TAC 15/15i Basic Unpublished Information

I agree wholeheartedly in believing the manufacturer must have known what they were doing when selecting a completed arrow weight and grains per pound of draw ratio. The lightest ratio allowable I have seen that will not void manufacturer's warranty is 5 grains per pound of draw weight. Most agree 6, 7 or 8 grains per pound promotes a quieter shoot, less vibration and longer bow life.

In a "normal" modern compound bow, less arrow weight than 5 gpp and the energy that would have been used in propelling the additional mass of the projectile must be absorbed by the bow's components (i.e. limbs, riser, cam(s) and axles). This condition leads to premature wear and potential explosive failure…not pretty.

The PSE designers have somehow compensated for this otherwise destructive, near dry-firing condition.

As to you impending acquisition of new shafts, I will be anxious to see your results.

K
 
Konrad, I guess we need to start thinking in crossbow terms as far as GPI.

Take a Scorpyd 165 SLP. It shoots a 408 grain shaft at 425. It is a 165 pound draw weight. That is 2.472727272 gpi. That is even lower than the TAC.

And those numbers are fairly consistent over most crossbows. Take a Telson 130. It shoots a 400 grain shaft at 390 fps. That is 3.0769 gpi

Take a Middleton crossbow. They have one that shoots a 350 grain shaft at 245 pounds draw weight at 375 fps. That is 1.42857

Now we are talking ridiculous GPI's here right? But we must also factor in the fact that most crossbows only have a 12-18 power stroke, give or take an inch or two. More food for thought. But it appears that the TAC is right in the midst of the number there anyway.
 
i thought i knew a lot about archery,until i got on this site. i do alot of testing
as well, but you just saved me hours and hours of testing with the info ive read.
i use goat tuff glue and you cant pull the vanes if you try,i promise. of coarse
the arrow has to be clean.
thanks for all the info.
ronmc
 
Let's try to quantify what we collectively agree is the existing accuracy at 100 yard

Guys

Would this be a good time and place to define the TAC arrow accuracy quest goal?

  1. Let's try to quantify what we collectively agree is the existing accuracy at 100 yards of the current system.
  2. Then perhaps we could discuss what we hope to achieve in terms of increased accuracy at 100 yards.

I'll defer to you to fine-tune the definition since you are residing on a different planet in a different galaxy compared to me and my archery experience.

My reasons are two. The first reason is the normal one for any scientific endeavor. The second reason is that I would not want the world who read this thread to get a poor impression of the existing accuracy.

Rather, I sense that this group will only be satisfied with the TAC arrow accuracy after wringing every last bit of potential out of it.
 
Len, I think what you have said is very important. Please do not let our craziness in our extreme testing make anyone reading these threads that the TAC-15 is not a extremely accurate weapon right out of the box. What we are striving for is ULTIMATE precision for extreme long range shots.

From 0-50 yards the factory shafts, fletched just as they are will work very well. Most of the time. But I would suggest shooting however many arrows you have at the target, off of a bench and record the POI of each shaft. You will have to number the shafts to keep track of each arrows characteristics.

Once you have this done, you will need to keep a log of groups of arrows and their POI so you will know how to either adjust your POA to compensate, or you will need to re-zero the scope for each group of arrows so that you will not be off each time you go to the range or hit the woods. This is very time consuming and tedious, but if you want to tweak your TAC-15 to the nth degree, this the way to do this.

We are trying to take this sort of testing to the next level. We are trying to establish whether the fiber woven shaft indeed has a spine. I suspect it has "multiple" spines, and it will be harder to ascertain if it has one side that is stiffer than another. Once our testing is complete, we will better understand what steps the average shooter might be able to take to achieve incredible accuracy with each shaft, instead of only having a few to hit the same spot out of the dozen shafts they may buy.

Jon Henry and Konrad both know what we are after here, and over the course of the next 2-3 months, we should be able to show our findings backed with some strong facts. My hope is to indeed find a true spine that can be located by use of a RAM QC Carbon Arrow tester. If that is the case, it will be easy to mark the spine of each shaft, and then fletch each shaft according to the spine. Then if we can get PSE to not glue in the inserts, and we can orient the insert so that each broadhead is resting the same way to the spine, I think we can reach levels of precision shooting that have not been attained before.

So the TAC-15 is fine the way it is, but we, the anal tweakmasters of ultimate accuracy, need something to focus our need for discovering the unknown in arrow accuracy on. Or something like that....gun)
 
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A site entitled "Long Range Hunting Online Magazine" implies an address where the quest for the ultimate accuracy obtainable in order to fulfill the long range hunting goal is the primary subject for discussion. Many folks think discussion regarding the intricacies in custom ammunition crafting as arcane and if I may say so…obsessive. I view the TAC process we are engaged in here as exactly the same thing as custom tailoring ammunition for rifles, pistols or my modern compound bow.

Perhaps, if someone were to read the process I use in hand loading for any of my rifles, they would readily come to the conclusion either I couldn't shoot or all of my weapons were cheap junk. In my opinion, few casual web-surfers will take the time to digest the thread we are working on here. If some were to read through, perhaps a question or two would be sparked (and possibly some interest) and additional knowledge could be brought to the conversation.

As yet, I do not even own one of the TAC 15 weapons (as stated in a couple of places earlier); however, the topic of accurately driving a projectile by use of springs and mechanical advantage is near and dear to my heart. I am currently engaged in an engineering project dealing with many the same technical issues and the opportunity to gain valuable information from those actively using the TAC system has been a gold mine of information for me.

To my mind, the goal is to understand the accuracy potential of the launch platform. Discovering that platform potential necessitates eliminating variables associated with the ammunition. A distillation of what I have read is that the launch platform has a high level of accuracy potential but it is currently limited by the single source of ammunition and/or manufacturing techniques and/or assembly. The bulk of the posting relates to understanding the system variables and manipulating the existing ammunition to promote consistency/accuracy.

One hole groups with one arrow proves the launch platform's stability. The search continues for that five shot group that damages two of the arrows at 100 yards!

This would not be the first time I was called obsessive. My wife accuses me of being an inveterate "tweaker" all of the time.

I don't know about anyone else but I'm having great fun!

Thanks, Mr. Backus.
 
ive been a compound shooter for thirty-five years and did all the testing and
tweaking with bow and arrows that you guys are doing. i was shooting 88lbs
with my mathews when it only went to 70.we practiced at 100yd with 8 in
groups to be confident at60. keep the info coming,im learning every day.
thanks
ronmc
 
Hi All,
Just as a reminder, when we started this forum we were suffering from not enough detailed technical information and very little substance. I strongly we believe that we're quickly overcoming that problem.

I also think Super 91 and Konrad have summed up our positions and the level of focus as well as can possibly be stated.

For the record; the PSE TAC 15 Crossbows are incredibly accurate as crossbows go, but we are also well aware that they have a great deal of untapped potential with the ability to do what no other crossbows have previously done.

Like my two counterparts, I have a strong engineering background by trade and believe that almost anything can be made to work better if you just analyze it, expose any weaknesses and improve the system.

We are down deep into the nuts and bolts of PSE's product line and are identifying things normal shooters never get near. To operate at this level is an obsession for excellence and often boarders on the being obsessive / compulsive!

I fear my associates may be in the same boat, but sometimes chasing perfection requires these traits.

Like Konrad and Bob, I wouldn't change them even if I could.

Jon
 
Hi Konrad,
I was doing some minor testing recently and found that your previous information was absolutely accurate.

The exact weight of the PSE TAC 15 arrows is not 425 grains as stated by the manufacture. That's an even round number for advertising purposes. The actual weight varies shaft by shaft, but comes in at between 422.0 and 422.9 on the dozen that I was testing.

If we redo the calculations for grains per inch of arrow we come out with 3.22 which is way light for any known acceptable range. This explains why they fly so flat over longer distances, but also they likely are pushing way beyond the acceptable spine limitations even for carbon arrows. The amount of dynamic spine deflection during each shot must be incredible on these shafts and it's hard to believe the limbs are withstanding that type of force. It's almost like dry-firing the crossbow with that little weight on each shot.

I'm going to leave it to Super 91 to add or fill in more details when he has time to reply, since he has most of the information.

Jon
 
This ratio of arrow weight in grains per inch (gpi) to draw weight in pounds is somewhat confusing to me. I have been looking into the common ratios stated in the crossbow market and as Mr. 91 points out, those ratios are way down when compared to vertical bow ratios.

I can easily rationalize the static spines (the "standard" crossbow shaft diameter seems to hover around .375 inches) due to the much shorter over-all-length of the finished arrow lengths for crossbows in relation to those of vertical bows. My personal vertical bow ammunition is 29 inches from end of insert to throat of the nock.

I have real difficulty in understanding how these crossbows can handle the punishment of such light ammo??? I suppose that is a completely different topic for discussion.

The range of weights you observed in the particular dozen shafts you weighed does not seem too terrible; however, when seeking the ultimate in accuracy, as with firearms, variations in time of flight (velocity deviation) translates into vertical stringing at the target. Physics dictates the slower the average velocity, the more pronounced the deviation becomes. The greater the distance to target, the more aggravated the condition becomes, as well. All of this discussion brings me to pointing out that very few long range marksmen use light for caliber projectiles. Sacrificing velocity for stability and retained energy with less shedding of velocity downrange (smaller trajectory and side wind effects) is no true gain.

There are questions now out there and I am still awaiting replies.

Rob Smith at Barnett says Easton Technical manufactures the ammunition with Barnett's brand name. They are the C2 Power Bolt shafts. The C2 carbon composite is the least expensive of Easton's carbon product line. Barnett's top of the line compound Predator launches at 375 fps, has a 175 pound draw weight with an arrow of only 18 inches. This bow only has a power stroke of 15 inches verses the TAC's 17.25 inch stroke.

You do the math.

"I'm still collating…"
 
Hi Konrad,
As for the most common shaft diameters for crossbow arrows, I thought the 11/32 shaft was more common than the 3/8's that you were specifying (.343 versus .375), but I'm going by insert sizing not actual shaft diameters. My guess is that you are using the actual shaft sizing, is that correct?

Like you, in my humble opinion and that of some long time industry experts, it would stand to reason that a heavier shaft propelled at a slightly slower rate of velocity would provide better spine deflection and a more stable flight. This would also yield much better penetration capabilities due to the shaft carrying a greater amount of Kinetic Energy over the distances.

We were almost ready to test these crossbows using one of Easton's top of the line Hunting Shafts. They were one of the N-Fused Carbon Core shafts (Axis Full Metal Jacket - Dangerous Game Shafts). They are Easton's heaviest shaft with a .002 straightness factor from beginning to end. They are available in two shaft spine sizes (.250 and .300) and are factory sorted by spine and weight, and properly marked and indexed. The only gotcha was the shaft diameter is only 9/32's which won't support the needed 11/32 nocks to operate the PSE TAC15 Anti-Dryfire mechanism on the TAC15 cranking block.

The thought was to see how these shafts would both group at medium and long distances and their overall performance in comparison to the very light TAC shafts being used by PSE.

I'm still working on a shaft alternative, but as you now understand alternatives don't grow on trees for this beast.

Regards,

Jon
 
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