VLDs, throat angle and accuracy?

[constructor]

Lets hear some opinions on WHY VLDs shoot better in the lands and WHY the angle of the lands make a difference with secant type ogives like the Vmax and VLD type ogives Vs tangent type ogives.

 

[ballistic64]

VLDs shooting better jammed is dependent on the individual gun.There was a write up in the Sept. and Oct. 2006 Precision Shooting by J. Boatright on the angle of the leade for secant ogive VLDs titled "The Well Guided Bullet",which was a very interesting read.I asked E. Stecker as to his thoughts on the subject of leade angle for the VLDs and in his observations he stated he has seen as many winning guns with 1.5 leads as other guns with 3 or 4+ degree leades using VLDs.IMO,I'd just prefer to match the leade angle to the ogive,just because.

 

[WayneShaw]

Go to Dan Lilja's website, he has an article which addresses this very subject.

 

[ballistic64]

Donovan, here is the link to the article Wayne posted:

http://www.riflebarrels.com/articles/bullets_ballastics/throat_angles.htm

There is a throat angle calculator on the page but doesnt appear to be working.I believe Mr Boatright included the procedure to figure the leade angle in his article.I'll look tonight,if the formula is in it,I'll try and get an email of it to you.
There is one 6mm 15-cal secant ogive listed in a table at a 2.77 angle on Dan's website,but I have to believe it would be dependent on the various manufactures bullets,as the dimensions of the bullet forward of the ogive would impact the matching of the leade angle.I also have to believe that matching ogive to leade,if in fact it is benificial,would be best for a rifle with long barrel life,as with anything else the angle is inevitably going to change with erosion.

 

[constructor]

Spit it out Donovan I know you have something.

So in a rifle that will more than likely use secant type ogives like a benchrest or varmint rifle should we go 3 degrees or split the diff between 1.5 and 3.
It seems most shooters use a standard tangent type ogive bullet and I have always used reamers with a 1.5 degree throat.
Now with a lot of Varmint shooters using the Vmax I am thinking about trying a reamer with a slightly shorter leade and a 2.25- 3 degree angle.
I've read the articles but just wanted to hear some honest opinions.

 

[expiper]

case mouth-jam bullet length of mark
Krieger 6mm-8 twist .120 85-HPBT .080"
3000 rds...237" bore .120 105-VLD .060"

Krieger 6mm-8-twist .100 85-HPBT .080" -.060"wide
300 rds...237"bore .100 105-VLD .060"

Shilen 6mm-14-twist .120" 85-HPBT .060"-.045"wide
300 rds....237"bore .120" 105-VLD .045"

Here are the bullet engraving marks in three of my bbls....as you can see the new one with 1.5* per side leade leaves the same mark as a bbl with 3000 rounds thru it.....it doesnt matter what you make it initially ...it will wear to ~~around~~ 1.5* whether U like it or not.....or at least that is what I have found to be true since I started fiddlin with these things,,no matter what the brand or # of groves,,,etc,,etc,,...Roger

 

[Bob3700]

Lets hear some opinions on WHY VLDs shoot better in the lands and WHY the angle of the lands make a difference with secant type ogives like the Vmax and VLD type ogives Vs tangent type ogives.

Why VLD type bullets shoot well when seated into the lands: If you measure those bullets along their main bearing surface and then along their ogive, you will see that the nose of the bullet has a lot of length variation in it. So if you were to seat the bullet .020" off the lands the variation in the dimensions of the bullet's nose would throw that figure off considerably.

So, with a bullet that has variations in their nose dimentsions, you eliminate it by seating the bullet into the lands. The variation in dimension problem is not solved, you just worked around it to get consistent results.

RGDS

Bob

 

[dreever]

I think you'll find the freebore of a barrel is going to be way more important than throat angle. Most reamer manufactures spec a 1.5 degree lead. VLD's don't necessarilly need a long freebore. Case in point the Berger 6mm 95 grain VLD which has a short bearing surface. To use this bullet and still have enough bullet in the case neck a max freebore of .060 is about it to get you into the lands. A .040 or .050 would probably be even better.
99% of the time VLD's like being in the lands, it's the nature of the beast so pick your reamers freebore in regard to what bullet you plan to use at your desired seating depth.
I agree with Roger, after a number of rounds what ever leade you start with will eventually wear into a 1.5 degree.
One more point if you jam a bullet into a 3-4 degree leade you better plan on firing the round since extraction of the loaded round will be pretty much impossible without dumping a case full of powder in your action.
Contact Dave Kiff at Pacific Tool he'll give you the straight skinny on everything that has to do with reamers.

Danny

 

[constructor]

Dave already makes all of my reamers. I just like to hear a few opinions.
Most of the reamers and even the chambers I did not cut had 1.5 degree throats but, I have never had much luck with the VMax and in general bullets with sharp secant type ogives. For the last 25 years or more I have mostly shot Sierra match and Nosler hunting bullets. With the Lapuas and Bergers that are out now I thought I may try a different throat angle and spend a little more time tuning the load and thats why the post. I can try a new reamer and if it doesn't work I know Dave can change it in a minute.
I have read the article on Lija's site and others in P.S. and elsewhere and that was 4 opinions, now I have 5-6 more.
Thanks to everyone.

To expand a little what do you think about a wider land in a 3 groove VS my typical 4 groove Krieger? Lilja said his original idea was that a wider land may slow erosion.

 

[expiper]

...you know ...i kinda missed the original ??/...imagine that...I dont think VLD's like to be jammed or closer to the lands than anything else...just about every bullet in every cal. that I have ever used ..."likes to be jammed or touching the lands!!!"...not just VLD's....however I do think the short bearing surface on some of the long bullets --regardless of cal...--are somewhat stabilized or pioloted,sp-haha) ...by the cylindrical freebore area in "some" chambers...
and to your inquiry about 3 groove vs. 4 or more...I think there are more important things to bbl. wear ...such as heat treat..cut vs. button ...and metalurgical properties of the metal...there are some manufactures that produce a bbl that shoots good for a cupla hundred rounds ...then "poof",,,I have been involved with just about all of em...since you asked.. Krieger and Hart last longer and usually give more accuracy for "ME"..your mileage may vary,,Roger

 

[constructor]

With the interest I have,shooting at unknown distances) I am always looking for more speed and that makes it hard to stuff them in the lands especially with auto-loaders. I've been playing with a 243 AR for about 6 mths shooting the 95gr SMKs accuracy was OK but I just finished a 29" Krieger 8.5 twist .243 on a Stiller and started seating the 95s in the lands.
To say there was a difference would be an understatement.
How long the throat will last at 3250fps I don't know but, I don't think it will be long before I will know. LOL
I think I have experienced that evaporating stainless you speak of. Have you ever shot a Lothar LW50 SS?
The Bergers came in last night, I hope they shoot as well as the Sierras.
thanks again

 

[Shotist]

My experience has been that on my 6mm/6.5mm/7mm/30cal barrels with 1.5 degree leade, the VLD's,Cauteruccio, Berger, JLK with Sierra or J4 jackets) would give very good accuracy using a .025" jump. It was set there initially and the throat was followed until the barrel finally gave up. With the 1.5 degree leade angle, seating depth was not the primary factor to ultimate accuracy as long as the bullet did in fact jump,as opposed to being buried into the lands)! I'd set the seating depth at .025" and worry more about case prep, neck tension consistencies, uniformity of ignition, etc.

 

[GerryM]

After all of the calculations and formulas
Dan lilja had a final statement at the end
1.5 degrees is usually the correct angle.
,the happy medium}