Mathews atlas arrow question

[831hunter]

Hey guy just recently bought a new Mathews atlas. I had some arrow built and had a few questions. I’m shooting the atlas at a 70 lb draw weight 33” draw. The arrows I had built are Easton axis 260 spline uncut at 34” with a 50 grain insert and 125 grain head with an FOC around 12. My math put the arrow weight around 566. My issues are obviously with that heavy of an arrow it is slow which doesn’t bother me however with my sight (fast Eddie xl 5 pin) my pin gap is the entire length of the scope as you can see in the picture. I’m thinking about ditching the 50 grain insert. Will this make a noticeable difference in pin gap? I have the scope all the way in on the dovetail as well. Thanks for any input.

 

[Wannabebowhuntr]

Personally I probably wouldn't change anything. That thing is probably still faster than the average bowhunters set up with a 33inch draw. Any idea of FPS?

 

[DB29]

What yardage are your pins set to? Something doesn’t seem right.

With that bow and DL you should have no problem that arrow weight.

 

[Wannabebowhuntr]

What yardage are your pins set to? Something doesn’t seem right.

With that bow and DL you should have no problem that arrow weight.

agreed

 

[831hunter]

My pins are set at 20 30 40 50 60

 

[831hunter]

I haven’t put it on chrono so not sure on speed

 

[Mighty Mouse]

With 30 gr on the back (which is about average for an unlighted nock + 3 vanes), your total arrow weight should be around 600 gr (34" × 11.5 gpi + 125 gr + 50 gr + 30 gr = 596 gr). I would estimate 270 fps for a 600 gr arrow out of your bow at 70#/33".

A 16 gr aluminum hidden insert (HIT) is the lightest insert option for a 5mm/.204" shaft. If you replaced your 50 gr insert with a 16 gr aluminum HIT, you should gain around 8 fps. You could also shave some weight by trimming the shaft a couple inches and/or switching to 100 gr heads. But if you want to significantly decrease arrow weight/increase speed, you should probably consider a lighter shaft. A 260 spine 5mm Axis is pretty heavy at 11.5 gpi.

 

[DB29]

qSpine shows you are way underspined.

How is the tune on the bow?
How are the groups you are shooting?

Edit: Changing to a 16gr insert and 100gr head and cutting down the shaft to 33in looks like the 2nd photo.

 

[831hunter]

Wow I guess your right I didn’t take account vanes and nock. I could bump up my weight to 75. If I bump up my spine the arrow gets even heavier in the axis hmmm

 

[831hunter]

It’s out of tune this pic shows the deflection. Bottom group is 60 yds top arrow is 20 yds

 

[Mighty Mouse]

Wow I guess your right I didn’t take account vanes and nock. I could bump up my weight to 75. If I bump up my spine the arrow gets even heavier in the axis hmmm

If you're wanting to significantly reduce total arrow weight, 5mm Axis isn't the answer. They're a great shaft, just comparatively heavy.

 

[DB29]

It’s out of tune this pic shows the deflection. Bottom group is 60 yds top arrow is 20 yds

I would say the first thing is to get an arrow that isn’t shooting weak. Then shoot bareshaft with fletched to get it tuned correctly. Then see what your pin gaps do.

Can you take any amount off the arrow length? If yes, how much?

 

[Mighty Mouse]

It’s out of tune this pic shows the deflection. Bottom group is 60 yds top arrow is 20 yds

Shooting two groups of fletched arrows tipped with field points (assuming that's what's in your photo) at different yardages doesn't really tell you anything about the tune of the bow.

When folks talk about in-tune/out-of-tune, they're usually referring to how the arrow is flying immediately after launch before the fletching takes effect. This close range arrow behavior can be deduced by shooting through paper at close range and studying the shape of the tear made by the fletching (paper tuning), by shooting fletched shafts and unfletched shafts (both tipped with field points) at distance and comparing their points of impact (bareshaft tuning), or by shooting field points and broadheads (both on fletched shafts) at distance and comparing their points of impact (broadhead tuning).

 

[Mighty Mouse]

qSpine shows you are way underspined.

How is the tune on the bow?
How are the groups you are shooting?

Edit: Changing to a 16gr insert and 100gr head and cutting down the shaft to 33in looks like the 2nd photo.

What IBO speed did you put into qSpine?

 

[831hunter]

The bow is shooting 255 fps via the chrono. The shop is going to attempt to cut an inch off the arrow and remove the insert. Shop claims arrow is not under spined. I admittedly am not squared away on all the details of archery. So just going on the shops word. My foc is currently around 12 and I asked since we are removing the weight that will drop my fox and shop said it didn’t matter?

 

[831hunter]

Part of the problem is I need a 33-34 in arrow. I can’t be the only guy that needs this haha. Any shorter then that and the blade of a broadhead is going to cut my finger

 

[DB29]

What IBO speed did you put into qSpine?

350

 

[DB29]

FOC should not be a concern.

What is the length of the shaft only? Not including the nock and point?

I don’t agree with having to have your BH past your hand. My BH sit inside my shelf and we’ll behind my hand. I understand the risk but I feel it is minimal.

If the arrow isn’t weak then it should be easy to tune it.

I don’t know everything but let me know if have questions, I enjoy archery rabbit holes.

 

[Mighty Mouse]

The bow is shooting 255 fps via the chrono. The shop is going to attempt to cut an inch off the arrow and remove the insert. Shop claims arrow is not under spined. I admittedly am not squared away on all the details of archery. So just going on the shops word. My foc is currently around 12 and I asked since we are removing the weight that will drop my fox and shop said it didn’t matter?

Reducing insert weight will reduce FOC. But the importance of FOC is often vastly overstated. Build for whatever total arrow weight you want and let FOC fall where it may.

Compound bows can typically handle a fairly wide range of arrow spines. 260 spine will likely work just fine at your specs (regardless of what any spine chart/calculator says). Shaft options really get limited if you go stiffer than 250-260.

Part of the problem is I need a 33-34 in arrow. I can’t be the only guy that needs this haha. Any shorter then that and the blade of a broadhead is going to cut my finger

Draw length is measured at a point roughly 1.75" in front of the Berger hole (rest mounting hole) and most rests sit well behind the Berger hole. In most cases, an arrow with a carbon-to-carbon length 2" shorter than draw length will stay on the rest at full draw with a comfortable margin for error. With a shorter arrow you do have to be more careful about bow hand finger placement (i.e., don't let fingers "float" up into the arrow path).

@5MilesBack is another long draw guy...he'll probably chime in with some ideas.

 

[5MilesBack]

350

That's at 34" draw. The real IBO is equivalent to 310 IBO at 30" draw. The Atlas is NOT an aggressive bow. Try 310 IBO and see what the program shows.

Part of the problem is I need a 33-34 in arrow. I can’t be the only guy that needs this haha. Any shorter then that and the blade of a broadhead is going to cut my finger

Keep your fingers out of the way. I shoot at just under 33" draw, like 32 7/8" and all my arrows are cut to 30" carbon to carbon. I'm shooting RIP TKO 250's with 200gr up front with 75gr brass HIT's and 125's. They come in right at 500gr and are shooting 294fps out of my Mathews Traverse with 1/2 a turn out of the limbs. Everything tunes up great. If I add more limb bolt twist, bare shafts will go left with nocks right. If I turn the bolts out at all, the bare shafts will go right with nock left.......the opposite. So this is my sweet spot.

Also, I wouldn't have a problem with those pin gaps for hunting. Just more room for visibility. But if you want faster arrows out of that bow, I'd try the RIP TKO's.