Point weight how to?

Discussion in 'Crossbows' started by chieffan, Dec 11, 2016.

  1. chieffan

    chieffan Weekend Warrior

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    Using a crossbow for the first time this year. Bought a less expensive one to start with. Due to shoulder injuries can't draw a compound. Field points are hitting within an 8" bull at 30 yds. Have shot twice at a deer and both shots went low but heard one hit something in flight. Using 100 gr. 4 blade broad heads on same bolts as used for sighting in. What is the best way to weigh the different points? Will a powder scale work or is there something better? Have done no "fine tuning" as I would not know where to start. Haven't hunted with a bow for 50 years and that was with a re-curve and cedar arrows from Herters.
     
  2. Arkyinks

    Arkyinks Weekend Warrior

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    Yes you can use a powder scale... if it will measure 125 grains. Crossbows are very sensitive to FOC. Fieldpoints and broadheads may not fly the same if FOC is not close to 15%. Spine is very limited for bolts. (weak / stiff show up as up / down)
    Crossbows will quiet down and group better when total bolt weight meets the bows sweet spot. So you will need a scale that goes to 600 grains.
     
  3. chieffan

    chieffan Weekend Warrior

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    Thank you for the reply and information. I understand that if the scale will weigh up to 125 grains it will work to weight the points. If I want to weigh the bolt the scale would need to read up to 600 grains. Now, what is FOC?

    I have a scale that measures in oz. and grams, up to 225 grams. Metric is hard enough let alone a bunch of conversion so want to get a scale that will measure in grain to start with.
     
    Last edited: Dec 11, 2016
  4. Arkyinks

    Arkyinks Weekend Warrior

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    1 gram is 15.43 grains. I have a AWS -100 scale (Google it) you can do it in grams because you are just wanting everything to be close to the same.

    FOC. Is a percent of weight Front Of Center. 15% is Ideal for crossbows (some will argue this but just what I have learned in 30+ years) . Measure total length of bolt (tip of broadhead to end of knock, this is L) . Then balance on something (dowl rod, pencil, old shaft) and mark the pivot point. Then measure from knock to pivot point. (This is B) Now divide B by L then subtract 0.5 from that then times 100. This is your FOC %.

    My bolt is 24 inches long (L) and balances 15.5 inches from knock (B) 15.5 / 24 = 0.6458. 0.6458 - 0.5 = 0.1458. 0.1458 × 100 = 14.58%

    So my FOC is 14.58%. If I add a lighted knock it will move to less and if I move up broadhead weight it will increase. This is true for all shafts. Just need a tape measure. All your shafts should be very close to the same (+- 1/8 inch)

    Weight needs to be with in 5 grains but 10 for sure. My bolts weigh between 522 and 528 grains and are written on the cock vane.

    Hope this is clear as mud.
     
  5. chieffan

    chieffan Weekend Warrior

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    Thanks for the information. I finally got the FOC figured out. My 16" aluminum bolts are at 12.5% and the 20" carbon are 11.5%. Field points and broad heads weight the same. I use the alum. bolts for practice and the carbon for hunting. I think I may try getting the points a little heavier to bring the FOC up closer to 15%. Going from 100 to 125 grain points may be to mcuh and expensive. May try something else.
     
  6. Hillbilly Jedi

    Hillbilly Jedi Die Hard Bowhunter

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    125g broadheads should be the same price or within a couple of bucks of the 100g. My question is the 16" alum arrow weight vs. the 20" carbon arrow weight. I know the alum is heavier than carbon but why shoot 2 different arrows for practice and for hunting? Are the carbon arrows and the alum arrows the same weight? I use the same arrows for practice and hunting. I also shoot my hunting arrows with the broad heads a couple times throughout the season just to make sure they are still good. Going back to your original post, an 8" group at 30 yards is not very consistent in my opinion and I would probably not hunt with it.

    I'm not trying to be mean or anything but 4 inches in any direction from your point of aim to impact on an animal is significant. Arrant shots happen but if you know this is how your bow shoots from the get go, I'd think something isn't right. If it were me, I'd expect no more than 4" groups at 30 or better. This should be easily achievable.
     
  7. picman

    picman Grizzled Veteran

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    Perhaps you could install brass inserts instead of replacing the broadhead?

    Hillbilly makes some valid points. Need to get the group size down. Shooting the same bolt for practice and hunting could help. I know bolts are not cheap but you could swap out a FT for the broadhead on one bolt to practice and then put broadhead back on to hunt.

    To me, that would be preferable to using aluminum to practice and carbon to hunt. Just our opinions-ultimately you have to decide what is best for you and your situation.
     
  8. Arkyinks

    Arkyinks Weekend Warrior

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    At 30 yards with a rest I can not aim at the same point twice with out busting bolts. You may want to look at getting some new bolts so you practice and hunt with the same shafts. Look for ones with brass inserts to begin with. Maybe Santa could get you some? GoldTip makes good bolts as does Eastman, do not care for Beman.
     
  9. chieffan

    chieffan Weekend Warrior

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    This is my first year with a cross bow and the last bow hunting I did compounds were just making the scene. I then hunted with a re-curve and cedar arrows. I have a lot of learning to do and that is why I am here. I will never shoot enough to be able to consistently shoot a 4" group at 30 yds. For never picking up a cross bow till a month ago I thought an 8" group was not all that bad. The reason I am shooting both aluminum and carbon arrow is that is what I have on hand right now. I have 6 new aluminum arrows coming along with new broad heads. Once they get set up that is what I will be using for both, hunting and practice. Spending big bucks for something I know nothing about would be like buying a Caddy to haul pigs to town. I also realize that the bow I bought as a first purchase is not the best either. Figured it better to start low and work up. I know the fletching has to be straight for the bolt to fly right. How important is having the broad head lined up with the fletching? Have not seen any way to change where the BH happens to get tight at. I need a better scale as the one I have is a dial unit that reads in oz and grams by 2 gram increments. Would like to get out and practice more but with temps in teens and wind blowing not fit to be out in it. Won't hunt under these conditions either. This 76 yo body knows better than that. Thanks for all the advise guys. Definitely going to be a learning experience on this end.

    Forgot to mention; My 16" aluminum and 20" carbon bolts weight the same, 25 grams. Carbon have 3" vanes and 4 short blade BH and the alum. have 3.5" vanes and 3 long blade BH.
     
    Last edited: Dec 15, 2016
  10. picman

    picman Grizzled Veteran

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    Used to take my pigs to town in a Lincoln. LOL!

    The broadhead does not have to align with the fletches/vanes. It is more important that the broadhead ferrule is in line with the arrow shaft. To determine that, you could go out and buy a spinner or even construct one of your own. You could even roll it along the edge of a bowl or kettle if you are cheap I mean FRUGAL like me.

    You spin the arrow along the horizontal axis and watch the tip of the broadhead. There should be no wobble.

    Are you using a rest when you shoot? I find that I couldn't hold a xbow steady if you put a gun to my head-they are generally heavier than a vertical bow but not as heavy as a rifle.

    Are you using a scope or pins for sights? Even a cheaper xbow with a scope and using a rest should get you to under 4".
     
  11. chieffan

    chieffan Weekend Warrior

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    I use a piece of slate, old black board, to check for any bowed shafts. Can surly find something that would work to check the points for true to shaft. Yes, I am using an camera tripod as a rest. My 8" group was free hand. I don't try to hold right on the target. I use a loop sighting method I learned about 50 years ago in Law Enforcement. Start below the target and come up across it loop to the side and come back across and fire. Have to learn the speed to fit each person. Your body wants to move rather than hold solid so let it move, just control where it moves. This is for targets, not hunting. I mounted a 3 X 9 scope off my .22 rifle on my cross bow the other day. Only shot it about a dozen times to get it zeroed in. Not there yet, got froze out. Will be using the scope on 4X only for shooting but may crank it up for some distance scouting. I checked out a couple of the bolts with brass inserts. Looked like $40 a piece as they did not state any quantity, Gold Tip and Eastman. May have been for a dozen but it was not stated as such. Did some experimenting with measurements on the FOC. Found if I measure to a 32nd, and added 4 wraps of 1/32" solder around the base of the BH, it changed the FOC by over 3%. Need to do some more work on that angle with it being to cold to be outside for anything.
     
  12. Arkyinks

    Arkyinks Weekend Warrior

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    I use Snuffer broadheads (which are 3 blade) and line them up with the fletching. Gives the "tickle) on pass through. Does not have to be... just something I do that seems to make a very small difference.

    Bolts come in 3, 6, and dozen packs so make sure you know how many are in there. I buy mine with the inserts loose, and they cost a bit more for some reason.
     
  13. chieffan

    chieffan Weekend Warrior

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    Replaced the vanes on all my aluminum 16" bolts. Made a good difference as the groups are now at 5" at 30 yds. Part of this I am sure is the shooter and not the equipment. Will finish this season out with this set up - maybe. Have a new Jackal on the way. Picked up some 20" carbon bolts, ordered a 4 x 32 scope also. If I get it set up and zeroed in good I may use it the last 10 days or so. Deer have changed their travels considerably. I think most are moving at night and going different routes. Still spooky from being chased all over h _ _ _ and half of Georgia during the shot gun season. Not seeing them and not showing up on the game cameras either.
     

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