position of meplat pin hole in bullet holes

[alinwa]

I'm callin' BS on this!!!!

BTW, the FB bullets weren't great because I made them - it's simply a GREAT design. RG

Yeahh they were.....

It takes more than good jackets to make great bullets..... RANDY MAKES GREAT BULLETS!!

 

[goodi]

One, of a number of examples of IBS 1000yd HG groups shot by Townsville's, Jeff Rogers ( aJR) with Mr Robinett's BIB flat base projectiles.

the black marks on some holes, are from the scorers felt pen and for other holes, the petals have not been positioned or flattened for the photo.

Notice, the centrality of the pin hole locations.

 

[johara1]

Dave you just may be on to something, I think you need need to get in touch with BIB and order some 108 flat base.... jim

 

[dcali]

Been there, done that, got the T-shirt. Such bullets (FB) were used, by a hand-full of individuals, to win/place//show, & set records in 1K bench-rest competition - at a rate greatly disproportionate relative to their opportunity (usage). Still, wasn't/isn't a FB going backwards? Despite their record, people just wouldn't buy them . . then, the grim reaper knocked on the door, jackets became unobtainium, and time marched on.

I have long been called an idiot for my belief - based upon empirical results - that regardless of FB/BT, the heel should be sharp - as sharp as possible. That said, most of the ball-tailed [contemporary BT] bullets seem to work well enough. Brian's books expose a good deal of myth and mystery - great works especially in conjunction with the works of Robert McCoy and William C. Davis Jr., great works.

BTW, the FB bullets weren't great because I made them - it's simply a GREAT design. At known distance, BC is highly over-rated - I'd bet that only the upper tier of the ultra elite could observe a 0.070 difference in BC - maybe.

Imagine how quickly an engineer would get demoted, or, canned, for proposing the addition a FB bullet to the long-range line-up! Perhaps Dave Tooley, or some of the other instagators/users will chime in. aJR, from Down-under could offer some useful dope. RG

I just discovered some research that indicates that a flat base is actually superior to a *very* short boattail when it comes to drag. Still inferior to a typical boat tail, but food for thought.

I also found a paper that tested boattail configurations as it pertains to yaw limit cycle, which shows that a sharp cornered base tends to reduce this effect. If only the jackets didn't have to bend at the corner...

 

[DaveTooley]

Been there, done that, got the T-shirt. Such bullets (FB) were used, by a hand-full of individuals, to win/place//show, & set records in 1K bench-rest competition - at a rate greatly disproportionate relative to their opportunity (usage). Still, wasn't/isn't a FB going backwards? Despite their record, people just wouldn't buy them . . then, the grim reaper knocked on the door, jackets became unobtainium, and time marched on.

I have long been called an idiot for my belief - based upon empirical results - that regardless of FB/BT, the heel should be sharp - as sharp as possible. That said, most of the ball-tailed [contemporary BT] bullets seem to work well enough. Brian's books expose a good deal of myth and mystery - great works especially in conjunction with the works of Robert McCoy and William C. Davis Jr., great works.

BTW, the FB bullets weren't great because I made them - it's simply a GREAT design. At known distance, BC is highly over-rated - I'd bet that only the upper tier of the ultra elite could observe a 0.070 difference in BC - maybe.

Imagine how quickly an engineer would get demoted, or, canned, for proposing the addition a FB bullet to the long-range line-up! Perhaps Dave Tooley, or some of the other instagators/users will chime in. aJR, from Down-under could offer some useful dope. RG

Randy
You calling me a problem? It was good times. Damn it was fun.
This is repeating past conversations. I say this over and over. You need enough speed and enough BC to get the job done. But you need accuracy first. As we, the IBS, crowd caught up with Williamsport it became very clear we needed the most accurate bullet that could be made. Coming from the short range game and having made umteen thousands of bullets I knew we needed a custom, well designed bullet. I got laughed at for even suggesting a FB bullet. Joel P. had the biggest laugh but was laughing more when years later he set a new small group record with these bullets. Back then I didn't know what I didn't know but years of shooting and experimenting yielded a few clues. It easier to make a good FB bullet. You reach a point of diminishing returns. Going to extremes yields difficult, sometimes complex problems to solve.
My friend Charles E. listened and I guess he pushed over the first domino and called you. The rest is history. I never had a barrel that didn't love that bullet. I can't tell you how many times I had a new barrel on, not a round through the barrel, and went to a match. I would always be in the hunt.
I still have a few blue boxes stashed away.

 

[RGRobinett]

Randy
You calling me a problem? It was good times. Damn it was fun.
This is repeating past conversations. I say this over and over. You need enough speed and enough BC to get the job done. But you need accuracy first. As we, the IBS, crowd caught up with Williamsport it became very clear we needed the most accurate bullet that could be made. Coming from the short range game and having made umteen thousands of bullets I knew we needed a custom, well designed bullet. I got laughed at for even suggesting a FB bullet. Joel P. had the biggest laugh but was laughing more when years later he set a new small group record with these bullets. Back then I didn't know what I didn't know but years of shooting and experimenting yielded a few clues. It easier to make a good FB bullet. You reach a point of diminishing returns. Going to extremes yields difficult, sometimes complex problems to solve.
My friend Charles E. listened and I guess he pushed over the first domino and called you. The rest is history. I never had a barrel that didn't love that bullet. I can't tell you how many times I had a new barrel on, not a round through the barrel, and went to a match. I would always be in the hunt.
I still have a few blue boxes stashed away.

Dave, you - a problem ? NO way! Remarkably, to this day people do not want to hear your words (bold italics above): it's all about uniformity - reliable, repeatable uniformity. I do not recall the exact time-frame, but a member of the AMU, who, for his personal use, had purchased some, took his hand-loads to his units White Sands, NM test session: they ran some through BIG [real] Doplar ( they were looking for, "the best bullet"), and recorded the most uniform BC of any projectile tested up to that date! Oh, and also, for those which survived the 1:10" twist (90%) the best precision. Hoy, "that'll never work!" Never comprehended why they didn't begin making their own FB bullets!??!

Every bullet survived through the 700Yd. targets, but after that distance, 10% didn't make it to 1100, disappearing between there and 900 Yd. No failures were ever reported via 1:11" twist, or, slower - of course, 1:12" to 1:13" was the optimal range (Sg 1.4+ to 1.5+ a little). . . and the primary users were running well north of 3250 FPS. Yep, those were interesting times.

I always wonder what was wrong with the most uniform BC they had ever measured - FB is a truly elegant simple design. Again, can you imagine one's job rating if he were to bring up such a prehistoric concept! Thank you for responding! RG

 

[DaveTooley]

I shot them in barrels from a 10 twist to a 14. Velocity between 3050 and 3150. Never had a problem.

 

[Coyotefurharvester]

I do not consider the off center bullet holes unusual at all. The longer the shot, the greater the impact angle into the vertical target.

 

[Laurie]

I do not consider the off center bullet holes unusual at all. The longer the shot, the greater the impact angle into the vertical target.

.......... but then they would all be in the same off-centre place - tending towards the bottom of the shot-hole for a long-range strike - whereas all the evidence is of a considerable dispersion around shot holes.

 

[dcali]

I do not consider the off center bullet holes unusual at all. The longer the shot, the greater the impact angle into the vertical target.

It's not the impact angle. There's a subtle difference between a bullet flying with zero yaw at an angle to the target, and one flying with a small yaw, but (more or less) perpendicular to the target. Int he first case, the point is still in the center, but the hole becomes (slightly) oblong in the vertical direction. In the second, the point is off center, and the hole becomes oblong (slightly) in a random direction (but aligned with the point's direction). In both cases, the ovalness (is that word) is very small, so they still look round, at least at normal ranges.

 

[goodi]

It's not the impact angle. There's a subtle difference between a bullet flying with zero yaw at an angle to the target, and one flying with a small yaw, but (more or less) perpendicular to the target. Int he first case, the point is still in the center, but the hole becomes (slightly) oblong in the vertical direction. In the second, the point is off center, and the hole becomes oblong (slightly) in a random direction (but aligned with the point's direction). In both cases, the ovalness (is that word) is very small, so they still look round, at least at normal ranges.

Expanding and surmising on the comment by damoncali, if it is accepted that many vld’s are not demonstrating zero yaw, then consider the following.

As an example

for a 6mm projectile producing .030” pin hole displacement from the centre (a conservative allowance), the maximum cross sectional area of the ovality of flight would be approximately -

area of a round .243 hole + (.030x.243) = .046376976 + .00729 sq inches. = .0536669976 sq inches

however if it is accepted that the nose of the projectile is oscillating from the centre position (zero yaw) to a .030” displacement, then the average cross sectional ovality during flight would be :-

.046376976 + (.015x .243) = .046376976 + .003645 = .050021976 sq inches

Now, providing the correct procedures and calculation buttons have been followed, the percentage increase of the cross sectional ovality compared to the projectiles cross sectional area during zero yaw would be:-

.050021976/.046376976 = 1.078595034 =approximately an increase of 8 percent.

Throughout this discussion, the existing extremely high accuracy standards being achieved by modern designed/manufactured vld projectiles has never been questioned.

However if it is feasible for the vld projectiles in question to achieve zero yaw in flight (a possible 8 percent yaw and or drag reduction ??), is it unreasonable to consider what a related reduction in trajectory, time of flight, wind drift, drag etc would have on achievable accuracy standards?

 

[goodi]

Just wondering if in the time since this original discussion, if anyone has done any further experimentation or can provide factual and or relevant information explaining the cause of the projectile meplat target imprint offsets and or the effect this phenomenon might have in terms of inhibiting improvements in accuracy standards ?