Berger FB bullets

[Milo 2.0]

Hi,
I recently started a thread on building a 6BR, my first. Long story short, I picked two bullet types to shoot, 88gr FB, 95gr VLD's. I got the vld's dialed in right away, with the best group at .160", tested the load on a prairie dog sized steel target at 500 yards and it's deadly as heck, in moderate winds of course!
My problem is I can't get the 88's to group, I've ran seating depths up to 40 thou, best I can manage is 1/2" at 100 yards, 5 shot. Going into the lands seems to tighten it up, but read in a separate thread that fb's like to jump close to .015". Basically I'm lost here, and have only about 25 bullets left to try. Plan on a diff bullet at that time.

The load is 88gr, 30.5gr of Norma 203B, 205M, 22" 8 twist barrel, there's no reason to me why it wont shoot it. Any ideas?

 

[RDavies]

The 88gn Berger has a VLD style ogive. I have only just started using the 88gn LD bullet and it went well with a .010" jam as most 6mm VLDs do for me.

 

[Milo 2.0]

Thanks RDavies, that's what I took on looking at the two bullet types, they look the same up top. I'm .005 in right now and getting better, maybe things will work out.
For a custom built gun, this is by far the most difficulty I've ever had finding a load!

 

[BoydAllen]

Try about .003 off of jam (the length that a bullet is pushed back to when loaded overlong and chambered, using the neck tension that you plan on shooting) and do a pressure series, starting low, one shot per load, .3 grain intervals, up to the point where the bolt lift gets a little stiffer than you like on a FL sized case. Shoot all shots on the same target, on a good day, paying close attention to your flags, and when you have finished note any clustering near the top where change in charge did not make much difference in impact, then load three to the middle charge weight of that group. If that looks promising you can start backing off your seating depth, in increments of .002 to see if you get any improvment (still working in a range that engages the rifling) Let us know what happens. When you note the max load, be sure to indicate what the temperature was. Of course all of this is much easier to do if you are loading at the range. Shooting all of your test shots over a chronograph is a good idea as well.

 

[searcher]

Having only a few rounds left, I'd increase your neck tension a bit and incrementally jamb deeper in .003" increments up to .015" in. I've had more loads shoot poorly off the lands than jambed in this caliber, especially with the "mid-weight" bullets you are using. Good luck!

 

[Milo 2.0]

Try about .003 off of jam (the length that a bullet is pushed back to when loaded overlong and chambered, using the neck tension that you plan on shooting) and do a pressure series, starting low, one shot per load, .3 grain intervals, up to the point where the bolt lift gets a little stiffer than you like on a FL sized case. Shoot all shots on the same target, on a good day, paying close attention to your flags, and when you have finished note any clustering near the top where change in charge did not make much difference in impact, then load three to the middle charge weight of that group. If that looks promising you can start backing off your seating depth, in increments of .002 to see if you get any improvment (still working in a range that engages the rifling) Let us know what happens. When you note the max load, be sure to indicate what the temperature was. Of course all of this is much easier to do if you are loading at the range. Shooting all of your test shots over a chronograph is a good idea as well.

Boyd,
That's pretty much what I did with charge weights, only in .2 increments, with the bullet just contacting the lands. Velocity was increasing at around 35fps with 30.5 yielding 2850, 30.7 =2856, 30.9=2859, so I settled on 30.5, it was a nice 70 degree day, and I don't sun bake ammo so I'll be ok.
So I'm counting on seating depths to bring the load in. I'm not about to search for powders right now, the only other powder I have is N540, which most likely get more velocity, but 2850 is fine for me, a 200 yard max load. I've got the vld's for lr plinking.

Searcher,
I'm still on new brass, and didn't buy a neck die, my 2 bushings are .266, and .263, the 263 by smith's measurements???? and will yield up to .006 tension, I don't want that much, so right now I'm limited here.
So far you guys are helping, thanks!

 

[BoydAllen]

For bullets of that shape, I tend to think of touch as being sort of the worst of all starting places, but that is just me. I would expect much better results .020 off or near jam.

 

[Milo 2.0]

For bullets of that shape, I tend to think of touch as being sort of the worst of all starting places, but that is just me. I would expect much better results .020 off or near jam.

Touching is just how I've always done it, never had it explained differently. Jamming may produce more, seating deeper less pressure. Knowing full well a guy may have to revisit charge weight. Next gun I'll heed the advice!

 

[BoydAllen]

The problem with exact touch is that variations in bullets and neck tension will inevitably take you from slightly in the rifling to slightly out of it, and those conditions cause significant differences in pressure. By starting close to Jam, you only have one way to go with seating depth experiments. Of course free advice is often worth exactly what it cost.;-) Good luck.
Boyd

 

[6BRinNZ]

Check where the 88s finish relative to the neck shoulder junction (very long bearing surface)...you are using new brass so no donut should exist yet...but...

 

[Milo 2.0]

Check where the 88s finish relative to the neck shoulder junction (very long bearing surface)...you are using new brass so no donut should exist yet...but...

So I'm going to be neck turning another cartridge?

 

[6BRinNZ]

Check where the 88s finish relative to the neck shoulder junction (very long bearing surface)...you are using new brass so no donut should exist yet...but...

So I'm going to be neck turning another cartridge?

Not sure about that - the rule of thumb I use is - if I can't keep it away from the neck/shoulder I don't shoot it.

 

[searcher]

BoydAllen is right on the money as to the "touching the lands" and the significant variations that result from differences in the bullet base-to-ogive, etc. I'd definitely go at LEASE .005" OFF or In at LEAST .005. Sure, one can measure their bullets to minimize this problem but is easier to just avoid it if your gun will shoot in a different position.

 

[Michaël T]

not to change the subject but how far in/out are you seating the 95 vld, i have the same problem with the 88fb

 

[Milo 2.0]

not to change the subject but how far in/out are you seating the 95 vld, i have the same problem with the 88fb

If my measurements are correct, I'm .009" into the lands, it was starting to click at .005", just kept getting better.
31.2gr Norma 203B, 205M, Lapua case. 2900fps.

 

[Michaël T]

Thanks , just what i was looking for