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Post by Buckfever on Mar 10, 2006 23:48:24 GMT -5
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Post by ncboman on Mar 12, 2006 0:44:58 GMT -5
that's real interesting but often to gain in one area, there is a sacrifice in another.
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Post by ncboman on Mar 12, 2006 0:50:33 GMT -5
This is another hotly debated issue among archery enthusiasts. Some claim that FOC makes little or no difference, others swear that FOC has a profound effect on accuracy. Even the industry experts don't seem to agree, as the ballistic physics for FOC include some rather elastic variables that make finding an "mathematically optimal" FOC very difficult to declare and prove. To make matters worse, we even see a variation in how FOC itself is calculated, depending upon which "expert" you ask. So while we have no interest in the fine points of the debate, we will agree that the tricky issue of FOC is at least worth considering when purchasing a new set of arrows. With all that said, it is generally believed that an arrow with a high FOC will fly well, but with premature loss of trajectory (nose-diving). While an arrow with a low FOC will hold it's trajectory better, but it will fly erratically. So again, another trade-off for you to consider. While there doesn't seem to be a magic number to aim for, it is generally agreed that the optimal FOC balance for an arrow is somewhere between 7% and 15%. In the example on the left, the 30" long arrow has balance point that is 3" forward of the arrow's actual center (15"). So it's FOC is 3/30 or 10% - a reasonable FOC balance. So when you order your custom arrows, keep FOC in mind. If you choose heavy 5" vanes and an anorexic 50 grain tip, you'll likely have an FOC that is too low. On the other hand, if you choose 3" lightweight feathers and a jumbo 175 grain tip, you'll likely have too much FOC. Choose an arrow setup that will give you an FOC balance of roughly 7-15%. www.huntersfriend.com/arrowhelp/arrow-selection-4.htm
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Post by Buckfever on Mar 12, 2006 9:24:42 GMT -5
nc, have you played around with FOC and if so what have you found?
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Post by ncboman on Mar 12, 2006 14:54:33 GMT -5
I haven't even checked and calculated foc on the 371s I'm shooting. ;D
I use to do alot of the stuff you're doing but over time I've got lazy and gone to a different method of analysing my bow/arrow performance.
The results at the target tell me what I need to know. I look at accuracy first, then penetration, and straightness of arrow impact.
Sometimes I'm too rusty (shooting wise) to make comparisons but usually when I'm tuned in out to 60 yds, I can tell a lot about different arrows just by shooting them.
For me, uniformity is most important.
foc? as long as it's the same on each arrow, I'm fine with the stock arrows and 100gr or 125gr points/heads.
The 60 yd mark is where headweight makes a marked difference. For that reason I like 100gr broadheads. Since I have shot thru several deer at that range with 100gr thunderheads, I don't regard foc/penetration as an issue that needs attention.
As a bowhunter and a guy that really enjoys precision archery in a fun setting, I'm much more interested in having a combination that shoots well in a variety of circumstances over a setup that needs ideal conditions and flawless form to perfom well. Often touchy setups become absolutely worthless in less than perfect settings, accuracywise.
Watch someone trying to shoot a 300+fps bow in moderate to high winds and you'll see some wild misses. ;D
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Post by Buckfever on Mar 12, 2006 18:00:35 GMT -5
I hadn't concerned myself that much with it till I got the ACCs. The broadhead that I like comes in at 80 grains so that brings FOC down to 7%, way lower than I've ever done, so I just considered it. I'm going to compare the 100 grain point and the 85 grain point and see if there is a grouping difference at the longer ranges. If I have to I'll add a little weight to the insert.
I'm not that worried about penetration. I've settled on 2.5" of cut and out of my setup, I don't think I'll run into a problem.
The thing about the ACCs is that even when the bow was out of tune for the 7595s the ACCs punched clean. From what I have seen so far they are a more forgiving shaft, both in terms of bow tune and form flaws.
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Post by ncboman on Mar 12, 2006 19:17:56 GMT -5
7%, you may be very good accuracywise. I'd sure check out long range penetration side by side with a heavier head though. I had questions when I dropped down to 100gr but after killing a few deer and getting passthrus I feel better. I still think a heavier head is better for spine shots. I've already seen a slicktrick fold like an accordian and while in most instances these lightweight heads perform ok but I dont trust any of them in bone like I do 125grs and up. Once again I like the happy medium, a head heavy and solid enough for close range spine shots yet able to shoot comparably flat out to 60yds and passthru.
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Post by Buckfever on Mar 15, 2006 9:24:38 GMT -5
"I'd sure check out long range penetration side by side with a heavier head though" I did post mortum testing with that head that I like mounted on the 7595s total arrow weight is only around 380 grains and put it through the near shoulder. Now this is at point blank range. I also checked through the shoulder, higher up near the spine. That was like 4-5 inches of penetration. It's not enough for a shoulder spine shot: I think this confirmed what I saw in the field. It's just enough to get it done in most instances, but a little more punch would be nice.
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Post by ncboman on Mar 15, 2006 22:39:12 GMT -5
er, how do I post nicely that I don't think the pm test tells much? ;D First off, the skin on a live deer is very elastic and the farside resistance is considerable. That's why you often see what looks to be a stop and go motion of the arrow before it passes thru. The hide on the far side stretches a good bit out before the arrow actually punches thru and resistance is lessened quickly. Shooting dead animals seldom approaches live shots in penetration result. second, Shooting an animal is apples and oranges for arrow comparison. To compare penetration at the target, you need a target of relative density, like an unshot 3D or block type target. The desireable is to have everything exactly the same except the heads or whatever is being compared. Doing this type test at various ranges can show some interesting differences between 100 and 125 gr heads. (Field points can be subbed for broadheads so as not to eat the target and the results will still show enough for a relative comparisons.) I'm always amazed at the differences in long range penetration between the compound and recurve. The recurve isn't impressive at all beside the compound but I know for a fact recurves can shoot thru deer at 60yds. Looking at a target, you'd never believe it.
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Post by Buckfever on Mar 15, 2006 23:13:50 GMT -5
nc, I guess my thinking on the pm is that, if I'm not blasting through the animal, while catching only the flat part of the near shoulder, that suggests to me that I could use some more. Unless I'm misinterpreting what you're saying.
In 6 cases with that setup, on live deer I did manage to get through except for the fletching on 2. So that was from what I was concluding that in most cases, it would be alright.
I mean wouldn't you say I need to increase the arrw weight some?
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Post by ncboman on Mar 15, 2006 23:31:13 GMT -5
Honestly, there's no way to tell based on the pic alone. You shot at point blank therefore the arrow is still yawing and penetration isn't as good that close. Arrows penetrate better at 15yds, after the arrow has straightened and is flying true. You can check you arrow's optimum penetration distance in a target, usually from 12 to 15 yds.
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Post by Buckfever on Mar 16, 2006 20:41:26 GMT -5
"You can check you arrow's optimum penetration distance in a target"
nc, what kind of target medium would you suggest?
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Post by ncboman on Mar 16, 2006 22:15:35 GMT -5
an unshot area of a block type target works well. My arrows penetrate the block target a little deeper than a McKenzie so small differences are more readily seen but a McKenzie works also. As long as the target medium is relatively consistant and stops the arrows, you can judge what's what by shooting 3 arrows, each one a little apart from the previous and recording measurements of depth. I wouldn't want my arrows to penetrate to the fletchings regardless because I like my feathers and don't like damaging them. Also to be fair, each arrow shaft should be wiped with lube before the shot. Corn oil or any kind of cooking oil works well. New ACCs have a finish on them that makes them out penetrate most other shafts so keep that in mind. Usually the lube treatment puts arrow finishes on more even ground. When it's all said and done, the only thing that changes is your knowledge. You'll likely still screw on your favorite head and hunt with it. ;D Precision archery is good but I actually killed far more deer when I was shooting aluminum gamegetters and didn't know or care much about the finer details of tinkering.
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Post by Buckfever on Mar 16, 2006 23:34:55 GMT -5
"You'll likely still screw on your favorite head and hunt with it." No doubt I'm hunting with that little 4 blade mechanical. I think the only question is which shaft and whether I'll add weight to the insert. I'll run the test tomorrow in the 3-d target and the Yellow Jacket, with the 3-71 and the 7595, with both an 85 and a 100 grain point.
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Post by ncboman on Mar 17, 2006 0:16:24 GMT -5
;D 125gr thunderhead on 29 1/2" goldtip 75/95.
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