GTA
Support Equipment For PCP/HPA/CO2 and springers ,rams => Optics, Range estimation & related subjects => Topic started by: Sqrl_chsr on October 25, 2017, 12:36:25 PM
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Is this a rifle/scope cant problem?
I'm shooting from a rest and at the same distance.
On the right side the difference between the top and bottom red circles is 5 inches.
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What distance? Since everything is left, it looks to me as though there is no problem.
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We need more data ...
Oups ... misread the same distance.
Cheek weld pressure, too firm a grip at trigger hand will CANT the gun which can change POI at a fixed distance.
These pressure points can create motion under the recoil before pellet exits muzzle ...
Having a bubble level if just for testing purposes will eliminate this possibility of cant if present.
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I answered before your post was complete. Since they are all at the same distance, it could be several things. It would help to know what rifle?
But, possibilities are - pellet selection, trigger pressure, change in location of rest, shoulder pressure, loose barrel, loose scope or mounts, bad scope. But for sure, cant will not come into play if shooting at only one distance.
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I'm shooting a Crosman F4 (same as the Crosman Fire). The pellets that seem to give the best groupings are Benjamin hollow points.
The fifle appears to shoot better when held tight as opposed to an artillery hold, more like a sniper would hold it.
I've been reading on scope cant for the past couple of days.
I just hung a rope just behind my target and held a small bubble level on on a flat spot on the stock just behind the compression tube assembly.
The cant does appear to be off but only 1 inch (?) as the rope is left of the vertical at the top of the scope but right of the vertical at the bottom of the scope.
Will I end up building a jig to hold the rifle to fix this? Or spring for a level fastened to the scope rings?
Looks like I've got some work cut out for me over the next couple of days!
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Again, cant only comes into play at different distances. Since you are shooting at the same distance, cant has nothing to do with the groups opening. The problem can probably be traced to a loose pivot. Crosman guns are bad about the pivot washer wearing out and the pivot bolt backing out a little. The barrel should be firm and smooth after cocking. It should just stay wherever you let go without dropping.
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I just checked the pivot. Hard to tell without clamping the stock in a vise but I did see where people have replaced the pivot washers with brass washers.
The Crosman part # is B18-00-15B. Anyone have a source for alternate washers or do I go to Crosman?
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You need to modify some washers. As far as I know, they are no longer available commercially. I use 5/16" X .032" bronze thrust washers from Ace Hardware. The O.D. has to be turned down to fit the recess, about 3/4". There are several tutorials on here.
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. But for sure, cant will not come into play if shooting at only one distance.
Your smoking crack ... or not ???
A scopes cross hairs vertically get set over bore center line, Gravity has the pellet fall vertically and if guns shot level the pellet falls along the vertical line of scopes reticle.
Tilt the scope ( change CANT ) you move the cross hairs to the side of bores center line and gravity will still pull pellet down vertically but not along the lines of the reticals vertical line but to one side or the other.
If we were shooting LASERS then the intersect of optics and POI of the flat & straight laser light at a given range would not change with cant !! .... Gravity however skews the pellets flight and soon as cross hairs move out of the vertical plane with bore shots will go sideways .... FACT !
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I just put a level above my target station and hung a rope with a weight tied to it behind it.
Holding the rifle as steadily as I could if there looks like no more than 1 degree of difference in the alignment.
I emailed Crosman and their reply was check my hold, check the stock screws and high winds.
The target was only fastened at the top and I wait until the target stops moving before shooting even though it is fairly sheltered from the wind.
Could I be canting the rifle even though there is only a 5 inch difference between the top and bottom red circles?
Possibly. Time will tell.
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POI is to the left. Adjust the scope so the group is centered.
And if it's springer, the rest could be you.
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It has to be the scope or the gun itself.
The left target is from last week. The right is from today.
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What distance are you shooting at and with what rifle?
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Crosman F4 at 50 ft on a sandbag for a rest. 4X scope and Benjamin hollow points.
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Shooting from a sand bag should give a lot better groups.
Maybe the gun doesn't like that, so I would try something else to support the gun.
I use a roll of toilet paper which makes the gun stay more "alive".
And if you look, even the group from last week, kinda leans to the left.
Also, is this your first springer/NP gun?
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Actually the 2nd as Crosman replaced the 1st. Roadworthy says to get rid of the Crosman but being retired and on a budget.....
The POI keeps changing.
I've tried 2 3X9 scopes and returned them both as they both shifted to the right after sighting in.
The Crosman Incursion that was posted on Midway's site is tempting me.
I sent the last image I posted to Crosman and am waiting on their reply.
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I would first check the sandbag and/or the Rest/Bench you are using, I was having a similar issue and it turns out it is my support that is shifting from under the sand bags when I slightly change the AG angle to hit the higher targets on the same sheet, when I shoot straight at the target apparently my grip keeps everything in line and there is no shifting.
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I would first check the sandbag and/or the Rest/Bench you are using, I was having a similar issue and it turns out it is my support that is shifting from under the sand bags when I slightly change the AG angle to hit the higher targets on the same sheet, when I shoot straight at the target apparently my grip keeps everything in line and there is no shifting.
Natural point of aim ... torque in corrections prior to releasing shot, gun shifts against the applied torque and POI changes proportionally.
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Mackado:
I was reseating the bag when switching to the 2nd target.
Motorhead;
I would think just by adjusting the barrel vertically the difference in torque would also be vertical.
I changed the breech seal tonight and will try again tomorrow depending on the rain.
I did notice that if the breech seal is too thick it does affect the point of impact.
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I switched to a heavier pellet (Did I get a bad tin of pellets from Crosman?) and artillery hold.
It was still shooting to the left so I adjusted the scope but still not a happy camper.
Heading to Wallyworld to see what scopes they have in stock.
I was there the other day and saw an air rifle with a fully adjustable stock.
Will I return with another air rifle (don't think it was a Crosman)?
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Try JSB Exact pellets. Crosman's don't shoot great in any of my guns.
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. But for sure, cant will not come into play if shooting at only one distance.
Your smoking crack ... or not ???
A scopes cross hairs vertically get set over bore center line, Gravity has the pellet fall vertically and if guns shot level the pellet falls along the vertical line of scopes reticle.
Tilt the scope ( change CANT ) you move the cross hairs to the side of bores center line and gravity will still pull pellet down vertically but not along the lines of the reticals vertical line but to one side or the other.
If we were shooting LASERS then the intersect of optics and POI of the flat & straight laser light at a given range would not change with cant !! .... Gravity however skews the pellets flight and soon as cross hairs move out of the vertical plane with bore shots will go sideways .... FACT !
LOL....this chart seems to agree.........
(https://i.imgur.com/UNlDqtAl.jpg)
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How do I check the scope/bore alignment?
I've checked the scope and it does appear to be aligned according to a level sighted at my shooting distance.
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How do I check the scope/bore alignment?
I've checked the scope and it does appear to be aligned according to a level sighted at my shooting distance.
Not all guns are the same but my HW95 and R9 have a flat top on the barrel pivot block that allows me to attach a magnetic torpedo level (pre-checked to be accurate). I first attach the level like this..........
(https://i.imgur.com/aU2yYyQl.jpg)
Then tilt the gun in the cardboard cradle till the bubble is centered in the vial. Next I point the gun at a hanging plumb line hanging 18 yards away and rotate the scope till the reticle is aligned with the string while the bubble in the level is centered.
LOL.....here is my plumb line........
(https://i.imgur.com/E8E45o7l.jpg)
This works OK for me and here is a target I shot outdoors from 10 yards to 50 yards showing that the pellet drop is more or less vertical........
(https://i.imgur.com/5ko3WLgl.jpg)
By the way, I never bench my recoiling springers (HW95 and R9) preferring to shoot in a way that can also be taken into the "squirrel woods". For me that's sitting on a bucket resting the gun on cross sticks.
I've read that the reticle can also be aligned with the bore by focusing on a mirror and rotating the scope till the verticle crosshair bisects the bore. This method never worked well for me but if you gun doesn't have a "horizontal flat spot" perhaps this would be a good method.
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Thanks nced.
No flat spot to mount a level.
I tried the mirror trick but need to paint the end of the barrel white. I tried white medical tape but that wasn't bright enough.
I just mounted another scope and will try again.