Switching bullets effecting zero?

[T3ninja]

Boy that'd be a hard decision to make.... where would you rather be lucky... shooting, or.???

 

[T3ninja]

I thought "getting lucky" only applied to horseshoes and the bedroom Great discussion - I continue to learn from LRH

 

[User4302021]

Appreciate the explanation. Now my next question is: How do I anticipate this or predict this? I'm assuming when the sun is low in the sky the refraction 'illusion' would be greater?

None of that is a given. It depends on where the thermal interfaces are in relation to the target and the angle of the sun.

In the example I mentioned, the deep shaded valley was a cooler body of air about 400 yards deep, and the sun was skipping of the surface of it as if it were a pane of glass. The target was 800 yards away in the bottom of the valley. Our bullets, which had been hammering that exact target with regularity 4 hours earlier, were now 1mil high.

Less extreme examples would be like what I was seeing just a couple days ago. I was on a flat 200 yards range, and the sun was peeking in and out of heavy clouds. My POI formed 2 distinct groups, one 1 moa above the other, with all rounds fired under cloud cover going high.

When you dope your rifle, confirm zero in the exact conditions you are going to dope in. If you can zero and dope your rifle under gray skies, so much the better. Next best thing is very early in the morning before the sun gets strong.

 

[Cesky fousek]

I used the search but didn't see what I was looking for.

So just a quick background followed by simple Q.

Rifle- .300 win 28" proof in XLR chassis Meopta optika6 <—- has performed flawless and I have no reason to think the scope is on the fritz.

2 loads ... 215 Berger and 190 Nosler CC. Both loaded with Ramshot magnum.. rifle is zeroed at 100 with the 215's

So I get to the range and first shot of the day is at 600 yards and it is perfect! So I follow with 2 more perfect shots at 1k! I am EXTREMELY happy. I put the rifle away and plink with the .308 for a bit. Pull it back out and start to burn up my 190 noslers (8-10 shots in about 35 min)

After letting everything cool off and re painting targets I wanted to finish the night off with the 215's. 800 yards... boom, Nothing. Sent another, nothing ???? After the 3rd shot I found the round hitting .4 mil low. With only one round left I shot again and it hit .2 low... out of ammo and range is closing so no more testing...


So the Q is, has anyone noticed a big change in impact from switching bullets? I never changed my zero. I keep my zero set for the Berger's and used the noslers just as trigger time. My ES/SD is very good (under 10), weather conditions were essentially the same, and I had a kestrel with me.

Thanks in advance !!

My advice is check you scope cause Meopta has issues with holding zero

 

[T3ninja]

Ok, so I was able to get back to the range today. Conditions were near perfect. I essentially did a repeat of last week. This week it started with a CLEAN, and cold barrel. Temps and environmental was really similar to last week. Anyway.

Started with berger 215's at 600 yards cold/clean 1 shot. Bingo, less than .1 low. Put first round hits after that within .1mil of POA at 700,800,900,950 and 1000.. so total of 6 round in about 25-30 min...

Now I shot some of the 190 noslers, 8-10 of them, plinking at 3,4 and 500 yds...

Killing time with .308 for about 45 min or so...

Now, back to the bergers, 800 yards, same dope as before, same conditions etc, shoot... miss, Send another round, impacted about .4-.5 mil low, sent a 3rd and it was about .2-.3 mil low. Let the barrel cool for about 15 min, then sent a 4th and was only .1-.2 low. So, seems like the rifle is going back to "normal", I waited a few more min and then ran it from 1k back down to 600. 1k,950,900,800,700, and finished at 600...

This picture is of the very first cold/clean shot of the day, and also the very last shot of the day.. 600 yards.

 

[T3ninja]

And also the 950 plate.

 

[T3ninja]

So, thanks to everyone who put some thought into this. I guess moral of the story, clean your barrel when you switch components around. !! Good luck, happy shooting and have a great holiday weekend !!

 

[User4302021]

I have seen that sort of stuff when going between gilding metal jacketed bullets and solid copper, but I have never seen it between two jacketed bullets.

Good to know, I'll have to file that for later reference.

 

[Gunpowder]

It's interesting that it came back into zero after several shots.

Also I've noticed the changing light affecting poi, and it took me a long time to figure out what was going on. My home range of 200 yards is facing west, and I usually have the most time in late afternoon/evening. After sunset, you can count on your poi being .5 to 1 moa high. I would really think this could wreck a long range shot on game at last light. The old adage I read somewhere "suns down, sights down".

 

[CMP70306]

I had a similar issue with my AR using 77gr Berger Handloads and Federal 55gr FMJ. When the barrel was clean it would shoot the Berger's around 0.75 MOA, I would do some positional shooting practice with the Federal's then let the rifle cool. When I would then shoot the Berger's again the groups would open up to almost 2", cleaning it brought the groups right back down to 0.75".

The only explanation I could find was that the copper from the Federal's did not play well with the Berger's so I switched to Frontier .223 and it seems to have removed the issue.