TAC 15/15i Basic Unpublished Information

[Super 91]

I think one think you might consider when shooting alternative shafts is not so much the weight of the shaft (unless it is less than the 422 grains over all) but the spine. There is no way a .250 spine is going to survive the G-forces of the launch in my opinion. As we already know, the power to weight ration is way off the standard. It might make it out of the bow, but which direction it will be pointed is anybody's guess due to the extreme flexing that will take place.

That is just my opinion and not fact so you won't know till you try it. And the problem with the TAC nock is not that it is 11/32, it is the size of the throat that makes it unique. A standard nock would work to deactivate the anti-dryfire, but it will not lock onto the string due to the serving size being so large. If you got rid of the extra wrappings they put under the D-loop, you might could use a larger variety of standard nocks.

 

[jon.henry755]

Hi Bob,
You are totally correct on your spine assumption for the .250 shaft.

I was hoping the .300 might work, but the shaft diameter also plays a big roll in the stiffness factor. That's what I was stating in my last response to Konrad when we were talking about the 11/32 (.375) shaft sizing being used for most crossbows. Most manufactures seem to be using the wider shafts to achieve the stiffness needed to handle the extreme torque produced by today's crossbows.

When you do the math on these things it adds up to some very extreme numbers, so if I'm reading the numbers correctly, it also puts some limitations on what we can or can't play with from an alternative shaft perspective.

I'll wait to hear what Konrad has to offer based on his research, but I'm fairly certain he's going to tell us that our best bet is still to sort these arrows by matching the spines and re-fletching them accordingly after indexing the nocks to the spines.

If not, I'm always willing to learn something new and we're definitely on the right website for that.

Regards,

Jon

 

[Konrad]

Hi Guys,

I learned something new today:
Easton is now offering FMJ shafts of a larger diameter for crossbows. The factory shaft diameter for the Easton Full Metal Jacket Bolt is 11/32 diameter.

When I first made the suggestion about using the Easton FMJDG, I was unaware the smaller diameter would present mechanical issues. These new crossbow shafts are offered in either 20 or 22 inch lengths.
My 2010 Easton catalog does not list this shaft.

The web site lists the bolts as 13.7 gpi and that falls between the 300 and 250 when going by gpi weights alone. I am willing to bet this is a response to the TAC shooter's demands. As to the nock issue, I'll also bet some combination of nock/bushing could be sized properly or an Easton product is forthcoming. Without knowing the shaft ID it is difficult to know what nock combination would work. Perhaps the anti-dry fire mechanism could be temporarily by-passed for shaft evaluation purposes.

http://www.eastonarchery.com/products/product/68

Jon,
You were right in correcting my comments about shaft sizing. 24/64 is actually .375.

 

[Super 91]

I still do not think the spine will be stiff enough. And also you will need a 26.25" shaft to fit the TAC-15. 20 or 22" is too short and will not work.

If the ID is .300 then the Firenock "D" nock will work and the factory nock as well.

 

[Les1580]

During my "Learning Curve" with my TAC15i, I didn't quite nock the Arrow onto the String - End Result - the last 1/2 inch of the Arrow was annailated.

There is so much power being whacked into the back end of these Arrows that I don't think Eastons Finest would be up to the job.

I will post the Photos

 

[jon.henry755]

Hi Konrad,
Once again, surprising information. I have a couple of quick points on the new Easton FMJDG's. As long as the new shafts are 11/32's we have no issues because we could use Firenocks or the standard PSE Nocks, but I would lean toward the Firenocks for a number of reasons. The work fine and present no problems with the anti-dryfire mechanism.

A quick item to help everybody cheat a little when doing decimal to fraction conversions or the reverse: If you go to your "Google Browser" and go to the search bar and type in any decimal or fraction and just hit enter, it will instantly do the conversion for you, so it doesn't take any math skills to figure out these sizings.

Sorry for the deviation Konrad, I was trying to help some of the non engineering types that may follow this thread. The new shafts that Easton will be producing only has one possible flaw that may be a problem. We need them in the 26.25 length, so do you know if they will produce them as full length shafts that can be cut to length or will they only be available in the lengths you specified? If you don't know, don't go crazy chasing an answer, I'll know the answer probably by tomorrow late afternoon. I have some TAC shaft testing scheduled with somebody who might know something about these new shafts.

Super 91,
I think the .300 is a spine deflection measurement, but no necessarily a fixed diameter measurement. I thought a manufacture could potentially obtain a given spine rating on arrows of different diameters, such as the current Easton FMJDG's which can be ordered in either .250 or .300 spine, but until this new news they were all 9/32 diameter shafts. The weight per inch was much different between the 2 shafts sizes, due to the thickness of the shaft walls, which is where the extra stiffness in the spine comes from.

The way the N-Fused Carbon Core is created is different than the PSE Woven Filament Shafts, but it's similar in the respect that it's designed to be extremely strong and durable. Another key difference is the straightness factor of the Easton Shaft at .002 measured end to end, which no other manufacture uses as stringent a measuring system. Also keep in mind that these shafts are a metal outside with a carbon core. This is where the extra weight comes from that makes them usable for the largest big game animals.

As we know, when it comes to the very best of the best in competition arrows .001 is as perfect as has ever been produced, so we are bordering super high grade competition arrows with these new offerings.

Although I'll finish testing and analyzing the PSE TAC arrows until we know everything about them, I will switch in a heartbeat to the arrows we're talking about if I find they become available in the 11/32 size in a full length version.
There's a high probability Easton may be looking for some outside field testers.

Any volunteers????

Jon

 

[Super 91]

Jon, there are a few things I wold like to speak about here.

First, I personally have never gone by the fraction as a way to measure a shafts OD. Many time the fraction is not the OD of the shaft, but actually the inserts outer edge. Sometimes the inserts outer edge has a "flare" to it to make it ever so slightly larger than the shaft. Then the point needed to match that "flare" will be what the manufacturer recommends such as 11/32 or whatever so that the field point or broadhead does not hang over or be smaller than the insert.

All shafts are measured in their spec sheets in decimals such as the ID of .300 and OD of .375. This gives you an idea of how many layers the shaft wall is made up of if the shaft is wrapped. Since PSE is a filament wound shaft, you would just know the overall thickness of the wall of the shaft. If you notice, the insert protruded ever so slightly past the shafts outer wall. Take a caliper or micrometer and check this and you will see the edge of the insert is 11/32 and the shaft wall is slightly less.

This OD number does not correlate with the spine deflection. The fact that at times they do end up the same is mere coincidence. Here is a chart for a Carbon Express arrow called the blue streak.

SPECS - Maxima Blue Streak™ Select

Model GrainsPerInch Spine Diameter
250 7.4 0.413" 0.290
250 7.4 0.413" 0.290
350 8.3 0.347" 0.295"
350 8.3 0.347" 0.295"
Notice how the spine and OD are very different.

The other thing is most people consider a shaft to be extremely straight at .001. Trophy Ridge has a Crush arrow that is in such high demand I cannot get any till close to Fall. They have a straightness tolerance of .0008 and are a smaller diameter shaft with a half in/ half out insert which makes it much wider in diameter than the shaft itself.

Just some observations on my part. Nothing set in stone of course. And I will volunteer provided we get within acceptable and comparable specs to the TAC shaft.

 

[jon.henry755]

Hi All,
I have a great deal of new information to provide on this thread, but unfortunately I won't have time to do it all tonight. It might need to wait until tomorrow or until I can speak with Super 91 and have him verify my current findings.

For now, what I can tell you is that nobody in the industry currently makes a shaft that can supplement for the TAC15 Arrows.

The spine on these arrows is in fact a .140, therefore the length and stiffness is not possible to reproduce with anybody's existing shafts, so it's a matter of making the best with what we have until somebody comes out with a shaft to meet the crossbows spine requirements.

As Super 91 pointed out in his previous thread, the point .250 would most like not come out of the bow in the direction you wanted it to.

The next area of information should help anybody who wishes to get that last bit of exceptional accuracy out of their shooting, so stay tuned.

Jon

 

[Konrad]

Hello All,

Well, barring another shaft manufacturer jumping into the TAC arrow market, I think we will continue to be forced to deal with the equipment at hand. That is not intended as a negative but statement of fact.

In our search for optimum accuracy obtainable in the TAC system, we must follow the same rules that have produced success with other archery projectiles of the past:

Wall concentricity
Straightness standards
Weight standards
Spine standards
Spine orientation
Squareness of nock and point ends of the shaft
Center shot adjustment
Arrow rest fit
Nock to string fit
Experimentation with fletching rate of twist

In the case of the TAC system we should also be interested in the quality of trigger pull (i.e. crisp break and little over travel), quality of optics, correct secure mounting of optics and mating of the bow assembly to the lower receiver of the AR platform (if one is using the AR).

We may be able to live with relatively wide tolerances with one or more of any of the above listed; however, ignoring all of the above will certainly lead to disappointment.
In my opinion, to extract the maximum accuracy from this system today, particular attention will have to be paid to each specific item listed above.

Just remember to have fun!
Konrad

 

[Len Backus]

In my opinion, to extract the maximum accuracy from this system today, particular attention will have to be paid to each specific item listed above.

Konrad, that sounds just like the recipe for precision rifle shooting. gun)

 

[jon.henry755]

Hi Konrad,
This is a great recap of the corner stone standards for shooting accuracy with a bow, but it's concise and totally factual. These elements are not up for negotiation or compromise, since they are long established laws of physics and arrow flight.

The sequence of priorities can be argued to some degree if anyone wants to get political, but the elements are all there and as stated some may have more importance than others, but all are need to be checked and verified or adjusted to achieve optimal shooting performance.

I believe we learned years ago that spine alignment, shaft deflection, shaft straightness and shaft weight / F.O.C. were the four big critical factors affecting arrow grouping and flight performance, but these only become critical after the others you've listed have been set up and tuned during the initial bow set up sequence.

I like to equate these items as similar to what a "Long Range Precision Shooter" does. Let's face it, he's probably not going to be able to walk into a store and by a stock rifle that's going to give him the type of accuracy and performance that he's looking to achieve.

Like wise, store bought ammo isn't going to give him the type of consistent pin point accuracy that he's looking for either, so what does he do? He customizes his gun in many different ways to get it shooting the way he ants it and he may hand load special ammo with different powder measurements and different bullets until he has just what he wants and needs to provide the accuracy that few others ever attain.

We are chasing the same type of special accuracy, just with a slightly different type of shooting instrument, so it takes some customizing of both the weapon and the ammo to achieve the highest level of performance possible with today's components.

We'd love a straighter shaft if one was available, but in light of what we have available and can do, we can do quite well with today's materials.

I think all TAC15 owners will be pleasantly surprised within the next week or two once we complete our research and we publish the findings and how-to's.

Collectively, we have gone from knowing almost nothing about these crossbows and their arrows to knowing almost everything there is to know in a very short amount of weeks. Thanks to everybody's intellectual input and help, we've unraveled a great deal of information. Much has been tested, thanks to Super 91 and a great deal of technical know how and engineering data has been brought to the table by yourself (Konrad and a few others).

I'd like to say more, but I dare not, since the actual verified bare facts come from somebody else who's compiling and crunching the data.

Stay tuned over the next few days!

Jon

 

[ronmc]

this info is getting better every day, i love it when i shoot compound bows
20 yards or 100 yards fletching contact was a major concern. dont yo think
shooting thru the wisker bisket is causing problems at longer ranges? i always used a fall away. i know the speeds are faster here, but there are
rest that still have less contact???

 

[Konrad]

Hello Everyone,

For all intents and purposes that list is indeed straight from a precesion gun makers "to do" list for accuracy.

I liken center shot to verification of chamber axis to throat/barrel bore axis and squaring of the bolt face to same.

No precesion rifle marksman ever succeeded using poorly balanced or unmatched weight projectiles. "Center of Balance" fore and aft is a large part of bullet stabilization along with jacket concentricity. Bullet base squareness produces evenly applied gas pressures to the bottom of the bullet as it exits the barrel in the same way squared nock ends of an arrow distribute the driving force of the string evenly to the shaft. Weight variables affect time of flight (velocities) and as such produce vertical stringing issues. Thankfully, most custom bullet manufacturers have eliminated those issues all together.

Fletching type and twist are exactly the same as matching the rate of rifling twist to velocity and projectile weight.

Limb to riser to human fit is the same as barreled action to stock to human fit. A poorly bedded action will never "settle" into the stock. The microscopic movements between the two components affect force distribution differently with each shot. A poorly fitting stock promotes shooter error because he is constantly trying to compensate for the poor fit as consequently never gets the shooting platform into the exact same position before firing the next shot. Once again, inconsistent distribution of recoil forces negatively affects point of impact and group size.

Poor optics and/or poorly mounted optics are a subject on its own. Much has been written and the fact remains that if the internal mechanism shifts between shots or the mating between the optical device, the mount and the shooting platform changes, point of impact changes.

And then we come to triggers…
Even were all of the above perfect, a horrible trigger pull will destroy accuracy potential. Dragging a harsh, heavy sear across an engagement face disturbs even the best aiming concentration and position. An excessively long trigger over-travel allows for platform disturbance after primer ignition but before the projectile leaves the barrel.

The first time I dabbled in custom "tuning" was when I began weighing stones for my Wrist Rocket on Mom's kitchen scale.
But that is a story for a different day.

In short (he said as he rambled on), I stand guilty as charged in "borrowing" from my firearms experiences.

I eagerly await the upcoming testing reports.

Thanks for all of the kind words,
Konrad

 

[Super 91]

Okay guys, here is a preamble to my final testing that should be taking place over the next several weeks.

First off, I have modified the Aerovane Jig from Firenock and made some corrections that will put the jig into the 30th century. It should be more accurate than any other jig on the planet once the mods are complete, and it will be able to fletch the 60 x 120 degree spacing without having to move the shaft like you do now with the current setup. The Bitz conversion is okay, but we have found that the indexing on the Bitz can be off as much as 10 degrees total. But if you fletch each shaft exactly the same, you should get very acceptable results, which is the key.

I have had the chance to speak with Jon Henry here on the forum as he is extremely knowledgeable in the areas of the testing that needs to be done to and is my "go to" guy if I need to bounce a query off someone. If you see him post, take note, there will have been some serious research or at least serious thought taken place before his fingers hits the keyboard.

We can get these shafts to shoot. Yes, they are fairly decent by most peoples standards and if someone bought a TAC and NEVER did any of the things I am going to outline, they would have one of the more accurate modern crossbows on the market regardless. So don't think you have to go through all this to get your TAC to shoot, you don't. This is sort of like the reloader who could go out and buy factory ammo and get plenty good enough results. But he doesn't want to settle for "good enough". He wants to squeeze ALL the accuracy he can out of that weapon. And so do we. So that is what this is all about.

Moving forward. Wait till you can buy the bare shafts only if you want to keep from doing hours of work that is time consuming and tedious. That is stripping the fletchings. You have to cut them off, and scrape the shaft till you get all the glue off and then thoroughly clean the shaft. Trust me on this one, wait till you can get bare shafts. Stripping is a pain and you can damage the shaft if you are not careful.

Next you will need to break the nock loose and remove it. You can do it several ways, but I would recommend putting the nock in a vice and gently twist the shaft till it pops loose. That is easiest for me. You can also get some non-slip material that you might put in drawers or cabinets to keep things from moving around and use that to grip the nock with pliers and remove it by holding and twisting till you pop the nock loose that way. Any way you do it, just get the nock out and you will be ready for the next step.

Now this step is not 100% necessary, but I think it would help if you are going to want to line your broadheads up the same way each time. It is removal of the insert. Put the 85 grain field point in the insert. Take a propane torch, and gently heat the field point a little at a time, and do not allow any direct heat or flame to touch the carbon as you will ruin the shaft that way. Just run the tip through the flame back and forth till you warm the glue, then pull the insert out by gripping the field tip with pliers and removing both at the same time. Just make sure you do not get the shaft hot or you will have to throw it away. Go slowly and like I said, if you do not want to do this part, don't. It's not something that will really need to be done to get incredible accuracy anyway.

Now you will have to have access to a carbon arrow tester do move on to this next step. I happen to have a RAM QC Carbon Arrow Tester with a 1.94 pound weight that will show spine deflection on any standard shaft. You cannot go by any chart on the TAC shafts because there is no standard way to measure these shafts due to their short length. But that does not matter. So long as you can get a reading, you will want to measure the deflection and make a mark on one side (high or low) next to the dial indicator to show the high or low side of the shaft. You need to pick which you plan to mark and mark all of them the same, either high or low reading.

Now you will need to transfer that mark to the rear of the shaft, and one way to do this is to lay a marker down flat on a very flat surface. Now lay the shaft on the surface and roll the shaft till your markers point will be dead center of the mark you made. Keep the shaft from moving, and move the marker to the nock end of the shaft and make your new mark there.

Now you will need to fletch the shaft so that the mark is either up or down, or in the exact same place when you place the arrow in the bow. I prefer up so I can see and know the shaft is flexing toward gravity, but that is just me. I like to think of gravity and an invisible helping hand that helps push down on the shaft as it is trying to push up. Now you can glue the factory nock back in place so again that your shaft is indexed up or however you choose. Now there is a much better alternative to the factory nocks. The problem with the factory nocks is the mold they are using to make these nocks is 25 years old and not precise at all. The plastic is also very poor as far as memory. Once you have nocked the nock a dozen times, it will not spring back like it did the first time, and after a time your arrows will tend to get loose on the string due to the low memory. I suggest the only alternative which happens to be one of the best nocks on the planet and that is the Firenock "D" nock, made specifically for the TAC shafts. I worked with Dorge in their creation and was his product tester for this nock. His last version is very precise, fits very tight in the shaft so you will not have to glue it in place, and you can put the lighted circuit in it if you decide you want to be able to track these lasers we call arrows going down range. You will have to install the Extreme Shock End Caps so that the battery and circuit will not fly out of the nock. The energy generated by the TAC requires the ESEC. But I would at least spend the money for his nocks if you really want to get the most out of the TAC.

Now you will have a set of arrows that will all behave like a group. It will not matter which arrow you pick out of the quiver, they will all shoot very close to the same POI. You will have some very slight deviations from time to time that might show up in extreme long rang shooting such as 100 yards, but over all you will be slapping shafts at 50-60 yards and you had better not shoot at the same dot at less distances than that unless you like wasting arrows.

I'll let Jon chime in here and fill in the voids I have left in my procedure. I have been distracted a number of time during the writing of this and had to get my thought train back on track several times so I know I did not get everything I really wanted to in this post. But it is the basic meat of what we are doing to get these shafts to shoot the absolute best out of this awesome shooting machine. And don't forget to start with the TAC and make sure it is shooting bullet holes and is square to the rail and get that right first, then move to the shafts and get them right. From there, you will just have a hard time wiping the grin off your face when you get to the range and shoot that 1-2" 100 yard group off the bench.

More later and hopefully Jon and Konrad can join in here and fill in the blanks I've left.