The final version of the QAD mounting brackets have been available for about two months now. Frank from Archery Unlimited sent me the updated final version a couple of days after Christmas and the major change was that he moved the center line of the bracket by 1/4 inch to the left because we found that almost every person who put the QAD on their crossbow, needed to make a quarter inch adjustment to the left in order to get the rest to align correctly. He made the adjustment in the machining process to correct this issue. He also adjusted the bracket, so it will now adapt to all TAC15's regardless what year they were produced in. Previously, if the crossbow was older than 2010, it would require a small spacer between the bracket and stock. This is no longer needed since the new brackets are universal, so they bolt right on and are designed to align dead center on the TAC15/15i stock.
Len Backus and his son Andy are also carrying and selling the units in their online store, so you can go either way if you decide to order one.
If you don't have access to a Carbon Spine Tester or don't have the time to do the work involved, I'd be willing to do it for you for a nominal fee of $25, if you don't mind covering the shipping charges, in both directions. It's always better when you can do it yourself, so you know exactly what you've got in the grouping ranges, but understandably, not everybody has the time or tools to do the work and it does take a few hours to accurately test and measure each shaft.
The 100-yard data through the chrony published back on page 1 let me answer an interesting question, which is: What is the Ballistic Coefficient (B.C.) of an arrow? (Or at least, this arrow) I was shocked how low it is.
I used the on-line ballistic calculator (web-link below) and typed in the 'point blank' muzzle velocity (394 fps), the arrow weight (433gr), and then started playing with the BC until I got the ending velocity that was close to 333 fps (actually 332fps). The BC turns out to be 0.065!
This is worse than a 50-cal round-ball which is 0.068! Looking at a sleek arrow I somehow suspected that the BC might have been better than this.
While it's an interesting statistic, it only applies to bullets or guns. It has no relevance in the field of archery unless you wanted to compare the results to other bows or crossbows.
The reason is because bullets don't have razor sharp points that cut and slice their way through anything they hit. The only measurement that is of a major significance for an arrow is K.E. (Kinetic Energy). This can be calculated using the following formula: Kinetic Energy = Weight x Velocity / 2 x Acceleration of Gravity
Here is a simple chart which depicts the amount of K.E. needed to efficiently penetrate some common game animals:
Kinetic Energy Hunting Usage
< 25 ft. lbs.Small Game (rabbit, groundhog, etc.) 25-41 ft. lbs.Medium Game (deer, antelope, etc.) 42-65 ft. lbs.Large Game (elk, black bear, wild boar, etc.) > 65 ft. lbs.Toughest Game (Cape Buffalo, Grizzly, etc.)
The PSE TAC15 with a 100 grain broadhead is generating approximately 154 foot pounds of K.E., so way over powered for its intended job and will likely blow straight through anything your ever going to hit with it.
Last edited by jon.henry755; 03-05-2012 at 09:42 PM.
Reason: Table was out of alignment
Jon - you're preaching to the choir.
I agree with you 100 %.
I have no interest in fables such as knock-down power and the like, for the reasons you state.
Arrows kill by hemmorage. Hemmorage reduces blood pressure to zero, the animal blacks out and the brain dies. That's how arrows kill.
The BC is only interesting to me from the perspective of computing the arrow's trajectory, which gives me some insight into external ballistics performance.
For example, the drop rate at 80-86 yards from the prediction seems to match my experience.
Occupational hazard - I'm a physicist, and interested in such things.
Well, in the short time you've been playing with the crossbow, you're hitting on all the right areas and questions. I don' usually see this many questions covering all the key areas from people in the first six months.
Most people don't understand most of the information even when they receive it anyway.
Keep up the learning and the shooting. You're way ahead of the majroty of shooters.
I probably should have mentioned that using this BC (0.065) that it's then possible to play some what-of games about where you should zero your crossbow without actually having to spend a lot of time at the range figuring it out. After you pick something, then you can verify it at the range.
I've been wonder if I should zero at 20, 25, 30, or 35 yards?
Here's the result from the ballistic calculator:
Zero Max Error @ Range
20 yd -1.1" 5-25 yd
25 yd -1.5 0-30 yd
30 yd +1.9/-1.9 0-35 yd
35 yd +2.9/-2.2 0-40 yd
So for hunting deer you might zero at 25 yds, knowing you can hold pretty-much right on out to 30 yards, and your arrow will fall within 1.5" of point of aim.
For Elk, with a bigger KZ, you might zero for 35 yards and be able to hold dead-on out to 40 yards.
Armed with these predictions, a little range-time should easily validate the assumptions.
I've been toying with zeroing at 30, but know that a lot of people on this sight start at 20. That's where I currently am.
Don't follow the crowd because most people don't know where to start and often get information from others who don't know anymore than they do.
The idea of starting at 20 yards comes from the instruction steps in setting up an HHA Optimizer Speed Dial. Other than for this purpose you can start anywhere you want, but through lots of experience my good friend and side kick Super 91 always liked to set his zero at 30 yards for hunting season. He learned from experience that most shots were 30 or under, so it minimized having to make elevation adjustment when deer hunting.
Super 91 takes at least several deer each season and he's also taken wild turkey's on the same days he was deer hunting. There's no question about it, his crossbows have been as tuned and accurate as its possible to get. He comes from the same school of thought that I do. It's called "Good Enough" is the arch enemy of "Better and Best". We never stop at Good Enough and we tinker and test everything until it's perfect.
I'm not saying this is the only way to get the job done, but it definitely works well and sets you up for faster readiness.