Had quite a bit of drift; I think I know what it may be but wanted some input

[TheGerman]

I've been kicking this around as to what could be wrong all evening as its made me miss a good amount of my first round hits at distance today, and now that I've really noticed it, its been happening for a while.

Wanted to see what everyone else thinks it is so I can start narrowing things down to look at. It's NOT a loose scope rings, loose stock screws, scope malfunction, bad ammo, dirty barrel, bad technique issue. Personally, I think that my optic is just a hair canted to where at 200y with a 22LR its making a huge difference.

Today went out and shot 5 x 5 round groups at 100 with my usual Center X ammo. POA/POI all center, all 5 groups were at or less than an inch with some basically making one large hole in the 2 inch sticker.

Put some steel gongs out at 180 and 215 and check my data card, make elevation adjustments and there has been barely a 1-3 MPH wind going the entire time. I've been walking around with my kestrel for fun while putting targets out and stopping at the target, mid way, etc just to see if I can estimate the wind and to see if there is anything weird going on like gusts coming over a hill, etc. Nothing, all day the wind never went over 3mph wile shooting; herein lies where I think I noticed something due to the fact there was next to no wind, with some times the mirage being a straight sleeping boil at the target.

For 180 (at a 100y zero), I need 4.4MILS on the gun. Dial it, hold .2MIL left for the 2-3MPH wind coming from my 9 o clock and first round I can see I am a good bit to the right but elevation is dead on. Adjust on the reticle for the miss .4 and hit. 3 more held at .6 right, all 3 hits. 5 more at .6 right, 5/5 hits on a 2 inch steel spinner gong.

This exact same thing happened at 215 shooting at a 3.25 spinner gong. Was .4-.5 to the right on the first round, adjusted and made 4/5 hits.

I know for the 22LR wind is much harsher than for centerfire. But in order for me to need .6MILS left, I'd need a full value 5-7MPH wind to push it that far. I'm not crazy, and I wanted to prove/disprove what was going on so I kept walking around and checking wind at the gun, midway, at the target and would stay at each for a minute or two. The entire time I was there, MAYBE 3mph on a gust which would still only account for roughly .2MIL wind but most times there was so little that the propeller in the kestrel wouldn't even move.

I put some cardboard behind the 215 target to see what the rounds were doing; dead center hold, follow through, reticle never left the target and all 5 would group very nicely on the cardboard .6-.7 to the right of the gong. I dial or hold .6MIL and hit almost every shot.

So its had me trying to figure out, where in the hell is basically .6MIL of horizontal shift coming from in basically no wind?I'm sure that with the 22LR trajectry at 200 there is SOME wind and can probably eat .1-.2 off of the shift, but even if I went and added spin drift, thats only .1MIL at that distance. The only thing I can think of is the reticle is slightly canted (doesnt seem like it to me) and may be the obvious answer. Question is, how little of a cant can kick you .5-.6MILS off at 200?

 

[J!m]

Hmmm. I know you know more about the science then I do. But if your groups are tight, but require windage, did you do a thorough check of the camber and bore? Next I’d re- boresight it. You know where you are, and are consistently dialing more wind than you have, so maybe your zero is not correct due to a loose scope turret perhaps?

im not able to give a “it has to be xxxx” answer but I do know that with the .22 you better know your dope (not suggesting you don’t) because “fly farts” blow those bullets off line.

 

[jbell]

It sounds like a canted scope to me. I have a few questions:

-Is this the first (or only) time you have seen this or shot this rifle at that distance, or does it happen each trip to the range? If it is the only time then I would simply shoot the same course of fire on another day and see what happens (to help eliminate environmental conditions).

-What distance are you zeroed at? If your zero is at 100 then shoot it at 50 or less and see if you have a shift in the opposite direction. If zeroed at 50 you should see some shift at 100 yards, but you may need to get very particular about your POI. Finally on a good calm day shoot a tall target test shooting the full range of your elevation adjustment. *Note on the tall target test: if your scope is zeroed at the mid point of its travel then include adjusting down on your test to get the full range of adjustment, but this requires to start somewhere in the middle of the target. You can also verify your scopes accuracy if you precisely measure the distance to target and POI shifts.

I know this is a bit basic, but it should answer your questions.

 

[jbell]

Oh, that made me think of one other possibility. You said you needed 4.4 mils from a 100 yard zero to get to 180. What rifle, scope, ring height, and base are you using, have you checked how much vertical adjustment you have from your 100 yard zero?

What I am getting at is rimfire's use up a lot more elevation than centerfires to zero, this is why a canted base is a must for shooting up to or past 100 yards. With that said if you have a scope with minimal internal adjustment, and use up a lot of it just zeroing then you may be getting close to max travel. Even if you have a canted base, but have a scope with a small amount of internal adjustment mounted in rings higher than needed giving you a scope mounted way over bore center you use up more adjustment. A rifle with a barrel mounted with the bore center not indexed to 12 o'clock can also cause you to eat up adjustment before you ever start shooting too.

Those were just some things to think about when shooting long distance with a rimfire. But getting to the point an erector tube is round and depending on how your scope is made internally you may experience some horizontal POI shift when you adjust your elevation to the extreme limits especially if you initially have to adjust left or right to get your initial zero. So if your close to maxing out your scope at 180-215 yards it could be from this.

One other thing you can try the next time you shoot is if you see the same POI shift go back to your 100 yard zero and confirm, then shoot at 215 but use your reticle as opposed to adjusting. That will tell you if it is a scope issue or atmospherics.

Good luck, keep us posted.

 

[Sheldon N]

Question is, how little of a cant can kick you .5-.6MILS off at 200?

Doesn't take much cant to affect things.

Bubble level on scope, trued up to the reticle against a plumb line?

Shot a tall target test to make sure the erector travel matches up to the reticle?

 

[TheGerman]

I'll sum up for some of the questions:

- Vortex 4-16 Viper PST FFP; for the 4.4MIL adjustment, I still have another 10 MIL in the scope left after I make it
- Badger Rings, 1.85 center bore to center optic measurement; the objective barely clears the barrel by roughly 1/3-1/2 an inch.
- Zero'd at 100
- DIP base on the CZ455
- I shoot 150+ all the time. I normally am not lucky enough to get a totally still day, so most misses to the side would likely have been (or blamed on) shooting in 5, 10, 15 mph wind. Since yesterday was amazingly still, even for a 22, this error became apparent which actually makes me a bit happy overall as now some WTF moments for first rounds can be explained.
- While shooting yesterday, I went from the 215y while having the cardboard behind it and grouping 5 shots very close together, but to the right, then switched immediately to the target at 100 and put 5 rounds basically all in the black middle of the 2 inch sticker

I figure it has something to do with cant. The only thing that made me second-guess this is that apparently I am VERY consistent because its exactly the same amount of distance to the side I need to adjust for due to it, EVERY time. If I wasn't consistent, it would be all over the place with some flying way to the right, then a few coming back in, etc.

 

[jbell]

Very solid info! With all that taken into consideration I would definitely run a tall target test at like 50 yards. Get a big enough target so you can max out the scope in both directions. That should tell you what you want to know. Also like Sheldon said compare the reticle against a plumb line, but do it so you are holding the rifle naturally (close your eyes and get your natural POA at the plumb line and then open them without moving the rifle and see how square your reticle is). You want the scope plumb to gravity with the rifle held naturally (not necessarily the scope plumb to the rifle. Again info you probably already know, but worth checking to properly diagnose the unexplained POI shift.

 

[TheGerman]

I think I may have stumbled across the problem. As with all things, its something you're not looking at that you looked over before and it passed review and it comes back to cause a problem later. Unless I am reading this wrong, I think its less of a cant issue and more of a ghost in the machine.

For my 22LR data I use data cards I made and updated from JDM using data I compiled down to what the length of the actual 40g projectile I shoot is. I was going through a data chart in the process of truing BC/velocity to get a match for some marker distances I set up along the way and compared the actual adjustments for a hit versus the numbers JBM gave me and something peculiar happened. Check my logic on this, because if my train of thought is right, I just found the missing .5MIL. Basically, I had it assume I zero'd the gun in 5mph wind, so no use adjusting for a 5mph wind deflection twice.

So JBM gives you a checkbox that says 'Windage correction for zero range' as well as 'Elevation correction for zero range'. You always check the elevation correction otherwise you are getting a cumulative adjustment rather than adjustment from zero; I was under the impression this was the same for windage and upon further review I don't think it is. Why? Well, it dawned on me that when it calculates the windage data card and you checked 'windage correction for zero range' it now gives you 0 as the windage adjustment, regardless of the wind you entered. This then basically does the opposite of why you removed the elevation adjustment; it removes the zero distance wind from the equation (why youd want that, I have no idea). So here's a quick calculation I just did with the exact same bullet, velocity, distances, 5mph 90 degree wind, everything. Only difference is 1 had the windage zero correction checked, the other does not.

First is checked

0	***	***	***	***	1071.3	0.941	101.9	0.000	***	***
10	-0.4	-0.4	-0.4	-0.4	1055.8	0.927	99.0	0.028	0.0	0.0
20	1.7	1.7	-0.4	-0.4	1041.3	0.914	96.3	0.057	0.0	0.0
30	2.1	2.1	-0.3	-0.3	1027.6	0.902	93.8	0.086	0.0	0.0
40	2.1	2.1	-0.3	-0.3	1014.6	0.891	91.4	0.115	0.0	0.0
50	1.9	1.9	-0.2	-0.2	1002.2	0.880	89.2	0.145	0.0	0.0
60	1.6	1.6	-0.2	-0.2	990.5	0.870	87.1	0.175	0.0	0.0
70	1.2	1.2	-0.1	-0.1	979.2	0.860	85.1	0.206	0.0	0.0
80	0.9	0.9	-0.1	-0.1	968.4	0.850	83.3	0.236	0.0	0.0
90	0.4	0.4	-0.0	-0.0	958.0	0.841	81.5	0.267	0.0	0.0
100	-0.0	-0.0	-0.0	-0.0	948.0	0.832	79.8	0.299	0.0	0.0
110	-0.5	-0.5	0.0	0.0	938.3	0.824	78.2	0.331	0.0	0.0
120	-0.9	-0.9	0.1	0.1	928.9	0.816	76.6	0.363	0.0	0.0
130	-1.4	-1.4	0.1	0.1	919.8	0.808	75.1	0.395	0.0	0.0
140	-1.9	-1.9	0.2	0.2	910.9	0.800	73.7	0.428	0.0	0.0
150	-2.4	-2.4	0.2	0.2	902.3	0.792	72.3	0.461	0.0	0.0
160	-2.9	-2.9	0.2	0.2	893.9	0.785	71.0	0.495	0.0	0.0
170	-3.5	-3.5	0.3	0.3	885.7	0.778	69.7	0.528	0.0	0.0
180	-4.0	-4.0	0.3	0.3	877.7	0.771	68.4	0.562	0.0	0.0
190	-4.6	-4.6	0.4	0.4	869.9	0.764	67.2	0.597	0.0	0.0
200	-5.1	-5.1	0.4	0.4	862.3	0.757	66.0	0.631	0.0	0.0

Second is not checked.

0	***	***	***	***	1071.3	0.941	101.9	0.000	***	***
10	-0.4	-0.4	0.1	0.1	1055.8	0.927	99.0	0.028	0.0	0.0
20	1.7	1.7	0.1	0.1	1041.3	0.914	96.3	0.057	0.0	0.0
30	2.1	2.1	0.1	0.1	1027.6	0.902	93.8	0.086	0.0	0.0
40	2.1	2.1	0.2	0.2	1014.6	0.891	91.4	0.115	0.0	0.0
50	1.9	1.9	0.2	0.2	1002.2	0.880	89.2	0.145	0.0	0.0
60	1.6	1.6	0.3	0.3	990.5	0.870	87.1	0.175	0.0	0.0
70	1.2	1.2	0.3	0.3	979.2	0.860	85.1	0.206	0.0	0.0
80	0.9	0.9	0.4	0.4	968.4	0.850	83.3	0.236	0.0	0.0
90	0.4	0.4	0.4	0.4	958.0	0.841	81.5	0.267	0.0	0.0
100	-0.0	-0.0	0.5	0.5	948.0	0.832	79.8	0.299	0.0	0.0
110	-0.5	-0.5	0.5	0.5	938.3	0.824	78.2	0.331	0.0	0.0
120	-0.9	-0.9	0.5	0.5	928.9	0.816	76.6	0.363	0.0	0.0
130	-1.4	-1.4	0.6	0.6	919.8	0.808	75.1	0.395	0.0	0.0
140	-1.9	-1.9	0.6	0.6	910.9	0.800	73.7	0.428	0.0	0.0
150	-2.4	-2.4	0.7	0.7	902.3	0.792	72.3	0.461	0.0	0.0
160	-2.9	-2.9	0.7	0.7	893.9	0.785	71.0	0.495	0.0	0.0
170	-3.5	-3.5	0.8	0.8	885.7	0.778	69.7	0.528	0.0	0.0
180	-4.0	-4.0	0.8	0.8	877.7	0.771	68.4	0.562	0.0	0.0
190	-4.6	-4.6	0.8	0.8	869.9	0.764	67.2	0.597	0.0	0.0
200	-5.1	-5.1	0.9	0.9	862.3	0.757	66.0	0.631	0.0	0.0

Look at the 100y zero difference, as well as every wind call from 100-200. They're all .5 different.

Can someone check their data book and confirm that for a 40g 22LR round going 1066fps or thereabouts, you're having to adjust for/close to the 2nd charts wind holds? I'm betting this is my problem as well as a slight cant.

 

[steve123]

22's are weird like what you experienced.

Yesterday at our NRL22 match with light and switchy winds, but changing to calm conditions on occasion, I saw some funny things happen.

One stage at 100Y I could aim right on with little to no wind, but the next stage at the same distance, in what seemed like only 2-3 mph half value wind I had to aim .5 mil out to hit center. No choice but to believe the bullet and get 10's??!! This phenomenon gets worse at 200Y.

The problem is it's different every time I go out, hard to make sense of something like wind that is invisible for the most part - unless one has a bunch of benchrest flags strewn all over.

 

[TheGerman]

22's are weird like what you experienced.

Yesterday at our NRL22 match with light and switchy winds, but changing to calm conditions on occasion, I saw some funny things happen.

One stage at 100Y I could aim right on with little to no wind, but the next stage at the same distance, in what seemed like only 2-3 mph half value wind I had to aim .5 mil out to hit center. No choice but to believe the bullet and get 10's??!! This phenomenon gets worse at 200Y.

The problem is it's different every time I go out, hard to make sense of something like wind that is invisible for the most part - unless one has a bunch of benchrest flags strewn all over.

That's why I do 100 as a warm up and then do further targets as well as UKD with a 22. It makes you pay attention to even a 2mph wind, whereas with most centerfire guns don't even register it yet.

So with enough of that practice, switching to ELR centerfire it becomes much easier.

 

[JG26_Irish]

Have you considered the affects of spin drift on your projectiles? Most 22lr's spin the bullet clockwise (right hand twist) in such a way as to cause it to drift from left to right over time during flight. The longer the shot the more drift you will see. If you are zero'ed at 100y and shoot at 180 or 210y you should see both more vertical drop due to gravity and a small increase in drift to the right based on time of flight, causing the POI to be to the right of the POA. It is very difficult to see this unless you are shooting on a dead calm day since the affects of cross winds usually over shadow the drift variable. If you watch your projectiles as they fly down range they look like a pitcher's curve ball as they arc down and to the right. This can be seen with the naked eye when the light angles are right. As I recall, it is easier to see when the sun is behind your shoulder to one side or the other. A good clear optic helps and good clear eyesight. Slow-mo camera is another method if you have access to one. It is a small variable in the bigger scheme of things but is noticeable with the slow 22's when shooting at extreme distances using precision equipment and technique. Plus as the bullet travels to the far reaches of its trajectory it drops faster and this tends to increase the rate of spin drift plus it is going slower making it more noticeable at longer ranges. If you are consistently seeing your POI going a little right of what you expected at longer distances and the winds are dead calm, this could be your culprit. As I recall, it was working out to about 1 click left for each 100y past my zero range, but I do not have my ballistics data card with me at the moment. I would still check for a canted optic too. It is all about variables and this one (spin drift) is a small item. What tipped me off was your saying it was while shooting on a calm no-wind day.

One less likely culprit can be swirling winds due to terrain and/or building structures. I sometimes compete at a range which features a peaked roof shelter on the firing line and a 2nd structure to the right of the range. The two buildings combine to create air movement that swirls from left to right and up and down as the vortices travel off of the roofs and across and down range. It can be maddening even at 50y tgts to shoot a 10x perfect shot and then have the next shot go down 1/2" and the next go up 1/2" when the winds are only about 5mph. It does not do it all the time so adjusting for it can be frustrating. Placing wind flags down range at 10y increments will show the wind blowing left in some places and to the right on others and no wind at all in yet others all in only 50y. Crazy. Reading the mirage can help but above about 10mph it gets wiped out.

Irish

 

[TheGerman]

Whatever it was its fixed.

Put on Badger rings I had instead of the Vortex rings that came with the optic, replumbed the reticle on some 550 cord at 100 yards and managed to shoot out past 300 today with zero issues.

 

[steve123]

That's why I do 100 as a warm up and then do further targets as well as UKD with a 22. It makes you pay attention to even a 2mph wind, whereas with most centerfire guns don't even register it yet.

So with enough of that practice, switching to ELR centerfire it becomes much easier.

What I meant was a 2-3 half value wind should be 2 clicks not five. My point was that there is no way to determine wind sometimes and I won the match BTW.