GPR sights

[Robyn]

Hi everyone. I have just bought a GPR 50 cal and I have found that it shoots low. I have the adjustable rear sight lifted to the max and still have to use a 12'oclock Plus a bit hold to get in the black on a 50 yard target, which means I can't see the bulls eye which is making it a bit hard to get a good score. The question I have for all you experienced GPR shooters is what would be the average amount you have filed off your front sights to get a six o'clock hold at 50 yards... This rifle is for target shooting only. I have found that with a 498 ball and 14 thou patch with 60 grains of FFG works really well it is just the sights. Cause I cant hit what is hidden behind the front blade hahahhah

 

[FPDoc]

I'd recommend working up the load that shoots well for you first. Then start filing the front sight.

 

[boar]

This is the way I do it. It may not be the right way, but I find it the easy way for me. This is with the sights that just move sideways in the dovetails. I use a small metal ruler. I measure the bottom V of the back sight. Then I take this up to the blade of front sight and mark a line across it. I find when I am done filing, I will be close to the mark. It depends on how you like your sight picture on how much more you will file. Like do you want the top of front blade level with top of back or do you want it down in bottom of V. I shoot then file. You have to remember 10grs will raise your poi. If you get the front to low you will have to cut back notch deeper. I use a knife to cut the V. Hope this helps. Dilly

 

[jtmattison]

The first thing I do with any new Lyman muzzleloader is file half the front sight off. They are way too tall. Taking off half right away makes sighting in a lot easier. I have done this with six so far.

HD

 

[Old Salt]

If you plan to keep the adjustable sight on your GPR I would recommend centering the vertical adjustment before doing any filing. That way when you get the filing done you will still have some vertical play to raise or lower the point of impact.

Old Salt

 

[jtmattison]

Good point Old Salt.
I meant to say that in my post.

HD

 

[Haleh]

I have gone with fixed rear sight. Filed a good bit off of the front sight height and also filed the front sight thinner. Thinning the front sight to let a little light in on each side and getting rid of the adjustable rear sight helped me a lot.

H.Hale

 

[Stumpkiller]

"6:00" hold on what sized bullseye? A 10" circle means you're aiming 5" low. 12" = 6" low.

You can use good 'ol 10th grade algebra and figure exactly how much you need to shorten the front sight. You've got a triangle with the adjacent (base) from your rear sight to the backstop. The opposite leg is the difference between the desired impact point and where the shots are hitting, and the hypotenuse is the distance from the desired impact point back to your rear sight. Assume the base is a 90º angle to the backstop (it ain't but it's near nuff).

Sooo. If you want the base to equal zero (hitting where aiming) and lets say you're hitting 6" low at 50 yards (1,800"). 6"/1800" = Amount to file front sight (or raise rear)/sight radius. Simple. Lets say for argument you've got a 24" sight radius. 6/1800 = X/24", x=0.08", or 5/64" needs to be hacked off or the rear sight lifted that amount.

Now don't you wish you'd paid attention in class instead of daydreaming?

 

[jtmattison]

:snore:

Huh? :shocked2:

Sorry, I missed that. Could you start over?

:haha:

HD

 

[Robyn]

Thank you to all that have replied. Stumpkiller it is a bit hard to use your formula cause I am down in the land of OZ and we are shooting upside down!
seriously thank you I can work it out from there.
just got to work on a magnet that attracts lead to put behind the target.

Gee there might be a big market for them .... every shot a bull... imagine 100.10 I like that ha ha ha ha

 

[ravenousfishing]

Didn't take a tape measure to it, but marked the tape that I had put on the back side of the file so I could judge my progress, and when I was done, looked like I had removed about 1/8". Also, it wouldn't hurt to tape the barrel for protection in case you get impatient and start filing like a mad man like I did after I finally realized how much metal I had to remove.
Only one slip, but....

 

[pepperbelly]

Robyn, I have a magnet like that!
Unfortunately I installed it with the poles reversed while I was shooting bullseye pistol. It looked like my X-ring had a force field around it! :grin:
I swear, I once shot a half circle around it. Fortunately the 10-ring is generous enough for me to have still scored a clean!

Jim

 

[longcruise]

Measure your sight radius. It should be 21.75 inches on a GPR. If the radius is 21.75", then every .020 reduction in sight height (that's 20 thousandths) will change your point of impact 3.31".

If you do things metric, do yur own math!! :haha:

PS, that 3.31 is MOA, so for 50 yards you would change the POI by 1.655"