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    lets talk accuracy

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    roonie
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    lets talk accuracy

    Post by roonie on Sat Feb 02, 2013 3:01 pm

    Hi all....im going to be starting my build. I might as well try and find out what it takes to make a xbow more accurate. What can i do to make less mistakes on my build and improve accuracy BEFORE the build takes place. I was told by the late Robin Allen that his xbows were way more accurate than the store bought xbows but we never got any further due to his passing. Any input would be great.
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    Todd the archer
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    Re: lets talk accuracy

    Post by Todd the archer on Sat Feb 02, 2013 3:23 pm

    For starters make sure the prod is centered AND square when mounted. Also just as important make sure when cocking the string to center it in the catch. Goes without saying to use matched arrows consistant in weight, size, and stiffness.

    Maybe other have suggestions.



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    Re: lets talk accuracy

    Post by roonie on Sat Feb 02, 2013 5:51 pm

    very understandable. I guess im thinking more along the lines of track width...track drag....catch shape. Maybe it would be best that the bolt be supported by an arrow rest type design so that the bolt only makes contact out near the end and not even touch the track or is this playing with fire? Why do xbows need a track? When a person thinks about this a regular compound or recurve bow is shooting off of a rest...why not a rest for a xbow? By the way......how does one go about "tuning" a crossbow once its built and ready to shoot.
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    Geezer
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    Re: lets talk accuracy

    Post by Geezer on Sat Feb 02, 2013 10:54 pm

    Groove vs. rest: In fact, plenty of late-medieval and renaissance crossbows (1450-1600) shot off a bone rest rather than a groove. In some cases, the rest was a simple saddle mounted in a dovetail. In other cases, the 'rest' was a raised bit of bone/horn at the fore-end of the table. A dovetailed rest can actually be adjusted very slightly right-left. A ramp-rest gives the bolt a little bit of 'loft' when leaving the bow, which will extend 'point-blank' range a few yards. Under optimal conditions, a rest should give slightly less friction, hence better velocity and accuracy. A groove is a bit more secure for holding the bolt in place if you're moving about, stalking game or whatever. Each solution has its place. Geezer
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    Geezer
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    Re: lets talk accuracy

    Post by Geezer on Sat Feb 02, 2013 11:00 pm

    An addition to what Todd said about accuracy above. For crossbows with a roller-nut. If your bolts are narrower at the butt than the distance between the lugs of the nut, it MATTERS whether you put the butt of the bolt against the right lug, or left log, or perfectly balanced between. In most cases, one side will shoot better than the other... but a sixteenth of an inch variance at the lock can result in a couple of inches (or more) at the target. If you pull the bow square and center your bolts, you'll get the best accuracy possible with a given set of bolts... but everything you do matters, and even if you do some things wrong, doing it the same every time will eventually give you reasonable accuracy. Geezer
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    Re: lets talk accuracy

    Post by shiloh on Sun Feb 03, 2013 5:06 am

    I concur with what the above Masters mentioned. There are a lot of variables, but in the end whether a bolt rest or groove is employed, it boils down to shooting and getting comfortable with any given weapon.

    Case in point. my lite weight target bow is square, plumb and balanced in every way, but it shoots left and low, couldn`t figure it out until a buddy noticed that when the bow was bent, one side was arching more uni-formally than the other. I thought my tillering was pretty good, but with use and as the wood limb settled in this is what resulted. This is what I contribute to the way it shoots, But at 20-25 pace I`m getting consistent 3-4" groups, it`s a fun bow, I just aim low and to the left.
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    Re: lets talk accuracy

    Post by stoneagebowyer on Sun Feb 03, 2013 5:12 am

    Almost any weapon you can think of has that is well designed and constructed has far more accuracy than humans are capable of. Eliminating the variables like bad form, trigger jerk, etc goes a long way toward good shooting. Breathing is important - either exhale completely or inhale and keep your breath before you shoot helps. Very smooth trigger pull is important. Jerking the trigger leads to bad groups and innaccuracy. Matched ammunition is critical. So is consistent sight picture. And as Shiloh has pointed out, understanding how a particular weapon shoots and learning to get good groups with that is important. If you can't adjust the sights or the bolt rest, you have to adjust how you shoot the weapon.
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    ferdinand
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    Re: lets talk accuracy

    Post by ferdinand on Sun Feb 03, 2013 10:26 am

    Maybe a sight is a good option?! Consistancy is what its all about.
    In my opinion its not that big of a problem if ur bow goes a little left or right.
    As long as the projectiles are uniform and the string is centered u can adjust ur sight to compensate for the other deviations.
    And as Stoneagebowyer says, breathing
    is important!
    I have done 6 years of match rifle shooting and breathing makes a 9 into a 10.
    Trigger pulling is the most common error, gently pull it and pull all the way back till it stops even when the shot has gone off.
    And keep looking thru the sight till the arrow hits the target.
    Breathing is personal, is look, breathe 3 times slowly, third time out i hold breathe at 70% and after the third or second heartbeat my sight stops moving and i pull the trigger.
    Thats what works for me!
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    jds6
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    Re: lets talk accuracy

    Post by jds6 on Sun Feb 03, 2013 7:26 pm

    Greetings;

    I agree with what all these guys are saying about how the get the best accuracy with your xbow. But it is your build. Hand made,not some computer cut model off an assembly line. What I trying to say is after all the fine tuning possible it may still be off a little. Get to know your bow, each have their own personality so to speak. Of the three I made, each shoots differently. Know your bow and practice!!!

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    Re: lets talk accuracy

    Post by roonie on Sun Feb 03, 2013 8:02 pm

    Let me refraise my question then.....what do tournament xbow shooters do to increase accuracy to a xbow. Is it a whole other ball game or the same as us guys that shoot for fun. I remember reading on Robin Allens pagess (somewhere) that he makes the string contact the upper part of the bolt nock. I guess im looking for the finer building and tuning aspects
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    Re: lets talk accuracy

    Post by Geezer on Sun Feb 03, 2013 9:32 pm

    To increase accuracy... lubricate top of your stock (groove or table) with spray silicone. Reduce string thickness and weight as much as possible... related, go to a very hard, strong fiber, like 'fastflite' for a bowstring (this will reduce your prod-life, but it will go faster) polish your trigger/tickler interface, and reduce it's bite as much as you can without compromising safety (make sure the roller-nut has no roll-back on release) Learn to hold your sight-picture with bow still lined up on target until you see the bolt strike the target. Learn about Kentucky windage... banking your bow left will make you shoot left, banking right shoots right. If you have to shoot into a side-wind, banking the bow is more accurate than holding off-the target.
    Lastly, invest in really good bolts: perfectly straight, matched for spin, weight, length and balance (fore/aft) see that butts are perfectly square and consistent from one to the next.
    Gime me time and I'll think of some others. Geezer
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    Re: lets talk accuracy

    Post by stoneagebowyer on Mon Feb 04, 2013 2:24 am

    Roonie, the more exacting you phrase your questions, the better.

    You probably should find and discuss things with a tournament crossbow competitor. Lessons would probably not be cheap, though. And taking a basic rifle marksmanship course would not hurt, either. Also, perhaps finding a manufacturer of tournament weapons may give you the answers you are seeking.

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    Re: lets talk accuracy

    Post by roonie on Mon Feb 04, 2013 6:20 pm

    All this time i thought i was getting top drawer xbow buiders advice on here.......I WANT A REFUND...hardy har har

    All kiding asside....I am a retired Canadian tournoment archer. I even have a bronze medal from a sanctioned shoot by the Canadian Federation of Archers. Cough...Cough...brag brag. Oh the glory days.

    But....that is with a compound bow and I was very proficient at tuning my bows. Some of what ive learned over there could be applied to a xbow i am sure. Just wondered what may be different with a xbow. I am wanting to kill big game with my xbow build so in my opinion taking the life of an animal, and not wounding, is more important than missing the ten ring on a target.
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    hullutiedemies
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    Re: lets talk accuracy

    Post by hullutiedemies on Tue Feb 05, 2013 6:26 am

    From engineering point of view any projector device has three sources of inconsistency.

    1) The device itself aka. crossbow
    2) ammunition - the bolt
    3) operator - you

    An accurate design minimizes the effects of these inconsistencies. There is no such thing as perfectly measured - inconsistencies allways happen.

    1)
    a) - Mounting the prod so it cannot move , or optionally so its movement does not effect the line of acceleration.
    - trigger assembly
    claw(s) should have minimal sideways movement and release the string without random interference.
    - There are multiple ways of implementing these.

    b) Bolt track should not have any bumpms or dents that catches parts string during acceleration.
    - notice bolt clip also

    2) Bolts will vary in diameter, stiffness, fletching, mass centre smoothness and straigthness. Trackless crossbow deals with thickness and straightness plus any dirt & damage of tiller. But with track shorter stiffer bolts with less spining issues can be used. ( also see geezer above about bolt placement&lock )

    3) Operator causes variation with centering the string, placing bolt, canting bow during aim, and pulling trigger.
    Trigger pull should cause minimal movement of the nut before full release. ( Two stage strike hammer mechanism was one classic solution ) Trigger,grips & buttstock should allow smooth squeezing of trigger without jerking the bow.
    A bubble scale on sights helps with canting.

    Low string angle = long string and short power stroke reduces effects of variation with cocking the string.
    Also a lock with single claw nut and a string with center loop remedies a lot of the issues above.

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    Re: lets talk accuracy

    Post by roonie on Wed Feb 06, 2013 12:28 pm

    this is turning out to be a great thread.

    Tell me guys....why do i see some xbows (mostly custom) with the prod mounted up above the rail? Does this have to do with accuracy as well? I cannot see how this would work for hunting situations though. Curious more than anything

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