Round 2 EXOMAX and Speed Tach Custom Chronometer

Crossbow Hunting

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LoneWolf
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Post by LoneWolf »

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LW
Last edited by LoneWolf on Thu Mar 10, 2005 4:34 pm, edited 1 time in total.
Ontario Trophy Bucks
Bill T
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Post by Bill T »

I'm confused....
First, is your chronograph correct, I see chronograph results that are all over the map, but my chronograph agrees with most I've tested. Remember that you are talking about more or less 2.5% difference.

Second, check your weight carefully, you claim the arrow weight is 350 grains, but in my experience the arrow should be more. Remember that the lightweight nock end you are using can't weigh 30 grains less than a standard insert.

Third, every bow loses a few fps almost immediately from being strung and shot repeatedly, then stabilizes. This will catch a bit of the difference.

Fourth, is there anything on the string or limbs? Any extras you add for silencing the bow will reduce velocity.

There will always be a slight variation from bow to bow, but overall the testing we have done puts the Max between 350 and 360 fps.
ExcalBeliever

Post by ExcalBeliever »

From Easton's Spec Sheets:

XX78 2213 Super Uni-Bushing System:

Bushing = 9 grains


A RPS Aluminum Insert = 30 grains.

A difference of 21 grains.

That's right Bill T.!!
Bucktail
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Joined: Fri Jan 14, 2005 9:55 am
Location: Southren Maryland

Round 2 EXOMAX and Speed Tach Custom Chronometer

Post by Bucktail »

Bill T & ExcalBeliver,

I was going to do a round 3, but decided not to post the results. I had my friend bring nis new ExoMax over yesteday and we shot thru my chrono again. I have no way to check my chrono till I can borrow another to check side by side.

I do know that his Max would shoot a Dan Miller GT Laser 11 with brass insert, alum flat nock with internal threads, 3 - 4" plastic fletch, weight of 250 grs, with 100 gr bullet point for a total of 350 grs at 351- 352 fps every time. It would also shoot the 350 gr 2213 with 5" feathers at 350 - 351 fps. A 2219, 463 grs, 3- 5" feathers at 320 to 321 fps.

My Max using the same above arrows would do 346-347 fps with the GT, 344-345 fps with the 2213 and 316-317 fps with the 2219.

Brace heights were 1 1/8" on both bows and his has the new endless FF string while mine has the FF Flemish twist. Nothing on either string.

As for the 2213 XX78 Super Slam shaft at 20" weights 200.6 grs
Alum RPS insert 29.7 grs
Alum UNI bushing 8.7 grs
3 5" feathers 11.4 grs
100 gr bullet point 99.8 grs
Total 350.2 grs.
measured on two different Lyman LE 1000 electronic scales.


I bought my bow Nov. 11 2004 and it has taken two deer and I'm happy with it. I just tried the chrono to see if it was as fast as everyone says their Max is. 350 - 355 would make me verrrrrrrrry happy. :D

Bucktail
ExcalBeliever

Post by ExcalBeliever »

Brace heights were 1 1/8" on both bows and his has the new endless FF string while mine has the FF Flemish twist. Nothing on either string.
I don't know if this would make a difference. Have you tried switching strings?



'course....the % difference between 351 fps and 346 fps is


351 - 346 = 5 divided by 351 = 0.0142 x 100 = 1.42% difference.

Which is probably less than the acceptable error % of most chronographs.



My chronograph velocities are typically within 2 - 3 fps of Excal's advertised velocities. It is interesting, though. Maybe your buddy's crossbow is 1 or 2 pounds "heavier" in draw weight!!
GaryL
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Location: Ohio fer now!!

Post by GaryL »

Quote ExcalBeliever "
My chronograph velocities are typically within 2 - 3 fps of Excal's advertised velocities. It is interesting, though. Maybe your buddy's crossbow is 1 or 2 pounds "heavier" in draw weight!!"

Same here, and some limbs are heavier as Bill T. stated some Exomax'x tested between 350fps and 360fps..So therfore you may have a lighter or heaviers shooting Max.. :wink:
Always learning!!
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Woodsman
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Location: Montreal, Quebec

Post by Woodsman »

My chrony shows a little slow too. About 4-5 fps to be exact.

Also, if you have access to a powder scale, you will get actual bolt weight.
Pete

The great outdoors is where I want to be.
Bucktail
Posts: 146
Joined: Fri Jan 14, 2005 9:55 am
Location: Southren Maryland

Round 4 (final) EXOMAX and Speed Tach Custom Chronometer

Post by Bucktail »

To all that have been following.

I borrowed my friends new EXOMAX today and run my final speed tests.

Brace heigth set at 1 1/8" to start and then lowered or raised by 1/16 for a low of 1" to a high of 1 1/4"

I removed his new (shot in) endless FF string and installed the flemish FF string from my MAX. A loss of 4 to 5 FPS using a 350 gr GT Laser 11. All other bolts as used in previous test had the same loss of speed (-4 to -5 FPS). Installed my spare (shot in) flemish FF string and run the test again with the same results. Reinstalled the endless FF string and picked up the missing 4 to 5 FPS. Speed on other bolts tested in test two remained the same withe the endless string.

I really expected to see an improvement in the speed with my MAX with the endless FF string installed. Well it did, if you call 1 FPS an improvement on all bolts as tested in round two. I installed my flemish FF and lost that 1 FPS.

Don't really understand why Jim's new MAX lost 4 to 5 FPS with my flemish strings installed, and then picked them back up with the endless string, while mine only picked up 1 Fps with the endless string with all bolts at all the different brace heigths. Oh well, I'll just have to live with it. The two deer this fall didn't notice the missing 4 to 7 FPS. I'm happy with my MAX :) but would be verrrrrrrrry happy :D if it was shooting the 350 to 355 FPS.

I want to thank all who pm'ed and helped with this test, especially JIM who loaned me his new Max (from BJ'S) for my testing. I think I (rope cocked) these two MAX'S more in the last week then most people will do in a life time. Makes one feel his old age.

Bucktail
GaryL
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Location: Ohio fer now!!

Post by GaryL »

I have a Excel string on mine and it's faster... :shock: :wink:
Always learning!!
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