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07-25-2018, 02:48 PM
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Join Date: Nov 2013
Posts: 52
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Little help on arrow spine and broadhead selection
Apologies in advance for the long post. Wonder if some folks out there might want to offer an opinion or two to help set a guy straight.
I've been shooting my bow for about 5 years now. Not a hardcore shooter by any means but I would consider myself reasonably capable. Not much of an expert in the more technical aspects of FOC, spine, ideal grain and the like. So I'm hoping to get a bit of guidance.
Bought my bow (Bear Agenda 7) without out really shopping around. Pretty much walked into Cabelas and said to the young guy in the bow shop....hook me up. Those were the days before finding this forum unfortunately.
Anyway, draw weight range on the bow is 60-70 lbs. I fitted my quiver out with some 400 grain FMJs cut to 28.25 inches with 100 grain field tips and broadheads. For the first year or so of practicing I could never get any sort of consistent groupings. Figured it was more "driver error" than anything. Then after reading a bit I got a sense that the bow settings needed some attention. A guy at the range spent a little time with me and helped quite a bit. Did some paper tuning, played with a few things and voila.....started to get some decent groupings. Not great, but decent. In order to get there though I ended up dialing down the draw weight. My crappy luggage scale tells me I'm at 58 lbs.
Wondering if my arrows are not the tool I need for this setup. Looking at Easton's website I think I am right on the borderline for what they recommend, maybe even still a touch on the high side. Ideally I'd like to up my draw weight a bit but I believe that doing so will result in me being underspined. Also, if I change the arrows would there be any measurable benefit to moving to a 125 grain head?
Any help or insight is appreciated.
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07-25-2018, 03:10 PM
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Join Date: Sep 2013
Location: Central Alberta
Posts: 971
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Did you mean 400 spine fmj’s? If so, 340’s might be a better fit
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07-25-2018, 03:25 PM
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Join Date: Nov 2013
Posts: 52
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Yes....sorry. Bit too focused on the number and not the terminology. Currently running 400 spine FMJ's.
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07-25-2018, 06:03 PM
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Banned
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Join Date: Aug 2016
Posts: 1,338
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My 70 lb bowtech is shooting the 340 that 28.5
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07-25-2018, 06:39 PM
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Join Date: Mar 2009
Posts: 1,521
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Grab some Beman ICS 340s, throw a 150 grain VPA up front with a stainless steel half out. Bob's yer uncle.
Put her back to 70lbs and Send it!!!!!
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"We're not polishing fine china here"-Belichick.
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07-25-2018, 07:17 PM
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Join Date: Oct 2015
Location: Cold Lake
Posts: 179
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It is possible that if you are on the bubble you could add more weight to the back of your arrow (4 fletch instead of 3, longer vanes, vane wraps, bushings, lighted nock, etc.). The more weight you add to the end of your arrow the stronger it will be. Also, if your arrow is a tad long shortening it can help increase arrow stiffness, but I’d go to a pro shop before you start cutting arrows. Don’t add more weight to the front of your arrow (heavier weight broadheads for example) because that will weaken the spine of the arrow.
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07-25-2018, 07:30 PM
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Join Date: Oct 2015
Location: Cold Lake
Posts: 179
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I'm no expert, and I'm assuming you have blaser vanes right now I think if you change to AAE max stealth vanes, go to 4 fletch, and add vane wraps then you could increase your draw weight 5 lbs and be okay with the spine of your arrow. If they aren't grouping well you could add a lighted nock and that should tighten up the groupings. You'd have to make sure you have the aluminum inserts (standard for the fmj arrows) and stay with a 100gr head.
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07-25-2018, 08:15 PM
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Join Date: Sep 2013
Location: Central Alberta
Posts: 971
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Quote:
Originally Posted by ks.snow
I'm no expert, and I'm assuming you have blaser vanes right now I think if you change to AAE max stealth vanes, go to 4 fletch, and add vane wraps then you could increase your draw weight 5 lbs and be okay with the spine of your arrow. If they aren't grouping well you could add a lighted nock and that should tighten up the groupings. You'd have to make sure you have the aluminum inserts (standard for the fmj arrows) and stay with a 100gr head.
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Pretty sure that would make the FOC worse. I understand the thought process but typical hunting setups should be at least 10 to 15% FOC and he’s shooting fmj’s which are heavy grains per inch to begin with. You don’t want a heavy back end. After buying all that stuff and adding to the rear of the arrow he might be better off just getting a different spine in my opinion but I’m no expert either. Maybe one of the pro’s on this forum can chime in
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07-26-2018, 06:42 AM
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Join Date: Oct 2015
Location: Cold Lake
Posts: 179
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Quote:
Originally Posted by Passthru
Pretty sure that would make the FOC worse. I understand the thought process but typical hunting setups should be at least 10 to 15% FOC and he’s shooting fmj’s which are heavy grains per inch to begin with. You don’t want a heavy back end. After buying all that stuff and adding to the rear of the arrow he might be better off just getting a different spine in my opinion but I’m no expert either. Maybe one of the pro’s on this forum can chime in
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It would defiantly make the FOC worse that’s for sure. I was just giving him an option considering he wants to stay with the same arrows. His best bet is to definitely go up a spine.
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07-26-2018, 09:33 AM
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Join Date: Dec 2010
Location: Look behind you :)
Posts: 27,780
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Weight added up front breaks down spine...weight added to the back has the opposite effect while shifting the FOC.
You tried turning down your bow poundage slightly to see if the issue improves, it did...so you likely need stiffer arrows. Always err to the side of stiffer spined arrows if you are right on the cusp with your setup.
I have found if you have things tuned and the arrows are spined properly, with my hunting bow I have perfect bare shaft flight and same point of impact out to 20 yards. That will allow me to properly tune and shoot fixed blade broadheads at 300+FPS.
LC
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07-26-2018, 09:35 AM
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Join Date: Nov 2013
Posts: 52
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Thanks for the feedback folks.
Based on my limited knowledge I think I get what you're saying. Its possible to tweak the 400s to perform better but the simpler solution is likely to move to 340s. That's kind of where I was heading. I was already shopping for new tackle and I am trying to decide why to spend the loonies on. So 340's it is.
Couple of follow ups:
1 - given the move to 340's would moving to 125 broadheads be advisable? Pros and cons?
2 - How significant of a retuning job would you think I'd be looking at. Fairly minor tweaks or fairly significant.
Thanks again!
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07-26-2018, 09:58 AM
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Join Date: Dec 2010
Location: Look behind you :)
Posts: 27,780
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Depends, if you are using the same shaft with a stiffer spine (stiffer spines are typically heavier in a relative GPI). You will definitely need to re-sight in going to heavier arrows and switching tip weights.
Are you planning on hunting mostly deer? I would use 100gr heads... elk and moose? Use either 100-125gr. I use 100gr heads in a 400gr total weight arrow for everything and I haven’t had issues passing through. I switched to fixed blade heads this year.
LC
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07-26-2018, 10:04 AM
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Join Date: Nov 2013
Posts: 52
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Primary targeting Moose and deer. Running G5 Strikers in 100 grain right now. Got 6 unused heads right now with a few replacement blades at the ready if needed. Also have 3 dinged up heads for practice. I'm pretty set with a good tackle box full of 100 grains so I'm not too fussy about dropping coin on a pile of new heads if not needed. Unless there's a strong reason to move to 125 I'd rather not.
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07-26-2018, 10:47 AM
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Join Date: Dec 2010
Location: Look behind you :)
Posts: 27,780
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Quote:
Originally Posted by Slapshot100mph
Primary targeting Moose and deer. Running G5 Strikers in 100 grain right now. Got 6 unused heads right now with a few replacement blades at the ready if needed. Also have 3 dinged up heads for practice. I'm pretty set with a good tackle box full of 100 grains so I'm not too fussy about dropping coin on a pile of new heads if not needed. Unless there's a strong reason to move to 125 I'd rather not.
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Do real world calculations to determine the pros and cons: chronographed FPS, KE and momentum.
LC
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07-26-2018, 11:00 AM
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Join Date: Dec 2010
Posts: 27
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Quote:
Originally Posted by Slapshot100mph
Primary targeting Moose and deer. Running G5 Strikers in 100 grain right now. Got 6 unused heads right now with a few replacement blades at the ready if needed. Also have 3 dinged up heads for practice. I'm pretty set with a good tackle box full of 100 grains so I'm not too fussy about dropping coin on a pile of new heads if not needed. Unless there's a strong reason to move to 125 I'd rather not.
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Most arrow manufacturers now will have brass insert options that will increase your weight up front without requiring you to switch to heavier broadheads. Gold Tip inserts allow for you to add weight with their FACT weight system so you can tweak your insert weight without having to invest in new broadheads as well.
If you like, feel free to PM me and I can run your specs through OnTarget2 to calculate your optimal spine.
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07-26-2018, 11:27 AM
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Join Date: Nov 2013
Posts: 52
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Thanks gents. Unfortunately I don't have access to a chronograph or anything like that so real world testing for speed, KE, etc might be tough.
Think I'll just go with the 340 arrows for now and stick with the 100 heads for some initial testing. I'll see how she tunes once I increase draw weight a bit. If things seem erratic I'll maybe dig into it a little more.
Thanks for all the feedback!
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07-26-2018, 01:13 PM
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Join Date: Apr 2015
Location: Calgary
Posts: 316
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Also with your limbs backed out all the way to 58lbs you are losing efficiency. With the switch to 340s tighten them up to at least 65 lbs.
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07-26-2018, 06:02 PM
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Join Date: Sep 2015
Location: Red Deer
Posts: 512
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Perfect setup, I wouldn't change a thing.Well, except for changing to a nice mechanical broadhead, like the trypan. From what I have read, tuning and form is what I would suggest to focus on.
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07-27-2018, 05:17 PM
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Join Date: Aug 2011
Posts: 5,167
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400s are definitely underspined at 60, unless cut very short.
As a general rule, it’s always better to err on the side of stiffer and heavier.
Lastly, set your draw weight and leave it. As soon as you change it, you have to go through the whole tuning process again.
Probably worth a visit to jimbows or your local pro shop to get an education and proper tuning.
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