Guns & Ammo, Van Zwoll, Grey Bull

[BIG MO]

Van Zwoll teamed up with Grey Bull and laid down a pretty good long range hunting article in the current Guns and Ammo. One paragraph addressed "precession" and the bullet "going to sleep" over distance. I have heard differing viewpoints on this subject, but what Van Zwoll describes has mirrored what I have experienced at the range with long, heavy for caliber, VLD bullets.

"Precession, or the rotation of a bullet's nose about its axis, increases drag but is generally greater near the muzzle than down range, when the bullet's spin overcomes the physical flaws that cause precession. Like a top that "goes to sleep" as it recovers from the force that spun it, a bullet can become more stable as it travels, shedding drag and actually shooting tighter groups (in minutes of angle) at long range than it does up close. Thats why a rifle that prints one-inch groups at 100 yards may give you two-inch groups at 300, even 400 yards."

I've seen more than one rifle struggle to get sub-moa at 100yds with max load, heavy, long for caliber vld bullets but then impressively print sub moa groups at 1000yds.

Good food for thought when developing a long range hunting load with these VLD bullets.

 

[liltank]

Yeah, I have been told that several times. I guess it is one of those things that you have to get the ".5MOA at 100yrds" theory a break. I have tried to start shooting reloads at longer distances to get a more accurate read of what the bullet is doing. Thanks Mo!

Tank

 

[Chas1]

Do you think this theory only applies to VLDs or to similar non-VLD bullets? If not why do you suppose only VLDs?

 

[jmden]

Interesting those two would team up. I've read a number of Van Zwoll articles over the years in 'Bugle' and have come away with a fairly strong feeling that he's not fond of the idea of long range hunting. I'd like to read that article.

 

[jmden]

Do you think this theory only applies to VLDs or to similar non-VLD bullets? If not why do you suppose only VLDs?

In general, I believe the theory goes that is is more of an issue for long for caliber bullets. Some good discussion on this in Bryan Litz's book.

 

[BIG MO]

Based on my limited experience I feel its the long heavy for caliber bullets that may take more time to "go to sleep". Particularly the Berger VLD'S. Some of the rifles I've had experience with would put together sub .5 groups @ 100yds with regular mid weight boat tails but with the heaviest available bullet for that caliber it took a bunch of load development and range time to get that same rifle to squeek under 1 moa @ 100. But it would hold .7 moa @ 1000.

Twist rates are probably a factor in all this also. A twist rate too fast or too slow would surely have some effect.

 

[BIG MO]

Its good the long range hunting segment is getting some main stream attention by a main stream writer like Van Zwoll. It doesn't surprise me too much, Van Zwoll is a rifleman, he prides himself on marksmanship in the field, appreciates an accurate rifle, and lives to hunt big game.

Kudos to the guys at GreyBull, based on the article, they made Van Swoll a believer. Looks like they had him on the range ringing steel at 800yds and in the field dropping mule deer with 180 7mm Bergers.

 

[liltank]

It stands to reason that flat base bullets are accurate to say 600yrds. I was at the range one day and an old fella there gave me an education on bullets. He said in WWI that the U.S. was not having any luck at hitting targets at extended ranges and wondering how the Germans could accomplish this. They eventually discovered the "Panzer Foutz" or "Boat Tail." The U.S. learned through German engineering that they could get a better exhibit of fire control on indirect fire with machine guns when the transition was made.

Through this, it was discovered that a flat base bullet will pretty much stabilize directly from the bore. As we all know, the boat tail takes a little time to stabilize. This is only a theory so take it for what it is worth. Through discussion and shooting we have both the "Secant" (VLD) and Tangent (SMK) ogive. I am only going to assume that we see a great deal of distance needed with a "Secant" ogive because there is less resistance due to its design. Because of this less resistance it requires more flight time to straighten its trajectory out.

With the "Tangent" ogive there is a little more resistance in the nose design causing it to straighten out quicker. Hence the reason that they destabilize through the transonic period where the "Secant" ogive allows for an easier transition. Again let me stress, this is based on discussion and theory. SMK's in my experience will give a one hole or bug hole group at closer distances for this very reason described above. So will the Flat Base, but the VLD may exhibit a need to go longer. That is probably why you see a lot of hunters using two different bullets in the field. One for long shots (VLD of some type) and one for short range (Flat base, or shorter boat tail).

Tank

 

[johnnyk]

Wow, Jeremy, I was impressed after reading that. It sounds plausible. I have always had a hard time getting the secant ogive(s) to stabilize. I didn't know why they seemed to be "not as accurate", they just were. I never thought about less wind resistance being the culprit.
It somewhat goes along with reloads that have moly coated and lubricated bullets as opposed to the same "naked" bullet. For instance; the 150gn Ballistic Silver Tips that I have tried in the past, with a known good load, have never flown the same as the 150gn Ballistic Tip and the powder charge had to be tweaked. I assumed this was because of less barrel and wind resistance.
I have never done load development at extended ranges because if I couldn't get it to shoot under 1/2" at 100yds I sure as heck wasn't going to waste more powder on it, and walk more! These bullets, by the way, have usually been Hornady bullets and in one instance, Bergers. I always thought it was because of the missle design (secant) and tried to stay away from them, as in not buy them. Sometimes I can't help it and talk myself into buying them because I just know "this one" will be the exception. My favorite bullets are Noslers and Sierra's which have tangent ogives and usually exhibit great accuracy at 100yds and as far as I need them to. Thanks for that tidbit. JohnnyK.

 

[Chas1]

While I knew Secant and Tangent Ogive bullets were different, I didn't know what caused them to be different. In an attempt to understand this I came across this by Dan Lilja which explained it in a manner I thought was easy to understand. I thought it might be helpful to possibly someone else coming across this post that wanted to know what makes them different.

Bullet Design–Secant vs. Tangent Ogive AccurateShooter.com Bulletin