Sleepy Bullets VS Sleepy Arrows(Archery)

[Glock119]

Kyle,
If you don't mind I would like to give you some input on your first post. I'm not picking at you, just trying to help you understand and if you go back and read the whole guide you will see that I am only tring to help.

>>I can shoot proportionately smaller groups at 50yds than at 25yds.

This is usually because of your set up. you could be fishtailing which is where the rest is to the left or right of the centerline of the arrow, or you could be porpoising which is cause by the knock being set to high or low to the center line of arrow, or you could be minnowing which is cause by the arrow flecthings hitting the string or rest or something else upon leaving or it could be that your arrows have too week or stiff of a spine for your draw weight or it could be the way that you have your set up your release in relationship to the arrow and the string just to name a few things that could cause this problem.

In regards to:
>>>What is shows is that an improperly tuned bow will project an arrow off the string and the arrow will rotate around an axis for some distance until it stabilizes

unfortunately an arrow does not always rotate as you might think, as this rotation is only going to be noticeable where the flechings have been fastened at some degree of cant also known as right or left helical vanes. not all arrows are fleched in this fashion, such as most aluminum arrow. today's carbons are generally done in either a 2*, 4* or 6*degree cant depending on the manufacturer. The movement you see in the pictures is not that of the shaft spinning but of it flexing. as the shaft leaves the bow under force it flexes generally left to right for finger shooters and up and down for release shooters thus the need for different rest for both shooting styles and if the spine is too soft the shaft flexes violently which could cause your example where the short shots group larger than the longer shots, this is because at the shorter distances the arrow is still under considerable flex thus causing larger groups and at the longer distances the shaft recovers and is now flighing straight with little to no flex thus allowing you tighter groups.

also to getsmart:

>>>>Arrows have fletching to stabilize flight.

Yes but not as most think, the fletchings are there to do several things but they may not rotate the shaft as i stated earlier in this post the arrows will only rotate as you think if they are fletched with some type of cant to them, one with a helical design to them where they cant to the left or right of the center line. One of their real purpose is to stabilize the arrow in the wind thus the larger fletching used on those in hunting outside compare to those used indoors for targets as well as to stabilize the rear of the arrow to some degree with the heaver broadheads that are used for hunting.

I agree with you when you stated:

>>>>I am not convinced on the similarity

You are correct - Apples to cookies not even close.

Thanks,
Ben

 

[5Redman8]

Shadowman...no offense taken. My groups avg around 3 inches at 25 and about 5 inches at 50yds, thus being disproportionate. My bow is tuned....however....I do use a Whiskerbiscuit rest with Quickspin fletchings. The bristle to small fin contact causes some instability in the first 25 yds. After this, everything is good. My field points impact with my broadheads.

My original thought was....this action seems similiar to what we see with rifle bullets. Disproportionate groups at different dinstances.

Kyle

 

[Glock119]

3" at 25yds is not too shabby, you should see some of the folks that come in and use the range 2 days prior to season. I love the whiskerbiscuit and have it on my hunting rig that I also shoot in our league with. I have a few guys that also think it should cause some disturbances with the arrow but that has not been my experience. I typically shoot in the 420-435 range with an average of 427 so far this yr.

I have found that almost anything with a helical design to it normally does not do so well with whiskers. I use xx78's 2315 for both uses. I also fletched mine straight and put cock feather up to avoid clearance problems with the lower section of biscuit.

If you are able to paper tune at the longer ranges, start at 5yds and paper tune back to the 50 yrd mark in intervals of 5 yds. you should be able to get good holes out to that range. If not and you have look at all the other most common problems try to look at your forward point of balance.

This is something that the shops don't do or even look at and many of them don't even know about. I keep mine right at 9% which I have found to be the best for my setup. This can make a significant impact on your arrow flight if done correctly as part of the final tuning process.

I have seen where after several techs had tried to tune a bow that was giving a 4" rip that by using this process, I noticed the tip weight needed to be reduced to get a point of center that I was happy with, and after several minutes of trying to convincing customer that they have nothing to loose by trying it my way, that we were able to retune bow with lighter tip arrow that now shot bullet holes at 5, 10, 15 and 20 yrds. And now I have another loyal customer, just because I was willing to take the time to try everything.


Good luck to ya,
Ben

 

[Centre Punch]

Kirby,
Thanks for that excellent reply and explanation of the bullet yaw.
The only part where i can see your differences of opion are on the principles of precession, again i am not going to believe one persons views over another. This an area my friends and myself have discussed at length without any firm conclusions either way. I would like to see "mechanical" evidence, before i make up my mind.

Basically, Dr Kolbe says,if a bullet goes completely to sleep it will not track along its trajectory, point first which means it would strike the target at the same angle at which it was launched above the sightline,theoreticly producing an elongated hole.

I would have to see this before i believed it and think there are other factors in a bullets flight which we will never be able to investigate without very sophisticated high speed photography able to film the bullets complete flight(maybe this technology is already available?).

I don't know if you are aware, but the NRA of Great Britain (for what they are worth) have set specifications for the size of the 308 chambers used in the discipline of "Match rifle". This and poor handloading is probably the cause of bullet yaw.

On the other hand the more popular and formal "Target rifle" does not allow handloads, competitors must use "as issued" ammunition in competition. this is usually 7.62 sniper grade, which leaves a lot to be desired.
Again, rules govern chamber specs and barrels are specials that are up to .0015" smaller on bore size and groove diameter than standard 308" to suit this ammo. Custom rifles are built accordingly. This may again count for some bullet yaw.

The bullet "wringing" that you describe is very similar to the base deformation of soft lead bullets used in BPCR, which on exit from the muzzel get upset by gases escaping past one side of the bullet before the other.
I must admit i have witnessed this phenomena of relative group size whilst shooting BPCR with heavy for calibre bullets, although 400grn bullets grouped tightly at 100yrds, 520grn bullets did not, averging 4" to 5", these groups being the same at 300yrds, does this show unstable heavy bullets at less then 200yrds? or could it be that most of these haevy bullets are launched at the speed of sound or just below it from a 45/70.

your comments will be appreciated, thanks.

Centre Punch