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Discussion Starter #1
Outside of the Bison 200g specialty subsonic load which they do, thankfully, inform is unstable in a 1:11 and 1:10" rifle:
http://bisonarmory.com/6-8mm-subsonic/ ,
the following below is what I've found, by a man of the name, "constructor" (now where have I....?) who has listed some loads for a 1:10" barrel and I wonder if they'd be okay in my 1:11" Wilson. I am grateful for your sharing these loads, Mr. Constructor, and I bet they're a good base we can work off of if you say so:

http://www.ar15.com/content/page.html?id=217

Of course I'll try my own home-brews, but any red flags or just great, sub 1200fps+- loads that would maybe avoid the "baffle strike" for suppressor greenhorns like me, well....I'm all ears. I don't think I'm alone on this one, either.
God bless you pioneering folk for your efforts and I do hope it didn't come at too great a cost.
I might be about to find out myself. It's sometimes just a part of the deal, unless we listen to our elders in the game...
Godspeed in our ventures, and thank you.
 

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I'll lob this out because it's vague data at best .
I "built" a bolt gun with a .007 neck up to 7mm . It has a 1-8.5 twist. I managed to get 150 gr cast flat point bullet ( http://noebulletmolds.com/NV/product_info.php?cPath=29&products_id=176&osCsid=ckv6n4hvuhcmoa7fec0a8us3g7 ) down to subsonic on 3.5 gr of Unique. I didn't get to try the 168 gr RCBS SP . I didn't make notes for for the IMR 4350 loads with a 140 gr RCBS cast for that rifle because that wasn't what I was looking for in that rifle . Basically it was case volume minus bullet space gave about 1600 fps . The heavies might be faster with 4350 as the pressures will be slightly higher . The 140 and probably the 150 would stabilize, probably, because they are shorter than the jacketed cousin. The 140 works in the 1-11 I loaded for.
 

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Discussion Starter #4
Ive heard of 6.8 subs out of a bolt gun. Getting to reliably cycle in a AR has proven elusive that Ive seen. There was one video floating around early this year about a guy that did it. Seems like his load details never came out though.

http://bisonarmory.com/6-8mm-subsonic/
Word, Speedster. Rather than mucking about with what I've got, maybe messing it up and turning it into a slow-witted weapon, I'm considering going ahead and committing to a "designated subsonic" rifle. While heavier could be used with slower to attain subsonic flight, Newton's Rule of Thumb, mass x velocity=energy/momentum gets added to it that extra variable when a spinning, rotating bullet is added to the equation: rifling. So some inform that stabilizing a heavier bullet takes faster rifling (see Bison's 1:7") but--then at range the information at the site admits that their 200g loses said stability and keyholes targets far downrange, which makes me wonder: is it spinning too slowly at that point, or is it spinning too fast and losing it with slower forward momentum?
I'm leaning Wilson rather than a 1:7" twist rifle. And to what I can actually do, with a 1:11" 6.8 from Wilson one man at least informed me that bullets heavier than 130g are not recommended/i.e. a bad idea and he's probably talking about baffle striking with the heavies, though subsonic or otherwise wasn't clarified. So, I'm looking at the 130g recipes our Constructor posted way back in -'08 (see first post this thread). The plan is for close work, inside 100 yards, mostly around fifty (fave blind distance to Cornholius the feeder) and I don't think it'd be practical at all to sling a subsonic bullet more than a hundred yards, anyway. WSY?
 

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I know just about enough about balistics to look really stupid . So bear with me .

Most likely what is happening with the long 200gr boolits out of a 1-7 or 8 twist is that it isn't loosing the gyroscopic stability but is at the ragged edge anyway the aerodynamic stability is what is failing. Short version the air flow over bullet slows and the heavier end wants to be out in front while the bike wheel effect wants to make a left turn.

With a heavy for twist bullet you will have to walk that ragged edge of twist vs velocity vs design.

You can choose a bullet with a high good BC but it will be to long to stabilize.
You can choose a bullet with a poor BC short enough to stabilize but it may not build enough pressure to cycle sub sonic .
Last you can pick a bullet with a long bearing surface to raise pressures and split the others.
Odds are that a,140 gr RN is as close as you will get with a 1-11 twist . There may be some exotic bullets that are shaped like a 120 SST hybrid with a NOS partition and lead in front and a tungsten base plug or a solid of a similar design.
Last best option goto a heavy cast lead bullet and a slow powder . A cast FN that will feed and stabilize will be maybe as much as 10 gr heavier than a jacketed RN and the same length . Aerodynamic drag changes with cast by design . I will put 150 s on my list to try . 140s work but I haven't tried to slow them down as I'm seeking a peak number at this time .

I have a 150 gr mould and could make arrangements for someone to try some for subs.
 

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Discussion Starter #6
Yes, Harter. A lot going on but I think you've got it on the heavy bullet just finally folding way out there. Makes sense.
I do love hard cast boolits for autopistols, but haven't seen a .270/6.8 cast, mostly the .308-9" cal and largetr like with Oregon Trail's
http://oregontrailbullet.com/shop/
It'd probably need to be a really hard alloy for smooth feeding out of the magazine against the feed ramp into the chamber. I do like those Oregon Trails. They don't list the Brinnell hardness, but they are a solid, hard bullet.

 

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Discussion Starter #8
I'm thinking more along these lines after what I've read about long, slow bullets in 1:11" rifling: short n' sweet
http://beartoothbullets.com/bulletselect/details.php?id=10
I like the look of their 140g, too. It might be too long but I should have fun finding out. The last Bear Tooth bullets took six months to get here, though. They're really busy these recent years. Nice folks...
 

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You are trying to make the 6.8 something it isn't... Have your fun but If you truly want subsonic performance, build a dedicated .300 Blk upper and call it good.
 

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Discussion Starter #10
You are trying to make the 6.8 something it isn't... Have your fun but If you truly want subsonic performance, build a dedicated .300 Blk upper and call it good.
You've got a point in that subsonic's all a 300 Black O. is good for.
We'll see if I can slow down the 6.8, slum a bit, on that. You may be right. But I'm not alone:
http://www.ar15.com/content/page.html?id=217
 

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I have a NOE 279-124 fp designed specifically for the 6.8 SPCII AR. I think you would be on a good track with a cast bullet intended for the 7mm08 or 7-30 Waters with the short necks . If you're really out for the learning curve there are several moulds suited to the 6.5 Carcano and it's 268 groove that would paper patch right to the 6.8 at about 160-65 gr. It might be a significant investment but 1 of those HP'ed might be a winner for the twist if the fp or RN is too long.

Going slow is much easier than going fast with cast .

Mountain Molds has a basic bullet design program you can fidget with and they will cut what you wind up with for not a completely ridiculous price and for just 1 mould not 10 or 15.

Here's a link to NOE current 270 stock with the same 17 available as 3 weeks ago .
http://noebulletmolds.com/NV/index.php?cPath=28&osCsid=4jjjjeo3i9h3ge8lsub08eis42

The 1st one is the 6.8 SPCII bullet the 2nd actually down about 8 lines is a make many cartridges happy 160 gr bullet .
You're right about the 270 cal choices being few and for short necks even fewer. Until there is demand there's no supply .
 

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Discussion Starter #12 (Edited)
Hey, thanks Harter! That is some nice looking stuff to pour molten lead into, but the end product looks damned intriguing.
Having experienced leading with auto pistols with--I guess--too soft lead, I gotta admit I'm hesitant. I have gone exclusively gas-checked since, even with slow hardcast pistol bullets, and have yet to see if it's made a difference, which is good 'cause I'm not seeing obvious leading yet. For a 6.8, I really want to designate a barrel for experimenting with hard cast lead, see what happens. I'd end up with a whole rifle for it, which is what usually happens. I don't mind cleaning it out, either. Got Eliminator and Aluminum Oxide I think.... what's that: AlO2. But just copper fibers on a bronze brush and Wilson's Bore Cleaner and Polish works, too. Gotta love old-school hard cast!
Edit note: And I don't think I should hesitate to drive those 124 FPs really fast, either. That'd be a bone smasher.
 

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Ive heard of 6.8 subs out of a bolt gun. Getting to reliably cycle in a AR has proven elusive that Ive seen. There was one video floating around early this year about a guy that did it. Seems like his load details never came out though.

http://bisonarmory.com/6-8mm-subsonic/
We are currently working on a piston upper that will run subs and supers with Dr Lucci (HTR) of WRR. Currently the testing phase is in a DI setup with an adjustable gas system.

We took several pigs the other night running two similar uppers (only difference was barrel length), one of us was running the 200gr subsonics and the other 90gr good dot factory ammo. Both ran successful and cycled the upper properly without issue. ImageUploadedByTapatalk1441062821.807888.jpg



Sent from my iPhone using Tapatalk
 

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Well looky here:
http://leeprecision.com/.278-lube-size-kit.html
"coming soon" it says. Tick, tock....I was ready yesterday. About time!
This means I'll soon be going into production.

I've had that one for years--used it with the 280642 in my 270 Winchesters...

Went to a H&I sizing die later because I had to use liquid Alox when I was done sizing in the push through. It's O.K. but very messy. Builds up in the seating die...

I use Carnauba Red from White Label Lube Company with the H&I die. A lot cleaner and less messy...

Good-luck...BCB
 

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Discussion Starter #17
I've had that one for years--used it with the 280642 in my 270 Winchesters...

Went to a H&I sizing die later because I had to use liquid Alox when I was done sizing in the push through. It's O.K. but very messy. Builds up in the seating die...

I use Carnauba Red from White Label Lube Company with the H&I die. A lot cleaner and less messy...

Good-luck...BCB
I hear ya, but with that Lyman we gotta have the whole separate sizing press and I took an oath: no more presses, after I got my T-7, no excuses, no word-play--but it's a sizer, not a press. No. What I've done with pistol is melt a stick of the blue stuff in a microwave proof tray and roll the boolits in it. It's a cleaner, drier mess. Then I size 'em and the blue sorta stays in the goove, man. Not tried it with rifle yet.
Lee says the .278" is "coming soon" on their webpage (listed in my above post). Well, what time are we talking about? American time or Siesta time?
Chop, chop, I've got boolits to squeegee.
 

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Discussion Starter #18 (Edited)
We will have a 220-225 grain bullet in .277 available soon. Game changer.
And will this bullet have stable flight through a 1:11" twist bbl, and if not, what's your preferred barrel for this mega-toad (tm) bullet?

Is it this muy rapido model and, if so, I wonder how many others make these fast-twists for our cartridge:
http://bisonarmory.com/6-8mm-subsonic/
Now, I take it you do, too, but do others also or is this too "specialty"?
 

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And will this bullet have stable flight through a 1:11" twist bbl, and if not, what's your preferred barrel for this mega-toad (tm) bullet?

Is it this muy rapido model and, if so, I wonder how many others make these fast-twists for our cartridge:
http://bisonarmory.com/6-8mm-subsonic/
Now, I take it you do, too, but do others also or is this too "specialty"?
I can have 1:7 twist 6.8 barrels made all day. That's what you want for a heavy sub. Those that sub more than likely suppress, those that suppress don't want baffle strikes, in order to avoid baffle strike you need the appropriate twist to stabilize a heavy, long bullet. Therefore, 1:7 twist for 277 subs in the 150-225 grain range.
 
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