Temperature affects on POI?

Pydpiper · Post by **Pydpiper** » Wed Dec 20, 2006 11:29 am

I shoot every morning and every night, consistent and accurate..
Last night I had my bow tuned right in, I was grouping 50 yards at about 3 inches.
Today I brought the bow out and my 50 is about two inches low. It's about 4 out right now.
I am scratching my head on this one.. I put a new string on (not FFF) in the morning, but that's about it for any changes to the structural part of the Xbow.
I don't want to have to tune this thing to each fluctuation of temperature, but seems to be the only variable.
Exocet 200.

Grizzly Adam · Post by **Grizzly Adam** » Wed Dec 20, 2006 11:37 am

If you changed from a Fast-Flight string to a dacron string, the loss of velocity would certainly be enough to lower your groups by 2" at 50 yards.

What sort of string was on it? What sort did you put on it? Was the new one brand-new or already shot-in?

BOB VANDRISH · Post by **BOB VANDRISH** » Wed Dec 20, 2006 11:49 am

I would add that the new string has probably stretched a bit,and that will affect your point of impact.
You may want to check where you are on the marks.
Grizz is right too,as changing from a FF will affect the speed.
If your old string is still OK,why not go back to it and experiment later with the new one?
Would hate to miss one because of that variable!!
Bob.

Pydpiper · Post by **Pydpiper** » Wed Dec 20, 2006 12:31 pm

My old string was discarded, it lost a strand or two. I am using the string that came on the Xbow, and that is also what I changed from. I was under the impression those things were not supposed to stretch.
Oddly, my 20 is still dead center, it just creeps away from center the farther back I get.
If it as simple as a string stretching I can live with that, I am relieved to see that nobody mentioned temperature changes.

Corvus · Post by **Corvus** » Wed Dec 20, 2006 12:42 pm

I guarantee you that changing your string is what changed your POI - not the temperature!

The string will absolutely stretch - keep an eye on where it is with relation to the marks on your rail. If it stretches to be ahead of the forward mark, you'll want to take it half off, twist it a few times to shorten it, and put it back on.

ComfyBear · Post by **ComfyBear** » Wed Dec 20, 2006 12:46 pm

Pydpiper wrote:My old string was discarded, it lost a strand or two. I am using the string that came on the Xbow, and that is also what I changed from. I was under the impression those things were not supposed to stretch.
Oddly, my 20 is still dead center, it just creeps away from center the farther back I get.
If it as simple as a string stretching I can live with that, I am relieved to see that nobody mentioned temperature changes.

If you're right on at 20 yards, then is seems that your speed has decreased, or you, inadvertently, moved your speed ring. In any case, if you turn down the speed on the ring of your Varizone, you should be back on track.

Pydpiper · Post by **Pydpiper** » Wed Dec 20, 2006 1:05 pm

I am sure I didn't adjust my speed, it's one of those things I watch closely, perhaps too closely. My dial sits just under the 3 on the 300 mark..
I will go out now and make the necessary changes to the speed dial, it's the unknown part that is frustrating me..
Thanks!

wabi · Post by **wabi** » Wed Dec 20, 2006 1:26 pm

The diameter of the string can change POI, too. Any change in the string (type material - number of strands - size of serving material - etc.) can change the POI slightly. I've switched serving types and changed the POI as much as 2" @ 20 yards!