# A Question OF Temperature and Speed ?



## wll (Oct 4, 2014)

It was about 45 degrees this AM when I went to test some ammo. My heavy steel weight (184gr) stuff did did a little better than yesterday at 175fps in the cold morning. The 205gr was in at 165fps with just one shot where yesterday I really had to work at it in the AM to get 165fps ( the retying of the pouch attachment and lightening it up 16gr may have made a difference, not sure yet.

My question is how much speed do you normally gain when temperature increases ?

If I'm shooting 165fps at 45 degrees using heavy ammo and large tubes, can I expect to get 180fps when the temp goes up to 65-70degrees ?, Is there a 5 % increase in speed, or is it more like 7% or 10% increase as temperature goes up ?

Also does pre-stretching a bit help with speed, giving 3-5 full pulls and slowly letting down, does that help ?

I would really like to know from you experienced shooters !

wll


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## treefork (Feb 1, 2010)

When I go shooting I gather all my data within the first five shots. It doesn't matter how cold or how warm it is. What is the shot doing ? I'll make adjustments from that data. Numbers and percentages are irrelevant. The only fact needed is if its really cold the bands retract slower. If its warmer , they retract faster. I like to keep it simple. My chrony and calculator sits on the shelf in the warm house collecting dust.


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## Wingshooter (Dec 24, 2009)

treefork said:


> When I go shooting I gather all my data within the first five shots. It doesn't matter how cold or how warm it is. What is the shot doing ? I'll make adjustments from that data. Numbers and percentages are irrelevant. The only fact needed is if its really cold the bands retract slower. If its warmer , they retract faster. I like to keep it simple. My chrony and calculator sits on the shelf in the warm house collecting dust.


There is the man with the right answer


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## wll (Oct 4, 2014)

OK, back to the question ....... to those who know.

Thank you,

wll


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## Can-Opener (May 11, 2013)

Can of worms opened you have


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## wll (Oct 4, 2014)

Can-Opener said:


> Can of worms opened you have


Ya, Can-Opener your right, I'm dropping it ;- )

wll


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## Byudzai (Aug 31, 2013)

Treefork makes a good point. I have a chronograph and I have measured stuff like that and I TOTALLY relate to the wish to know. Once you know, though, it's like.... well I guess I'll just go back to having fun now.

I took my slingshots over to Chris Kaiser's one 55 degree day. Normally shoot at 71 degrees in my apt. Couldn't hit ANYTHING! My tubes were like "thwump, I guess or something" instead of the usual "TWHIP!"

Treefork is the man to ask about how to get meaningful ballistics on cold days. I've shortened tubes up to less than half their normal length on sorta-chilly-but-not-really-all-that-cold days and still can't get anywhere near normal shooting speeds.

Chris, btw, keeps the slingshot in a pocket with one of those hand-warmer packets when he goes walking in the cold.


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## wll (Oct 4, 2014)

Yep, I'm going to wait till the temp is more like usual. I'm just doing the testing so I have an idea, other than that it is useless for sure. I now know that in the 50-55 degree range speed is around 170FPS for the 205 gr ammo. And once I get figures on speed at about 70degrees or so, that will probably be it.

Just a reference for me.

wll


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## Imperial (Feb 9, 2011)

save all this data you have so far and now try it out in a room and save all your data from that and then in the summer, during days of 110 plus temps, collect your data once again and then compare it with your cold weather reading and indoor readings. just make sure you use the same setups, ammo and slingshots. same draw length and anchor. all this that you're doing will maybe help someone in the future who will come along with the same questions.


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## wll (Oct 4, 2014)

Imperial said:


> save all this data you have so far and now try it out in a room and save all your data from that and then in the summer, during days of 110 plus temps, collect your data once again and then compare it with your cold weather reading and indoor readings. just make sure you use the same setups, ammo and slingshots. same draw length and anchor. all this that you're doing will maybe help someone in the future who will come along with the same questions.


That's exactly what I'm doing. When it gets to be in the high 70's that should be a good indication for sure. I just built another catch box, much more portable than the one at work. I'll be able to set that up at home and test a bit. As it stands now every time I want to test, it is a 15 min drive to the desert and it's a pain ... plus I loose my ammo to the sage brush and tumble weeds. I don't feel like loosing high quality/cost hunting ammo just to test velocity .... I'm so over that !

wll


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