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Discussion Starter #1
I am a new shooter. I zeroed my crossbow with a recommended brand of bolts and field points; shot wonderful at 20 to 40 yards and was pleased. The mechanical broadhead and same brand bolt was "supposed" to weigh the same but I weighed them and the difference is 30 grains (complete arrow and point). Before I weighed them I wanted to insure they would indeed shoot almost identical to the field points even though I may waste a few; I am happy I checked. At 20 yards, there was a 4" difference; all 3 broadheads shot about 4" low. I was able to recover them fairly easy from my target bag and will re-use them for practice.
I balanced each arrow setup and the center of gravity distance to nock is almost the same; however the BH extends farther forward about an inch +/-. I am wondering if the "weight forward" is affecting the flight path more than the weight differential.
This will start getting expensive, trying to guess what the controlling factor is and buying a lot of different bolts/heads. Once I zero for hunting. I will then make adjustments using field points when practicing but I will keep my bow zeroed for broadheads and hunting.
I do not believe the bow itself is making any difference; the patterns with both types of points are excellent; I can just raise the zero with the BH. I also was using a good rest and wind was no factor.

My questions are: 1- Is this normal to have this much difference with a 30 grain differential? I would have expected some but not nearly this much.
2- Do you believe the "weight forward" is contributing a large portion of the difference? I imagine both weight and forward weight differential are contributing but not sure which factor controls the most.
3- Where would you start? Would you keep the identical BH and bolt combo (which shoots consistent, just low at this time), re-zero with BH's and adjust hold-over/under for practice points OR buy a complete different set of bolts/field points/BH's that are matched closer; not only in weight but over-all length if the "weight forward" concept is valid.

Thank you for your consideration.
 

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What I have found is that most broad heads don't shoot the same as field points. I just zero with the broad heads I'm hunting with and go from there. The only broad head that I've ever found to shoot the same was the rocket steelhead and it is about the size of a field point.

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Did you weigh the broadheads to make sure they were the same weight as you’re field points?
X2 .....weigh just the components to single out where the difference is coming from.
 
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Discussion Starter #5
Yes, I weighed the individual components, summed them and compared to field points. The maximum total difference is 30 grains. My question is "Do you believe 30 grain difference will make an arrow drop 4" more in 20 yards than when using identical brand bolts?"
 

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Not sure if it will drop 4” but it here will be some difference. Get broadheads that weigh the same as your field points and try that.
 

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Yes, I weighed the individual components, summed them and compared to field points. The maximum total difference is 30 grains. My question is "Do you believe 30 grain difference will make an arrow drop 4" more in 20 yards than when using identical brand bolts?"
The arrows should weigh the same so the difference has to be in the weight of the broadheads if they are adding 30 grains to the overall weight. And NO there should not be a 4" difference when using a mechanical or any other head with only a 30 grain difference but seeing how there is with your bow and they are all hitting the same POI just sight in with them and go hunting.
I suspect your problem is heavier broadheads and a crossbow that is not quite tuned correctly.
 

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Yes, I weighed the individual components, summed them and compared to field points. The maximum total difference is 30 grains. My question is "Do you believe 30 grain difference will make an arrow drop 4" more in 20 yards than when using identical brand bolts?"
Summing them and then saying the difference doesn't do any good when trying to get to the bottom of why they are different.

What did your field tips actully weigh?

What did your broadheds actually weigh?

Agreed with @robertyb that even with 30gr difference you shouldn't see a 4" POI change at 20 yds. Weight is probably a small portion of that and tuning the majority of it.
 

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Look up calculating arrow FOC. Front of Center will make a difference especially if the arrows are in the 10 -12 % range. Personally, I like the FOC to be 17% and up depending on what setup I'm shooting. If you find different FOC on your arrows, try to minimize the differences but keep the higher percentage.

Another problem could be spine deflection matching. If your arrows have not been match for both weight and deflection your groupings will be wider than acceptable.

My 2¢.
 

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Eliminate variables. Low USUALLY means slow but could mean vertical plane flexing (porpoiseing). Slow means lower launch velocity or greater drag (loss of velocity over range). Variables can drive you nuts. Eliminate them by:
1. zero with field point on ONE arrow. Shoot it five times at 20 yards. Move the PATTERN to the bullseye. Repeat at 40 yards. If the pattern is not centered on the bullseye, the scope is off. Correct the scope.

2. replace the field point with the broadhead on that one arrow and shoot it at 40 yards again 5 times. If it's low, aerodynamic drag is slowing it down so that gravity has more effect or a weight difference is making it slower out of the bow with the same result as drag. Any vertical plane flexing should be fully damped out at forty yards if the arrow has adequate stiffness (spine). Thirty grains in my bow reduces fps about 10-11.

3. Zero THAT arrow and go hunt with confidence that it will go where you aim it.

4. While your tenpoint buck is at the taxidermist, shoot the other 3 arrows in your hunt quiver with their own broadheads. If they don't zero, they may be crooked, bent, misaligned or damaged.

Good Luck.
 

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Discussion Starter #11
Thank you everyone for a lot of good tips. I just returned from my archery shop and his scale showed a differential weight difference of 25 grains; compared the hunting bolt and BH with the target bolt and FP. The FP and BH measured within 1 grain of each other; The bolts were the same style, brand EXCEPT the hunting bolts had a lighted nock; the lighted nock added 25 grains.
Side note: my patterns of my previous shots were good, they were just dropping too much compared to practice arrows. I will re-zero using my hunting arrows and BH as Gingerjake suggested. Thank you all for your input, it is appreciated.
 

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Not all broadheads will fly true with field points. I believe a lot of it is due to design in the broadheads. 30 grains wont make a 4" difference IMO. Regardless, if you like the consistency of the heads then re-zero using the bh's and then shoot your fieldpoints so you'll know where theyre hitting. Aim accordingly at your targets without changing the zero. Closer to hunting season re-check with bh's to make sure theyre still "ON".
 

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Additional consideration. Those lighted nocks at 25 grains each are reducing your FOC percentage. Consistency of arrow types, vanes, nocks, inserts are essential components of accuracy. Spine and weight matching as well, probably most important.
 
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