Sat down tonight to size a bunch of brass after breaking in my 12.5" BHW 264 LBC barrel. It's supposed to have a Type 2 headspace and I'm using a group buy bolt. Measured a bunch using the Hornady Headspace Comparator with A330 insert and it measures a bit long - coming out at 1.246 base to datum line. I believe the SAAMI chamber spec is 1.230 but fired brass of course comes out longer. For comparison sake, brass comes out of my JP 6.5G barrel at 1.235 and came out of my old Satern / Stoner at 1.240 (always thought that was a bit loose). Then I measured some of the brass from breaking in my new 243 LBC barrel and it measures 1.234. That barrel is Type 1 and I'm using a Toolcraft 7.62x39 BCG.
1.246 seems a bit excessive and makes me think the barrel was mismarked (came from True Sporting Arms at 50% off). Conceivable since BHW always primarily made Type 1 and won't even do Type 2 anymore. If it is in fact Type 1 headspaced, would that manifest itself in an extra 0.01 of brass growth with that effectively being the difference in bolt face depths?
All your brass is long IMO. Both my Bartlien (well used to) and Lilja were 1.218 +/- on factory 1.210 rounds and reload 1.216. My Bartlien has grown to 1.225 and I have what looks like chamber cracking (posted in the trouble shooting section with few theories to help).
The datum measurement collet for 6.5 Gr is the B one, 0r 0.350. That one should yield a shorter measure of the fired brass.
What lengths do you get with the 0.350 B one?
1.216-1.224 are more typical (again, with the B insert).
"Down the floor, out the door, Go Brandon Go!!!!!"
Ok, now we have something to work with...
yeah the LBC-fired looks 0.01+/- too long for me. Idk maybe too long, maybe not?
Could be from using a 0.136 bolt for a 0.125-set chamber.
Do you have that no-go gauge - if so, do the test muvef talked about.
I know sometimes the LBC's have a longer throat and straight-angle vice compound... but the datum line should still be ~1.220 give or take. Mostly my chambers are 1.215-6, one was 1.219 iirc.... sold that one though; fired brass was 1.225/6/7 but never 1.230 out of that one.
"Down the floor, out the door, Go Brandon Go!!!!!"
Wouldn't using a .136 boltface with a .125 barrel not allow the extractor to snap over the case rim?
I tried a .125 boltface before with a .136 barrel and could not get the bolt to rotate into lock.
I suppose I will try the opposite now.
bj, your combo would definitely wind up short, the 0.125 bolt is "shallow" and a 0.136 chamber is cut "shallow" to accommodate the 0.136 bolt...
I think the 0.125 chamber ("deeper" forward) and a 0.136 bolt-face (also "deeper" backward) would allow 0.11 slop in front of the shoulder, therein the problem.
But I could have it backwards... Alzh-lexia or something??? LOL.
"Down the floor, out the door, Go Brandon Go!!!!!"
In my normal "information gathering" mode I've downloaded copies of chamber drawings.
At the .350" point on the shoulder:
The LBC .264 spec lists 1.2201" to 1.2251"
The Grendel II chamber shows 1.2201" to 1.2301"
And the Grendel SAAMI chamber lists 1.2201" to 1.2301"
I took a 7.62x39 AR15 barrel (.125" bolt depth) with receiver and inserted a Grendel bolt (.135" bolt depth).
I inserted a 7.62x39 round, closed the bolt and ejected the round many times. The extractor grabbed the rim every time.
I didn't think it would but testing revealed the truth.
Right... your 7.62x39 barrel + .135 bolt test is what I expected...
Randy true those specs go out to 1.2301... but for my little bit of experience I haven't seen brass (nor chambers) go out that far.
The ones (I had 2) that went out to the 1.225/6/7... I sold them both b/c it meant needing 2 separate resizing dies/settings, and I got tired of keeping the distinction of the 2. The ones I have all work with a single resizing die setup.
"Down the floor, out the door, Go Brandon Go!!!!!"
Thanks everyone - allowed me to consolidate my thinking enough to give them a call. Was lucky to have the guy who runs QC answer the phone. Had a nice long chat with the conclusion being that being .01 longer than the JP brass would not be out of the ordinary and being around .01 longer than the Type 1 brass would be expected. Long and short of is: remove the firing pin from a Type1 bolt and see if it locks down on Match Grade ammo. So I got home and did the test with StoneHendge Enterprises 123 gr Scenar ammo that gets fed to the JP and voila!
[ATTACH=CONFIG]12269[/ATTACH]
I might not be too happy with a chamber deep enough to make Stormy Daniels proud if I was using Hornady brass for anything else in 6.5mm, but I'm not so I guess I can live with it.
Other random takeaways:
He gushed praise about JP and his tolerances when I brought up the JP measurements - pretty compelling coming from a QC guy. This is the third company I've talked to that had that reaction. Conversely, he was uncomplimentary of some of the things he has seen in the market, such as bolt faces that could vary by .002 from side to side. Not necessarily a disaster in and of itself, but scary when tolerances begin to get stacked.
With having made close to 10k LBC barrels, they've seen very few problems with Type 1 bolts and don't see any real upside to AA coming out with the Type 2 given the confusion it created since the AR market already had an effective solution. (I'm not starting a debate here - just passing along the view from a respected barrel maker that decided to stop making barrels headspaced to Type 2)
I asked if they would do twist rates that aren't on their website and the short answer is maybe. But the one takeaway was that their 3 groove rifling can have a hard time gripping when long bullets start getting pushed fast at high twist rates. Made me start to wonder if this is one of the problems with the Valkyrie - Sierra says 1:7 isn't fast enough for the 95s, but the barrel makers haven't jumped to embrace 1:6.5 (aside from ARPs run which was a failure). Also makes me wonder if that's why my McGowen 1:7 6mm Grrrr barrel didn't really show promising accuracy (other than the fact that it was a hack job)
Interesting note on the 3-groove rifling... definitely a point to keep in mind.
I haven't gone the 3-sies but have several 5R's...
So, upshot is you're going to have a dedicated set of brass for this one, eh?
"Down the floor, out the door, Go Brandon Go!!!!!"
07-19-2018, 03:57 AM (This post was last modified: 07-19-2018, 04:19 AM by NugginFutz.)
That barrel is a 3 P. P for polygonal. The configuration is proprietary to BHW.
I find the notion that AA confused issues when it introduced the Grendel “type II” bolt subsequent to BHW’s “type I” amusing, given that the Grendel preceded the 264LBC by quite some time. I believe someone in BHW/Columbia’s QC department is confused about the timeline of the Grendel vs the 264LBC.
I specifically recall when black hole was debating whether or not to deliver their LBC’s with the type one or the type two bolt as the “default” setup. I already had one of their .136 headspaced tubes. Greg and Rich both lobbied for type I. My vote was insufficient to sway Carl and they relegated the .136” to being an option. Apparently they were later feeling the pressure of trying to keep the two straight, even among themselves, and they eventually dropped the “type II” from production altogether (But not before I ordered another .136” headspaced barrel). The only time the “type II” bolt was used by them again was when BHW produced a limited run of SAAMI spec Grendels.
grayfox Wrote:Interesting note on the 3-groove rifling... definitely a point to keep in mind.
I haven't gone the 3-sies but have several 5R's...
So, upshot is you're going to have a dedicated set of brass for this one, eh?
The more I think about it there is a heck of a lot more stress on the lead forced against the edges of the grooves.
The JP gets Lapua brass so this one gets most of the Hornady brass from my old 18" barrel. I used a little of it to get the 243 going and then just ordered 500 virgin Hornady from Graf's for that one at 35ยข per. So at least I can keep it long for the pistol.
