Lighted Nocks Changing Point of Impact

[jathtech]

Saw this post and has some theories as to why some people were experiencing a shift in impact location, while some are not.

First, whatever the grain difference is, (12 grains?) it should really be nominal.  In theory however, it might effect  the flight of the arrow ever so slightly.  The OP is way beyond what I would expect however.  Here are my theories as to why to  nocks cause this:

1, Nocking point.  If the nocking point is lower, it could cause the arrow to "bounce" off the arrow rest more with the heavier nock, accounting for its higher impact point.

2, Wind resistance.  You're going to have a slightly slower arrow, but it going to maintain its speed better than a lighter arrow.  This may cause the lighter arrow to slow down beyond where the slightly heavier arrow is, and drop more out to 40 yards. 

3, harmonics.  Sometimes, you just get things tuned just right where the vibration is perfect, and the least amount of wind resistance is achieved. 

4, String grab.  It's possible that the nocks are grabbing the strings differently, either tighter causing it to hang on to the string too long, or looser causing it to bounce off of the string and not get the full energy. 

Keep in mind, these are just theories, and not based on experience as I am new to archery (however not to marksmanship, or physics).

[Todd_ID]

4, String grab.  It's possible that the nocks are grabbing the strings differently, either tighter causing it to hang on to the string too long, or looser causing it to bounce off of the string and not get the full energy. 

This one was the problem... The Easton X nocks had a larger string gap than the Nockturnal X nock, so it was staying on the string longer.  I don't remember the actual difference off the top of my head, but it was substantial (something like .030" or .040" difference).  I filed the inside of the Nockturnals to the same internal dimensions as Easton's, and the problem went away.

[Russ McDonald]

Now that this came up again I thought of something mine did.  My groups at 20 and 30 yards we unchanged from none lighted nocks to lighted but when I went out to 40 and 50 there was a change.  It was shooting at least 2" lower with the lighted nocks.  Dead on center but lower.  Just dialed in the correction and it is on. 

[TommyH]

Good info here, I was hesitant to use these. I didn't want to have to change my set up when it was doing so good.

[RadSav]

I wish all pro shops would buy a trigger pull gauge.  Would save a lot of headaches for archers with these issues.  Back in my target days it was surprising to see how much each cavity in a mold would change.  I ended up sorting nocks by the cavity number molded into the nock.  Some do it these days some do not.  With the pull gauge it makes life much easier.  If you shoot a lot it is also a good practice to keep a shot journal for each arrow/nock.  Find out when impact points change by how many shots it has taken.  Back then aluminum arrows only had so many shots before spine would start to change as well.  Doubt that is an issue with carbon, but I no longer keep journals as I rarely shoot enough these days.

Todays nocks are polycarbonate instead of cellulose-butyrate like they were in the old days.  Polycarb is stronger, wears out at a slower rate but is stiffer and shows impact differences with less throat width change.  Watch them closely if you see impact points rise or fall.  Sometimes if you have one arrow that doesn't group with the dozen you can recover it with a simple nock change instead of sending it skyward off the mountain top

[bowhunterforever]

I wish all pro shops would buy a trigger pull gauge.  Would save a lot of headaches for archers with these issues.  Back in my target days it was surprising to see how much each cavity in a mold would change.  I ended up sorting nocks by the cavity number molded into the nock.  Some do it these days some do not.  With the pull gauge it makes life much easier.  If you shoot a lot it is also a good practice to keep a shot journal for each arrow/nock.  Find out when impact points change by how many shots it has taken.  Back then aluminum arrows only had so many shots before spine would start to change as well.  Doubt that is an issue with carbon, but I no longer keep journals as I rarely shoot enough these days.

Todays nocks are polycarbonate instead of cellulose-butyrate like they were in the old days.  Polycarb is stronger, wears out at a slower rate but is stiffer and shows impact differences with less throat width change.  Watch them closely if you see impact points rise or fall.  Sometimes if you have one arrow that doesn't group with the dozen you can recover it with a simple nock change instead of sending it skyward off the mountain top

Don't know really what your talking about but i'm glad you joined this site those few words I don't understand

[swift]

Thanks Rad , Great info !!!

[JJD]

29.5 " Carbon x maxima hunter 350, with accunocks, 100 gr Striker broad heads.   Draw weight at 62 lbs
Chrono at just under 300fps.
 Nocturnal "S", shoots less than 1 inch low (average) at 30 yds

[RadSav]

29.5 " Carbon x maxima hunter 350, with accunocks, 100 gr Striker broad heads.   Draw weight at 62 lbs
Chrono at just under 300fps.
 Nocturnal "S", shoots less than 1 inch low (average) at 30 yds

I was given a sample of the Accunock a few years ago.  Looks pretty neat, though the technology is older than one might think.  Seems a guy gave me a sample back around '93 or '94 with the same principle though I do not know what happened to him.  Guess it could have been the same guy.  I have yet to shoot an arrow with one.  I'm intrigued enough I might give them a thorough work up this off season since the new Carbon Express nocks are horrible!  And I am just about out of my Easton Micro Lite and Old clear CE.  Was thinking I might have to go back to shooting ACC's just so I could get the X-Nock.  Was that or make my own X-Unibushing for the Carbon Express shafts.

1" difference at 30 yards changing nocks and adding the extra weight.  That's not bad at all in my book   Do you know what you ended up in FOC?

[sakoshooter]

I've been really hesitant to try any illuminated nocks but after reading about simple minor point of impact changes, I might have to find some X Nockturnals. Especially after looking hard for my arrow from my blacktail. Finally found it but it would have been obvious with a lighted nock. With late elk coming up, days are going to be shorter and darker as winter moves in. A lighted nock might just be a smart move.
According to this thread, Nockturnals seem to be the best - Any other opinions as far as durability, reliability, etc?

[RadSav]

I've been really hesitant to try any illuminated nocks but after reading about simple minor point of impact changes, I might have to find some X Nockturnals. Especially after looking hard for my arrow from my blacktail. Finally found it but it would have been obvious with a lighted nock. With late elk coming up, days are going to be shorter and darker as winter moves in. A lighted nock might just be a smart move.
According to this thread, Nockturnals seem to be the best - Any other opinions as far as durability, reliability, etc?

I have found nothing that compares to the Nockturnal.  But you do need to make sure the switch moves freely.  Some that are sticky will not group with the others.  DO NOT TRY TO OIL THEM!  Just work the switch on and off until good and free.  Usually just a bit of flash in the holes.  The flash/burrs will break off if you work them a little.  I do still think in most circumstances stepping up to a heavier broadhead is advised.  Shooting on the range in good weather is vastly different than shooting in the field in not so perfect weather.  If you have poor FOC you will find that one out sooner or later.  Better to error on the side of caution than to screw up the shot of a lifetime to save a couple FPS or a few bucks on new broadheads.

[sakoshooter]

Rad, I'm just over 12% FOC with my Axis 300's and 125gr broadheads now. Putting on a Nockturnal would certainly change that but I really don't want to go to a 150gr broadhead. My total arrow weight now is 480grs and penetration is excellent. Accuracy is super based on our discussions earlier this year when I was trying to make 340's work. Speed is 270fps according to my Pro Chrono. Helical Blazers. Giving up some speed but accuracy and forgiveness is way more important to me.

[RadSav]

If you are 12% now I don't think it should be too bad.  But I no longer have your numbers so just guessing on that.

[sakoshooter]

If you are 12% now I don't think it should be too bad.  But I no longer have your numbers so just guessing on that.

70# Z7 @ 28.5" draw. 28" Axis 300's, 125gr Slick Trick Viper Tricks, 3 fletched w/Blazers - pink ones ol buddy.
I could probably add a 1/2" to the shaft length to overcome the lighted nock added weight and come close to keeping the FOC the same as long as they'd still broadhead tune as I suspect they would.

[RadSav]

Adding arrow length actually makes FOC worse.  Going shorter makes it better, but stiffens up the shaft rapidly.  So I would leave length where you are at.  You should still be at about 10.5% FOC with the Nockturnal nocks.  So I don't think you should see any problems as long as things are tuned well.  If you weren't already at 12% then you would experience some issues.  But, with that 125 grain point you should be just fine I would assume.