[litewings]

So changing arrows for some extra weight and hopefully tighter groups. Changed from Easton Helios 400, 28.5" to Easton FMJ 400 28". Both with 100gr tips.
Finished weight of the Helios 396gr, FMJ 430gr. Shot several groups and the FMJ's averaged around 1 1/4 inch low at 20yds. I wasn't expecting that much difference for 34gr more weight. Seem normal for those of you that change weights around frequently? Bowtech Reign 7 set at 62# and 29" draw. I did not do any other changes as far as checking tune for the new arrow yet. Not enough shooting at this time to say if the groups have gotten better with the new arrows but broke a couple nocks and ripped off a vane so maybe, but I'm not a great archer by any means.

 

[3D Pinwheeler]

The FMJ's are skinnner so they will hit low because they sit in your rest lower.
30 grains at 20 yards is nothing. I don't think you'd be that low at 40 if your shooting the same diameter arrows.

 

[litewings]

I was wondering about diameter. The FMJ's are .030 less diameter so in theory I should raise the rest .015. Thanks for the input.

 

[GoofyArcher]

The FMJ's are skinnner so they will hit low because they sit in your rest lower.
30 grains at 20 yards is nothing. I don't think you'd be that low at 40 if your shooting the same diameter arrows.

great catch on this post..
right on

 

[Keith t]

adding 34grns should not make the arrow drop that much, if at all at 20yrds. I added 20grns to the front of my arrows and seen about 1.5" drop at 60 yards. I didn't see any drop between the 2 at 20 yards.

Also, I didn't see any appreciable difference in group size between the 2, I stayed with the lighter (400grn) arrow.

 

[pasc43]

Could also use the same arrow but change points between 85/100/125 grain tips and see the difference. Assuming you are spined correctly that would be a better test.

 

[black feather]

The FMJ May hit lower out of the gate for the above stated reasons. An easy way to test the trajectory difference is shoot both arrows at 20 yards using the 20 yard pin. Then back up to 40 yards and shoot using the 20 yard pin and aim at the same spot you were aiming at during the 20 yard shot. Measure the difference between the 20 yard and 40 yard arrows. It might be closer than you think.


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[litewings]

Glad to hear that its probably not the weight change causing the low group. In a way its bad news since I want to keep using the Helios also with the FMJ's. Always keep a couple "expendable" arrows in the quiver. Will do some rest adjusting on the next outing and see how it goes.

 

[jim p]

34 grains should drop the arrow speed by 11 fps. You might be able to use a ballistic calculator to determine the drop with all other things being equal.

The small shaft is starting your arrow out on a little lower path.

 

[onesavage]

with the smaller diameter arrow, does the nock now sit higher on the string, making a downward angle on the arrow?

 

[hunter11]

I've experienced a drop of about 1in. @ 20yds. with a 25gr. increase. However, once the sight is adjusted for the initial drop, you won't see any difference in your pin gaps.

 

[litewings]

I've experienced a drop of about 1in. @ 20yds. with a 25gr. increase. However, once the sight is adjusted for the initial drop, you won't see any difference in your pin gaps.

This seems a bit strange. If the trajectory dropped 1in early (first 20 yds) I would think in would continue to drop the rest of the distance a faster rate. What yardages are your pins set at? Was the 25gr increase from a point/insert change or different, smaller diameter arrow?

 

[Finq]

This seems a bit strange. If the trajectory dropped 1in early (first 20 yds) I would think in would continue to drop the rest of the distance a faster rate. What yardages are your pins set at? Was the 25gr increase from a point/insert change or different, smaller diameter arrow?

Think of it this way,
the arrows that are 30gr heavier, and let's assume equal diameter, will hit lower at 20yds. Depending on your arrow rest and tuning of the bow, this can be significant (2-3").
However, once you compensated for that drop, by moving your whole sight housing, your 40, 50 and 60 marks will be very close as well.

I have experienced this every single time when I switched arrow weight. At first the difference will seem significant because your sight marks are way off, but the actual difference between the sight marks hardly changes. You will definitely be low at 50yds if you shoot an arrow that's 30gr heavier, I'd say 10-15gr starts to be noticable at 50yds for the average shooter, but it's not a lot.

Now if you were sight in with your lighter arrows and decided to just shoot one heavier arrow at 40yds, the heavy arrow will land very low and give the false perception that this is because of a higher trajectory.
Especially noticable with blade rest, and easily understood, they simply bend more and the arrow is launched with the tip just ever so slightly lower.

 

[litewings]

Think of it this way,
the arrows that are 30gr heavier, and let's assume equal diameter, will hit lower at 20yds. Depending on your arrow rest and tuning of the bow, this can be significant (2-3").
However, once you compensated for that drop, by moving your whole sight housing, your 40, 50 and 60 marks will be very close as well.

I have experienced this every single time when I switched arrow weight. At first the difference will seem significant because your sight marks are way off, but the actual difference between the sight marks hardly changes. You will definitely be low at 50yds if you shoot an arrow that's 30gr heavier, I'd say 10-15gr starts to be noticable at 50yds for the average shooter, but it's not a lot.

Now if you were sight in with your lighter arrows and decided to just shoot one heavier arrow at 40yds, the heavy arrow will land very low and give the false perception that this is because of a higher trajectory.
Especially noticable with blade rest, and easily understood, they simply bend more and the arrow is launched with the tip just ever so slightly lower.

Thanks for the explanation.

 

[bowshootn70]

30 grains will NOT cause your arrow to drop 1", and surly not 2,3 inches at 20 yards. No way in this world. Difference in arrow diameter will cause drop, not 30 grains.

 

[hunter11]

30 grains will NOT cause your arrow to drop 1", and surly not 2,3 inches at 20 yards. No way in this world. Difference in arrow diameter will cause drop, not 30 grains.

I'm sorry but yes it will.....there are even YouTube videos to confirm it. I just watched one the other day showing the different POI for different weight points.....all shots were shot with a shooting machine to eliminate human error.
The important thing to know, like I stated earlier, is that all it takes is a slight gang adjustment to set your first pin.....the pin gaps rarely change going from a 100 grn. point to a 125 grn. point. It takes a lot of weight reduction or increased poundage to have a significant change in pin gaps. Keep in mind that a heavier object retains its velocity at distance better than a lighter object. This should make it easier to understand why the pin gaps remain the same or so close to the same that you'd be hard pressed to tell any difference.

 

[ecfrost]

I added 30 grains to the front of the same arrows I was shooting before, and had very little drop at 20.

 

[deadquiet]

It's the diameter........it effects tuning slightly....which may or may not effect the POI. The bigger issue is however much smaller the shaft is would be the same as moving you sights that same amount.

 

[Tacoma#12]

With his Helios arrows with his specs he should be getting around 292+/- fps, adding 30 grains will drop that to 282+/- fps. So there's no way possible 30 grains dropped poi an inch. Wow. I shoot x-cutters from my target bow, had some Injections laying around and said I'll shoot a couple of them. (Deciding which bow I wanted to make 3-d bow), but the injections at 20 yards hit about 12 inches low . What could be wrong? X-cutters are wayyyyyyy heavier than injections. Nocking point position doesn't change, but where arrow drops down at rest postion. An 1/8th of an inch will drop poi alot. But the bow tune wouldn't change with those two arrows anyway. It's simply the diameter of the arrow, nothing else in this case.

 

[Tacoma#12]

I'm sorry but yes it will.....there are even YouTube videos to confirm it. I just watched one the other day showing the different POI for different weight points.....all shots were shot with a shooting machine to eliminate human error.
The important thing to know, like I stated earlier, is that all it takes is a slight gang adjustment to set your first pin.....the pin gaps rarely change going from a 100 grn. point to a 125 grn. point. It takes a lot of weight reduction or increased poundage to have a significant change in pin gaps. Keep in mind that a heavier object retains its velocity at distance better than a lighter object. This should make it easier to understand why the pin gaps remain the same or so close to the same that you'd be hard pressed to tell any difference.

This is funny at best. Post the YouTube video where one bow is shooting at 290 fps, and then shots 30 grain heavier tip arrow and it changes speed to 280 fps and arrow drops at 20 yards. It's not gonna happen at those speeds.