What about 3d printed inserts to make your HP more aerodynamic? I think that would lead to more BC in an aerodynamic way instead of with weight. Of course you have to have enough mag room and twist probably. As far as expansion it would probably expand as much BUT the percent error of bullet weight and concentricity would probably go up (if your 3d print is good and has a good press-fit).
Quote from: BigBird on November 14, 2021, 02:52:36 PMWhat about 3d printed inserts to make your HP more aerodynamic? I think that would lead to more BC in an aerodynamic way instead of with weight. Of course you have to have enough mag room and twist probably. As far as expansion it would probably expand as much BUT the percent error of bullet weight and concentricity would probably go up (if your 3d print is good and has a good press-fit).I don't think the important factor here is weight. It seems to me that the silicone is keeping the meplat (the hollow in the nose) from folding inwards, thus all the "expansion energy" is forced outwards.As for aerodynamics, a fully enclosed, "pointy" nose is evidently NOT the ultimate shape. (To my surprise.) I recently watched a video from Matt Dubber (The S. African guy who does a lot of testing for FX) in which he says that FX did extensive testing on nose shape, and they found that a fairly wide meplat was actually more aerodynamic than a narrow one, and both were better than fully-enclosed.As counter-intuitive as that seems, I'm accepting it as a fact. And that's why I question whether this silicone trick is going to affect accuracy, in a very well-designed HP slug. Something like a Javelin, or a, FX Hybrid. I'm hoping someone here can test this.I'm looking forward to trying this with the H&N Grizzly slugs. I have been using them with great success in low-wind conditions, as they expand like crazy. (I guess we'd call them "wadcutters?" ) But the BC of then .25 is only 0.07 (IIRC) so not great in windy conditions. (Although they have done much better, in accuracy tests, than other "wadcutter" type slugs.) Maybe the silicone will help.
As far as BC goes though, I believe "traditionally" the frontal area is part of the calculation. Maybe subsonically it doesnt matter as what works for supersonic powder doesnt always work fr subsonic.
I assume filling the hollow cavity with anything would help in initial expansion. The cup expands because it fills with fluids from the target animal which are incompressible causing the projectile to mushroom. I assume silicone, wax, or anything else that will stay in place pre-filling the cavity will make it deform on impact vs having to fill with fluid first. This is all conjecture on my part.
Just make you some up using whatever filler and start shooting them and confirm whats what in you testing.You may find its all hogwash or the best thing ever... Id be sceptical of the silicone myself, But i think you can buy the plastic tips to insrrt in a hollow point to make it bilistic tipped.Pages not found... Sorry we missed the mark..Well nope you cant anymore.. g0d bless america..Now one more thing is airsoft plastic bb's.When i been as looks ng for a bag of tips i ran wvross guys using them . I guess melting and forming or whatever ..Maybe a youtube vid on it...lolI guess a giy could snip hard steel wire to set in the hollow point with a fab of wax to hold it till it hit?.... Tee hee.
At subsonic speeds, wind tunnel results suggest that medium size meplats do not have a high drag penalty unless speeds approach 1000 ft/sec when there is a large drag increase. Putting a point or rounded insert into the hollow point will not give a drag reduction unless the speeds approach 1000 ft/sec. As meplats get bigger, after a value of around 0.6, the drag will start to increase significantly. In these cases, putting something into the hollow point to give a smooth nose shape will reduce drag but at the cost of a much longer projectile and possible stability problems.The reference drag law I produced for slugs with meplats was based on the same wind tunnel information and should give an idea of how the drag will vary with speed.The results seen in videos were produced using computational fluid dynamic (CFD) programs, which can be very tricky to use unless you are fully trained and experienced in aerodynamics and know more or less what the answer should be before you start. CFD is particularly difficult to get right on blunt fore bodies, but it is very good for producing impressive, pretty flow pictures for reports or videos.
A meplat of 0.6 means that the diameter of the flat at the front of the nose is 60% of the projectile diameter. So a flat front of 3mm on a 5mm slug would be a 0.6 meplat. Pointy noses at subsonic speeds are not really any advantage over hollow point type noses or hemispherical ones. As speeds increase, then we see differences begin to grow. A long pointed nose really is pointless (if you will excuse the pun) for most airgun projectiles unless you are intending to go at 1100 ft/sec or higher.
Bout all you can do is invest in the making of billistic gell, make up your test rounds and shoot and prove them to yourself.Your own hands on experience trump's everybodys hearsay...
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