Very Short bearing surface bullets...

[6BRinNZ]

Hi,

Any tips or tricks or suggestions to get these working.
My usual box of tricks just hasn't worked and I still get flyers. It'll go from .4 moa out to 1.5 moa at 100yrds.
This is 200 grn .308 in a 9tw FTR.
LRP Brass, Fed 210 primers, ADI 2208 powder

My testing and research suggests this bullet likes a jump of ~ .030". My velocity window has ended up where others suggest as well ~2680 - 2690.
I don't need amazing precision .6 moa or less is fine - its the lack of consistency that is doing me in.

I've checked run out and it sits between 0 - .002" with most sitting at 0 - .001"

I'm thinking of trying a different primer and going down one bush size for neck tension
I think a lot of shooters have given up on the new generation .308 200s but I can't get these to shoot worthy for a cub day let alone nationals.


Any help greatly appreciated.

 

[Rsadams]

Just 2cents here but have you tried slowing them down..? Or do you need them that fast for distance..?

 

[6BRinNZ]

Just 2cents here but have you tried slowing them down..? Or do you need them that fast for distance..?

I worked up to that and that is what indicated as an area to work in. These is an indication of slower "node" low ~2630. My past experience with 200s is that it doesn't matter too much which node you choose in that a faster node can be just as precise as a slow node so long as you aren't chasing the ragged edge.
Thanks - maybe I can get more consistency with a slower node with this combination.

 

[Dusty Stevens]

I think you have too much twist

 

[6BRinNZ]

I think you have too much twist

Could be. These are a very long bullet and need faster than 1/10 to fully stabilise and make use of the bc.
The holes in paper are nice and round.

 

[dcali]

I agree that the twist is probably too fast. Part of the problem is that these new long bullets simply trade inherent precision for Ballistics, and there is not much that can be done about that. A very short bearing surface can add to the problem in that they have less ability to resist tipping in bore. Just a hunch but seating them out long and using a tight freebore may help start them straight. But that’s pure speculation.

At the end of the day, there is such a thing as too much bullet.

 

[ALppc]

I would go to a different powder. N140, Varget, H4895 are common. The Berger 20x is the official US team bullet so they will work. Most 200s work well in a 1-10 twist. Don't get stuck on a seating depth, it is a way to fine tune a powder charge. All powders are sensitive to which primer makes it a consistent load.
Al

 

[LA50SHOOTER]

I think its a matter of finding what they 'like"
This is 5 shots @ 100 yds right after break-in of a 1-11 twist 5C Broughton in 300 WSM. - There was only 0.065 bearing surface in the case neck to get them at 0.012 off the lands - And Yes that is 5 shots.
I haven't yet tried them in a .308 but I can't see why they shouldn't shoot well. - I don't know if a 9.5 twist is going to yield your best with these bullets, I don't believe they need a whole lot more than a regular 10" twist.

Just my .02

 

[6BRinNZ]

I agree that the twist is probably too fast. Part of the problem is that these new long bullets simply trade inherent precision for Ballistics, and there is not much that can be done about that. A very short bearing surface can add to the problem in that they have less ability to resist tipping in bore. Just a hunch but seating them out long and using a tight freebore may help start them straight. But that’s pure speculation.

At the end of the day, there is such a thing as too much bullet.

Thanks. I will give jamming them a go as I suspect in bore yaw as a culprit but I haven't seen or experienced anything to know what excessive in bore yaw would produce on paper and look like to draw a conclusion.
They have indicated they like jump which marries up with what others are finding.
I'm thinking I can jam them and then try using the tuner to tune the barrel in. A different approach but one of the reasons why I got a tuner (more options)
To fully stabilise a 1-9.25 twist is recommended.
For the precision requirement I'm after (.6moa or better) I would have thought that would be achievable.

@LA50SHOOTER - thanks, nice group. I have the 200.20s working very well in .308. These are the new gen high BC 200s I'm playing with.

 

[C.E.Smith043]

Hi,

Any tips or tricks or suggestions to get these working.
My usual box of tricks just hasn't worked and I still get flyers. It'll go from .4 moa out to 1.5 moa at 100yrds.
This is 200 grn .308 in a 9tw FTR.
LRP Brass, Fed 210 primers, ADI 2208 powder

My testing and research suggests this bullet likes a jump of ~ .030". My velocity window has ended up where others suggest as well ~2680 - 2690.
I don't need amazing precision .6 moa or less is fine - its the lack of consistency that is doing me in.

I've checked run out and it sits between 0 - .002" with most sitting at 0 - .001"

I'm thinking of trying a different primer and going down one bush size for neck tension
I think a lot of shooters have given up on the new generation .308 200s but I can't get these to shoot worthy for a cub day let alone nationals.


Any help greatly appreciated.

I would try Lapua brass and Fed Gold medal match printers also.

 

[Someoldguy]

I agree that the twist is probably too fast. Part of the problem is that these new long bullets simply trade inherent precision for Ballistics, and there is not much that can be done about that. A very short bearing surface can add to the problem in that they have less ability to resist tipping in bore. Just a hunch but seating them out long and using a tight freebore may help start them straight. But that’s pure speculation.

At the end of the day, there is such a thing as too much bullet.

I am still on the learning curve for such things, so please bear with me. I'm not famaliar with this particular bullet, but it seems unlikely that it would have a short bearing surface. Is it intentionally designed with a long nose for ballistics reasons?

Thanks in advance for any helpful suggestions.

 

[boltfluter]

My first thought would be to jam them to help with alignment. Looking forward to your results from the jam!

Paul

 

[dcali]

I am still on the learning curve for such things, so please bear with me. I'm not famaliar with this particular bullet, but it seems unlikely that it would have a short bearing surface. Is it intentionally designed with a long nose for ballistics reasons?

Thanks in advance for any helpful suggestions.

Yes. Given a set overall legth, sacrificing bearing surface for nose length will yield a higher BC.

 

[Ggmac]

Thanks. I will give jamming them a go as I suspect in bore yaw as a culprit but I haven't seen or experienced anything to know what excessive in bore yaw would produce on paper and look like to draw a conclusion.
They have indicated they like jump which marries up with what others are finding.
I'm thinking I can jam them and then try using the tuner to tune the barrel in. A different approach but one of the reasons why I got a tuner (more options)
To fully stabilise a 1-9.25 twist is recommended.
For the precision requirement I'm after (.6moa or better) I would have thought that would be achievable.

@LA50SHOOTER - thanks, nice group. I have the 200.20s working very well in .308. These are the new gen high BC 200s I'm playing with.

The only way I know how to determine internal yaw is to retrieve a bullet and verify land impression length . Of course catching the dang thing is the hard part as it must be as pristine as possible . A very large Poland lower velocity helps .

 

[6BRinNZ]

The only way I know how to determine internal yaw is to retrieve a bullet and verify land impression length . Of course catching the dang thing is the hard part as it must be as pristine as possible . A very large Poland lower velocity helps .

Sorry can you clarify please. With the lower velocity would you see 60+ fps as making a difference or do I need to be significantly lower again?

 

[6BRinNZ]

What are peoples thoughts on trying the Berger VLD large jump test for these bullets? I think in the early days everyone jammed VLDs but the current recommendation is to explore large jumps.

 

[LA50SHOOTER]

I always start at a Jam with a Berger VLD - I try +0.015 and +0.007
I think that its worth a try on the Hybrids as well as they have the longer profile nose and have a transitioning secant to tangent ojive.
I've had VLD in most cases shoot well jammed but not in every case.

 

[6BRinNZ]

I always start at a Jam with a Berger VLD - I try +0.015 and +0.007
I think that its worth a try on the Hybrids as well as they have the longer profile nose and have a transitioning secant to tangent ojive.
I've had VLD in most cases shoot well jammed but not in every case.

Thanks - good to know on the 2 seating depths. I don't normally bother with jam in case I have to extract on a cease fire.

 

[LA50SHOOTER]

That group in the photo was probably one of the "Luckiest" things I've had happen on loading a bullet for the first time with a "calculated" powder charge to test. - I had just finished a barrel break-in routine that I do on any new barrel and the 200.20x was in row 1 in a box of test ammo that I shot. - I was amazed that it shot as well as it did with only 0.065 bearing surface seated in the neck.

 

[Ggmac]

Sorry can you clarify please. With the lower velocity would you see 60+ fps as making a difference or do I need to be significantly lower again?

If I remember correctly , as long as your overall length and loading procedure is followed you should get a good idea . Thinking behind this is the pressure , either 20k or 55k would only alter the bullets impact to the lands a minor ( if any amount ) . We are trying to determine loading procedure and bullet tilt in the bore , so bullet loading tools and depth should be the same as full power loads , changing only the seating depth .
With lower velocities its a lot easier to catch bullets . Measure the rifling marks , if longer on one side than the other you know it entered canted and spun around the wrong center .