pc screenshot So what do you think? This is a 290 Barnes TEZ with .020" per side removed. About 3.5 gr. reduction in weight. This could be taken deeper and/or longer? It could have an angled step from the minor to major diameter? Or maybe I'm peeing in the wind? Maybe a better route is to trim the base straight across? Part of my thinking here is elimination of the rounded bevel for quicker/better obturation? Who knows? I turned six of them and will see what happens next Tuesday. Don't know if I will use a wad or not?
But not rebated. I thought that maybe the 90* angle where the bullet actually touches the lands might cause a better seal/obturation along with maybe a little less drag? Its just something to play with - stuff like this occurs when you have a lathe
Post by bestill458 on Sept 4, 2015 21:21:02 GMT -5
I understand completely. The lead / paper patch shooters use a cup base to initiate swell. I hope your testing works out. The Barnes tez is a true deer killer im unable to get any accuracy sabotless with my low pressure blackhorn loads without annealing them and still marginal .
Since there is not much going on right now I thought I would expand a little on the design.........just food for thought? When you put a boat tail on like the TMZ, the taper starts right at the full diameter and then tapers to a smaller flat diameter. My thoughts here are: When the pressure rises, some is pressing against this "smaller" base while the rest is being somewhat diverted along the angle to the side of the bullet.........In other words not all the pressure is being exerted on the base of the bullet........which I think is what we need to get the bullet obturate? By having the angle cut 90* in and leaving the sides of the "boat tail" perpendicular to the bullet, all the force is being exerted on the base.............whether the smaller diameter or the ledge that was cut 90*. I guess you might give up some BC because of no taper (aero-dynamically) but might still be better than a straight flat base?...........Thoughts? I am no engineer but just my way of thinking! This boat tail could easily be made longer also and cut deeper too? In any event, all pressures would be directed directly at the entire base.
I see your point,but I'm on the thought train of an inverted cone shape cut into the base so pressure would act like a wedge to swell the base open...either that or as Bestill mentioned a cup or radius cut base....
Alan, it could work but doing it on a standard type lathe gets a little more complicated. With CNC equipment its probably a no brainer. I will see what type of results I get tomorrow? If it looks promising, I may make the cut longer and deeper and see what happens? Doing the "concave thing" just gets a little more tricky and without a precision collet chuck, repeatability becomes a problem.
I guess you might give up some BC because of no taper (aero-dynamically) but might still be better than a straight flat base?
A boattail may not reduce drag much based on angle (why Nosler BT suck for LR even though they look sexy) and I'm not sure what the angle on the Barnes is. A rebated boattail with a step over .015" can interrupt flow but on a large diameter bullet that step is comparatively small yet about the smallest that can be made with a swage die. It is easier to swage (rather it is easier to make that die) a rebated boattail than a standard boattail and that is why you tend to see them on custom bullets.