Spin drift?

[nchunterkw]

(but being a little OCD myself I know where you're coming from )

I like to call that "CDO" - because that way it's in alphabetical order.

[Kegbelly]

(but being a little OCD myself I know where you're coming from )

I like to call that "CDO" - because that way it's in alphabetical order.

Good one!

[Kegbelly]

Been giving this some more thought (slow day, sorry)...
OK, IF your bow shot to zero (with the expected drop) at varying yardages before you changed scopes, then therein lies the problem.
It's not limbs, tiller, arrows, spin drift or Coriolis, something is up with the scope or the mounting of it. Your POA and POI intersect at 20 yds and is spot on. From there they start to diverge, and I'd guess if you shot at 50 yds you'd be +- 3" right. Assuming you are in fact holding the bow level when shooting, it sounds to me like a scope alignment issue, like the scope isn't centered in line with the rail. If it were a rifle I'd say the scope is out of line with the axis of the bore, same principle. If the scope was mounted out of level very much at all, when you click the windage or elevation knobs your POI would move in two directions, not just strictly on the vertical or horizontal axes. I'd check to make sure the scope rail was tight, then maybe even remount rings and scope and try it again. It sounds like an alignment issue, but it could be something in the internals of the scope itself. And it could very well be I dont know what the hell I'm talking about, just trying to help.

[Onetimeonly x-->]

[quote="BravoKilo"]Was wondering if anybody here could comment on spin drift in regards to crossbow arrows?

Recently switched over to a Hawke XB30 compact scope and have been trying my damnedest to get everything perfect. One of the things I've been noticing is that I can get a perfect zero at 20 yards then when I start pushing out the distances to 30 and 40 yards, aside from the expected drop, I'm also getting a decent amount of drift to the right. Absolutely calm day so wind isn't the culprit.


"Perfect zero" lets just say every shot after the first lands in the same hole exactly everytime "Perfect zero". 1/4" +/- rt. at 20yds may end up being 1"+/- rt. at 30yds and so on... JMO.
Scott

[BravoKilo]

Thanks for all the replies guys!

Going to look at canting first to see if that's the culprit as it seems most likely. I recently replaced my arrow retainer and made sure to tighten down the scope rail and also used Loctite on the threads. Rings and scope were installed last night and used bubble levels to do so.

To be honest, I didn't pay that much attention to my previous setup everything was "close enough" and more than sufficient for "minute of deer" shooting -- a large fuzzy dot (cheap TruGlo reddot) and an astigmatism to further blur said dot made precision shooting a tad hard . It was only when I threw on the XB30c that my CDO ( ) kicked in and I wanted everything to be perfect.

Still am unsure about the scope tough as I have it dialed all the way down and I'm still shooting low at the respective distances and reticles. I have since re-zeroed it to be on at 30 yards, which puts it a tad high at 20 yards, and half-way between the 40 and 50 yd. reticle is on at 40 yards -- seems the most appropriate for a hunting situation, at least for the time being. Hitting the woods tomorrow so I won't be messing with anything major until next week when I'm home again.

[Kegbelly]

Good luck tomorrow!

[nchunterkw]

I recently just put on an XB1 and it took my a lot longer than usual to get thigs settled down and accurate. Mine is on a Vortex and I am shooting some heavier arrows. Download the Hawke app and go through the exercise to determine ballistic coefficient for the arrow. Then use that and your arrow velocity to see what yardages your reticles will be. Depending on how everything sets up you might not be able to get exact 10 yard increments. I don't think I will be able to do that with my 575gr arrow. In that case though you can adjust for 5 yard increments pretty accurately. But like you, I too am hunting now so I have not messed with this thing a lot yet.