Arrow tuning question.

[Gdpolk]

I got a new string for my 50lb longbow so I went out to the range and tuned the bow to shoot quiet, leave bullet holes in paper, and have the arrows stick into the target straight from both 15yds and 3ft out.  I then fine tuned my silencers to be nice and quiet.  

Then I started shooting to see if my bow was shooting the same as with the old string.  I discovered that with the new string tuned in some of my points of impact were different.

At close ranges it shot the same as before but out to my point on range (where the end of the shaft lines up to the bottom of the bull and the arrows hit the bull) was funny.  

My broadheads (125gr RFA Pheonix) hit spot on at the point on range.  There was no left or right deviation from the point of aim and from the line of sight down the arrow shaft.  

My 125gr field points, 125gr judo points, and 125gr small game heads (RFA Talons) are now all shooting left of the point of aim and line of sight down the shaft.

What would cause this to happen given that all of my arrows are the same spine and all of my heads are 125gr.  Before installing the new string, the field points, judo points, and small game heads all flew true; the broadheads were new equipment for today as well as the new string.

Can someone help explain what's happening and how to fix it?

[sawtoothscream]

did you try bareshafting again after playing with the silencers?

[Gdpolk]

Originally posted by sawtoothscream:
did you try bareshafting again after playing with the silencers?

I did not.  After getting it tuned in before I had all of my arrows fletched so I no longer have bare shafts.

One other strange thing I observed was that my broadhead tipped arrows repeatedly grouped slightly smaller at the point on range than my field point tipped arrows.  It's almost as if the broadheads helped to stabilize something during the arrow flight.

I had the blades of my broadheads lined up with the base of the feathers (near the nocking point) perfectly on all three arrows that had broadheads.

[JamesKerr]

If you don't have any bare shaft than you can use the same method just shoot a group of broadheads along with a group of field points and tune according to how they group.

[bbold]

Is it the same kind of string?

James

[Gdpolk]

It is the same kind of string.  I just measured the old string and new string.  The nocking point is exactly the same.  The new string has a brace height of 7" whereas the old string has a brace height of 6+5/8".  The old string was the one that came with the bow and I hadn't tuned it in any way since getting the bow.  I played with point weights and arrow shafts at the shop until it showed the right spine and thus have only bought 125gr stuff since.

Do you think maybe if I lowered the brace height by 3/8" it would group the field points/judo's/small game heads back on the vertical axis like it was before?  That would make the bow a bit louder but I'd take a louder bow to get my arrow flying straight again.

[Caughtandhobble]

Not all strings are equal. I would suggest that you have the new string maker make your backup string to insure that the construction and the materials are the same. Good Luck!!!!

[stickum]

I would try lowering the brace height and see what that does to your field tips.  Hitting left could indicate a sitff spine which makes sense because broad heads tend to slightly weaken the shaft due to them being longer than the field points.  So if this works, just note what the brace height needs to be for each.  Also, the new string will stretch after being shot awhile, recheck the brace height after shooting some arrows.

[darin putman]

I don't know how you store your bow, thats another matter all together. But when I get a new string I always leave the bow strung up for a few days, maybe shooting a few arrows through to help get initial stretch out before I try to put the final touches on it. That way I don't make any drastic changes, two stretched strings from same manufacturer, especially if d97 or other fflite material usually pretty close from my experience. Just an opinion.

[Gdpolk]

Originally posted by darin putman:
I don't know how you store your bow, thats another matter all together. But when I get a new string I always leave the bow strung up for a few days, maybe shooting a few arrows through to help get initial stretch out before I try to put the final touches on it. That way I don't make any drastic changes, two stretched strings from same manufacturer, especially if d97 or other fflite material usually pretty close from my experience. Just an opinion.

I stored the bow strung for a couple days and shot it about 100 times prior to tuning in.  Both of my strings are D97 but from a different manufacturer.  I'll try playing with brace height or may try some lighter heads on my existing shafts.  Maybe 100gr heads will do better.

[CoilSpring]

If the brace ht change doesn't get you there,
you might also try some 145-150 grain field tips compared to the 125 BHeads.

[Smallwood]

Please let us know when you get it figured out, what the fix is.

[Gdpolk]

I've got measurements recorded for the brace heights that work with field points, judos, and RFA Talons as well as the brace height for my broadheads, RFA Pheonix.

It's been too windy to get a really good accuracy shoot in here lately but I'm going to try tuning the bow to shoot the Pheonix heads perfectly then adding these to the shorter points until it shoots the same.

 http://www.3riversarchery.com/Product.asp?show=rate&c=57&s=2&p=431&i=5208X

I figure with the marginally higher weight and moving the points out farther, maybe my dynamic spines will equal out close enough to be confident that all my arrows will go to the same place out to normal shooting distances.