Elevation oddities

[Davy]

We have had a few days of rain here in less than sunny DK so it has been black gun time most days however this afternoon was nice enough to take the 6,5-284 S&L out. My calculations based on 2950 fps with a 139 Scenars and a 200m zero gave 12.5ish MOA elevation for the 600m distance I was shooting at and first shot was on the frame nicely albeit a tad high, then odd things happened. I took one MOA out (6.5" ish) and dropped a bit but had to drop more, in fact I was barely dropping the POI for each .50MOA I took out, in the end I went to 10.5MOA to be where I wanted to be.

 

Given that I know the distance is 600m and the round chronos at just over 2900fps and the 'scope is a new Kahles that *should* be right however as I took each shot and dropped a bit more on elevation the POI did not drop as I expected until about the 6-8th shot when at the 10.5MOA it had settled down. Letting the rifle cool off completely and then shooting again still gave a good POI at 10.5MOA so I am for the most rather confused.

 

Tomorrow I will confirm drops again at 600m and then take 2MOA off to see how that alters my POI, and repeat with another 2MOA.

 

What I will say is the barrel had been thoroughly scrubbed before hand and and this is a new rifle with under 50 shots through it so I do wonder if it needed a few shots to foul it after my last OCD cleaning routine. We visited the S&L factory on Monday and Mr Schultz & Larsen's all but spat at me when I mentioned I used solvents to copper strip. He said he did not care about other peoples barrels but with his copper stripping was not required and said they have some factory rifles that were not stripped until 4000 shots (Wahhhh!!!) Oil and patches is all it needs he said. He then took us down to the barrel shop and showed us how they make barrels, they are drilled, reamed, cut rifled and lapped with tin laps to produce a very fine taper towards the muzzle. All very impressive stuff I thought. So tonight after 25 shots I cleaned it but only with oil and patches. It seems so wrong in my mind to not give it a good clean but as he built the thing I am prepared to give him the benefit of doubt.

 

Accuracy wise it was OK for what is basically a hunting rifle with a 12X 'scope The well prepared Viking took a snap of my first group. The rings are 25mm apart and the bottom shot was called but still counts. My view is just under .50MOA but if someone has a copy of On-target and can confirm this I would be happy (It will not run on my Linux OS)

 

 

The Viking (Wife) also decided to take her gurlie rifle out of the slip as the rain had cleared up and managed to plink a 30mm 5 shot group with a second one which had three shots covered by one 16mm patch with two 'flyers' Quite good for an oddity (Cartridge that is) at 600m. Me being me left the camera and my phone at the firing point so without photographic evidence I have told her it does not count especially as she has equalled my last years best.

[DaveT]

Sounds like the scope clicks are not tracking properly?

[oaken]

Sounds like the scope clicks are not tracking properly?

 

Agreed.  As it's a new scope you could try winding the elevation knob from top to bottom a few times to "loosen it"??? A bit unlikely but it might help.  It does sound scope related to me, be interesting to see what happens next time.

I used to clean my barrels manically after buying a rifle that was badly pitted through lack of cleaning. I now only tend to use a pull through to remove the loose stuff and rely on a couple of big bags of desiccant to stop any condensation which is the real killer. I planned to clean thoroughly with solvents when accuracy starts to go off, still waiting!

[Davy]

I am hoping the tracking is good as it is a new 'scope. First thing today is to see if it holds the 600m elevation from yesterday after cleaning. Then I will go up and down a few MOA and measure the change in POI and finally wind it all the way up and down and back to the 600m elevation and see if holds the elevation. If it is all OK I will continue my testing at some other distances to confirm drops.

 

If you hear a scream all the way from Denmark you will know it has gone white side up.......

[DaveT]

I am hoping the tracking is good as it is a new 'scope. First thing today is to see if it holds the 600m elevation from yesterday after cleaning. Then I will go up and down a few MOA and measure the change in POI and finally wind it all the way up and down and back to the 600m elevation and see if holds the elevation. If it is all OK I will continue my testing at some other distances to confirm drops.

 

If you hear a scream all the way from Denmark you will know it has gone white side up.......

 

 

Hope all goes well!!! The only other thing that I can think of is to check that the crown has not taken a bash and throwing flyers but it doesn't sound that way from your posts.

[Davy]

It shot 14" low first shot at 600m and settled down at 10.5MOA again on the third. Tracking up and down seems fine and winding it to full elevation, back to zero and then back to 10.5MOA gave the same POI as the warm shot.

 

Shooting for 5 shot groups I see excellent windage but some significant verticals. Today it was stringing by 8" yet was under two inches wide as a group.

 

I am confused....

[The_Dogge]

Pejsa says 11.4MoA, which isnt far off your observations using factory figures for the BC.

 

I'm afraid I still havent fixed the bug to allow different drag functions, but the standard one seems to get closer than your current calculations :-)

[Predator7mm]

I had virtually the same experience as yourself with one of my rifles. I was convinced it was the scope. In the end after much diagnostics of various potential problem areas it was simply a bedding issue. Once that was done it was super consistent in tracking and noire weird "voodoo factor" anomalies creeping in.

 

Thought I would mention it as my issue was pretty much same as yours.

[Davy]

I had virtually the same experience as yourself with one of my rifles. I was convinced it was the scope. In the end after much diagnostics of various potential problem areas it was simply a bedding issue. Once that was done it was super consistent in tracking and noire weird "voodoo factor" anomalies creeping in.

 

Thought I would mention it as my issue was pretty much same as yours.

Beddding did cross my mind after I packed it away. It went back to the factory for a free of charge firing pin upgrade at the start of the week (Gave us the chance to see how they are made as well) The trigger was adjusted at the same time and I noticed he did not seem to do the action screws up very tightly afterwards. They are bedded at the factory but it is a very cursory job so I am will scrape the old bedding out, fit some pillars and re-bed it when I get home.

 

It is early days and I have already seen some good accuracy out of the rifle so I will persevere. One thing that I do notice is the barrel warms up very quickly however this is partly to be expected as it is a hunting rifle.

[Davy]

Pejsa says 11.4MoA, which isnt far off your observations using factory figures for the BC.

 

I'm afraid I still havent fixed the bug to allow different drag functions, but the standard one seems to get closer than your current calculations :-)

I expected around 12.7MOA so 10.5 is certainly low. I need to go back and confirm my zero, I can get out at 200/300m in the morning on electronics to do that. Which reminds me, I have some more data for the 22-6,4x47 now. She has shot some stunning groups with it this week including a 5 shot 80mm at 600m from stone cold, she is still to get that elusive 600m clover leaf she so badly wants. She has got close but always drops the third shot.

[brown dog]

I'm a firm believer in "if you hear hoofbeats, think 'horses' not 'zebras' "

 

An elevation glitch and we're binning the scope or re-bedding the rifle

 

Maybe you were having a bad day......

 

Maybe your position and hold were inconsistent for whatever unnoticed reason.....

 

Maybe it was vertical wind....... rising and dropping vertical could easily account for what's been described.

 

Maybe it was the squeaky clean still new barrel....

 

 

 

I wouldn't touch anything until it had happened on a second & seperate occasion

[Fergal]

Id be inclined to go with the bedding scenario too.

[brown dog]

Naaah, hoofbeats = horses.

 

Shooting for 5 shot groups I see excellent windage but some significant verticals. Today it was stringing by 8" yet was under two inches wide as a group.

 

So, it's a sporter barrel giving 8" vertical at 600m?

 

Sporter;

8" group;

656 yards?

 

 

Sporter,

656 yards;

shooting to 1.2 MOA ?!

 

 

Sounds normal to me.

 

Horses not zebras!

[Davy]

1.2MOA..Hmmmm not what I am used to but then nor is this type of rifle. I had far better out of it yesterday with a 5 shot and on was a called flyer. I could literally watch it climb over the 15 odd steady shots I took today. This does make me think I need to just check everything is nipped up as it should be.

 

I will confirm the 200m zero in the morning and start again. The electronic ranges are very sheltered, I think the most I have ever dialled in was 2klicks on my AI when it was blowing a gale.

[The_Dogge]

<snip>

I wouldn't touch anything until it had happened on a second & seperate occasion

I agree, the answer to the question "if your calculations don't match your real world observations, which are correct?" surprisingly often turns out to be the real world which was "wrong"!

[Davy]

Today I took it out to the 300m electronics. (As an aside from our room to the point I was shooting from was 34 paces, I do like this place) I checked the action screws and they were fairly tight (No torque wrench here) so took a shot to confirm my drops, I was high and right but this range is very sheltered so having adjusted my 300m POI I shot groups of three, typically they were around an inch to inch and a bit however the aiming point was not particularly precise. I shot a 244 EX 250 So in the 9 ring just 6 times in 25 shots. This included winding up and down the elevation range and letting it cool right off a couple of times. I had not cleaned the barrel since the day before no matter how much the thought of it had me cringing.

 

Final tick in the box for me was the Danish champion of the 2010 field sport competition showed up to zero for this weekend so I reset the electronics and offered him my firing point. He put his on zero and we took 5 shots back to back, I was delighted to shoot a perfect 50 to his 46. I am rather chuffed with that.

 

Back to the rifle... I think the issue is the scope rings are moving on the rails. The rifle is fitted with Apel mounts and rings, I know where I bolted the 'scope down and it has moved forward maybe 6mm. I will drop them off next week and fit a peg to the front rail and a similar recess in the front ring mount, that should stop it shifting any. I will also drill and peg the front mount for a mirage band.

 

So this could well be the start of the end of this problem.

 

Will I still pillar and glass bed it? Hell yes!