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    Practical differences in bolt tracks?

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    Basilisk120
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    Practical differences in bolt tracks?

    Post by Basilisk120 on Thu Aug 05, 2010 5:44 pm

    I was wondering if there was any noticable difference between a grooved bolt track and a dove tail mount thats at the end in a "trad" crossbow? Assuming both are properly made and using good materials.

    Is the dove tail mount faster but only noticable if you have a chronograph.

    I may be overthinking the issue too.



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    Tinker
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    Re: Practical differences in bolt tracks?

    Post by Tinker on Fri Aug 06, 2010 4:59 pm

    That was a question I had waiting in the wings. Be curious also to what the people 'in the know' say scratch

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    Geezer
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    Bolt tracks

    Post by Geezer on Sun Aug 08, 2010 9:04 am

    Geezer here, ready to spout off about bolt-tracks. In my experience, full-grooved tracks are the most secure... they'll simply hold your bolt in place better if you're hunting or playing combat games, but a full groove must be absolutely straight and very-very slick for best results. Lining the groove with polished brass, bone, or a slick synthetic, like Micarta or Delrin will noticeably improve your bolt-velocity (one customer reported a 10% (20 fps) increase in speed, just by lining the groove with Delrin)
    A simple bone bolt-rest (sometimes dovetailed into the stock, sometimes a permanent part of a bone top) should increase velocity, thanks to lower friction, (and you can circumvent necessity for a really straight groove). A rest will probably loft your bolt just a bit on takeoff, giving you a longer point-blank range, but if the rest is TOO high, you'll get erratic flight: porpoising or whirligging. Also, misfires or dry-firing can knock your bone rest right out of its dovetail, even if the rest is mounted as far forward as possible.
    For this reason, I often build rest-type bows with a simple ramp and partial groove. Ramps are fairly common on central european bows from 14th-15th centuries. I suspect they were partically intended to slow the string at the end of its run to reduce stopping-shock, which might cause the glue-bonds in composite prods to separate over time
    You can make your ramp out of any hard, slick material. Usually it starts at the string-rest position and will be about 1/4 inch high at the fore end of the table. Again, if you find your bolts tend to porpoise right after launching, your rest is too high.
    As for which is better: I regard this as another matter of choice based on needs. Grooves are more secure, rests, particularly those in dovetails, admit a certain amount of adjustment, but may also require some fiddling to get right, and they are subject to sudden disappearance downrange in the event of dryfire or misfire.
    Does that help? Geezer

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