simple question !!

[Devil_bri]

i was out zeroing s&b pm11 5-25 on my AIAW 308 yesterday

100 yards its perfect 2 inches high (i like it high at 100), however when i shot it at 200 yards it was shooting 3-4 inches to the right,(and 6 inches low - to be expected))

granted there was a left to right wind, but it was less than 10 mph

i am using Hornady 150gr SPBT with 47gr of vhit N150

i know i was steady on the target and the groupings were good even though 3-4 inches right

would a small amount of wind cause so much drift ?

i know this is a stupid question, but its really pissing me off, big time !!!!

[22-250jock]

Hi Bri,

 

is your scope level with the action?

 

cheers jock

[brown dog]

Doesn't sound crazy at all. Three inch deflection for a 308 in a 10mph wind at 200 yards is in the parish.

[Chris-NZ]

Doesn't make sense to me BD.

 

The way he described it was (windage) zeroed at 100 yds and if I look at the relative drift (100-200yds) of my std NRA load, it's drifted another 0.7" in a 10mph wind.

 

Summin' weird goin' on there Buddy..

[brown dog]

Doesn't make sense to me BD.

 

The way he described it was (windage) zeroed at 100 yds and if I look at the relative drift (100-200yds) of my std NRA load, it's drifted another 0.7" in a 10mph wind.

 

Summin' weird goin' on there Buddy..

 

If you hear hoofbeats think horses not zebras:

 

1" at 100, 3 to 4" at 200 is a good rule of thumb for 308.

The error is to the right, we've been told there was wind from the left.

No wind whilst shooting at 100 or unnoticed deflection (we don't know how big Bri's groups are, so can't assess the granularity with which deflection is being assessed), followed by unnoticed wind speed at 200 (overall or a fast wind channel) at 200 (again, without knowledge of 'granularity').

 

And background info was; this is with an AW and a PM2...so which is more likely, an AW or PM2 failure, or unnoticed wind?!

 

(My back up before blaming kit, other than checking the AW mount is on tight, would be inconsistent position and hold; but I'm assuming Bri is able to place his MPI consistently on POA from occasion to occasion. Wandering 'good groups' are often just inconsistent position and hold from occasion to occasion.)

 

So......I'm not going 'zebra' for a solution, I'm sticking with 'Horse'. :)

[Offroad Gary]

Just checked on bulletflight my 155smk load, 10mph gives 0.7" at 100 and 3" at 200.

[Offroad Gary]

Should you really be 6" low with that 100y setting?

[Chris-NZ]

I've re-read what he said twice and it hasn't changed my mind BD.

 

Correct me if I'm wrong DB- your 100yd impact was about 2" high but on for windage, and in the same conditions your impact at 200 was 3-4" to the right (and way low)?

 

(woops- was looking at MOA but the diff (100-200yds) is 2" in my std NRA Lapua 155 load. To double that is more than a breeze..)

[tackb]

the windage is exactly what i'd expect at 200 in a full value wind but with your +2" zero at 100yds then i would expect you to be about bob on for elevation at 200? not 6" low ? have you reshot the test again yet?

[gbal]

i was out zeroing s&b pm11 5-25 on my AIAW 308 yesterday

100 yards its perfect 2 inches high (i like it high at 100), however when i shot it at 200 yards it was shooting 3-4 inches to the right,(and 6 inches low - to be expected))

granted there was a left to right wind, but it was less than 10 mph

i am using Hornady 150gr SPBT with 47gr of vhit N150

i know i was steady on the target and the groupings were good even though 3-4 inches right

would a small amount of wind cause so much drift ?

i know this is a stupid question, but its really pissing me off, big time !!!!

 

Hi, wind drift isn't too alarming,as others confirm,especially as it wasn't measured at 200(all the way to the target,remember-not just at firing point).But 2 inches high at 100 and 6 inches low at 200 suggests a stampede,not just a horse or a zebra hoofbeat(in Matt's uber technical analogy!)It's way too low at 200,with that loading,more like expected 300 yards drop.If you had been able to try a few shots at a measured 300 and seen bullet splash it would have been helpful,too;'good groups' is a bit vague,but that hardly matters here if it means under 3 inches-if they are so low,something needs checking before working on groups.

george

[eldon]

Sounds like a mare of a problem.... in BD terminology, sorry couldn't resist.

 

I'm with gbal..... windage doesn't worry me but the drop is excessive.

On my 308 with 165s at 2700 ish 100 yrd zero has a drop of 1.8 moa or to put it another way 2" (moa same at 100) high at 100 would be on for me at 200 yds not sure whats going on there then.

 

I think best solution is to shoot some more groups methodically and let us see them.

6" drop at 200 is far too much as in effect that is 8" drop with your 2"+ start and most 308s would do it in half that i.e. 2 moa.

[gbal]

If you hear hoofbeats think horses not zebras:

 

1" at 100, 3 to 4" at 200 is a good rule of thumb for 308.

The error is to the right, we've been told there was wind from the left.

No wind whilst shooting at 100 or unnoticed deflection (we don't know how big Bri's groups are, so can't assess the granularity with which deflection is being assessed), followed by unnoticed wind speed at 200 (overall or a fast wind channel) at 200 (again, without knowledge of 'granularity').

 

And background info was; this is with an AW and a PM2...so which is more likely, an AW or PM2 failure, or unnoticed wind?!

 

(My back up before blaming kit, other than checking the AW mount is on tight, would be inconsistent position and hold; but I'm assuming Bri is able to place his MPI consistently on POA from occasion to occasion. Wandering 'good groups' are often just inconsistent position and hold from occasion to occasion.)

 

So......I'm not going 'zebra' for a solution, I'm sticking with 'Horse'. :)

 

Matt,when we were in the Serengeti recently (testing the Coreolis effect-confirmed),we heard lots of hoofbeats.We saw plenty of zebras,but we could not see a single horse.I have given away all my DPM/camo gear,and bought a mid chestnut brown jacket.

george

[brown dog]

Windage is not odd looking at all to my eye but, yup, didn't spot the huge elevation change

 

First question (after checking mount screws tight) would be 'how big are these groups'?

[Devil_bri]

I am going to have to make sure everything is level and tight, I was using a B&T surpressor at the time and it was screwed on fully

I will have to go out again in the next few weeks and try it again !!!

The groups were inside a 3 inch circle

[gbal]

I am going to have to make sure everything is level and tight, I was using a B&T surpressor at the time and it was screwed on fully

I will have to go out again in the next few weeks and try it again !!!

The groups were inside a 3 inch circle

I'd definitely do all that and shoot some more groups-my ''3 inch'' was just to see how low shots really were-so very,and quite dispersed esp at 100.You might reasonably expect 1/2 moa,but let's say 3/4'' at 100 and sub 2'' at 200.Has it shot better than it is doing now,in the past? With this scope and load,,or any other variants? If you can, try another scope,preferably one known to be OK,and ditto moderator-or leave it off and see how rifle shoots.There are four potential variables,rifle,scope,load,moderator-it's likely just one,but it might be more.Vary each systematically,as above and record results.It would be very helpful if we knew it did perform,and with what configuration of these variables.

georget

[eldon]

With the usual quality of the kit you are using these groups would disappoint me. With my factory Remy I would get better than 2" groups at 200 if I do my bit right.

With your kit I would hope to beat my kit easily.

 

Is your load a known good one with this set up as is i.e. nothing changed?

[Devil_bri]

Would the scope not being exactly level cause it to be so far off ?

[brown dog]

Would the scope not being exactly level cause it to be so far off ?

 

'fraid not. (An error of the scale described would require you to have the whole rifle canted by about 60 degrees )

 

 

 

I really don't see 'equipment fault' in what's been posted so far. I know everyone likes to jump to that, but with the kit you've described, it's far more likely to be operator error.

 

In your situation, my first question would have been "holy poo, my AW only groups to 3" "

 

Assessing MPI placement with large group sizes is a bit fraught; and it's quite likely that you'll end up chasing your tail; when what's really happening is that you're either not shooting the rifle well enough to place your MPI consistently or well enough (in terms of group size) to correctly assess where the MPI lies.

 

(eg amongst other things, a large group size can easily mask the effect of wind at 100yds; more so if it is placed inconsistently.

Ditto to large group size and inconsistent placement meaning you don't have the zero you think you have)

 

Of course, I've no idea if that applies.

 

Bri; not being funny: how experienced a shot are you? An AW should be grouping well below 3".

 

 

Right now all my instincts are still shouting "inconsistent position and hold"; and until you clarify how well you normally expect to shoot, I suspect that the solution has nothing to do with kit, but everything to do with applying the basic marksmanship principles.......and practice. [of course, I'm stoodby to eat my hat ]

[eldon]

Devil Bri considering the responses and detail you have been offered so far why don't you give us a rough location of where you are and then maybe somebody on here would offer to help you along?

Sometiimes an alternative shooter can show up the problem quickly and if you keep batting on and trying harder and harder the tension is probably spoiling your shooting anyway

[Devil_bri]

BD you are more than likely 100% correct, it probably is me, but then again my friend shot it at the same day and had similar results ! But then again we were leaning over the bonnet of my jeep

I am not a bad shot, but not anything special.

I think it is more than likely down to operator error ! It just really p#ssed me off on the day

Eldon, I'm in N.Ireland !!

[eldon]

Pity you aren't on the mainland but there are a few lads on here from NI.

Any offers to help Bri out?

[gbal]

BD you are more than likely 100% correct, it probably is me, but then again my friend shot it at the same day and had similar results ! But then again we were leaning over the bonnet of my jeep

I am not a bad shot, but not anything special.

I think it is more than likely down to operator error ! It just really p#ssed me off on the day

Eldon, I'm in N.Ireland !!

Ah...try with a reasonably steady rest,and the engine switched off.

george

[DaveT]

Also don't overlook the shot depression caused by a FV 10MPH L-R wind (assuming RIGHT barrel twist) ..... somewhere near 1/2 - 3/4 inch down toward 4 o'clock.... minor compared to indicated drop problem but still there.

[Chris-NZ]

Ah...try with a reasonably steady rest,and the engine switched off.

george

 

I was gonna suggest stopping the vehicle but you beat me to it

[Andrew]

the windage is exactly what i'd expect at 200 in a full value wind but with your +2" zero at 100yds then i would expect you to be about bob on for elevation at 200? not 6" low ? have you reshot the test again yet?

 

I'm with you. The 3" of windage doesn't draw my attention but the "expected" -6" POI at 200 got my attention. Should be close to dead on.~Andrew