What went wrong? Match question.

[seafury]

Hey guys. Hoping y’all could help me diagnose an issue I ran across in a match I shot yesterday.

Rifle: RPR 6.5 CM factory barrel, Vortex AMG (has been checked for tracking)
Ammo: 120 ELD-M 45g H4350 BR-2 Hornady 3x fired brass, neck sized.

I gathered velocities on the above load last week which according to my magneto speed was 2950 FPS however, I have had a helluva time getting lower SD, ES. For this load, SD was 12, ES 30 or so after shooting a five shot group to confirm zero.

So here I go at the match. First few stages have targets at 330 and 550. Shot those well. Misses I could easily attribute to my position stability and breaking the shot at the wrong time.

Here’s the problem. Later in the day I am consistently missing high. I end up back at 550 in a stage where I am taking a very stable prone shot with a rear bag. I take extra time to double check I have dialed elevation correctly (had been 3.2 Mils in the morning). I take my time with the shot. Impact is about half a mil high. I hold under .5 mil and still just over the target. I ended up holding under .5 at 550 for the rest of the match (still went over a few of the targets.)

What would cause this change in impact over the course of a 100 round match? Is my barrel speeding up? It had 500 rounds on it before the match started so it should be broken in plenty.

I’m confident the AMG is tracking and RTZ just fine.

Thanks for any input.

 

[PinesAndProjectiles]

I can't answer your question, however I found myself in a similar position on Saturday. Laying prone, targets out to 817. Went right over the top of most of them.

Next stage, elevation was fine again.

 

[seafury]

Weird. I should add, wind wasn’t doing much. 6 mph from 12 o’clock. Again. Max range was only 550

 

[diverdon]

It seems like you might need to recheck tracking. Could be the scope going haywire.

 

[_Raining]

Did you clean the rifle since the match? If not, you can go to the range and recheck your zero and MV.

 

[PinesAndProjectiles]

Weird. I should add, wind wasn’t doing much. 6 mph from 12 o’clock. Again. Max range was only 550

I also had winds from the 11:30 to 12:30 position.

At first I thought lift from shooting into a headwind, but I was nearly 3/4 of a Mil high.

 

[Mordamer]

Check the following:

1. Is zero still good? 9 times out of 10 the rifle zero is the issue. Many things can happen that could through you off .5 mil. Did you bump your muzzle device against something pretty hard?
2. If zero checks out then run a tall target test. Confidence in the scope means nothing if you haven't tested it. Scopes can take a dump at any time. A previous test before the issue showed up does not mean the scope is still good.
3. Velocity could be different, but it would have to be very different to be the only factor causing that much dope difference at 550 yards. I would check velocity anyways.
4. Check your ballistics calculator inputs. Did you make a mental error in using the 3.2 mils hold? Is it possible that dope was not correct the first time at 550? Punching your numbers into Strelok Pro and assuming a pretty average set of atmospherics I get 2.8 mils for 550 yards.

 

[sabrecross]

Hey guys. Hoping y’all could help me diagnose an issue I ran across in a match I shot yesterday.

Rifle: RPR 6.5 CM factory barrel, Vortex AMG (has been checked for tracking)
Ammo: 120 ELD-M 45g H4350 BR-2 Hornady 3x fired brass, neck sized.

I gathered velocities on the above load last week which according to my magneto speed was 2950 FPS however, I have had a helluva time getting lower SD, ES. For this load, SD was 12, ES 30 or so after shooting a five shot group to confirm zero.

So here I go at the match. First few stages have targets at 330 and 550. Shot those well. Misses I could easily attribute to my position stability and breaking the shot at the wrong time.

Here’s the problem. Later in the day I am consistently missing high. I end up back at 550 in a stage where I am taking a very stable prone shot with a rear bag. I take extra time to double check I have dialed elevation correctly (had been 3.2 Mils in the morning). I take my time with the shot. Impact is about half a mil high. I hold under .5 mil and still just over the target. I ended up holding under .5 at 550 for the rest of the match (still went over a few of the targets.)

What would cause this change in impact over the course of a 100 round match? Is my barrel speeding up? It had 500 rounds on it before the match started so it should be broken in plenty.

I’m confident the AMG is tracking and RTZ just fine.

Thanks for any input.

What were the atmospherics when you chronoed your load? What were the atmospherics when you shot the match. Were the two location different? What software were you using to get your numbers and were all the inputs double checked?

 

[AIAW]

3.2 MILs just seems high for a 120g ELD moving at that speed. I looked at my data versus some generic data based on your data (see below) and the numbers aren't off by much.

My data says 2.5 MILs to 550 yards for that bullet (granted I am moving it at 3030 FPS out of a 260R). Same atmosphere.

Your data ran though JBM (sight height guessed): 2.8 MILs

In fact, I have to slow down your bullet to 2825 to make the data match (again, this is sort of rough - but still valid in it's own).

You sure about that MV? Do you have DOPE for other distances that is known to be dead-nuts accurate?

 

[ShtrRdy]

Did you have a solid rear rest? I've noticed that if my rear bag isn't packed down the rear of the rifle can slide down off the shoulder causing a shot to go high.

 

[seafury]

Atmospherics on data gathering day and match day were pretty similar. Standard 60 degree California day. I was only able to confirm the Strelok Pro’s outputs at 450 before the match. Plugged 2950 MV into Strelok, it said dial 1.9 Mils. Shot at 450. I found I had to dial 2.2 Mils to center punch the gong. Plugged those numbers into Strelok’s truing feature. It said your new MV is 2800. WTF? Ok then. Those are the numbers I used for the match.

The weird thing is they worked for the morning half of the match, but not the afternoon. Weather did change much. No big temp swings.

Thanks for the suggestions so far fellas.

 

[seafury]

Did you have a solid rear rest? I've noticed that if my rear bag isn't packed down the rear of the rifle can slide down off the shoulder causing a shot to go high.

Yes, for those prone shots, I was very happy with my position. Using atlass bipod in front and a tactical udder in the rear.

 

[260284]

Atmospherics on data gathering day and match day were pretty similar. Standard 60 degree California day. I was only able to confirm the Strelok Pro’s outputs at 450 before the match. Plugged 2950 MV into Strelok, it said dial 1.9 Mils. Shot at 450. I found I had to dial 2.2 Mils to center punch the gong. Plugged those numbers into Strelok’s truing feature. It said your new MV is 2800. WTF? Ok then. Those are the numbers I used for the match.

The weird thing is they worked for the morning half of the match, but not the afternoon. Weather did change much. No big temp swings.

Thanks for the suggestions so far fellas.

How many round on the barrel?

Also, what was the mirage like on data gathering day and match day. Mirage can make a difference on where the target actually is compared to no mirage.

 

[Olen_4504]

These things are so frustrating. It's all science - it has to be something. but sometimes you just struggle to pin point the issue.

I shot a two day match a few weeks ago. Day 1 - fellow shooter telling me I was favoring high plate on most shots. Then we get to the long range stage at the end of the day - and i drop a few shooting a little high - but not much. It was wet and rainy on day 1 - so i attributed it to higher pressure/speeds.

No rain the next day. Next morning we start on the long range stage. 3 tenths high over the 950y plate. (prone - super solid and stable). So I true my data and it comes out to 2905fps (normal MV for that load is 2893). I shot the rest of day 2 with a 2905 MV and had no issues.

another buddy in my squad - also shooting a 6br with same bullets - had no issues on day 1. Day 2 - SAME ISSUE as me - 3 tenths high at longer range. he also adjusted his MV to 2905 and shot the rest of the day with no issues.

there was a 100y playing card stage on day 2 and my zero was dead nuts on. all environmentals in weather meter/ballistic app good to go.

shot my load over a chrono the next day - was actually 15-20fps SLOWER (2873).

shot the same load yesterday at 975yards, put a half moa 3 shot group dead center of the plate.

I still have no idea what happened that day. makes no sense to me. Nothing in my ammo prep, data inputs, gun, or scope changed from previous matches. I've just moved on at this point

my point being - i understand your pain. a lot of the posters above had good suggestions on things to double check still to try to narrow it down. good luck!

 

[seafury]

How many round on the barrel?

Also, what was the mirage like on data gathering day and match day. Mirage can make a difference on where the target actually is compared to no mirage.

Just a slight amount of mirage on match day. 500 rounds on barrel at start of match

 

[davsco]

ammo cooking in the sun, or sitting in your chamber/gun longer? yeah check zero and speed to rule that out.

 

[Mordamer]

Atmospherics on data gathering day and match day were pretty similar. Standard 60 degree California day. I was only able to confirm the Strelok Pro’s outputs at 450 before the match. Plugged 2950 MV into Strelok, it said dial 1.9 Mils. Shot at 450. I found I had to dial 2.2 Mils to center punch the gong. Plugged those numbers into Strelok’s truing feature. It said your new MV is 2800. WTF? Ok then. Those are the numbers I used for the match.

The weird thing is they worked for the morning half of the match, but not the afternoon. Weather did change much. No big temp swings.

Thanks for the suggestions so far fellas.

You should not have trued up your muzzle velocity that much. This is almost surely the main cause of your issue. You need to check velocity and leave that pretty dang exact in your calculator. Shoot at about 1,000 yards and change the B.C. in your calculator until reality and your dope line up. The free version of Strelok can do wonky things with B.C. some times, but once it is trued up at long distance you will have great results from there and closer.

 

[Alan101]

Lots of good suggestions here. To add my 2 cents I find that most of the time when I’m having issues, the problem is me. I have an RPR and find that if I load the bipod a little hard it will change my point of impact. Just for fun next time your out shooting prone, shoot a group while barely loading the bipod and then another group loaded the bipod heavy. If you have a change of POI, then work on consisistancy.

 

[Rocketvapor]

Have a question after reading all this.
Disregarding the gun warming up during the day, and that the calculated dope seemed to be high with 3.2 mils,
wouldn't a wind near 12 0'clock, like 11 hit a little low, while a 1 0'clock hit a little high?

 

[_Raining]

wouldn't a wind near 12 0'clock, like 11 hit a little low, while a 1 0'clock hit a little high?

Do you mean 12 and 6? Like a head wind and a tail wind? Or are you talking about the vertical associated with a crosswind?

.5 mil is a lot for 550 yards to be explained with wind.

Quickly plugging in info for 120 ELDM @ 2950 fps I get 3.14 MIL for 550 yards.

15 MPH head wind changes it to 3.16 MIL
15 MPH tail wind changes it to 3.13 MIL

15 MPH crosswind changes it to 2.93 MIL / 3.33 MIL. So it would take switching from 15 MPH crosswind in one direction to 15 MPH in the other to change vertical by .4 MIL and OP said "I should add, wind wasn’t doing much. 6 mph from 12 o’clock. "

So probably not wind.

ES off 30 would be 3.10 MIL vs 3.17 MIL assuming no positive compensation.

 

[elmuzzlebreak]

I feel your frustration on this. I know when shooting at distance here in frozen MN if I shoot a string beyond 5-8 rounds the mirage is so bad I cannot see the target.

Hard to really saw what went wrong on a forum but if anything check your torque, ballistic calculator and if you cannot find what happened then let it go. You'll wast too much energy trying to figure out the what happened. Easier said than done but there's always the next match.

 

[NovaHunter]

Deinitely dealt with being off vertically before and not able to explain it. Last year at Big Dog, my entire squad was basically .2 to .3 off from 400 yards and out. We were all scratching our heads. Then when we went home and confirmed zeros again we were all dead on, except for maybe one guy.

This past weekend at WAR, I think the wind was doing something that caused many people to be high by .2 or so. I know I was about .2 high on the 800 yards and out targets, and quite a few other guys in my squad were as well.

It's frustrating, but the answer might not be your gear or you. Could be the environment of that particular day at that place, and you might not be able to replicate it either.

 

[Erno86]

With my Savage Model 12 single shot in 223...It'll tend to lose accuracy (1/4" m.o.a.) after the 17th round --- without cleaning.

Like said before from another poster: Could be the ammo cooking in the sun.

The sun's rays could be cooking the barrel from just one side...causing a P.O.I. change.

Of course...the air gets less dense when it gets warmer.

Is the gun a clockwise twist barrel or vice versa? A right to left wind will cause the bullet from a clockwise-twist barrel to drift down & right at 4 o'clock. A left to right wind will cause a clockwise-twist barrel bullet to drift up & left at 11 o'clock.

 

[seafury]

It’s a stock RH twist RPR barrel. I tend to agree with the conclusion that wind wouldn’t have caused such a noticeable discrepancy.

I suspect I may have trued the velocity lower than it should have been. In addition, it would help to get the ES on my ammo down, exploring that area currently.

At the end of the day it was difficult trying to read between the lines....

Magneto Speed says.... X
Strelok says.... Y
Target says.... Z

I very much appreciate everyone’s suggestions and will be exploring them going forward.

 

[Erno86]

Maybe the barrel & receiver is getting too hot from firing and it's starting to string vertical groups. If that is the problem...may I suggest that you should a rapid 3 shot group before the receiver heats up. Once the receiver heats up...accuracy goes downhill.

i'm kinda shocked that some of these shooters on our range, are burning up there barrels so fast, because of continuous rapid fire; that brings their barrels past the 180 degree fahrenheit mark (barrel too hot to touch which can cause throat crack erosion). There's an old saying: "Shoot a family of six" --- meaning shoot a rapid fire six shoot group ---- stop --- or risk premature barrel throat erosion from heat-up. Go to another gun an let the big gun cool.

 

[Rookie]

I have had this happen to me many times during a match here in the South. I have always attributed to heat. Your gun heats up, your ammo heats up. I usually put an ice pack down in my pack and then I set my ammunition on top of that to keep it cool.

 

[bax]

Was the gun cleaned before the match or during the match?

Short story: I have a 308 with a 23-inch Hart barrel that was put on it maybe 15 or 18 years ago. The barrel has a LOT of rounds through it - 7,000 8,000 10,000 - I don't know, a bunch. It was shooting about an inch and that was okay. I was planning to take it to a match last year and I thought I would be a good guy and give the barrel a good thorough cleaning. So I get started. This turns into a marathon over several days before I finally get down to bare steel. I used JB, I used copper remover stuff, I used everything I had and I have a lot of cleaning crap. The weekend before the match, I take it to the range. I know it will shoot an inch, I'm just fouling the barrel. It's shooting 2 - 3 inch groups!! What the Hell! I take another gun and shoot the match, never mind. I am disgusted. I think about it and start to wonder if the cleaning was the problem. So I take it to the range and start shooting groups. 3 inch. Then they get smaller. After about 75 or 100 rounds, it is back to 1-inch groups.

I am a unrepentant former BR shooter and I clean my guns after I shoot them. Clean guns shoot better - that is easy to prove. Yeah, well, maybe it isn't quite that simple. I still clean after shooting but I don't scrub the crap out of them like I did last spring. Maybe it wasn't the cleaning but I think that I have pretty good evidence.

There is another approach. In the past I also tried cleaning every 400 or 500 rounds. In my experience, I started to see flyers after about 300 rounds. YMMV.

FWIW, when I clean I do five passes with a bronze brush then a wet patch of Hoppe's. I do those two things three times. Then I do a wet patch of wipe-out accelerator and a wet patch of wipe-out. I wait 15 minutes. 1 wet patch of Hoppe's. 1 dry patch. Maybe an oil patch. Done. I know that everyone has their system - I'm not trying to convince you to do what I do. But I strongly recommend that you don't scrub it down to bare metal or let it go until you can't see down the barrel. My approach keeps my barrel reasonably clean, I don't get flyers, and it doesn't change my zero.

 

[Cm308]

I can't tell you a scientific answer on why but I can tell you I have experienced almost the exact same thing on two different rifles in the past year. Both times it happened between 400-500 rounds on new barrels, one was a 308 the other a 6.5cm. my solution was to get back to the range verify scope tracking, and then start over with velocity and bc until I got the ballistics to match as closely as possible in strelock and Hornady 4dof. It stays in the back of your mind for a while but just sort it out and move on

 

[bschneiderheinze]

I would double check the scope I have an AMG and it's been back to Vortex if they are over torqued they won't have issues right away but down the line mine had issues with both tracking and parallax. I yknow many others that have had the same problems sheet on mine said they replaced all internals.

 

[Dthomas3523]

If your zero was still good and scope tracking properly, it was likely your breathing.

Breaking shot at different points in our breathing cycle other than at the bottom pause will result in vertical stringing.

Also, a huge, huge problem is when people true their data and are breaking the shot somewhere other then the bottom. They end up truing data to a physical imperfection and not an environmental one.

Then they get to a match and focus really hard on fundamentals, breaking at bottom, and boom......dope is off because they are doing it right.

Or, vice versa, they true with proper fundamentals, then start match doing it right, but fatigue or complacency kicks in and they forget to watch their breathing.

9.9/10 times, if I start shooting over targets, I focus back on my breathing and the impacts level out.

 

[Dthomas3523]

Or the temperature picked up enough or your ammo got hot enough as day went on to cause a difference.

Or carbon ring buildup, causing more pressure and such is possible too.

 

[Dthomas3523]

With my Savage Model 12 single shot in 223...It'll tend to lose accuracy (1/4" m.o.a.) after the 17th round --- without cleaning.

Like said before from another poster: Could be the ammo cooking in the sun.

The sun's rays could be cooking the barrel from just one side...causing a P.O.I. change.

Of course...the air gets less dense when it gets warmer.

Is the gun a clockwise twist barrel or vice versa? A right to left wind will cause the bullet from a clockwise-twist barrel to drift down & right at 4 o'clock. A left to right wind will cause a clockwise-twist barrel bullet to drift up & left at 11 o'clock.

It ain’t spin drift at 550yds......

 

[_Raining]

It ain’t spin drift at 550yds......

Isn't spin drift the left to right movement of a bullet purely from just its spin? I believe he is referencing how the bullet can impact higher or lower from a crosswind. But that being said, it would take a massive change in the wind to cause a .4 MIL change and they would also see a large POI change in the horizontal, which OP did not mention.

 

[Dthomas3523]

Isn't spin drift the left to right movement of a bullet purely from just its spin? I believe he is referencing how the bullet can impact higher or lower from a crosswind. But that being said, it would take a massive change in the wind to cause a .4 MIL change and they would also see a large POI change in the horizontal, which OP did not mention.

He’s referencing spin drift with the impact wind would have on it.