'Freechex' range report.

[Bass Ackward]

Larry,

How fast it happens is immaterial. And you missed my point. Obturation takes place at the base of a bullet cause that's where the pressure is. But with a tight fitting check and one that is sized down, no obturation ever takes takes place. It simply begins resisting obturation. Big difference to balance. And is this the key to powder speeds?

What is important from that is that you can't get to stage two without having gone through stage one first. That's all. And if you are going to deplete lube from any area on a bullet, the base area shouldn't be it. Especially if you plan on pushing ahead. This was just to get folks thinking about why accuracy goes south in a gradual fashion once the sweet spot is passed. That .... and to aggravate you. It's another theory. But it is one that Veral shared with me as he said he was surprised my 154 grainer was able to reach that velocity level since it was made for low velocity work. (narrow check groove) And he is right, it's sensitive to bore fouling with a slight temperature change.

What really holds a check on a shank is the rifling indented into the lead. The taller the rifling and the tighter the base, the better the grip. Surely you aren't naive enough to believe that a little teeny little lip inside of the mouth of a check that is in line with bullet rotation is going to hold all forces and brave 2000 MPH winds making all the difference? That's why you don't see much difference in brands. But that lip could be strong enough to prevent that check from pushing forward at stage one until it does get tight since it happens so fast.

As I go up in velocity, I believe fouling fills this space and tries to remove the check. Possibly while still in the bore. And this will throw the base outta square causing tipping. And this fouling is not uniform so it causes unbalance until it is flung off. And it would so happen that the faster you go to create more fouling, that the more you would collect. Which is exactly why lube or the type of lube makes a difference to accuracy.

That's why I like tight fitting checks and reasonable groove width. Too wide and you weaken the base area.

In Jeff's first picture, the helicopter check on the one bullet made me wonder how the check shape and condition would affect drag. I never thought about that in our discussions. We generally only think of the front of the bullet for ballistic coefficient while the GC is a common variable. Jeff was doing alright down low with the aluminum to the range he was using. But did a lot worse at 2400 fps than Larry's 3.77" group at the same velocity and RPM level. So something else wasn't in .... dare I say it .... check.

That's why I am thinking.

[Larry Gibson]

Bass

I understand your theory and even agree with parts of it.

In a previous post you mention Junior1942 claimed tails at 110,000 that he believed were lead, I too have seen these “tails” mostly on 6.5 cast bullets. The problem with your theory there is the GCs were Hornady and the mould is an old one. The GCs have to be seated as they are a very tight fit. I have recovered the very same bullets that gave the “tail”. The bullet was distorted from impact so I couldn’t tell if it was lead but the GC was intact and not cut or finned. I’m still not sure what causes the tail.

I guess I am “naïve” as I do believe that little bitty lip (the part crimped in) does in fact help keep the GC on. If both type GCs are loose on the shank and pressure is not sufficient to obturate the base then the Lyman will come off in flight. I have also recovered numerous Hornady GCs that were not tight on the shank before they were fired and were still loose on the shank when recovered, in other words they were held on by the crimp. If both types of GCs are tight fits on the shanks both type stay on during flight. I do believe the rifling engraving does help here as you mention.

You state; “Surely you aren't naive enough to believe that a little teeny little lip inside of the mouth of a check that is in line with bullet rotation is going to hold all forces and brave 2000 MPH winds making all the difference? “. Then you contradict yourself with; “In Jeff's first picture, the helicopter check on the one bullet made me wonder how the check shape and condition would affect drag”.

I do not believe that if Jeff’s loose fitting, non crimped on GCs were “helicoptered” by the rifling, torque or whatever, that they would have stayed on the base of the bullet and survived “2000 MPH winds” for 100 yards of flight and then proceed to cut cleanly through the target. No indeed they would have been sucked of the base of the bullet immediately outside the muzzle slicker than the scum off a Louisiana swamp.

Yes you are correct saying; “Jeff was doing alright down low with the aluminum to the range he was using. But did a lot worse at 2400 fps” but then you draw the wrong conclusion. As I stated in the earlier post of the comparison; the rifle I used is a 1 moa capable rifle with a 9X scope on it. I’m sure most here (I’ll not suggest you are naïve) understand that Jeff’s SMLE is not as accurate to begin with and thus the groups he shoots at 2400+ fps will be proportionally larger.

Jeff can very simply answer the question for us by shooting that same load only using Hornady GCs. Could you kindly do that Jeff?

Larry Gibson

[Larry Gibson]

Lefteye

Yes it is a theory. You are correct, the GCs might tear. But on the other hand they might not either. I don't think the GCs were the major cause of the inaccuracy. They may have increased the inaccuracy but the major cause for the inaccuracy is the high RPM. That cause was measured with the example provided and proffered that RPM was most likely the major cause of inaccuracy in with Jeffs load.

"As has been said, it may not be any better for the check to stay on, than it is for it to fall off, but if they fall off, they must all fall off, or it must be that none of them fall off, or else accuracy will be affected. AND if they fall off they must all fall off at the same point in their journey."

Conversely are you stating that the PPs of your moa loads are all shed at "the same point in their journey"? If so how do you know that any more than we know exactly when GCs are shed?

As to what happens to the torn GC on exit and how muzzle blast may effect that. If the base of the bullet is still square then the effect of muzzle blast is equal around the circumferance as only the sides would be torn or cut. Again I'll ask you as you are the PP garu; how does muzzle exit effect a PP that is torn/cut by the rifling to the base of the bullet and is shed shortly after exit? Wouldn't the effect on the bullets accuracy be the same on both?

Larry Gibson

[leftiye]

I thought you didn't want to argue (this is a "good" word - btw) ineffable theoretics. I didn't say I knew when the gas checks come off, I said it would be best ("they should") if they all did the same thing at the same point. What you're asking me to acertain is the very thing that - due to it's unpredictability - is the problem.

As for paper patches the ideal seems to be that they evaporate (make confetti) upon leaving the muzzle. If you make your patches right and out of the right stuff, this seems to be what happens (you can see it happen). If the patches were to hang on and flap around during flight, you can see what effect that would have. My suspicion is that paper shreds easier and with fewer side effects than aluminum does. Especially seeing how as the check covers the whole base of the boolit, the pieces of aluminum would hang on much more, and produce much more effect due to this and the metal resisting the muzzle blast more where the flaps stuck out.

Unless the check falls apart uniformly all around the base of the boolit there will be non uniform effects.

Dern Larry, Good question! I enjoyed discussing this with you!

[Larry Gibson]

See lefteye, no argument. I ask a question reference things you've stated and you answered. I'll accept your answer without further comment.

Larry Gibson

[Bass Ackward]

Larry,

Good points. But I have also recovered bullets where the check apparently became engraved into the diameter of the base of the bullet. You might say that it became part of the slug as if it were molded in there. Almost as if it came off and was reseated .... by force.

I suppose that drag is going to be affected by the nose shape. The more distortion created by the nose and velocity, the wider and farther the ....... wind tunnel or vacuum is so to speak. Meaning that in some cases, or until enough velocity is lost, wind never hits the back part with the check. Until it does.

But like with Jeff's spitzer design, that is slicing through the air with little disruption, so I would expect more air closer to the body and to the check. And as Bob mentioned, paper quality, target angle, or humidity could have been responsible for the strange cut. That's why I hope Jeff is successful in recovering some examples oneday.

Off to the range. PM to follow that later.

[Junior1942]

Larry, I'm firmly convinced that the commas I see on bullet holes in paper targets are bullet bands in process of being thrown off the bullet. All due to too high RPMs tearing apart the bullet.

[Larry Gibson]

Junior1942

I've looked at the bullet holes with such "tails" under some fairly decent magnification and the "smear" on the tail part of the hole appears the same as around the edge of the bullet hole proper. I suspect you may be correct. Perhaps we could right a murder story and CSI would solve the mystery for us

Larry Gibson

[Larry Gibson]

Bass

We are pretty much in agreement there except that shadow graphs of cast bullets in flight show shock waves coming off each driving band so there should be pressure on the front edge of the GC. Unknown with Jeff's bullet design though. Be interesting to see what results his further tests produce.

Good luck shooting, I do hope you succeed.

Larry Gibson

[quasi]

So, how are your FREE CHECS working?