Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by BIGMAC, Jan 29, 2019.
What fb and twist are you using with this bullet?
9 and .220
9 and .235
Matt, are you able to stay above the donut?
1-8.5, .245 for me
Haven't tried them yet but have 2000 on order and have an 32" 8.5 twist 4 groove Brux waiting to be used - I'll let my gunsmith determine freebore but I'll be running them in a 280AI.
8.25 and 230, it is above the donut. Straight 284
That is comforting. I spec'd my reamer for .225 fb educated guessing I would be fine with the 184's.
I just sent a 7 RSAUM dummy round to JGS and they say it was .230" FB. My barrel will be an 8.5-twist.
.230 at touch or some specified amount of jump?
I assume they set it at touch. I set the bearing surface/boattail junction ~.070" ahead of the neck/shoulder junction on the dummy round I sent to them.
I'm running a 28" Bartlein with 8 twist. When starting the build, I called Dave Kiff at PTG and told him I wanted to seat just above the neck/shoulder junction, to avoid the donut, with 180 Hybrids jumped .005 and he recommended a .218 freebore.
How does that relate to the OP’s question?
Absolutely none. I was unaware that Berger made a 184 grain bullet as I don't shoot Benchrest or F-Class and keep up with the latest stuff that comes out. Thanks for keeping me on the straight and narrow.
Thanks for the clarification.
I suggest that you start your bullet seating depth testing with the 7mm 185 HYB TGT bullet ( or any of our HYB TGT and EOL/ELITE HUNTER HYB bullets) at .015 OFF THE LANDS. Then WORK BACK INTO THE CARTRIDGE CASE IN .005 INCREMENTS. When you find your bullet seating depth accuracy node and want to see if you can "tweak" it slightly. You can test at about .002 to either side of the CBTO of the accuracy node. There was a video by Bryan Litz on the Hybrid bullets when they first came out from the SHOT SHOW on this sight in regards to this also. But it may have been removed.
The above method is the one that works the biggest percentage of the time. However there are exceptions to every rule. In so cases setting the bullet out towards the lands from .015 OFF may have to be the way to go. If that is the case I suggest that do it in .002 increments. Any bullet seating depth testing should be done using the starting powder charge listed for the bullet/powder/cartridge combination you are testing. Hope this helps guys. Any questions . Please let me know
Thanks for all the info.
New to 284. I'm necking up 6.5-284 lapua. Could you explain the donut? I'm freebored at 220, and want to shoot the Berger 180VLD's or 180 Hybrids. Is this enough freebore? Bullet seems quite far down into case. Thanks!
the donut is a reduced inside neck dia. that forms @ the neck shoulder junction from brass flow . the problem is if a bullet is seated in this donut it increases outside dia. of that portion and can cause a crimping effect witch can be dangerous by creating extreme chamber pressure . this can be over come by proper free bore, and seating bullets in front of this area. be safe dave. also you will be ok with a 220 fb and 180s if you don't use a long jump,
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