Author Topic: H&N FTT .177 Ballistic coefficient? (Read 4013 times))

linoww · « **on:** April 05, 2016, 03:13:52 PM »

5.56g I can't seem to find it on their website and I'm trying to get something made up for this pellet on chairgun. For the first time a leaf free pellet actually shoots quite well in one of my guns.

OKHunter1 · « **Reply #1 on:** April 05, 2016, 03:19:14 PM »

A lot of variables, but .011 to .013 probably would get you pretty close. The Straight Shooters website in their Our Take section is a wealth of info. Their pellet comparison charts are fantastic as well.

jandrew · « **Reply #2 on:** April 05, 2016, 04:42:48 PM »

I've seen it listed as 0.015 and 0.018. I just got some FTT-green (5.56gr), but haven't had a chance to try them out at any distance to see what chairgun's BC calculator says.

rsterne · « **Reply #3 on:** April 05, 2016, 05:18:01 PM »

If you are talking about a lead-free version of the FTT, even if the shape is identical (same Form Factor), the BC will not be.... In fact, it will be less in exactly the same proportion as the weight (Sectional Density).... This is because BC = SD / FF.... The lead free is 5.56 grains, the lead version is 8.64 grains, so if the shape is identical the BC will be 36% poorer for the lead-free version....

Bob

linoww · « **Reply #4 on:** April 05, 2016, 10:59:42 PM »

Yes I understood that and that's why I'm asking because there's not very much sectional density in that darn thing. For pellets what is the form factor base?
15 years ago when I was shooting a lot of long-range cast bullets I read everything I could on ballistics and lower velocity projectiles. But that darn shuttlecock shaped pellet would seem to make things a little complicated. With the drag that the skirt adds for stability. And when I was playing that game I found it some of the bullets when analyzed ballistic coefficient did not always tracking actual shooting at paper.

linoww · « **Reply #5 on:** April 06, 2016, 01:33:48 AM »

I had very good conditions tonight so I shot it at my 25 and 50 yard range. I used the same Target just moved it from 25 to 50. The jsb exact 8.44g "control " dropped exactly what chair gun said they would @720 fps. The field Target trophies green 5.56g tracked just like a standard field Target trophy lead using chair gun data. Only one and three quarters plus drop inches at 50 yards @ 920 fps. So it appears in the ballistic coefficient seems to be very similar to the lead pellet. So using the sectional density and trying to do a percentage extrapolation of the ballistic coefficient does not appear to be accurate.

Ontarget58 · « **Reply #6 on:** April 06, 2016, 02:02:28 AM »

Check out my test of some 177 H&N pellets with Benj Trail NP in the pellet review gate. If you're interested in getting equivalent data for your lead-free pellets and don't mind sending me about 50 of them I will be happy to test them and report the results

linoww · « **Reply #7 on:** April 06, 2016, 02:05:52 AM »

I appreciate the offer but it looks like I have it figured out. It's kind of funny how the theories sometimes don't work out when you put bullet on paper . I would have thought that pellet would have dropped way more than it did . I can't quite tell but your avatar looks like a Belgian tervern.

Ontarget58 · « **Reply #8 on:** April 06, 2016, 02:12:39 AM »

Very close, he is a Belgian Sheepdog. Same dog, different color.

grimeszee · « **Reply #9 on:** April 06, 2016, 09:04:07 AM »

Quote from: linoww on April 06, 2016, 01:33:48 AM

I had very good conditions tonight so I shot it at my 25 and 50 yard range. I used the same Target just moved it from 25 to 50. The jsb exact 8.44g "control " dropped exactly what chair gun said they would @720 fps. The field Target trophies green 5.56g tracked just like a standard field Target trophy lead using chair gun data. Only one and three quarters plus drop inches at 50 yards @ 920 fps. So it appears in the ballistic coefficient seems to be very similar to the lead pellet. So using the sectional density and trying to do a percentage extrapolation of the ballistic coefficient does not appear to be accurate.

but you are also shooting the 5.56g pellet 30% faster so if they were at the same velocity there would be a bigger difference to show the lower ballistic coefficient.

linoww · « **Reply #10 on:** April 06, 2016, 11:24:36 AM »

The ballistic coefficient is the ballistic coefficient. If you plug in a ballistic coefficient number 36% less then the drop is way more than what actually is happening in the field.

grimeszee · « **Reply #11 on:** April 06, 2016, 11:36:54 AM »

According to chairgun if the velocity is the same then the drop at 50 yards would be .6 inches more for the 5.56g pellet. when you change the velocity to 920 fps the drop at 50 yards is .89" while the leaded pellet at 720 fps drop is 2.42". is that what you are seeing with your target? This was based on a 30% less BC

OKHunter1 · « **Reply #12 on:** April 06, 2016, 11:38:05 AM »

I got lost somewhere. The BC used in some charts for the Field Target Trophy (FTT) 8.64gr is .020. Subtract 36% for the Field Target Trophies green 5.56g and you get a .013BC. I am not familiar with chairgun, but in the same gun and with two pellets of differing BC's .013 Vs .20, the difference based only on the BC in drop is pretty insignificant at the ranges we shoot. JMHO. Have I missed something?

linoww · « **Reply #13 on:** April 06, 2016, 12:02:19 PM »

The field Target trophy does show .022. And if you put the Velocity in at 920 like my 5.6 grain pellet is going the data matches exactly.(I even changed the weight) If you change your ballistic coefficient .012 and it does not. If you adjust the weight of the pellet in the program it does not change in trajectory chair gun comes up with.

The difference between .012 and .022 is over an inch at 50 yards. I understand that's not a lot of trajectory but I'm questioning the theory of ballistic coefficient guessing.

grimeszee · « **Reply #14 on:** April 06, 2016, 12:07:23 PM »

The mobile version of Chairgun has the BC at .022 for the 8.5g H&N FTT

OKHunter1 · « **Reply #15 on:** April 06, 2016, 01:07:07 PM »

I would think that at the same velocity, the difference in weights and BC would give a plus 1" drop, but in comparing the two with the real world BC, weight, and Velocity, the drop would be sub 1". Lots of variables for sure. Anyway I thought this was an interesting quote. "Sporting bullets, with a calibre d ranging from 4.4 to 12.7 millimetres (0.172 to 0.50 in), have BCs in the range 0.12 to slightly over 1.00 lb/in². Those bullets with the higher BCs are the most aerodynamic, and those with low BCs are the least. Very-low-drag bullets with BCs ≥ 1.10 can be designed and produced on CNC precision lathes out of mono-metal rods, but they often have to be fired from custom made full bore rifles with special barrels." Just goes to show you how really bad the aerodynamics of a pellet are. Comparing BC >1.10 of a superior sporting bullet -vs- < .021 for a superior pellet is pretty funny when you think about it, especially in light of the lower velocities we shoot at. Rainbows for sure.

grimeszee · « **Reply #16 on:** April 06, 2016, 01:54:47 PM »

The highest BC pellet I have found and shot is the H&N Pyledriver .177 21g at .082 bc.

rsterne · « **Reply #17 on:** April 06, 2016, 08:49:54 PM »

You are correct that when you change the weight in the program, but not the BC, the predicted drop does not change.... However, your light pellet was going 200 fps faster start with.... Try that in the program (or real life) and see what happens....

Bob

linoww · « **Reply #18 on:** April 06, 2016, 10:55:28 PM »

Quote from: rsterne on April 06, 2016, 08:49:54 PM

You are correct that when you change the weight in the program, but not the BC, the predicted drop does not change.... However, your light pellet was going 200 fps faster start with.... Try that in the program (or real life) and see what happens....

Bob

The trajectory is identical in chairair gun regardless of weight.
What I am saying is in real life the trajectory matches the standard field Target trophy .022 ballistic coefficient.

I put a pellet weight of 2 grains in a pellet grade of 20 grains and with a ballistic coefficient being the same the trajectory is identical.

Maybe I'm not being clear. if I use field Target trophy data and input the velocity. the trajectory matches exactly what chair gun says. Thoughmy pellet is only 36% of the weight of the standard field Target trophy.

Bob I have tried it in real life in the program and I am reporting you exactly what happened. I'm telling you the pellet ballisticcoefficient appears to be the same

linoww · « **Reply #19 on:** April 06, 2016, 11:57:30 PM »

I just shot the same Target at 25,50 and 100.3 shots each Trajectory is reasonably close to what it should be at .022 BC.the piece of tape on top of the aiming point was the first shot before Iadjusted the point of impact down.

-1.8 drop at 50
-23.5 at 100.

The hundred-yard center of group is closr as that the pellet generally only groups about 5 inches at that distance. The three shots on target or better than normal at about 2 inches.
If I shot two more pellets who is to say where the center of the group really was.

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H&N FTT .177 Ballistic coefficient?

Author Topic: H&N FTT .177 Ballistic coefficient? (Read 4013 times))