Strange results zeroing - Your thoughts?

[FrenchieBoy]

Here's a little bit of a puzzler for you.
I went out the other day to set up a new set of scopes and mounts and to try changing over from 130g ammunition to 150g ammunition in my 270 rifle. The rifle is a Parker Hale Safari and the ammunition used was PPU (SP). The scopes (An unbranded set but guaranteed Fog Proof, Shock Proof and Recoil Proof) and the Scope Mounts (A brand new set of Nikko Stirling Platinum Mounts) were fitted to the rifle and were checked for tightness both before and again after the zeroing session. I am positive that they hadn't moved.
I checked the zeroing with the 130g ammunition while sat at a bench at (Aproximately) 100 yards and found the rifle's zeroing to be pretty much spot on. I then set out a new target (Exactly the same range and shooting position) and "double checked the zeroing" with 1 round of PPU 130g (SP) ammunition. The resulting shot showed that the rifle and scope was spot on for this ammunition. I then loaded the rifle with 4 rounds of PPU 150g (SP) ammunition and carefully shot them at the same target. The first round went 4cm low, which is something that I expected it to with a slightly heavier bullet head. However the next shot went marginally lower and left again from the previous shot. When the third and fourth shots were fired they did exactly the same, each shot going exactly the same amount further both low and left than the previous rounds, giving a very regular diagonal "laddering" effect.
I have my own thoughts as to what has happened but before I say what they are I would welcome your thoughts and opinions on this "unusual situation".
A photo of the resulting target is attached for you to form your opinions from. To put things into perspective the red "bull" is exactly 40mm dia.

 

[jonylandrover]

Hi frenchieboy. We couldn't do that if we tried! I am guessing it's the scope or mounts moving with each shot. However I do own the same gun as you but in .243 and it always gives me a headache zeroing it due to barrel expansion with the heat from each round. I have had similar results as you all be it not as accurate as your laddering effect and that was a mod come loose on a 22lr.

 

[8x57]

Try it again Frenchie with a cold barrel and only fire three rounds carefully aimed, this time with plenty of time between shots. Do not look at the target between shots and call any shots where you may have made an error. Then post the results for comparison.
Be very conscious of finger placement and trigger control. Try for a smooth slow controlled pull.

 

[Eric the Red]

With Mike on this - s l o w l y ......!!

 

[FrenchieBoy]

Thanks for the replies guys. Maybe I should have added that I took my time while shooting the 4 shots, about 6 or 7 minutes so that the barrel did not heat up too much. Jonylandrover is however thinking on very similar lines to me so now I will tell you what my thoughts are and what action I have taken to rectify the "problem"!
The scopes were a "Cheap as chips" set of 6-24X50 off "The Bay"! at £23.98 - http://www.ebay.co.uk/itm/221460255...2649&ssPageName=STRK:MEBIDX:IT#ht_2487wt_1190
What I believe that happened is that (being a "dirt cheap" set of scopes - False economy I know but worth a try) while they could just about handle the recoil (Initially) from the 130g shots the recoil from the 150g was just a little bit too much for them and this has caused a fractional of shift of the cross hairs with each shot fired.
I have now taken the scopes off and fitted them to my .22LR and tested them and found that after almost 100 shots there is no shift on the POI so that uis where they will stay - Unless they play up at all in the future in which case they will go in the bin.
The .270 is currently re-fitted with my (Very) old and well used set of 8X56 (Unbranded) scopes and they are fine, so much so that I was out on Thursday and was shooting a (Tightish) 3 inch group with them (In pretty strong wind) at 250 yards - The only think that I ca fault with these scopes is the fact that the reticules are a bit on the thick side fo my liking. These however are going to be replaced with a brand new set of Hawke 3-9X50 HD (Mil Dot) Scopes which I have just ordered and paid for this morning.

Thanks for your thoughts guys!

 

[8x57]

The scope is certainly one possibility. While I am not exactly equipment obsessed I have to admit that my thoughts are you normally only get exactly what you pay for with scopes and that cheap ones are exactly that.
You have done right to eliminate the questionable scope from the equation but I would be inclined rather than to fit another new untested scope to test using one of known proven reliability.

 

[bewsher500]

it would have been interesting to put another 130gr down the tube to see if the POI had shifted down and left

FYI - heavier bullets don't always hit lower than lighter bullets
depends entirely on where in the barrel whip cycle that they exit the muzzle

i have a 52gr AMax and 60gr SP load for my .222
60gr hit exactly 2" higher at 100yds

If the scope change doesn't solve it I would be surprised if the stringing group pattern is down to barrel temperature alone otherwise you would have already seen this with the 130gr..if not even more so with more powder and more velocity

what is the rifle sitting on/in?
what position are you firing from?
stringing like this is often "muscling" of a shot. i.e. the shooter is applying pressure to get the reticule on target
when the shot goes off the recoil allows the natural lie of the rifle to resume slightly pushing the shot in the direction the rifle wants to naturally go

get it set up for the shot so that without you holding the rifle at all the cross hairs are on target.


report back when homework has been completed!

 

[devon deer stalker]

More often than not it always comes down to one of two things, mounts or scope.
Been down this road before.
Cheers
Richard

 

[Muir]

My guess is that it's you. You're not following through with the slower, heavier bullet. ~Muir

 

[FrenchieBoy]

In reply to the most recent replies:

8x57 - I have tried it with a "proven scope" and this has solved the problem so I am fairly confident that the fault is with the cheap scope - Typical false economy!

Bewsher500 - The rilfe was sitting on it's bipod on the top of a fairly steady table. This change of POI was not noticable when using the 130g bullet heads, even after puttung 10 rounds through it in a matter of 5 minutes which fairly warmed up the barrel so I would be inclined to eliminate barrel temperature as the problem. I haven't tried it again with 130g heads since changing to the "proven scope" and zeroing with 150g PPU Ammunition, but that is something that might be worth trying to check to see the difference in POI between the 130g and the 150g heads. I will (When we get some better weather - It's pretty wet and windy here at the moment! I will also try doing a string of "more relaxed" shots (Maybe prone position which I prefer whenever Practical/possible) and see what results I get but with the "proven scope" fitted the problem has been solved so I am fairly certain that it was down to the cheap scope, however time will tell, especially when the new Hawke Sport HD scope arrives and is fitted.

Devon Deer Stalker - I am pretty sure that you have hit the nail fair and square on the head with your reply. I suspected scopes straight away and the other "tried and tested" scopes seem to have confirmed my suspicions. Once again the new Hawke Scopes will kopefully help things along!

Muir - I can see what you are saying but all seems well with the 150g ammunition now that I have re-fitted the "tried and tested" scopes.

Many thanks to all of you for your thoughts, opinions and helpfull advice!

 

[bewsher500]

Mix up some a ammo!

you should get two distinct groups!

 

[VSS]

My P-H safari deluxe was doing similar things. Scope was only part of the problem.

 

[User00001]

Zeroing

To be brutally honest, the dramas that you are having are not a 'strange result', they are entirely predictable. Using the kit that you have described, especially with the 150grn loads, I think you should be very happy to have got more than one round on the paper!

Joking apart, I would urge you to thoroughly test this set up for reliability before using it for stalking as its far preferable to discover problems on the range than after you have lost a deer.

 

[bewsher500]

To be brutally honest, the dramas that you are having are not a 'strange result', they are entirely predictable. Using the kit that you have described, especially with the 150grn loads, I think you should be very happy to have got more than one round on the paper!

Joking apart, I would urge you to thoroughly test this set up for reliability before using it for stalking as its far preferable to discover problems on the range than after you have lost a deer.

sorry I may be misreading your post but I find that a very odd comment that perpetuates the myth that unless sporting a custom rifle topped with a PM2 and using the latest VLD that you will struggle to hit deer!!

There is nothing wrong with old ph rifles and cheap scopes.
They have probably accounted for more deer shot than all the custom rifles put together


he has just shown that the 130gr is on the money.
he has a variable with a new round.

IMO it's not worth exploring as the 130gr in .270 is the one and only round to use!

 

[User00001]

sorry I may be misreading your post but I find that a very odd comment that perpetuates the myth that unless sporting a custom rifle topped with a PM2 and using the latest VLD that you will struggle to hit deer!!

There is nothing wrong with old ph rifles and cheap scopes.
They have probably accounted for more deer shot than all the custom rifles put together


he has just shown that the 130gr is on the money.
he has a variable with a new round.

IMO it's not worth exploring as the 130gr in .270 is the one and only round to use!

Correct, you did misread my post. Nowhere did I mention custom rifles.

I agree with you on the 130grn recommendation.

 

[bewsher500]

Using the kit that you have described, especially with the 150grn loads, I think you should be very happy to have got more than one round on the paper!

I would urge you to thoroughly test this set up for reliability before using it for stalking.

Correct, you did misread my post. Nowhere did I mention custom rifles.


I agree with you on the 130grn recommendation.

So you weren't critiquing the use of old ph rifles and no name scopes?

the 150gr shouldn't be any more inaccurate, I just don't see the benefit when the 130gr trump them on velocity, energy and drop across the entire 300yd likely range

 

[Muir]

My old Howa 270 would toss 150 grain Sierra's into a single hole at 100m. I wish I hadn't given that one away.~Muir

 

[User00001]

So you weren't critiquing the use of old ph rifles and no name scopes?

the 150gr shouldn't be any more inaccurate, I just don't see the benefit when the 130gr trump them on velocity, energy and drop across the entire 300yd likely range

Of course I was commenting on the quality of the components in the set up, in the real world its called ribbing, its something blokes do to one another about their choices of cars, dogs, girls etc.

If you insist on taking my comments too seriously then I will explain my thoughts in more detail. With the benefit of a reasonable amount of experience, I think that it is foolish to put a £25 ebay variable scope on a .270 regardless whether the rifle was built thirty years ago by Parker Hale or yesterday by Callum Fergerson. I stand by this comment and I would go further and say that if this equipment intended to be used for killing deer then it becomes irresponsible rather than just foolish. It is simply a problem waiting to happen.

I apologise if my comments caused offence, I will say no more on the matter.

One final point, if you are going to use the quote facility then please do not edit my comments.

Thanks.

 

[8x57]

With three different .270w rifles that I owned they all shot 150 grn bullets more accurately than 130 grn bullets. I always put it down to the longer bearing surface of the bullet making it more stable.

 

[Shadrach2986]

I find my .270 to prefer the 150gr bullets, but I prefer the 130gr as I have never had anything run from one yet?