OAL with VLD Bullets

slimjim · Posted: Fri Jan 16, 2015 10:49 pm Post subject: Re: OAL with VLD Bullets

BigBlue wrote:

Doesn't Berger list some VLD bullets being suitable for hunting and others as strictly for target use? One question I have is which means more in determining the twist rate's ability to stabilize the bullets, the length of the bullet or the length of the surface that actually bears against the rifling? We usually see it expressly based more on the weight of the bullet.

I have only used the VLDs promoted as hunting bullets. Longer projectiles typically need more twist. If projectiles are of equal length, then the lighter one needs more twist, e.g. 150 Partition vs 130 Barnes.

MacD · Posted: Sat Jan 17, 2015 7:47 am Post subject: Re: OAL with VLD Bullets

The whole subject of VLD bullets is pretty new to me and I have been learning alot these past few days. The twist rate of my CG63 is 8.66. This was supposedly optimized for a 139-140 grain bullet. The original bullet was a 140 grain BT spitzer running at 2600 FPS. According to the Berger stability calculator a VLD bullet, in this case the Hornady Match HPBT, is comfortabley stable with this twist and velocity. To get to this velocity I have to load to maximum according to Hodgdon's load data. If the velocity is dropped to 2300 then the bullet falls into the marginally stable zone. The 139 grain PRVI bullets are shorter and should remain stable at lower velocities.

In another thread I noted that the sights on this rifle are calibrated for 2,730 FPS. Elvis suggested this was for a 120 grain bullet not the original 140 grain one. It appears he is right as I was able to reference the use of a 120 grain bullet in competitions in Sweden. Unfortunately I didn't find this out before I ordered several hundred of the 139 and 140 grain bullets. Using the lighter bullet I can get the required velocity below maximum charge weights. The rifles twist is also well suited for this bullet weight

Love this hobby.

slimjim · Posted: Sat Jan 17, 2015 9:33 pm Post subject: Re: OAL with VLD Bullets

The parameter you will need to watch out for is temperature - assuming you shoot in the cold up there. I think most 6.5mm have 1:8 twist for the 140gr bullets. You may find they are stable in the summer/warmer weather and not in the winter.

These calculators are estimaters though this Berger version looks like it has a couple more bells and whistles. I have run bullets through the calculators and had bullets that were unstable print 0.5 MOA groups at long range. Then I have had bullets that were supposed to be stable go unstable. Here is another calculator to try.

www.jbmballistics.com/...ab-5.1.cgi

PaulS · Posted: Sun Jan 18, 2015 10:03 am Post subject: Re: OAL with VLD Bullets

Colder, higher pressure, and lower humidity all make the air denser. This requires more twist than warmer, lower pressure and higher humidity air which requires less twist for stability. The length of the bullet from base to tip affects twist as well. The longer the bullet the more twist is required. Not just the bearing length but the full length of the bullet. The bullets shape is also a determining factor but only in so much as it affects the center of gravity position within the bullet. As the center of gravity moves forward the bullet is more stable and as it moves rearward the bullet is less stable. The "ideal" bullet shape would be a spire pointed bullet with a very long boatail placing the center of gravity well ahead of the center of its length. Short of the ideal but nearly completely stable is the round ball. Its center of gravity is at the middle of the projectile but the center of pressure is nearly always behind the center of pressure. The round ball requires very little twist to remain stable.

Azar · Member Joined: Jan 04, 2010 Posts: 275 Location: Utah

Mac,

Another great bullet for the 6.5x55 is the Hornady 129g Interlock. You'll have no stabilization issues with a 1:8.66" twist and you should be able to safely get it between 2700-2800 fps. It's also quite accurate and stout and penetrates well for a cup-and-core bullet.

A few years back there was a discussion on favorite bullet in the .260 Rem / 6.5x55 SE on a different website. The most popular choice was the Horn 129g SP. Many people claimed that if they were to start over, they start (and stop) with the 129g Horn SP.

And I may just agree with them...

MacD · Posted: Mon Jan 19, 2015 12:58 pm Post subject: Re: OAL with VLD Bullets

Thanks Azar,

I will put some on my next order along with some 120 grain bullets. I don't plan on hunting with this rifle as it is a real brute and that 29.5 inch barrel is just too long for comfortable use in the woods.i

chambered221 · Posted: Tue Jan 20, 2015 6:38 pm Post subject: Re: OAL with VLD Bullets

Mac, how far do you plan on shooting ???

MacD · Posted: Tue Jan 20, 2015 8:52 pm Post subject: Re: OAL with VLD Bullets

I am limited to 300 meters as I can only use it at the range unless I hold a big game license. Without a scope I probably won't shoot it much past 200.

PaulS · Posted: Wed Jan 21, 2015 12:46 am Post subject: Re: OAL with VLD Bullets

You're doing good Mac! Without a scope I can't shoot at 100 yards anymore. I was forced to put a scope on my 03A3 some decades back because even with the military peep sight I couldn't see the target to shoot it. I resisted as long as I could but I had to get glasses and then a scope. Now, all my rifles have scopes except for the SKS - which I don't expect to shoot beyond 50 yards for the sake of accuracy anyway. Even my 22 rimfire has a scope on it and without it I wouldn't be able to compete in small bore silhouette.

MacD · Posted: Wed Jan 21, 2015 7:25 am Post subject: Re: OAL with VLD Bullets

bulletin.accurateshoot...-old-eyes/

Ever thought of trying one of these? I am seriously considering one as I have two rifles I do not want to scope for esthetic reasons.

Here is some additional information

www.muzzleblasts.com/a...46-5.shtml

slimjim · Posted: Wed Jan 21, 2015 7:39 am Post subject: Re: OAL with VLD Bullets

MacD, you should make a pirate patch to go with it. You would look real Bad-ass at the range! Arrrrh!

chambered221 · Posted: Wed Jan 21, 2015 6:58 pm Post subject: Re: OAL with VLD Bullets

I apologize if I've missed something but I don't understand why your considering VLD's !!!

slimjim · Posted: Wed Jan 21, 2015 7:05 pm Post subject: Re: OAL with VLD Bullets

The VLD bullets I have used have been very accurate plus I can use all the help I can get when trying to knock the X out of a target when there is any kind of wind, even at 300 yards.

MacD · Posted: Wed Jan 21, 2015 10:17 pm Post subject: Re: OAL with VLD Bullets

Actually, I have some old welding glasses that I think I might be able to make an insert with the hole to replace the dark lense for my right eye. The glasses have a clear and a dark lense in each eyepiece.

Chambered, I wanted match quality bullets and only realized after purchasing that one lot was VLD's. The others are not as long but still are touching the lands with the bullet base even with the bottom of the case neck. Since loading such long bullets is new to me I was just looking for some help from those with VLD experience.

slimjim · Posted: Wed Jan 21, 2015 10:23 pm Post subject: Re: OAL with VLD Bullets

MacD, it is not uncommon to seat bullets with their base below the case neck.