View Full Version : Fun with the chronograph

05-06-2013, 03:31 PM
So after deer season ended in September, I put my Onza and my hunting gear away, and didn't shoot for a couple of months. In December, I got the bow out and went to shoot... it was grouping 3-4" low. :confused: I double checked all the specs, everything was good, everything was tight. I checked the peep and the sight and rest as well. All good. Got the chrono out, 5 fps slower than I remembered! Damn. Checked the poundage. Same as normal, 70# on the nose.

I had just ordered new strings from Hutch and I asked his thoughts on it, and we decided it was probably the change in temperature, went from 80-90 to 35-50. String came, I changed them out, got it all set up and tuned, Same speeds as the old strings. Fine, we'll work with that; I lowered the sight housing lol.

Fast forward to this weekend, temps in the 80's, beautiful weekend. Decided to get the bow and chrony out again. What do you know, I gained my 5 fps back, and am grouping 3-4" high lol. Its enough to drive a guy nuts I'll tell ya! ;)

I decided that since I had the chrony out, I'd play around a little bit. Right at release, I'm getting speeds between 286 and 288 fps. Not bad for my short draw length. At 20 yards, the arrow clocked about 277. At 30, 266. At 40, 255. It seems to consistantly drop 10-11 fps every 10 yards. Start plugging that info into a kinectic energy calculator, and I get 70 fp at the bow, 65 fp at 20, 60 fp at 30, and 55 fp at 40 yards. How far out could I shoot (assuming I could hit what I'm aiming at lol) and still have a deadly amount of kinectic energy? How far would you push it lol?

Anyways, just a little fun this weekend and some info I thought I'd pass on.

05-07-2013, 05:17 PM
Thats some good speeds, I been eye balling a 2012 Onza 3 for a good price. I don't have a chrono but I'm looking into getting one. I want to know what speeds my bows are getting but I'll have to wait. I have a spot hogg 7 deadly pins shooting 50yrds, I'm not shooting 80 yards yet havent sighted it in that far. I'm very interested what my fps and KE are at various distances. I can group fair with my Alien X out to 60 yards thats all my TR cypher 5 can shoot. I know these bows can shoot at these distances and farther but is it ethical? idk.
I'm shooting 70#, 29" DL so I should get good numbers.
Now to me it depends on the situation; if its my only shot I'd take a 60 to 80 yard shot with alot of pratice to back it up. So how far would I push it....80 yards.

05-09-2013, 07:38 AM
Wscywabbit; have the same issue even worse in Northern Az, know add altitude to the mix. I live at 7300 feet and hunt mule deer at around 5600 with a temp change of 30 degrees. I have to reset the pin housing or re-zero each time I drop down to hunt the Prescott National Forest for mule deer. Your right it will drive you crazy. I recently am trying BCY 8190 on the strings and 452x on cables, I'll find out how much of a difference this year will have using this set up to 452x and or trophy on both strings and cables?, as I will use a chrono to see the effects.

Sonny Thomas
05-09-2013, 12:09 PM
How far could you shoot and still kill a deer? Just about as far as the bow can shoot, but most realistically the arrow must a sharp cut on contact broadhead and must go in the "boiler maker." Foot pounds doesn't mean as much as you think. Now, most states have a minimum draw weight, 40 pounds within a 28" of draw is Illinois's. Now, the law reads only draw weight and no arrow weight.

I am at odds of the change of velocity, but then I never chronographed my bow when hot or cold and then my deer hunting was limited to 40 yards max.

Today it seem no one competes farther than 80 yards. FITA does for sure has longer distances than the NFAA, but I'm unsure of. Both the NFAA and ASA for 3D have unknown distances limited to 45 yards. ASA does have the Known 50 class. IBO, 3D of course, I believe has 50 yards.

It's been years, but when I practiced Field I'd get ticked off when I didn't hit that 5" bull's eye at 80 yards. If not hit it then been close enough to scare it ;)
Longest shot I ever took were at a Delta Buffalo some 110 yards out. It took abit to figure out the what scope setting I needed, but after that the big 10 ring was dead meat.

More; 13th century, I believe. I think England was the country; "Target practice began at 200 yards." Every male of 16 thru 60 was to be accomplished with a bow of his length (able to draw). Now, figure this was in defense of the country. Arrows were wood and tips were nail like, really pointed to penetrate chain mail.

You have a not unuique issue of both temperature and altitude change. Randy Ulmer once penned a article of altitude change and his findings were something to take note of. Of course altitude effect comes into being due to density of air.

Sonny Thomas
05-09-2013, 12:23 PM
I once played with my chronograph when setting center shot. Having the NAP QuikTune 3000 adjusting windage in quite easy. I moved the rest off a fair amount and then began shooting, two shots per per rest setting. Velocity climbed and peaked at 270 fps for my hunting rig. Further adjusting the rest began to drop the velocity. I then went back to the fastest velocity of 270 fps. I then shot through paper and got a pretty decent hole. I then tried French tuning. My center shot was just a tiny bit off and I do mean tiny bit, maybe 2" at 60 yards, which translates to thousands of a inch for adjustment of the rest. I then tuned the bow for best French tuning results. Another check with the Chronograph gave 270 fps.

That was a lot of shooting and I don't believe I'll try it again, but it is another way to find good center shot to some good degree.

05-09-2013, 04:16 PM
You have a lot of good points Sonny, and the bit about using the chrony to find center was interesting! Goes to show how efficient a well tuned bow can be, and what the effects can be if it isn't tuned properly. Makes you wonder how many people complaining of their bow not reaching IBO arent tuned right.

I've shot my rig somewhat accurately out to 80 yards, and can dance around the bull's eye pretty well. I only have pins out to 60 so at 80 I was happy to just be hitting the target, let alone the middle-ish area lol. Tried out to 130 yards once, that was fun. Danced around the target on that one. My buddy hit the metal sign we were trying for with his older Martin and a field tip; arrow bounced back a good 10 yards but only after it made a nice round hole in the 1/16inch steel.

Would I ever shoot out that far for an animal? No. 60 yards is about max for me, I took a shot this last season at 63 yards, and the arrow was right on... but that buck wasn't there anymore. Took less than a second for him to drop and turn enough that my arrow found the stump behind him... suffice to say that a lot can happen in 60 yards.

The difference in altitude, air density, and temperature never dawned on me though. I guess that's one more reason why you should always double check your equipement and point of impact once you get to camp. ;)