BT65 in.177 is a real jaw dropper

[Mod90]

Just got done setting Big Sexy up for the coming hunting season that's due to open in a little over 2 weeks, & so far I must admit I'm pleasantly shocked. As she sits now I can only get 20 useable shots out of a charge.

But at a wickedly powerful 43.65 FPE/shot  .

And since I don't plan on leaving the forest with any more than 1-2 animals at the end of any outing, that low count is just fine for me. Color me tickled 

[blackdiesel]

Just curious but why get such a powerful 177 cal?  Obviously it will be shooting far too hot, even the AT44 short is too hot for 177 cal without detuning.  Not being negative just want to hear your thought process in choosing this caliber of BT65?

[Jr_Explorer]

But at a wickedly powerful 43.65 FPE/shot  .

I don't know what pellets you are shooting but with JSB's you'd be pushing that pellet WAY supersonic at about 1300-1400 fps.  it is highly unlikely you'll have any kind of accuracy with those speeds as the pellets will be very unstable. 

Blackdiesel's question is a good one.  In fact I didn't even know they made the BT65 in .177.  That's like putting a 3,000 hp top fuel dragster motor in a Mini Cooper.

[Mod90]

Well all we get here are .177 guns. The BT is my hunting rig, & we take some sizeable critters here with our overpowered .177 guns.
As to the pellet, I was using the 15 grain H&N Sniper Magnum pellet moving at 1145 fps. So far as I can tell it's a very accurate pellet out of this gun, stacking pellets at 20 yards at this velocity. I will be using it set at this power level when the hunting season opens up here in 2 weeks to take caimans, peccary, paca, agouti iguana, armadillo & if possible, brocket deer at 50 yards or less.

I will be doing some testing later today to see how well they perform over distance. Once I can hit a 1" target consistently from 20 to 50 yards with it set like this I'll be happy. The way it was before I was getting 36 fpe for 40 shots, & it was proven to be literally a tack driving hammer. I could use it to drill the head of a thumbtack from anywhere between 10 to 60 yards.

[robertr]

 I am a bit of a speed freak as long as I still have my accuracy, I am shooting 7.9 gr hp's at 1009 fps right now and are accurate up to 30 yards so far. I have to try farther out to see if accuracy holds.

[Jr_Explorer]

Well all we get here are .177 guns.

You poor creature!  Where is "here" that you are so oppressed?!?

[Ribbonstone]

Do run two airguns at over 1000fps (but try to stay under 1030fps).  One is a .177 (but I kind of limit myself to 13.4gr. JSB’s @ 1010fps) and the other is a 5mm (14.3gr. limited to about 1030fps.)

Odd stuff seems to happen at 4 digit speeds. Really-really odd stuff seems to happen when passing though the speed of sound.

What seems to help with long range shooting is to START from a pretty wind sheltered  hide.  If the pellets can make 15-20 yards pretty well sheltered from the wind, they seem to shoot pretty well out at distance.

Looking it over, seems that if I start from a spot that shelters the pellet from the wind for 12-15 yards or so, it would have dropped to 950-970fps or so, which might be one of the reasons I get away with 80yard shooting with these too-fast pellets.  Seems I have a good bit of trouble out in the open, wind playing with the pellet right at the muzzle, compared to that kind of sheltered start.

SO I usually play along side of a building, hedge row, under the shelter of big oak trees, etc. and shoot across open ground after a pretty wind resistant start.

May just be imagination, or that I’m in a well hidden spot to shoot from (so likely a well set up steady rest), but it seems to work for me with those two “4 digit rifles”.

[Mod90]

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Well all we get here are .177 guns.

You poor creature!  Where is "here" that you are so oppressed?!?

good ole backward Trinidad & Tobago. I'm just glad we're not limited by power too.

Ribbonstone I have a theory about shooting pellets over 1100 fps. Now its been my observation that when i dont shoot diabolo  pellets faster than 1050 fps my shots dont lose any accuracy and we all know thats to be expected.

But I have noticed that although diabolo pellets do lose accuracy when being shot at high speeds over 1050 fps over long distances I've also noticed that when shooting heavier cylindrical pellets such as the jsb monster & h&n sniper pellets at speeds above 1050 they tend to retain their accuracy.. . And i think it may have something to do with one of the specs our guns here must have as well as the shape of the pellet thats shot out of the bore.

[StevenG]

Do you have to shoot pellets or could you shoot .177 cast slugs?

[Mod90]

I have no idea where supplies or how to go about making  .177 cast slugs.
Besides, heavy .177  pellets are cheap enough to make the time and financial costs of casting ammo less than attractive. .177 pellet weights on the market today span from 5 grains all the way up to 21 grains, so theres more than enough variety in shape and weight readily available.

But to answer the question no I'm not restricted to pellets.

[Rdsail]

To me it is a waste of sit shooting over 950 fps .  Efficcieny goes to *(&^. Also 20 yards with a pcp is no accuracy test. I would expect an average pcp to stack them at that distance. The real rest is shooting 40-50 and up.
 
The other thing too look at is that pellets loose speed significantly faster the closer you get to he speed of sound. Hence undoing the speed gains as distance increases.

The other thing is to see how the wind is going to affect the poi with distance specially with a 177 with low bc.

[pllagunos]

To me it is a waste of sit shooting over 950 fps .  Efficcieny goes to *(&^. Also 20 yards with a pcp is no accuracy test. I would expect an average pcp to stack them at that distance. The real rest is shooting 40-50 and up.
 
The other thing too look at is that pellets loose speed significantly faster the closer you get to he speed of sound. Hence undoing the speed gains as distance increases.

The other thing is to see how the wind is going to affect the poi with distance specially with a 177 with low bc.

If you are using a pcp for hunting it doesn't matter if it stacks pellets in the same hole, if it groups under your kill zone (which mine is 1.5") you can take the shoot and be certain you won't miss if you do your part, and you will have more know down power. But IMO it's better to have less power and more accuracy for longer ranges, if I had a .177 it would be set up for 900 fps.

[Mod90]

For the purpose that i am setting this gun efficiency isnt a concern. Like I stated previously, I dont plan on taking more than 2 animals at the most from an outing. So afaic 20 shots is a lot for my intended application.
And also as stated before, I still intend to test the accuracy of this particular pellet at this speed at various ranges out to a maximum of 50 yards & no further. I will not test further simply because i have no intention of taking a shot at an animal past that distance.
With regard to the low BC,  from my previous tests this pellet has a particularly high BC for its caliber of approximately .035 iirc. That said, my max range is still going to be just 50 yards so the benefits or shortfalls of that BC wont be that important unless i take shots past 50 yards, which again I will not be doing. With that BC and that velocity, atm the gun will generate almost 44fpe and by the time the pellet reaches its intended target 50 yards away it still has over 26fpe at poi while still moving at roughly 890 fps.

[sawtoothscream]

enjoy it, would love to see some vids

[Rdsail]

I have found a correlation between efficiency and accuracy. My rifles and also others I have worked on are most accurate around the optimum efficiency or just a little higher. I have not done research on this but my theory is that the all the air wasted creates  turbulence around  the pellet once it exits the barrel reducing accuracy.

[Mod90]

Thats a very interesting theory & sounds completely plausible. But it leaves room for a question.
If thats the case then that issue of instability being caused by turbulence of excessive air moving past the projectile should be able to be countered by an air stripper with a very precise clearance in relation to the choke in the barrel. For arguments sake say maybe the choke squeezes the pellet down to 4.35 mm, then a stripper with an aperture of 4.39-4.4 may be able in negating those negative effects. Just a theory on my part here.

I'm aware that diabolo pellets because of their shape do have a stability issue when pushed at supersonic speeds that starts to show when they begin slowing down into transsonic velocities. But like I said, for some weird reason that I dont quite comprehend and havent fully researched yet I dont see this issue with cylindrical shaped pellets. Maybe its because they have less drag due to the skirt not being much bigger than the body. This is just a guess but its possible.  If thats were the case then cylindrical pellets like the JSB Monster and others would be acting a little more like bullets, while still retaining some of the characteristics of pellets.

I was hoping to take a few shots today to see whats happening with them down range, accuracy and penetration wise as well as how they hit the target. Sadly for me the weather here has decided not to cooperate, so i may not be able to do anything till weekend.

[PakProtector]

What seems to help with long range shooting is to START from a pretty wind sheltered  hide.  If the pellets can make 15-20 yards pretty well sheltered from the wind, they seem to shoot pretty well out at distance.

Looking it over, seems that if I start from a spot that shelters the pellet from the wind for 12-15 yards or so, it would have dropped to 950-970fps or so, which might be one of the reasons I get away with 80yard shooting with these too-fast pellets.  Seems I have a good bit of trouble out in the open, wind playing with the pellet right at the muzzle, compared to that kind of sheltered start.

This would of course point to the validity of the calculations( and measurements) of BC at 4-digit speeds; the BC gets very low and the pellet slows down significantly. Get it protected from the wind until it slows down( and BC comes back up) and it works well.

With a restriction of .177 I would be very interested in developing a swaging around 25 grains and run a twist fast enough to stabilize them...whereupon a new restriction would no doubt be written once it was discovered...LOL
cheers,
Douglas