What I learned today

I have read about your zero changing from day to day, depending on multiple things. I was shooting low today, mostly 8 ring. I decided to kick up my match dot 4 clicks and bam. The next target I fired a 95 with all shots inside the 9 ring. I had a hard time believing that the zero would change depending on the day, but now I am a firm believer. One question I have is, at the end of the day, do you reset your zero back to what it was before you changed it?

I am still working on my blank target lesson and came close 3 times today of getting two strings of 10 shots in the circle.  I was getting two groups of 5 shots one group high the other low.  I changes out grips going back to the slabs and I started to get one group centered.  Still can't complete the drill I get one string all in the circle overlay and then one shot just out side the next string.  

The change in elevation could be grip or if you are shooting outside the tempature.  Were you shooting the LL?  Don

25 yards slow fire today

Bright sun vs  cloudy over cast makes a difference for me at 50 yards.  This is with iron sights.  Seems to change the size of the black when holding at 6 o'clock.

I dont know that your zero changes with a red dot, at least at 25 yards. I've had my zero set for six months, when my groups are off center I know its just me.

It's a well known fact that the sun will effect iron sights. My thoughts on red dot sight changes is due to expansion. I shoot slide mount only and thinking that Aluminum expands at almost twice the amount of steel the difference in expansion maybe the cause of zero change. So when making a scope base I cut quite a bit of aluminum out of the ejection port location. The screws to attach the mount are only under the spot where the rings are placed.This will allow the base to distort yet not have enough force to effect the slide. I never use loctite on the rings, I prevent movement by having the ring located to prevent forward movement of the scope. If I change scopes I make a spacer ring. That will allow the scope to expand yet not distort to move zero. I have yet to experience zero change from day even hot day to cool day.

Possibly could be your NPA being off a little. I have seen it more often with left and right but it could be up and down if your shooting narrower or wider than normal. I adjust my foot position before I will touch my sights. Just something to keep in mind.

Could be shooter but Adam has told me the AMU shooters have experienced the same thing! These guys are some of the best in the country, train every day. When High Master 2650+ shooters have a similar problem I'm thinking something is creating it. Plus Their having the best you can get in Ammo, Guns, Scopes and everything else tends to have me look for something other than shooter or equipment
 For example Adam shot well at Perry this past year. Gun shot as expected in every event as expected. On 45 day the first shot slow fire was a 6 o'clock 6, thinking he did it he shot again, same thing in the same spot. Moved sights up and shot great for the rest of the match. If it were only him having the problem other AMU shooters claim the same thing, shot is out of called impact, adjust the sights and everything is OK for the rest of the match until a match or 2 later.

Froneck wrote:Gun shot as expected in every event as expected. On 45 day the first shot slow fire was a 6 o'clock 6, thinking he did it he shot again, same thing in the same spot. Moved sights up and shot great for the rest of the match. If it were only him having the problem other AMU shooters claim the same thing, shot is out of called impact, adjust the sights and everything is OK for the rest of the match until a match or 2 later.

In high power most shooters know to adjust for the angle of the sun in relation to the target.  This is because we don't actually see object, rather we see the light that is reflected off them.  Refraction?  

The above stated, its hard to comprehend that at 50 yards the reflections of light off the targets could change more that a fraction of an inch.  Hard to comprehend but add factors like air density, air rising or falling due to temperature changes and so one and...

I wouldn't normally adjust. But I was calling X's that were directly 6 o clock in the 8 ring

I understand the sun and also heat created mirage in rifle shooting. I'm sure it will happen in pistol too but not to the extent being reported at 50 yards and to a lesser degree at 25.  Sure an X could be shifted to a 10. Remember the AMU Pistol is in with the same group that shoots rifle and did also shot international so information about sun and heat would have been explained if it was that drastic. Some Pistol shooters do shoot some rifle when time permits.
 Sun does effect Iron sights so impact change will follow the sun and well known by those that shoot service pistol.

VolScorpion wrote:I have read about your zero changing from day to day, depending on multiple things. I was shooting low today, mostly 8 ring. I decided to kick up my match dot 4 clicks and bam. The next target I fired a 95 with all shots inside the 9 ring. I had a hard time believing that the zero would change depending on the day, but now I am a firm believer. One question I have is, at the end of the day, do you reset your zero back to what it was before you changed it?

To address the last question... I would leave the sight where it was at the end of that session, but make a note of what happened, and the conditions (time of day, indoor/outdoor, sunny, windy, hot/cold, etc.).  If it changes again in the near future, I'd do the same thing (adjust it at the beginning, then leave it and take notes).  After a few of those changes, you might see pattern (like it toggles between 2 adjustments based on hot/cold), in which case you'll have a pretty good idea of what's happening.  But if it happens pretty much every time you shoot, and the POI is moving all over the place randomly, it's probably either something wrong with the scope, or your stance/grip is not consistent.  It's hard to meaningfully analyze 1 data point.

Elevation change is well known to Metallic Silhouette shooters. Using iron sights with 6 o'clock hold against black targets on long distance. They say: "Sun's up - shots up, Sun's down - shots down".
The rationale behind it is usually attributed to the amount of light they see between the front post and the target. To assure the upmost precision the amount of light "strip" they see is very small. On the sunny day its easy to identify. On the overcast day the perceived amount of light is less and to compensate the shooter allows for larger gap by aiming lower. Sights setting is normally different for sunny day and overcast day and noted in their logbooks, or sights setting cards. Also sights settings are verified before the match to correct for the weather and light conditions. For shooting 1/5 scale targets (~4" x 6") at 100m with iron sights IMHSA shooters need to consider every variable and sun light is one of them.

Most likely it is expansion or spdistortion of the dot laser and or the reflective lenses more than the mount.

I wasn't going to, but I'll chime in:

All this discussion has me wondering:  How many of you that have noticed changes in zero have written in your journal about those changes? (bdas has the right idea about noting changes.)

Score books used to have all kinds of entry spaces for details like:

range
date
time of day
angle of sun
elevation of sun
sun or rain
temperature
ammo used
gun used
etc.

There were reasons for all these details - the first shot down range counts.

Those that are serious about competing seek every advantage.  What better advantage than knowing how the environment affects your zero and being able to make informed adjustments beforehand?

Even more basic, how many of you have a particular base zero either painted on your sights or noted in your journal?

In the open sight days, top shooters knew how many clicks from bottom and how many clicks from left (or right) extreme to place their sights to get a basic zero.  They then used their empirical data in their journal to trim those settings for the environment.

For today's dot shooters, how many have marks on their scopes showing 25/50 yard base zeroes?  How many know how far a click/line moves their impact?

Based on the above, I would suggest the OP strive to have a base zero and trim data to use at the next match, rather than wondering where to leave the sights and hoping.  To be fair, I know that it takes a lot of note taking and observation to do justice to all this, but if you really are trying to do your best, seek every advantage.  If you don't yet have enough data, now's the time to start gathering.

Note:  I always have to figure out a reason for everything.  It may not be the true reason, but as long as it makes sense to me, it's adequate to calm my inquiring mind.  But, if possible, forget about figuring out the reason and focus on the observed results.  In the long run it doesn't matter why the zero changes if you can look in your journal, make adjustments and start with a good zero.  This leaves you room to focus on your shot plan rather than wondering.

Ed Hall wrote:
All this discussion has me wondering:  How many of you that have noticed changes in zero have written in your journal about those changes? (bdas has the right idea about noting changes.)
.......
For today's dot shooters, how many have marks on their scopes showing 25/50 yard base zeroes?  How many know how far a click/line moves their impact?
.......

I have marks on my BE pistol RDS sights and I know the click values and number of clicks between the distances.
For my MS guns I have a sighting cards for every gun/scope/ammo combination for every distance, number of clicks to zero and between distances.
Zeros verified before every match and corrected as needed. 22 ammo I buy in the case/lot quantities and when lot changes, zero verified and corrected on the card as well. Also my 22 ammo is gun specific, depending on the barrel preferences and I have to maintain inventory of the target ammo for each gun.
BE with two (closer) distances only is so much simpler and targets are much bigger comparing to MS. Many animal's angle size is like x-ring only and missing it is a lost score. Missing X-ring in the BE will yield 10, or 9, or even 8, but not a total score lost.

AMU gets quite involved with testing of ammo lots and assigning lots to what ever gun it shoots best in. 45 ammo is tested before acceptance. They shoot every day and know exactly where their zero is and the amount of impact change each click makes. They have a group of armorers along with the shooters that constantly are checking every thing. Remember 10, 9 0r 8's may not be a total score loss for the average shooter but at the top level it is. A few years ago the top 3 winners at Perry were only separated by X's. All 3 shot the same score. This past year Adam beat Zurek for second by X's and those two 6's cost him first place, he was leading up to the 45 match but fell behind with 2 unexplained 6's dropping him only 3 points behind the winner. All the team members are experiencing the same unexplained zero movement. Shooting the assigned lot the same day the 45 zero moved after shooting OK in CF in smaller matches that have only one relay yet after zero is changed it remains OK for a match or 2 then happens again! If it were Sun, the moon, temperature, Ammo or any other condition change all will have the same similar problem at about the same time but seems to be random effecting different shooters at different times.