No4 (T) Collimation Check Using Laser Boresight

[Troglodyte]

As the title suggests, I’m using a laser boresight to check my collimation, with the target at 25m per the instructions that came with the boresight.

I can adjust the sights to put them right at the six o’clock hold position where the laser hits, but how do I identify true collimation, versus being boresighted to 25m?

I understand that the mount is what gets collimated, but how are y’all checking that?

Thanks,
Trog

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[Bindi2]

At 25m/yds the POA should be at least the centre of the scope above the centre of the bore in height. If the scope is not in line with the barrel ( no hope )The way to check this is to fire a shot then wind the scope up 100 fire another and so on. This will show if the scope is parallel to the bore or the scope is not level in the rings. The bullet holes should rise in a vertical line with no bias. There are 25 m/yd zero targets with range hashes for the distances marked in the vertical plane.

[CINDERS]

Ok here is the correct sighting plate/target for the 303 MkVII to be set at 25 yds (22.8m) so I think the Privi fly pretty close to the MKVII but if your using SMK's it may be close but not perfect.

See my targets the only real way to get the scope colminated to what you always going to feed it is get on a range at the distances your going to shoot and do a DOPE chart up for yourself its what I have had to do and many others here have had to do.
Because nothing out there today fly's the same as Ball MKVII ammo and shooting that vintage stuff today will yield you spurious results P.O.F ammo is notoriously bad (Don't ask!) HXP Greek ammo if you can get it but again stuff is getting hard to find costs $'s and can be collectible.
So more range time is no bad thing, go to it bloke and keep us all up dated.

[Roger Payne]

If you centralise the scope graticule in both vertical & horizontal planes so that the pointer is in the centre of your field of view (with equal number of clicks either side), then if the rifle, scope & bracket are genuinely matching & not messed about with then this should give the same results whether bore sighting or looking through the scope. If it gives a substantially different result - your grat pointer & your bore are not in line, then work needs to be done on the bracket/pad mating surfaces. I'm afraid I've never used a laser, nor do I regularly use the 25 yd targets, as I ideally use a distant aiming point, or a commercial scope collimator if I'm pushed. The former is more accurate but the latter will get you onto the board at 300, if not somewhat better. You can then walk yourself into the centre of the black.

[Warren]

I believe this is the target you are using..

[Warren]

I also go with Roger in setting up the scope to the rifle.
If it is a matched set you SHOULD not run into much problem unless you have a damaged mount, which I did find once......
I have a distant aiming point and it has worked well but the ultimate is the north star at night...also good for bore sighting.
Even on the miss-matched units by using the V blocks and rotating the scope I have found no appreciable error from bench to range unless it is a home job of pad installation.

[Alan de Enfield]

Peter Laidler spent some time writing 4 articles on setting up a 'clone' No4T and, much of it, in great detail on fitting pads and collimating the scope.
They can be found here :

Part 1 : http://www.milsurps.com/content.php?...ter-Laidler%29
Part 2 : http://www.milsurps.com/content.php?...ter-Laidler%29
Part 3 : http://www.milsurps.com/content.php?...ter-Laidler%29
Part 4 : http://www.milsurps.com/content.php?...ter-Laidler%29

[Surpmil]

All the laser boresights I have seen are IMHO hopelessly inaccurate for this purpose; they're intended for hunters who just want to zero at say 100-200 yards and don't really care, or usually know, about collimation at all.

if you get hold of one of the old N.22 or 22C artillery sights they have a reticule that should be perfectly centered and a 1" tube that can be set in the bracket for a reliable reference.

High accuracy laser "pointers" are available out of China I see, but they're not of 1" OD, and unless a special mounting was made up to adapt them to the bore at the muzzle, I can't see how they could be used otherwise as they're too big to for the chamber and the boltway itself is not the control surface.

The other problem is centering even a rod set down the bore from the muzzle, unless it is ground exactly to the ID of the bore - wrapping thin tape around the rod is one option - but the tape has to end at the 6 or 12 o'clock positions, and the same on every roll!

Drilling a hole through the base of a cartridge case fired from that particular rifle and then sighting through it is probably still the best option, although we've all noticed the uneven expansion of fired cases when they're not perfectly centered in the chamber on firing...

Just some random thoughts on the matter!

[Troglodyte]

Great advice, thanks to all.

[RobD]

Here's my 5c worth:
If you clamp a 1 inch broomstick in the cradle in place of the scope, you' may get a quick idea whether your cradle is parallel to the bore. I imagine a 1 inch copper tube could be even better. Roll the broomstck on a flat surface to establish it's not warped, ditto if you use a 1 inch tube.
Rob