn't worry about it.

[BaileyMoto]

For varmints ? Why not rezero ?? Get a data book and keep track of your dope for what you shoot , then you can switch back and forth willy-nilly as you wish .

Only makes sense .

The idea would to be zeroed for varmints, but not worry about the 77gr zero when going between rounds or having to pick it up for SD

On a side note, the difference in max rise between the 60gr vmax and the 77gr SMK is about .4 to .5" a bit after 100 yards, assuming a 200 yard zero. I'm not sure how that would translate if the zero wasn't calibrated when switching from the 60gr to the 77gr. Guess I'll just have to get out to the range and shoot the 77's and see how close I am at ranges and see if I find it acceptable. As mentioned, the 77gr I keep for a SD situation...which equates to relatively short distances in all reality. I keep 77gr on hand due to the fact that it's all I shoot from my mk12.