Been doing some tuning for my new 60" 53@28 John McCullough Griffin with CX Terminator Selects 45/60's. I draw this bow a little over 28". Initially, I shot a FL bare shaft using the stock insert with 235 points. Shaft showed weak at full length so I started trimming a shaft back to where the BOP was 30.2". Overall, the shaft seemed good so I fletched up two. Later I trimmed one of the shafts for a BOP of 29.92". With both these set-ups I was getting good flight and the bow seemed PDQ and shot where I looked.
I decided to start from the beginning and see what happens with these CX Terminator Selects. Took a full length fletched and bare shaft and loaded up the shaft with 50 gr brass insert and 235 gr points (using 160 grain point and 75 grain steel adapters) for a total head weight of 285 grains.
To my surprise both shafts flew extremely well. Both shafts ended up side by side with the bare shaft 2" to the right. Observing this I took my other two cut shafts and loaded them up with the same point weight and brass insert. All I can say is WOW! These arrows with this bow are like a lazer guided missles.
What truly baffles me is when I plug these shafts into Stu's calculator they all show dynamic spines being extremely weak for this Griffin's Dynamic spine of 59.7#. A spread of 15.5#-28.7#.
Here is a breakdown.
FL Shaft 32.874" BOP
612 grains FOC 22.1% 11.4 GPP Dyna Spine 31#
30.2" BOP
587 grains FOC 23% 10.9 GPP DSpine 42.8#
29.92" BOP
584 grains FOC 23.1% 10.9 GPP DSpine 44.2#
So all these shafts shoot extremely well and will group together. It's a coin toss between the 30.2 and 29.92 BOP set-up. I'm leaning toward the 30.2 BOP arrow for this elk season. I think it's gives the best of both worlds: heavy arrow and EFoc. Still have a way to get to the 650 grain arrow but that's another day.
Well after some experimenting last week, I went and purchased some 100 gr brass inserts and 125 gr steel adapters. Loaded up this new combo on the some arrows for a total point weight of 385 gr.
As before I am not seeing a bit of difference in arrow flight when loading up the some arrows. The 29.92 BOP, 30.2 BOP and the FL 32.874 BOP are all grouping together. I guess there are no complaints other then deciding what shaft length to use. As you can see in the photos the Fl shaft 32.874 BOP is the top one, the 29.92 BOP is on the left and the 30.2 BOP is just right of it. This arrows were shot around 12yds.
Here are the stats for the arrows:
29.92 BOP
682 gr
12.7 GPP
27 FoC
Stu Cal Dynamic Spine 31.5#
30.2 BOP
685 gr
12.8 GPP
26.9 FoC
Stu Cal Dynamic Spine 30.2#
FL 32.874 BOP
710 gr
13.2 GPP
25.9 FoC
Stu's Cal Dynamic Spine 20.4#
One thing for sure this arrow hit with authority!!! Bow is quite as a whisper!
Mike
(http://img.photobucket.com/albums/v676/MSwickard/2010_0610CXTerminatorselects0176.jpg?t=1276308190)
(http://img.photobucket.com/albums/v676/MSwickard/2010_0610CXTerminatorselects0177.jpg?t=1276308190)
Cool! What 3d target is that? I am going to try putting more and more weight up front on my ics bowhunters until they start showing weak just to see how heavy I can get without taking it too weak. That is what I am loving about traditional bows, you can never really predict how they will behave with a given arrow and point setup. Both compounds I have owned had a very small spine window to operate in and anything outside of it did not work at all. I am planning on getting the heavy field point test kit from 3rivers to fine tune my setup. Hopefully I can get well over 20% foc with my bemans with weight tubes inside and heavy point weight. Thanks for sharing your findings! :bigsmyl:
It's the cheap Bass Pro deer target. It really needs a new insert. Bucky is having a bad day! LOL
Load a FL shaft up with as much weight you plan on shooting. I shoot 160 gr points so I used the 125 gr adapter and 100 gr insert. Just play with the weights before cutting shafts.
Mike
Don't use weight tubes! They counter all your efforts at FOC. Keep all the extra weight at the front of the arrow. As you add more weight up front you move the bending point of the arrow forward on the shaft. This adjusts the way the spine of the arrow reacts to being fired. I am shooting trad only 600 spine arrows out of a 55lb @ 28 longbow with 400 grains up front. The fly like bullets and only weigh 584 grains. Stu's calculator seems to stop working when you push past 20% FOC.
One chap I met here uses an aluminum arrow over footing behind a brass adapter. There is a small "collar" but I use my reloading tool to champfer the leading and rear edge. Just hot melt in place, then insert the brass insert. Walla!
Overfoot really helps strengthen the front from what he has tried... and it stiffens the shaft a bit...adds some front weight and ups foc.
I'm using the .400 spine Entrada GT Ultralight as they're thinner walled and somehow, appear stiffer without all the weight of a 5575.
With 100 gr. brass weight tube, 3" 2117 over footing, and a 200 gr. point, it comes to 27.X % EFOC. They're flying nicely with a 4 fletch 3"x7/8" A&A feather.
They're flying pretty well out of the morrison Cheyenne with his carbon/foam core longbow limbs. I shimmed out my sideplate from Bob's 3/16" past center cut to 1/16" shy of center.
I couldn't get the shafts to fly for peanuts before I shimmed the sideplate out.
John McCullough used to make all his longbows IBO legal at a full 1/8" shy of center...
What happens to your different length/weight bareshafts at 25 yds?