Range Report 100 yard Zero changes with different ammo?

[Target In Sight]

Tried to zero my new AE MK3, S$B scope with AI mount, checked all equipment and all nice and solid.

The result shows that Fed 168/175gr. SMK both have a POI that is 0.2~0.3 lower than my hand load. Hand load is Lapua 155gr. Varget 45.5gr. with Lapua shell and CCI BR primer.

Since I plan to (always been) using my handload, I went ahead and used the hand load POI to zero.

Question: Does POI change over different ammo? or was it the recoil differences that influenced the shooter (me) and caused the POI to change?

Thanks in advance for any comments

 

[gstaylorg]

Re: 100 yard Zero changes with different ammo?

POI commonly changes between different loads. In general, the greater the difference in MV and projectile weight/length, the greater the difference you can expect in POI using a common zero.

 

[Target In Sight]

Re: 100 yard Zero changes with different ammo?

Thanks for the reply, for some reason, I just did not think 100 yard will have much of difference on the POI. Now that you have mentioned it, I do recall the POI differences when I did load development on my previous rifle. The hotter loads do have higher POI, but I thought it was due to more recoil.

Thank you!

 

[Graham]

Re: 100 yard Zero changes with different ammo?

Record the zero shift. Then you can keep track of two zeros.

 

[Target In Sight]

Re: 100 yard Zero changes with different ammo?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body">Record the zero shift. Then you can keep track of two zeros. </div></div>

Yes Sir., I did, and will get the MV for all 3, then work up the DOPEs.

Thank you!

 

[Oneteam]

Re: 100 yard Zero changes with different ammo?

Yes, poi changes often occur using different weight bullets if they are not in the same velocity neighborhood.

 

[grayghost]

Re: 100 yard Zero changes with different ammo?

+1

 

[tomcatfan]

Re: 100 yard Zero changes with different ammo?

I've gotten POI shifts of about .5" at 100 yds switching between 178 Amax and 175 SMK's. Both were pushed by 44.0 gr of Varget and Federal Brass. I think in general, your poi will change based on different ammo, at least me experience tells me so.

 

[skinnypitt]

Re: 100 yard Zero changes with different ammo?

yep, I even had a slight POI from just changing 140Berger VLD to 139 scenar keeping load and everything else the same.

 

[SaepeExertus]

Re: 100 yard Zero changes with different ammo?

POI can change even with the same box of ammo. It'll all depend on the bullet, the powder load, and as you shoot the barrel is gonna get hotter. As far as the shift between the 168/175 and the handloaded 155 all has to do with bullet weight probably a difference in powder load. Can't forget though that as you fire the poi is going to shift a little as your barrel heats up and even if your ammo is sitting in direct sunlight.

 

[opshin556]

Re: 100 yard Zero changes with different ammo?

Yes, POI will change quite a bit not only in regards to bullet weight, but powder charge, brass, primer, all kinds of stupid shit you wouldnt even think of.
My 168 fgmm is .6 mil high at 100 yards to my 175 fgmm, which is 1.2 mils LOW at 100 yards from 150 fmj federal red box.
go figure

 

[timelinex]

Re: 100 yard Zero changes with different ammo?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FORECON</div><div class="ubbcode-body">POI can change even with the same box of ammo. It'll all depend on the bullet, the powder load, and as you shoot the barrel is gonna get hotter. As far as the shift between the 168/175 and the handloaded 155 all has to do with bullet weight probably a difference in powder load. Can't forget though that as you fire the poi is going to shift a little as your barrel heats up and even if your ammo is sitting in direct sunlight. </div></div>
You definitely hit on a 'sore' subject there. Lowlight has argued to no end about no POI shift from the heating up of a barrel, and even did a video of it.

 

[Target In Sight]

Re: 100 yard Zero changes with different ammo?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FORECON</div><div class="ubbcode-body">POI can change even with the same box of ammo. It'll all depend on the bullet, the powder load, and as you shoot the barrel is gonna get hotter. As far as the shift between the 168/175 and the handloaded 155 all has to do with bullet weight probably a difference in powder load. Can't forget though that as you fire the poi is going to shift a little as your barrel heats up and even if your ammo is sitting in direct sunlight. </div></div>
You definitely hit on a 'sore' subject there. Lowlight has argued to no end about no POI shift from the heating up of a barrel, and even did a video of it. </div></div>

Yes, you beat me to it, I was gonna comment on the barrel heating subject too [video:youtube]http://youtu.be/3UZ-mApuUoM[/video]