NugginFutz Wrote:Fired cases from my Larue Tactical Grendel, also with a .136" headspaced chamber, measure right at 1.220", which puts the brass deadnutz on.
Know whutz funny here? My LaRue measures 1.221". Dead to the Nutz to the on.
Ba Dump - Tssss...
SH, you gotta stop pullin' random crap off the shelf buddy. Just succumb to temptation and get yourself a LaRue and join us cool kids over here in the cloudy corner...
Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.
Forgive me if I'm wrong but I get the impression some don't know how to deal with those chamber dimensions.
The 264 LBC is good if it is within 1.2201" to 1.2251", a tolerance of .005".
The other two are 1.2201" to 1.2301", a tolerance of .010", anywhere within those ranges is within spec tolerance.
Another thing to consider is that there must be some spring-back of the case, so they should measure shorter than the chamber when they cool. I would expect a case to measure at least a couple thousanths shorter but have never seen a scientific study.
I would think you'd want to see measurements at the short end, indicating a precisely lengthened chamber considering that a bit 1-2 thou of snap back would be expected. I def. wouldn't want to see anything longer. You are correct, as far as I know though.
Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.
Kswhitetails Wrote:Know whutz funny here? My LaRue measures 1.221". Dead to the Nutz to the on.
Ba Dump - Tssss...
SH, you gotta stop pullin' random crap off the shelf buddy. Just succumb to temptation and get yourself a LaRue and join us cool kids over here in the cloudy corner...
1.220 - just like my JP - which printed this 5 shot group this afternoon :p
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This one would have been better if I didn't suck like a McGowen barrelsmith
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Which begs the question - what does it mean / what would happen if brass from an alleged Type 2 headspace was coming out at 1.218/1.219?
07-20-2018, 07:37 AM (This post was last modified: 07-20-2018, 09:55 AM by Klem.)
StoneHendge Wrote:Which begs the question - what does it mean / what would happen if brass from an alleged Type 2 headspace was coming out at 1.218/1.219?
New, unfired Lapua brass measures 1.202". Factory ammunition will be similar. That length will go into a 1.218/1.219" chamber easily and it doesn't matter that the chamber is slightly shorter than Mr Whitetail's amazingly mass-produced LaRue. As long as the chamber is not shorter than new brass or factory ammo then all good. In fact, 1.218 means less stress when it expands than other guns, which can only be a good thing for the brass.
07-20-2018, 04:18 PM (This post was last modified: 07-20-2018, 04:21 PM by Randy99CL.)
StoneHendge Wrote:Which begs the question - what does it mean / what would happen if brass from an alleged Type 2 headspace was coming out at 1.218/1.219?
Brass that measures 1.218"/1.219" is absolutely normal. That is only .001" or .002" shorter than the the shortest acceptable chamber (1.220") listed for all 3 specifications. It's within spec and likely shrunk a tiny amount when it cooled.
I just checked a couple of sheets of regular paper and they are .004" thick. 1 or 2 thousandths is a tiny amount. I've read/heard of cases that stretched 10+ thousandths and didn't fail (though they have to be considered unsafe at that length).
Randy, does your diagram use a 0.125 bolt face depth? BHW dude told me that brass coming out of a Type 2 would be expected to be 0.01 longer than out of a Type 1. Since the LBC is supposed to be identical to Grendel except for the throat, I would surmise that I'm on the outside fringe of spec. Although my caliper might be a nice shiny red, it might now be as old as the kids who made it on the outskirts of Shanghai. I'm going to try to remember to bring my NAPA caliper home from my shop to see if there's any difference. I might also try it with my JP Grendel bolt - might be a case of tolerance stacking with the group buy bolt.
Thx Klem - that's what I thought. The brass from my super exploding 6mm McGowen barrel came out at 1.218/9. I used virgin Starline bumped down 0.001 to be sure I got all of the neck sized down, so that probably wasn't a contributing issue
StoneHendge Wrote:Randy, does your diagram use a 0.125 bolt face depth? BHW dude told me that brass coming out of a Type 2 would be expected to be 0.01 longer than out of a Type 1.
None of the 3 drawings list bolt face depth, they all just label the base line "bolt face".
The BHW guy is wrong. The brass from either a type 1 or type 2 should be the same length if each has the right bolt.
If the front of the bolt lugs are against the breech, the type 1 chamber has to be cut .011" deeper into the barrel than the type 2 chamber.
The chamber has to be the same size, that is what the specs call for. Anything else creates a potential failure.
I saw a video that showed a case with about .015" stretch and it was dangerous. The web was thinned (on the inside) to the point where the case probably would have failed within a few more firings.
muvef Wrote:These fired rounds were w/ a .136" bolt when the chamber actually needed a .125" bolt. The shoulder of the cases are "ballooned" out.
The other picture shows how far a fired case sticks out of my case gauge.
Thanks for posting these pics!
Very informative. It's hard to predict where a case will stretch when it is fired in an oversize chamber. Yours is what I would guess to be the less dangerous result?
FWI understand, the firing pin usually pushes the case forward in the chamber until the shoulder hits, so when the case expands the main body is held by the chamber walls and the base has to stretch backward to take up the slack. This can lead to a catastrophic case head separation.
Johnny's Reloading Bench switched out a Saturn barrel for a Faxon and the fired brass length difference was .010". The sized reloads made for the Saturn would not even chamber in the Faxon. He rants about it in this video at about the 15 minute mark: https://www.youtube.com/watch?v=1Ecjvr-o...jTRb-JJmto
The funny thing to me is that his Saturn brass looks to be within spec at 1.224" while the Faxon brass measures a little short at 1.214".
StoneHendge Wrote: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!
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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)
Bill Alexander introduced the .136" face depth on the .50 Beowulf after doing a lot of research, which included the Colt 7.62x39 program.
Extractor lip geometry and material thickness is what gets you with the thicker and wider rim.
There is no Type I or Type II relevant to the whole industry. There are bolts that were engineered around the cartridge, and bolts that were engineered around convenience for the after-market, not fully understanding all the details of what it takes to make the whole thing work.
Barrel makers specialize in making barrels.
Firearms manufacturers specialize in sourcing all the components after RDT&Eing their overall design, and holding component suppliers to their standard as part of the TQM process. The firearm manufacturer is the one responsible for whether or not the extractor holds up, not the barrel maker. Same for bolts, springs, carriers, gas keys, gas blocks, tubes, fire control parts, etc.
What I've come to learn is that there are some very gifted people in this industry within their own discipline, but once they step even a little bit outside of their expertise and into another component or process on the gun, they are underwater really quick.
Even within the barrel-making process, that is true. Some places can drill a nice hole and rifle it, lap it, but the moment you ask them to finish profile, thread, attach an extension to it, you get a monstrous abortion sometimes.
The same goes for bolts and extractors. I will rarely place much value in what a barrel maker has to say about components they don't make, other than usual observations about quality and characteristics from different shops they've seen. It doesn't mean I'm trashing their reputation or hating on them, just putting into context where expertise should be recognized.
If I'm a home-builder, I'm not going to ask the plumbers how to do my foundation. The plumbing and drainage will certainly be taken into consideration when pouring the foundation, but the plumber won't be doing the job.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
Also, if someone is saying that ".264 LBC" standard is .125", they are left having to explain why the originator of the .264 LBC-AR (the name for Les Baer's chamber) uses .136" Grendel bolts, and has done so before anyone else attempted to chamber in ".264 LBC".
Someone who seemed to have connections with BHW stated on AR15.com that they never have had problems with extractors breaking on the .125" bolts.
Right after that, one of their customers posted a picture of his broken extractor with the .125" face depth.
Even the guys running LMT enhanced AerMet 7.62x39 bolts were breaking extractors on the lobster tail extractor, and it was after 1200-1300 rounds. The LMT AerMet bolts are probably the toughest AR15 bolt for this case head diameter out there. There just isn't enough extractor lip to fit in the spaces and necessary mechanical articulation given the AR15 bolt dimensions, unless you take the face back and allow more lip material on the extractor.
What you'll see with 7.62x39 in terms of real stress testing is those who have registered machine-gun lowers that like to blast a lot of full auto.
They go through x39 bolts regularly, and pop in a new one when they break.
The LMT gave them the option to have a bolt that wouldn't shear lugs or snap at the cam pin hole, but alas...the extractor breaks.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
Randy99CL Wrote:Thanks for posting these pics!
Very informative. It's hard to predict where a case will stretch when it is fired in an oversize chamber. Yours is what I would guess to be the less dangerous result?
FWI understand, the firing pin usually pushes the case forward in the chamber until the shoulder hits, so when the case expands the main body is held by the chamber walls and the base has to stretch backward to take up the slack. This can lead to a catastrophic case head separation.
Johnny's Reloading Bench switched out a Saturn barrel for a Faxon and the fired brass length difference was .010". The sized reloads made for the Saturn would not even chamber in the Faxon. He rants about it in this video at about the 15 minute mark: https://www.youtube.com/watch?v=1Ecjvr-o...jTRb-JJmto The funny thing to me is that his Saturn brass looks to be within spec at 1.224" while the Faxon brass measures a little short at 1.214".
It was for this reason that I kept my fired brass separated. The BHW brass is .004 longer than the Larue. Not as severe as the .010" difference between JRB's two barrels, but enough to make me notice.
With mixed brass, I would have to choose a compromise on the shoulder setback. If I were to setup the dies to bump the shoulders .003" for the BHW, the brass would be on the long side in the Larue. On the other hand, setting up the dies to bump the shoulders for the Larue would tend to overwork the brass fired in the BHW.
The working solution has been to setup the sizing die for each rifle's fired brass, and keep the brass separated throughout the life cycle of the ammunition.
However - with the new found abundance of cheap loaded ammunition with quality brass, the point may be moot. Brass life may have become a little less critical, given the introduction of the American Gunner ammunition.
If it's true that we are here to help others, then what exactly are the others here for?
To quote Johnny at JRB talking about the type 1 and 2 bolts: "I'm aggravated that the market for a really great cartridge has been confused and muddied and made to be ridiculous."
NugginFutz Wrote:It was for this reason that I kept my fired brass separated. The BHW brass is .004 longer than the Larue. Not as severe as the .010" difference between JRB's two barrels, but enough to make me notice.
With mixed brass, I would have to choose a compromise on the shoulder setback. If I were to setup the dies to bump the shoulders .003" for the BHW, the brass would be on the long side in the Larue. On the other hand, setting up the dies to bump the shoulders for the Larue would tend to overwork the brass fired in the BHW.
The working solution has been to setup the sizing die for each rifle's fired brass, and keep the brass separated throughout the life cycle of the ammunition.
However - with the new found abundance of cheap loaded ammunition with quality brass, the point may be moot. Brass life may have become a little less critical, given the introduction of the American Gunner ammunition.
This was the battle I was having with my 18"-Arp, the fired brass was too long for any other chamber so I was doing 2 dies and 2 sets of brass for a while. It happened to be an LBC-style but he used his own name for it... bottom line was it stretched new brass out to the 1.225/6 (new Hornady is more like 1.209 at the datum point) and I had to resize such that it was too long for my other, more (what I would call) normal chambers. Didn't like having to stretch brass like that out of the box. Running 2 sets wasn't really getting me any bang for the buck either, so I sold it to a guy who doesn't reload and doesn't worry about brass lengths.
"Down the floor, out the door, Go Brandon Go!!!!!"
randy99cl Wrote:to quote johnny at jrb talking about the type 1 and 2 bolts: "i'm aggravated that the market for a really great cartridge has been confused and muddied and made to be ridiculous."
exactly!
Knowing everthing isnt as important as knowing where to find it.
07-21-2018, 08:32 PM (This post was last modified: 07-21-2018, 08:52 PM by StoneHendge.)
Well, we can throw some instrument error/variation into the equation. Measured 5 virgin Hornady cases with 0.350 collet. Results on left are from the shiny red Hornady Digital Caliper. Results in the right are from an ADT-8657 from NAPA.
The quandary is which to trust more. The caliper from the company that sold me a digital scale that never worked (it would simply run from 0 gr to 15 gr then back to zero, rinse and repeat), or the chain that's living off its reputation and who sold me a hecho en mecho alternator for an E350 that lasted 3 months and a hecho en mecho starter for a 96 Tacoma that lasted less than 3 years (anyone whose ever replaced a starter on a gen 1Taco will feel my pain in that one!) I'll probably go with the ATD-8657 because it sounds more scientific.
Then there is of course the question of instrument variation in the collet. We can all guess where the factory those come from is..........
The Hornady tool is only a comparator, not meant for absolute measurement. It is good to have a headspace guage to zero from, (a standard) that is what I do with my .308's.
As long as you are using the same calipers, and same bushing, you should get very usable dimensions. Also depends on how consistent your "touch" is, but as long as one doesn't try to use calipers for a monkey wrench they should be within .001-.002. Won't get much better with calipers.
. As long as the chamber is not shorter than new brass or factory ammo then all good. In fact, 1.218 means less stress when it expands than other guns, which can only be a good thing for the brass.
