FOC and point of impact

Cossack · Post by **Cossack** » Fri May 01, 2009 3:41 pm

Shot two sets of arrows today from my Phoenix, Beemans (left over from my pre roll-your- own days) and the GT's I normally practice and hunt with. Both weight the same 405 grns. But the GT's, with 110 grn brass insert, have higher FOC than the stock Beemans. Despite the same weight, the Beemans hit about 3'' higher than the GTs at 20 through 50 yards. In fact they still hit about 1.5'' higher when I added 25 grns by changing their tip. (Their FOC would still be lower than the 18% for GT's). Both arrows are fletched with 2" Blazers, both have the same shaped bullet point before and after the tip change. Hmmmmm.

crazyfarmer · Post by **crazyfarmer** » Fri May 01, 2009 4:23 pm

A higher FOC will cause the arrows to nosedive quicker.. which is why your GT2's hit lower

the arrow with the lower(10-12%) FOC would fly on a flatline more so out to 40 yards compared to the 18+% FOC arrows

more than likely, the Bemans probably have a 12% FOC.. the GT2's should have a 19% FOC

its nothing new, but you proved that the more FOC you have, the more drop off you will get. However, the arrows less effected by wind and twigs

ManX · Post by **ManX** » Fri May 01, 2009 7:01 pm

I quote crazyfarmer.
If you can increase your foc more of 20% you can also use shorter vanes.
I have 25% of foc and it allows me to use 1,5'' miniblazer vanes 3° inclination with eccellent result over 60y.

less than 4'' and 1/2 from the point
Also small vanes are quieter in flight, are influence less by the wind, are lighter (+ FOC).
If I should be able to increase foc more than 30%, I will use micro blazer 1''
bye

Wishbone · Post by **Wishbone** » Fri May 01, 2009 10:15 pm

Man you guys rock !! I can learn more here in five minutes, then spending all day at Bass Pro archery shop.

Thanks for the tips.

Cossack · Post by **Cossack** » Sat May 02, 2009 8:23 am

" I can learn more here in five minutes, then spending all day at Bass Pro archery shop."

Pleeease! That's no a compliment

Nine out of ten clerks why offer to "help" me have never even SHOT a crossbow. ( I make it a habit to ask). Or if so, only in the back room. But I agree, there are some very knowledgeable folks who are very willing to help here.

DMc · Post by **DMc** » Sat May 02, 2009 9:17 am

Help me out a little bit here, guys. I'm feeling a bit dense this morning.

These are not the results I would have expected from this test. If the GTs with more FOC hit 3" lower at 20 yards and 3" lower at 50 yards, they sound to me as if they are flying the exact same arch as the lesser FOC arrows.

If they were nose diving faster, they would have hit 1" lower at 20 yards and 4" lower at 50, displaying a tighter or more reduced arch. So even though the point of impact is different, I would still have expected more of an arch change in the heavier FOC arrows.

Thus my dilemma.

Dave

vaguru · Post by **vaguru** » Sat May 02, 2009 10:05 am

I have seen this also. Now I want to know.....what is optimum FOC? Seems to me that anything over 20% heads to ground quicker in a more parabolic arc near the last yards of zero.

BUS314 · Post by **BUS314** » Sat May 02, 2009 10:47 am

you're not going to get a true result of each combination unless you do the test with individual sight settings for each------set sights with one, mark the shots, then set sights with other & repeat

awshucks · Post by **awshucks** » Sat May 02, 2009 1:32 pm

These are not the results I would have expected from this test. If the GTs with more FOC hit 3" lower at 20 yards and 3" lower at 50 yards, they sound to me as if they are flying the exact same arch as the lesser FOC arrows.

If they were nose diving faster, they would have hit 1" lower at 20 yards and 4" lower at 50, displaying a tighter or more reduced arch. So even though the point of impact is different, I would still have expected more of an arch change in the heavier FOC arrows.

I noticed that also. My best guess is the higher FOC doesn't really show up in trajectory diffs at hunting ranges.

I benched two good arrows once at 30 yds, one w/ 100 gr point, the other w/ a 125. Both shafts were touching, I'd of bet there would have been more diff than that.