The other week I was attempting to bareshaft tune my arrows as I suspected they were weak. I'm shooting a 2117 (well, a GG xx75 400) at 31.5 inches with 125 grain field points out of a 50@28 Martin Hunter (purchased 2008, if that matters). I pull 28 inches. I'm right handed.

Running the numbers in Stu's calculator tells me my arrows are 6 lbs underweight. I took some bare shaft with m to the range and tried to verify this. My group with bare and fletched at ten yards was the size of my fist. At fifteen yards it was bigger, but left-right alignment was pretty good. At 20 yards, however, my arrows went left - way left. At least 10-12 inches away from my fletched shafts.

So here's my question. Am I really overspined, or was I doing something weird at 20 yards that I didn't do at 10 or 15. It just doesn't make sense for 5 yards to make that much difference in how the bare shafts read.

Also as a note: I have Stu's calculator set to a Martin Hunter, and the strike plate set to 0.060. I have a Bear plastic strike plate from one of their rug rests. I think that the measurement is accurate, however I know that this could seriously affect the spine. Anyone know how thick these are supposed to be. I've tried measuring with a ruler but I'm not sure it's precise enough.

Anyway, any help is appreciated!

2117 fall in at 29"
2219 at 31-32"

http://www.eastonarchery.com/products/selection_hunting

The extra 5 yards makes a huge
difference.  Try it again at 30 yards.  The difference
will be huge.

I'd add a lot more point weight and see if that moves the impact point back to the center. You'll probably need to add at least 100 grains  to move 12" at 20 yds.

Of course, all bets are off, if you're short drawing, plucking the string, snap shooting, or your nock height is way off. Also make sure you have the correct nock tension. I also highly recommend using two tied on nock points, one above and one below. An arrow sliding down the string on release can reek havoc on your tuning.

I'd say listen to the shafts. Yeah Clay is right an extra 5 yards and you may miss the bale. I only shoot wood and as I recall 2117 is an extremely stiff shaft.

Too stiff.
I shoot the same 31" arrow 54 to 58# bows. It shoots best with 190 grain points and I draw 29"

John

A 2117 is way to stiff for that setup. It's going to take a lot more weight up front to get those to shoot right.

I agree, too stiff

I'm thinking a 2016 at 29" or a 2018 at 30/31 with that 125 gr point.

I agree with some others that the 2117's are too stiff.  As John49 stated, the 2016's will be a good arrow for you if you stick with the 125 grain points.  I would tune them to your set up before lopping them off at 29" though.  I can't comment on whether the 2018's will work since I have no experience with them.

According to Stus calc, if you cut those 2117's to 30 inches, you will be spot on. That would stiffen the arrow. Others say it sounds like it is too stiff already but you will never know for sure until you experiment. Id go with Stus calc, cut 2 arrows down to 30 inches. Cheaper than buying new arrows that may fly crappy. You should be able to do that easily since they are 31.5 already.

Try a soft strike plate. Maybe the hard plate doesnt jive with your release. Im trying out a new Martin deer hide shooting glove and my arrows get more wag in them using it than my calf hair glove. Different releases.

The weird thing about all of this is that I was attempting to tune out weakness in the shafts - my shots seem to consistently go to the RIGHT of where I'm aiming - not by much, but enough that I thought it might be worth it to stiffen them up.

I'm going to do another round of bare shaft testing the next time I can get out to the range (hopefully next week), and really focus on my form to try and filter out any issues from that area. It's possible that I was short drawing at 20 yards, and that was causing the stiff behaviour. However, if it comes down to it I think I'd rather shoot more weight than buy a bunch more arrows.

Thanks for the help guys.

The 2117 shaft spines at 81#. That's at 28", though, so leaving them longer, as you do, would result in a dynamic spine of around 65# or so. You can add point weight or make your sideplate thinner to bring them into tune.

Good luck!

Shooting 50# @ 28" with 125 gr. point, a 2016 shaft ought to be really good I be thinking. Works great for me. Search for an Easton aluminum arrow chart. Easy to find.

Check this out. It will give you the actual spine of various aluminum arrows

http://web.archive.org/web/20071229024852/www.arrowsbykelly.com/Spine_Charts.html

I like the 2117s. There is a lot of flexibility for boy weights 40 - 50# just by varying point weight. My 50# recurve likes 170 - 175gr points at 30.5". I would definitely try adding point weight before cutting anything. Field points are cheap, but arrow stretchers aren't.