Broadheads hitting left (but different)

[SlimTim]

Title says left but different.

Can you expand on the different part?

If individual heads, that are all else equal, are flying better or worse you’ve got at least one problem and likely more.

1.) You’re inconsistent. You can only tune a bow to the point your form allows. If your shot process is not repeatable, you’re going to struggle.

2.) There are inconsistencies in your arrows: broadhead isn’t square with the front end of the shaft and/or the nock isn’t squared with the back end.

3.) Your bow is out of tune. Some folks have mentioned moving the broadhead to the field point. I’ve set up and tuned something like 50 bows in the past decade, and that just doesn’t work for me. I know it works for some, because there are videos on YouTube showing it work that way. Then there are videos showing it the opposite to be true. Moving the rest the way I want the broadhead is the only thing that’s ever worked for me, IF it’s already really close: within a few inches at 60 yards. If the difference is greater than that, shim the cams/yoke tune to get it close then use very fine rest adjustment to get it to tune. If you’ve gotta move it more than 1/16” from manufacturer center shot, you’ve got problems that moving the rest can’t fix.


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I suppose I meant different in the sense not the usual rest movement. About 2-3 months ago FPs and BHs were really close, now they're not.

Beauty. My BHs have been the same. I reckon I'm generally about 2 inches left at 30 yards. Its probably now too far for me to confidently hunt with.

 

[SlimTim]

The chart below has always worked for me. However, pragmatism is the number one rule in tuning...if moving something in one direction doesn't fix the problem, try moving it the opposite direction (regardless of what anyone says is the "correct" direction).
View attachment 572561View attachment 572562


String/cable stretch can affect a bow in various ways. Stretching of the shooting string causes draw weight to increase. Stretching of the buss and/or control cable causes draw weight to decrease. It's possible that string/cable stretch could affect the horizontal tune of your bow, but it wouldn't be my first guess as to the root cause of your broadheads hitting left.

Also, the old "broadhead left = arrow is too stiff, broadhead right = arrow is too weak" (for a right-handed shooter) advice doesn't apply to a modern compound bow shot with a mechanical release. Today's compounds are cut well past center with the rest mounted in line with the string path, so the arrow doesn't have to bend around the riser during the shot (like it does on most recurves/longbows). And a mechanical release eliminates the left/right effects of shooting with fingers. Arrow spine can affect how a bow tunes, but the effect doesn't necessarily manifest as broadhead left if too stiff/broadhead right if too weak. Modern compounds can typically tolerate a fairly wide range of arrow spines.


Cam timing primarily affects vertical point of impact. If your broadheads are vertically aligned with field points, I wouldn't suspect a cam timing issue. It never hurts to check though.

Without a draw board, you could try taking a slow motion video or having someone else watch as you draw to see if the top and bottom draw stops are hitting at the same time. A draw board is fairly cheap and easy to build; however, you would (likely) need a bow press to actually make an adjustment if you were to find that the timing is off. APA bows and Mathews' V3X/Phase4 are notable exceptions that can be timed without a press.


Check for vane contact. Put a tattletale substance (e.g., lip stick, chalk, spray foot powder) on the edges of the vanes then look for marks on the rest, cables, etc. after shooting.

Confirm the trend with multiple arrows to make sure that what you're seeing is not just an artifact of one particular broadhead or shaft.

Put the arrows on a spinner to visually check for misalignment.

Try moving the rest the opposite way.

Try adjusting cam lean/lateral position per the chart above. This will likely require a bow press.

Try bareshaft tuning. If you can get bareshafts to hit alongside fletched shafts (both tipped with field points), broadheads (on fletched shafts) should follow suit. If they don't and a tiny rest adjustment can't get them there, you may not have enough fletching to adequately steer/stabilize your broadhead.

Awesome. Thanks. I'll start working through this process.


Massive list.

 

[SlimTim]

Thanks so much all.

So much gold.

Planned process:

1. Move rest left. Seems counter intuitive but I'll give it a go.
2. Check arrows on spinner.
3. Check cam timing. Unlikely to be issue but worth a look.
4. Send a couple of bare shafts down range. See what happens. I definitely got my bare shaft, BHs and FPs hitting pretty close at 40 yards about 18 months ago. 18 months of bashing it through Aussie bush could easily and likely has upset something.
5. I'll try some heavier heads just for completeness.

This likely depends on ones skill level but what kind of tolerances does everyone tend to accept?

Here is Aus, I have rarely shot an animal at great than 40 yards, so if FPs and BHs are close at 40 yards, then I'm happy that my practice will translate well to my hunts.

Sound about right?

 

[SlimTim]

Put two turns in your limb bolts or 6 twists in your cables. If that brings them together you know your over spinned. Drift left over a period time is almost always cable stretch

Cable stretch will lower the draw weight leading to a relative increase in stiffness of the arrow?

 

[jimh406]

Is the poundage still the same? If the string stretches that will change. Two years is a long time for a string if you are shooting regularly, and it sounds like you do.

 

[Trial153]

Cable stretch will lower the draw weight leading to a relative increase in stiffness of the arrow?

Yes, left broadhead/ bare shaft with a proper center shot is indicative of stiff spine reaction. Another correction would be too crease the load on the cable rod.

Generally you won’t notice a stiff spine reaction with most modern compounds and a release aid…however left drift of broadhead impacts is generally often indicate cable stretch.

 

[SlimTim]

Is the poundage still the same? If the string stretches that will change. Two years is a long time for a string if you are shooting regularly, and it sounds like you do.

Yeah, I could do with a new string. I've got to give it to the bow. I've been flogging it through the NT bush with barely any maintenance or care and this is the first issue I've noticed and its only appeared in the last few months, if that. I pretty mush shoot it every day and hunt every second weekend. Its been very good to me.

 

[Tilzbow]

I’d eliminate form issues first before you drive yourself crazy trying to tune a bow that might not be out of tune. Grip and face pressure on the string are the most likely culprits IMO. For me, as a right handed shooter, too much palm in the grip will result in left impacts while too far to the thumb side will result in right impacts. Gotta make sure your grip position is good and also make sure you aren’t torquing the bow since that’ll also create left or right impacts with FBBH. face pressure is way easier to identify and deal with.

 

[WMag338]

Interesting. I've definitely started a different gym routine that involves lifting way more.

Had the same issue as you. Can be super frustrating to figure out.

 

[SlimTim]

I’d eliminate form issues first before you drive yourself crazy trying to tune a bow that might not be out of tune. Grip and face pressure on the string are the most likely culprits IMO. For me, as a right handed shooter, too much palm in the grip will result in left impacts while too far to the thumb side will result in right impacts. Gotta make sure your grip position is good and also make sure you aren’t torquing the bow since that’ll also create left or right impacts with FBBH. face pressure is way easier to identify and deal with.

So do you find that form issue are exacerbated with broadheads on?

 

[MattB]

So do you find that form issue are exacerbated with broadheads on?

Yes, you are essentially adding steering to the arrow by putting blades on the front. If the arrow is not coming out of the bow straight, it can very well mis-direct.

 

[Marble]

When I've seen broadheads flying wonky it is usually tuning or more likely a spine issue.

If the OP lists all the info for his bow, someone here can look it up and give some input.

Most of the time guys do not properly take into account extra point weight. Field tips might shoot OK, by broadheads magnify minor issues.

If it was my bow, I would make sure the bow is in spec and then go from there.

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