MPBR at 100 metre zero - advice please

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oldhamstocks

oldhamstocks

Well-Known Member
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I’m trying this MPBR after using 100m zero with a ballistic turret on a previous scope. Have gone for a nice wee fixed mag GPO 7.5 x 50i for simplicity. Calibre is .308 20 inch Sako 85 shooting Sako Gamehead 123 gr factory with coefficient 0.250, scope height is 4 cm. The only recommended MPBR calc I can find online is US and in 100 yard zero. Was at a 100 metre pipe range today and put 3 shots through it after calculating (probably wrongly) that a 6cm high zero at 100 metres should see me ok out to c.200 metres.

Firstly, I’m not entirely sure of what the 4 different readings are but I think it’s zeroed at 6.2 cm high, any help with how the software interprets those shots appreciated, haven’t had time to try and look online at how this target recording system works, and secondly, if any maths whizz can help me find a way to put the data metrically through a MPBR calculator in order I can check whether this c. 6cm high is enough/too little it would be appreciated.

Thanks in advance!

IMG_6687.webpIMG_6688.webpIMG_6689.webpIMG_6690.webp
 
I’d question that as your 20” barrel is probably shorter than that used for the box speed.

Bag of the fag packet calc you’ve given me and assuming a 4” target is the aim your mpbr zero at 100 yards would be 1.8 inches (4.5cm). With a near zero of 33yds (30m) and a far zero of 205 yds (187m) MPBR of 239 yds (218m)
 
oldhamstocks said:
I’m trying this MPBR after using 100m zero with a ballistic turret on a previous scope.
Click to expand...
Don't get lured into MPBR promises. Think hard, how much off you want to be at, say 100m, even before usual shot dispersion and all other field shooting related stuff kicks in.

Of course it depends on what quarry you shoot etc. but e.g. 3" on roe would be usually judged as botched shot. Also people tend not to follow the MPBR principle of aiming center of the defined kill zone. They try to compensate depending on the distance.

MPBR is also flawed by design, using circular kill zone you miss more than half of your shots at maximum distance. By design, since in reality you have shot dispersion.

If you want to go MPBR, I suggest somewhat modified/optimized approach (more realistic kill zone and take shot dispersion into account).

- define a reasonable kill zone, by your own experience not literature (let's say 4")
- in field conditions, find out the distance you can reliably put shots in the zone
- zero at that distance, and calculate or shoot to find out if the trajectory remains within the zone at intermediate distances
- if not, shorten the zero distance until they do
 
Be wary of setting a ‘zero’ using an electronic target of any sort unless you can verify through your scope that the bullet impacts on the screen correspond visually with their impact on the physical target.

Electronic targets are great as they remove the need for putting new clean bits of paper with no holes in them out every time someone wants to use them. What that means though is the target can get a lot of hits in the same place very quickly. To make the backings last longer it is usual practice to offset the electronic centre so that whilst you still put your cross in the centre of what you can see your final ‘zero’ adjustment is putting your bullets in a less damaged part of the target. So, for example your first shot is shown 5cm left of centre so you adjust accordingly by moving poi 5cm right & next shot is a central bull. What you’ve actually done is move your true zero 5cm right.

I have first hand experience of this both personally & from being RO when other shooters have ‘zeroed’ using electronic targets. The most recent was a chap who had bought two different brands of factory ammo because he couldn’t get his usual stuff. He zeroed on the electronics at 200 yards & noted down his corrections between the two brands (one was copper the other lead cored). He then came to shoot in a competition at 100 yards at BSRC. He adjusted his elevation down 4” from his 200 yard zero in the expectation the poi would be near as damn it spot on at 100 yards. It wasn’t, the impact of his first 2 shots prone supported on a bag were 8” high & 5” left! Thank god he found this out shooting at targets & not at dusk shooting a deer!

To the OP, your idea of establishing & using MPBR is a sensible one, but, please put a piece of paper up in a field/wood at your chosen zero range & make sure your bullet hits the aiming point before you shoot at anything live.
 
Donkey Basher said:
To make the backings last longer it is usual practice to offset the electronic centre so that whilst you still put your cross in the centre of what you can see your final ‘zero’ adjustment is putting your bullets in a less damaged part of the target.
Click to expand...
Seems there is no limit to the stupidity of man...
 
Thank you for all the considered responses, much appreciated. I had previously zeroed this scope in the field at a measured 100 metres aiming point on paper shooting from sticks, and these 3 shots were taken sitting with elbows on a bench after adjusting the elevation up 6 clicks aiming dead centre on the electronic target, so it seems the 62mm height for the group is pretty accurate. I will field check at different distances before stalking as I had done with my Leica with the ballistic turret.
 


all you need is some targets range finder and bit of time ....

Jason Doyle explains well and how to find your MPBR here

old video but i found it explained and shown well

Paul
 
Donkey Basher said:
Be wary of setting a ‘zero’ using an electronic target of any sort unless you can verify through your scope that the bullet impacts on the screen correspond visually with their impact on the physical target.

Electronic targets are great as they remove the need for putting new clean bits of paper with no holes in them out every time someone wants to use them. What that means though is the target can get a lot of hits in the same place very quickly. To make the backings last longer it is usual practice to offset the electronic centre so that whilst you still put your cross in the centre of what you can see your final ‘zero’ adjustment is putting your bullets in a less damaged part of the target. So, for example your first shot is shown 5cm left of centre so you adjust accordingly by moving poi 5cm right & next shot is a central bull. What you’ve actually done is move your true zero 5cm right.

I have first hand experience of this both personally & from being RO when other shooters have ‘zeroed’ using electronic targets. The most recent was a chap who had bought two different brands of factory ammo because he couldn’t get his usual stuff. He zeroed on the electronics at 200 yards & noted down his corrections between the two brands (one was copper the other lead cored). He then came to shoot in a competition at 100 yards at BSRC. He adjusted his elevation down 4” from his 200 yard zero in the expectation the poi would be near as damn it spot on at 100 yards. It wasn’t, the impact of his first 2 shots prone supported on a bag were 8” high & 5” left! Thank god he found this out shooting at targets & not at dusk shooting a deer!

To the OP, your idea of establishing & using MPBR is a sensible one, but, please put a piece of paper up in a field/wood at your chosen zero range & make sure your bullet hits the aiming point before you shoot at anything live.
Click to expand...
I use that pipe range all the time and it’s bang on
 
JTO said:
Click to expand...
"The table below is designed to serve as a starting point from which a shooter can work."

In the age of more or less accurate ballistic calculators and chronographs, there's no reason to use approximate tables. E.g. non-usual scope height will play havoc on the trajectory if you use too close distance to "zero".
 
Rake Aboot said:
It is Braidwood yes
That’s shocking ! I’ve yet to have a zero off there but that’s pretty bad .
Did you feed that back to them ?
Click to expand...
I’m thinking it’s calibrated properly at the moment if my understanding of all the x and y stuff on the pics is correct - I had zeroed at 100m poa on paper and adjusted 6 clicks up before taking those three shots at Braidwood, and this group seems as tight as it was on paper from the sticks.
 
I’ve used braidwood a thousand times and always test on paper as well, POI is the same.

Mungo - was your experiences with their old equipment some years back? Because they have rebuilt the targets etc at great expense
 
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