Trouble with 90m/100yd sight mark

[chemical46]

Been trying to get a solid 90m sight mark for a FITA, only issue is that it seems to drop off super rapidly compared to my 70m mark.

I have a Shibuya Ultima RCIII, and all my outdoor sight marks are on the "8" stop, so pretty much most of the way out. I've shifted the evelation bar down one hole.

My 70m sight mark is at 8.5. I was hoping that 90m would just need the extension bar moved in a few stops or all the way to the riser. But i still have to invert it very close to the string, and my sight pin (the default shibuya one) ends up being bigger than the target so pretty much useless for aiming. (and the sight block is off the scale)

8.8 is about the lowest I can go before arrow clearance issues

bow specs:

70" bow, 38# OTF, from 32# kinetic honoric limbs.

.570 spine ProComps @ 30+7/8th inches with 50mm LP XS Wings and Beiter Pins + Nocks, 130gr points

bareshaft + walkback tuned, dead straight to any distance


is this consistent with other people's setups? i'm suprised that i still struggle to make the distance, considering i'm not exactly shooting a kids bow.

 

[Stretch]

38# measured or 38# worked out using a formula?

130gr is way too much point weight for a 38# bow expecting to shoot 90m. Shooting X10 off 45# and 100gr points I still saw a substantially bigger drop between 70m and 90m. I think you’re expecting a lot from a budget set of limbs. I’ve known people shooting ACE and well over 40# with high end limbs still have some issues at 90m.

Are the XS wing on dead straight? If you have any offset it could cause a heavy arrow off a relatively low draw weight to start to lose stability and parachute.

Even with superfast limbs there are a huge number of parameters affecting your overall sightmark. Tiller, length of face, hook, anchor position Etc. What is the gap between 18m and 30m? What is the gap between 30m and 50m? (Assuming you don’t have an fps measurement).

Stretch

 

[chemical46]

38# measured or 38# worked out using a formula?

130gr is way too much point weight for a 38# bow expecting to shoot 90m. Shooting X10 off 45# and 100gr points I still saw a substantially bigger drop between 70m and 90m. I think you’re expecting a lot from a budget set of limbs. I’ve known people shooting ACE and well over 40# with high end limbs still have some issues at 90m.

Are the XS wing on dead straight? If you have any offset it could cause a heavy arrow off a relatively low draw weight to start to lose stability and parachute.

Even with superfast limbs there are a huge number of parameters affecting your overall sightmark. Tiller, length of face, hook, anchor position Etc. What is the gap between 18m and 30m? What is the gap between 30m and 50m? (Assuming you don’t have an fps measurement).

Stretch

38# according to mine + merlin's bow scale. 130gr is default point weight for procomps, xs wings are as bloody well straight as I think I can humanly get them, using wraps with printed lines at 0 degrees.

sight marks: (all on stop 8, where 11 is furthest out and -2 is furthest in)
18m: 0.3
30m: 1.4
50m: 4.6

 

[bimble]

130gr is just what they come and so you can cut them down to what you require. It saves them from making 80-100/100-120/120-140 points when they can just make 80-130. You'd find most people in the 100-110gr range

 

[Stretch]

yeah Ok, sorry but your bow is very slow. Looking at a simple sight tape tool your 90m is way down at 11+ (if it could be). Judging by high 18m (assuming the T bar is not all the way down) it is probably not shape of face etc. (Sorry don’t have a Ultima in front of me)

I have no experience with your specific limbs but some lower end limbs are very heavy and therefore very slow. Frequently they also have very simple draw force plots too which makes for less stored energy. Borrow some higher end limbs and see what kind of difference they make.

All you can do is look for ways of making the bow faster. You could lose 40gr off your arrows, changing to 100gr and G nocks instead of pin nocks but I think you’d still have issues And the 570 would probably be stiff without more bow weight. So after that it’s working up your draw weight. GPI is pretty low so you’re not going to get lighter.

It is worth checking tiller and nocking point as this combines with bowhand pressure to affect the trajectory out of the bow but it typically gives you mm not inches.

Also worth checking with a relatively low strand count eg 16 strand, Dyneema string -if your already there a new/different string. A duff string can eat a lot of fps. As can overly tight nock fit - or too slack for that matter.

Best I can offer without being hands-on.

Stretch

 

[chemical46]

130gr is just what they come and so you can cut them down to what you require. It saves them from making 80-100/100-120/120-140 points when they can just make 80-130. You'd find most people in the 100-110gr range

Yep, would absolutely run less point weight but I trusted merlin to select spine when I got the new arrows - went back a second time and they said they were too stiff and wound the bow all the way up to get the bareshafts behaving. still slightly on side of stiff, but good enough tune that i'm in a straight line between distances.

How much stiffer would they get going from 130 to 100gr?

 

[Stretch]

How much stiffer would they get going from 130 to 100gr?

Couldn’t tell you. Different shafts reacted differently to point weight. X10s change remarkably little over 20gr. ACE a bit more. Most parallel shafts seem a bit more. Probably enough to affect performance if a bit stiff already. Removing weight at the nock end would counteract this (weight in the nock end stiffens). I’ve never shot ProComps so have no frame of reference.

Break the points down to 100gr in a few shafts and see what happens - first bareshaft and (might need a nocking point change) and then at 50m and 70m. How much does the gap close? But looking at the sight mark predictions I can’t see 30 to 40 gr being enough. But it is a lot, at 30”+ it is the difference between an ACC and an ACE.

You may also find on a slow arrow that you’d have less drop of with a lightweight straight vane. Some setups do funny things as the arrow slows. Even when I shot 47# I couldn’t shoot Elite Spin Wings. They shot great to 50m and then they went to hell by 60m. Other folks shot them to 90m with no issues.

BUT as the expected 570 tune was already too stiff I suspect the limbs are just a bit slow. Also doesn’t look like Easton have updated the selection chart since they released the weaker spine ProComps. Ironically the 610 is a heavier and fatter arrow than the 570 but would probably be a better choice with a 90 or 100gr point.

It is not necessarily a mistake by Merlin - their reading of the chart looks about right (For about 35#). But the charts say I should shoot a 410 and I shoot a 500. (32” excl point, 43# Velos limbs, 120gr point in Skylon, 100gr in X10)

Or restrict your distances to 70m until you go up draw weight/new limbs etc.

Only other thing worth mentioning is that a lot or archers start to lean back more at longer distances. This can lead to heavy string contact with chest and/or armguard and sometime release issues too. All of these can cause a dramatic loss in fps. Just a non-equipment suggestion, however, I would not expect a straight walkback in that case - would expect stiff.

Stretch

 

[Mark31121]

What anchor point are you using and have you tried a platform tab?

Trying to get 90m/100 yard sightmarks with sub 40 lbs on your fingers can be tricky - I used a similar setup last year due to a shoulder injury and I used the number board to aim at (or the top right corner at the one shoot as the wind was crazy).

As for the point weight making a difference to the spine, it's a hard one to say - you'll be making the point lighter but you'll also be making the point insert shorter (and thus the bendable part of the shaft longer) so it may cancel each other out.

 

[dottorfoggy]

My last experience with:
74" bow with 27" riser + xl border 7.2 39# @32,5"
Ace 470 with beiter nock #1 (166/1) and 1 3/4" spin wings
16 strand 8125g
I did try a week with 3 different point weight 130/110/100 gr, from 130 to 100 I have gain close to 1m in height at 70m, like 5mm or more on sight.
At 90m I don't need to move back the sight at all with a good clarence between pin sight and arrow and use it from 18 up to 90m, just muving up/down the sight