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Link Posted: 11/26/2008 1:54:40 PM EDT
[#1]
Thanks for the words and your time Doc, here at the circus.
Link Posted: 11/26/2008 2:04:15 PM EDT
[#2]
Tag for a lot of good info. These developments are exciting. For something else exciting take a look at the CMMG forum.  Jeff at CMMG just said a few days ago that ALL of his 6.8 barrels are sold out.  He then said that when he orders new stuff he is considering changing all the specs he wants in the barrels for the new builds.  He has seen Tim's work at kotonics and others input and said he is looking at higher performance for his new guns.  For those that may not know CMMG that well they have some cool stuff ie: 16 govt profile mid length .223 and a 14.7 inch .223 all with 1/7 twist.   The thread about the 6.8 was just a few days ago.  I bet if he gets enough input from the 6.8 guys he will have the next batch made to the specs we want.  I already told them that I'm in for another 6.8
Link Posted: 11/26/2008 2:16:25 PM EDT
[#3]
Link Posted: 11/26/2008 2:19:23 PM EDT
[#4]
Quoted:

and how far did that get?  Has anyone anywhere in the world been shot in anger with a 6.8spc?


I'm done with this thread, I started out being respectfull trying to ask legit questions and discuss ballistics but as usual I just get the same flames the 6.8 clique always dishes out to us non believers.


This is an AR-centric section of an AR-centric forum. If you want to discuss the merits of 6.8SPC as they apply to the wide wide world of cartridges irrespective of the launching platform - and seek an audience receptive to the notion that you're better off with a light bolt action vs a 6.8 AR for hunting - you might want to register on other forums that don't call themselves the Home of the Black Rifle.

Link Posted: 11/26/2008 2:51:47 PM EDT
[#5]
Link Posted: 11/26/2008 3:54:24 PM EDT
[#6]
Quoted:
Doc,
Does the 85 perform better than the 110 in the barrier testing?

As pushing the 85 to 3K doesn't get us much in drift or drop at extended range, and has roughly the same transonic range as the 110.  So that leaves some other performance criteria that must be driving this load.


Fellow Reloaders,
I have not seen the 85gr TSX offered for sale, is it cheaper than the 110gr?




Forest,

Forgot to answer this earlier.  At this time, only SSA has projectiles and they are not selling them.  However, I was recently told by Barnes that they will be making the 85 grain TSX available to reloaders in the future.  Probably sometime in 2009.  I am also trying to get them to release the TTSX in 90, 95 or 100 grains as well.

It wouldn't hurt to remond them how many of you might like to see these bullets released, too.  They have a 110 grain TTSX, but as I mentioned before, it is quite long.
Link Posted: 11/26/2008 6:08:22 PM EDT
[#7]
Link Posted: 11/26/2008 6:17:19 PM EDT
[#8]
All the bickering aside in this thread.........

I think this load is very very interesting. I really want to hand it to the people who have
worked hard to take the 6.8 to the next level.

A few people have really improved the performance of this cartridge over the years.

Very interesting indeed!

and thanks for the gel shots Doc
Link Posted: 11/27/2008 4:21:04 AM EDT
[#9]
Quoted:
The BC of the 85gr TSX is .246   ....

http://www.barnesbullets.com/products/rifle/tsx-bullet/

Goes transonic between 650yds - 750yds.

Which by the way, is pretty damn good from a 16" carbine.


I believe a 6.5 Grendel in a 120-123gr bullet goes trans sonic at 900 yards with a 16" BBL.
Link Posted: 11/27/2008 8:15:01 AM EDT
[#10]
Quoted:
All the bickering aside in this thread.........

I think this load is very very interesting.

I really want to hand it to the people who have
worked hard to take the 6.8 to the next level.

A few people have really improved the performance of this cartridge over the years.

Very interesting indeed!

and thanks for the gel shots Doc


+100

All of us who've wanted more oomph from our ARs are benefiting from the efforts of the above mentioned few.


Link Posted: 11/27/2008 8:37:09 AM EDT
[#11]
Quoted:
I hope you are kidding...what is this 85 gr load good for? How about meeting the required terminal performance guidelines while being relatively barrier blind, as well as lead free.



I hope you're kidding? You guys come up with the most off the wall high speed low drag "criteria" for this sporting cartridge[>:/]

and this does what in the real world vs other 100% copper bullet loads? Are you saying that any living thing, target or piece of equipment will be any deader because this load was used. Are you saying that a 115grn loading won't meet these "critera"

Gimmie a Break,  Fewer Tom Clancy novels and more range time would do this forum good.



Edited to follow the moderator's advice.
Sorry...posted this when I read it on page 2. It wasn't until page three that I read the moderator's take.
Sean

Link Posted: 11/27/2008 8:52:59 AM EDT
[#12]
Quoted:
 Since there are so many different barrel designs on the market, such as Model 1 sales barrels with SAAMI chamber and 1 in 9.5" twist, and the DPMS, with its ridiculously tight chamber, we have been forced to inform people that these guns are not safe testing platforms, when developing 6.8 handloads ....especially if they happened to use the old extreme bullet.




I have a safety question for your HTR (btw, I'm learning a LOT from your commentary...thanks).

I have a LWRC 10.5" 6.8 SPC with the SPC II chamber and polygonal rifled 6 groove 1:10 twist bbl.

I also have probably 700+ rounds of SSA Extreme copper plated ammo left over (was shooting about 500 rounds of it through my original SAAMI spec 6.8 LWRC.....that LWRC was gracious enough to swap out to the new chamber spec).  I never experienced the "copper rings".....but I kept checking it and cleaning it to make sure it never built up.

Is this stuff safe to shoot in my SPC II chamber or am I going to have a kaboom if I shoot the rest of it up?  B/c of the cost of this ammo originally, I hate to just pull the bullets and have really expensive reloading brass.

What about reloading the 500 rounds of brass?  Was the pressure likely too high to be safe to reload the brass too?

Any help you (or others can give) would be appreciated.  I don't currently reload, but I love the 6.8 round and can't afford to buy factory ammo and shoot it as much as I'd like.  Ever since hearing about the issue with Extreme ammo, I've been using Art's OTM, some old crappy Remington 6.8, and Hornady.


If you can answer this here or via IM I'd appreciate it....or I can start a thread on 68forums if you'd prefer.

Again, thanks for the help.

Sean
Link Posted: 11/27/2008 9:08:19 AM EDT
[#13]
Quoted:
16" 1/10 barrel, 3099 fps MV, block at 10 feet.  FWIW, the results are nearly identical when tested at 100 yards...

For civilian hunting, a 55K pressure is probably OK; for military use, 50-52K is a better way to go.  Here is what Cris Murray, a designer of 6.8 mm and 7x46 mm, wrote recently about the pressures in the two cartridges he has helped birth:

""Pressures must be kept below 52K or during a fight your rifle will be usless after the second magazine.  True, during slow fire you can push the pressures up, the Army's long range 5.56 match load is a 90 gr projectile over 60K, but its slow fire-single loaded for 1000yd matches only.  The old 1000yd, 180 gr 7.62 match load would literally melt down a M14 if you could've loaded them in a magazine and shot them for rapid fire.  This is the one reason I restarted worked on the 7x46UAC, because it allows excellent ballistics without 52K+ pressures that would render it usless in a real fight.  I've got factory made 7x46mm brass from Privi Partizan.  Their brass is made straight from long 7.62x39 blank cartridge case they make and has the nice thick Russian rim, I want.  Hopefully I'll be able to finish the pressure and powder tests this time, I'm trying to keep the speed at 2650 fps with a 130 gr projectile with pressure below 50K; all this out of a 16.5in barrel.  The last tests were good, but I need to document them with telemetry."


This, IMO, is the most interesting post in this thread and no one really commented on it.  Perhaps it's b/c you guys all understand the significance.  I do not and would really appreciate an explanation if possible.

Does anyone know what kind of pressures this new 85 gr. TSX round is building in a SPC II chamber?  


I have a SBR LWRC 6.8 10.5", SPC II 6 groove, polygonal rifled 1:10 twist bbl.  I've never really run it hard enough to go through 2+ mags back to back and at $.70+ per shot, I'm damn near too poor to afford it shooting even at a much slower pace.

Eventually, I'd like to take this thing to a carbine class.....but the above sounds like if I take "combat" loads, I could do something bad to the gun (what, I'm not exactly sure).

I normally run SSA OTM, but would like to buy some of the new 90 gr. TNT or varminter loads (admittedly mostly b/c of the price for practice ammo).....are any of these above the 52K pressure point cited above?

If so, what's the safest ammo that will run in the gun if I were to A LOT of fairly rapid shooting?

Thanks in advance for any help you can give.

Sean
Link Posted: 11/27/2008 9:30:35 AM EDT
[#14]
Quoted:
Quoted:
 Since there are so many different barrel designs on the market, such as Model 1 sales barrels with SAAMI chamber and 1 in 9.5" twist, and the DPMS, with its ridiculously tight chamber, we have been forced to inform people that these guns are not safe testing platforms, when developing 6.8 handloads ....especially if they happened to use the old extreme bullet.




I have a safety question for your HTR (btw, I'm learning a LOT from your commentary...thanks).

I have a LWRC 10.5" 6.8 SPC with the SPC II chamber and polygonal rifled 6 groove 1:10 twist bbl.

Though it is not what most of us would consider a "true" Poly (those usually have 5 "lands") it seems that LWRC's guns are handling the combat loads well.  Their rifling design seems to ge quite good in terms of relieveing pressure.  Art from SSA tested these guns and said that if they had the SPCII chamber they were GTG.  Unfortunately, we never got an upper from Jesse at LWRC, so we were not able to put the pressure trace transducer on one, so I can't give you the pressures of the combat versus commercial loads.  I would presume that gun is giving about 58K PSI, though.

I also have probably 700+ rounds of SSA Extreme copper plated ammo left over (was shooting about 500 rounds of it through my original SAAMI spec 6.8 LWRC.....that LWRC was gracious enough to swap out to the new chamber spec).  I never experienced the "copper rings".....but I kept checking it and cleaning it to make sure it never built up.

Is this stuff safe to shoot in my SPC II chamber or am I going to have a kaboom if I shoot the rest of it up?  B/c of the cost of this ammo originally, I hate to just pull the bullets and have really expensive reloading brass.

the SPC II chamber was initially designed so that the Extreme could not obturate as easily at the forcing cone like it was in the SAAMI.  That bullet is soft and plated not jacketed, so while it is still possible, I think the SPCII chamber alleviated the problem.  If I were you, though, I would take no chances, and contact SSA.  Ask them if they will exchange the extremes for some different ammo, since that has been pulled.  I belive that they will.

What about reloading the 500 rounds of brass?  Was the pressure likely too high to be safe to reload the brass too?

Doubtful.  I think you will be fine there.  I have about 8-9 reloads on my highest pressure loads without failure.  The SSA brass is awesome.

Any help you (or others can give) would be appreciated.  I don't currently reload, but I love the 6.8 round and can't afford to buy factory ammo and shoot it as much as I'd like.  Ever since hearing about the issue with Extreme ammo, I've been using Art's OTM, some old crappy Remington 6.8, and Hornady.

This 85 grain Barnes TSX is perfect for your LWRC 10.5 inch barrel.  1 X 10 twist is actually probably OK for SBR's as long as you have the SPCII chamber.  Twist is among the things that least changed the pressure.  We thing that Chamber, and rifling number & design is more important overall than just the number of turns.


If you can answer this here or via IM I'd appreciate it....or I can start a thread on 68forums if you'd prefer.

Again, thanks for the help.

Your welcome, HTH

Sean


Link Posted: 11/27/2008 9:53:15 AM EDT
[#15]
Quoted:
Quoted:
16" 1/10 barrel, 3099 fps MV, block at 10 feet.  FWIW, the results are nearly identical when tested at 100 yards...

For civilian hunting, a 55K pressure is probably OK; for military use, 50-52K is a better way to go.  Here is what Cris Murray, a designer of 6.8 mm and 7x46 mm, wrote recently about the pressures in the two cartridges he has helped birth:

""Pressures must be kept below 52K or during a fight your rifle will be usless after the second magazine.  True, during slow fire you can push the pressures up, the Army's long range 5.56 match load is a 90 gr projectile over 60K, but its slow fire-single loaded for 1000yd matches only.  The old 1000yd, 180 gr 7.62 match load would literally melt down a M14 if you could've loaded them in a magazine and shot them for rapid fire.  This is the one reason I restarted worked on the 7x46UAC, because it allows excellent ballistics without 52K+ pressures that would render it usless in a real fight.  I've got factory made 7x46mm brass from Privi Partizan.  Their brass is made straight from long 7.62x39 blank cartridge case they make and has the nice thick Russian rim, I want.  Hopefully I'll be able to finish the pressure and powder tests this time, I'm trying to keep the speed at 2650 fps with a 130 gr projectile with pressure below 50K; all this out of a 16.5in barrel.  The last tests were good, but I need to document them with telemetry."


This, IMO, is the most interesting post in this thread and no one really commented on it.  Perhaps it's b/c you guys all understand the significance.  I do not and would really appreciate an explanation if possible.

You are asking some good questions, Sean.  I'll give my answers and ask DocGKR to chime in if he can improve upon them.  Murray's comment details some of the weaknesses inherent to the AR-15 / M4 / M16 platform.  Namely, the bolt lugs are pretty small, and there are parts, which, when subject to rapid fire, and thus high and increasing pressure with heating, constitute such weak links in its design.  Parts like the extractor and bolt lugs are well-known to be subject to failure around 60-65,000 PSI and above.  So, the SAAMI limit of 55,000 is a mid point between the highest pressure rounds of around 60K and the lower pressure rounds in the 50K range.....easy.

Less simple (since it is often debated) is the idea that the AR-15 can consistently take pressures of 60,000 if single, slow-fired.  Thus, for civilian hunting (like what I do mostly)  loading to 58,000 is no problem, as long as you use really good parts, like the LMT enhanced bolt and the YNM carrier or the BCM carrier.  Another great upgrade is the H2 or even H3 buffer paired with a SSS flat-wire spring.

But if you are in combat, just think how disastrous a broken extractor or bolt lug could be.  Moreover, if you are in the heat of a desert, the rifle and the cartridges (and their powder)  heat up, and pressure rises.  This is the reason that a margin of 3-5000 PSI is needed to assure that the rifle can take hundreds upon hundreds of rounds in rapid fire and keep the soldier in the fight.

Perhaps if we had adopted the Robinson XCR, we might have gotten away with 60,000 PSI, but we did not.




Does anyone know what kind of pressures this new 85 gr. TSX round is building in a SPC II chamber?  

Not yet, but I would guess it must be in the area of 52-55,000 PSI because I see no primer flattening or ejector swipes on my brass.  In the pressure transducer testing, we approximated that these start to show up when you get over  58,000 PSI, and primers might start popping out at > 65,000 PSI (we never popped a single primer in the test).   The DPMS gun actually generated the higest pressure seen with all loads, because its chamber was the tightest.  Take that FWIW.  All Barnes bullets seem to reduce pressure since the gas rings reduce bearing surface area.


I have a SBR LWRC 6.8 10.5", SPC II 6 groove, polygonal rifled 1:10 twist bbl.  I've never really run it hard enough to go through 2+ mags back to back and at $.70+ per shot, I'm damn near too poor to afford it shooting even at a much slower pace.

Eventually, I'd like to take this thing to a carbine class.....but the above sounds like if I take "combat" loads, I could do something bad to the gun (what, I'm not exactly sure).

I normally run SSA OTM, but would like to buy some of the new 90 gr. TNT or varminter loads (admittedly mostly b/c of the price for practice ammo).....are any of these above the 52K pressure point cited above?

If so, what's the safest ammo that will run in the gun if I were to A LOT of fairly rapid shooting?

It is likely that any of the SSA commercial rounds will be right in the 52,000 range in that gun, but the Barnes' will usually be slightly less in all loadings as mentioned above, so if I were you, I would run either the barnes TSX's in you classes, or pehaps the 90 grain varminter.  You should be GTG.  Please give us a range report afterward!

Thanks in advance for any help you can give.

Sean


Link Posted: 11/27/2008 11:13:36 AM EDT
[#16]
HTR....

Thanks SOOO much for the explanation and recommendations.  

I've been in contact with Art about the Xtreme ammo before and he couldn't exchange them, but he did give me a deal on my last ammo purchase from them.

This whole small lug design of the AR has me seriously looking at an XCR (you may have seen my question in the 68 forum).  Finding one for a decent price may be the big hurdle though.



Thanks again for the help.  I'll letcha know how things go with the new ammo.

Sean
Link Posted: 11/27/2008 6:09:19 PM EDT
[#17]
Quoted:

Also, the 110 gr TSX generally penetrates beyond 20"


No it doesn't.  Brassfetcher tested the 110 gr TSX in bare gel and it penetrated about 15 inches.

http://www.brassfetcher.com/6.8mm%20SPC%20110gr%20Barnes%20Triple-Shock%20X-Bullet%20(Silver%20State%20Armory).html

Thanks for gel testing the 85 gr though!  It looks like a great round, and with more penetration than the 110 gr, I may just have to pick it up.

BTW, can you gel test the 115 gr Remington MC?  Pleeeeease..

Link Posted: 11/27/2008 8:03:52 PM EDT
[#18]
SnakeLogan,

You are in error.

The 110 gr TSX penetrates substantially deeper than the 85 gr TSX––you are misreading the Brassfetcher info; the shot pictured on Brassfetcher appears to have completely penetrated the 15 inch long block and according to the accompanying text then penetrated an additional inch into some sort of "polyester" backing material.  In every test I have ever seen of the 110 gr TSX, the bullet has penetrated beyond 18"-20" on unobstructed shots, while the 85 gr TSX stops in the 15-18" range.
Link Posted: 11/27/2008 9:46:27 PM EDT
[#19]
edit:  nevermind.  Posted before I saw Cold's warning on pg. 2...
Link Posted: 11/28/2008 6:17:12 AM EDT
[#20]
Quoted:
SnakeLogan,

You are in error.

The 110 gr TSX penetrates substantially deeper than the 85 gr TSX––you are misreading the Brassfetcher info; the shot pictured on Brassfetcher appears to have completely penetrated the 15 inch long block and according to the accompanying text then penetrated an additional inch into some sort of "polyester" backing material.  In every test I have ever seen of the 110 gr TSX, the bullet has penetrated beyond 18"-20" on unobstructed shots, while the 85 gr TSX stops in the 15-18" range.


Thanks for clearing that up.
Link Posted: 11/28/2008 7:43:07 AM EDT
[#21]
BTW, Doc, do you have a photo of the 110 gr TSX penetrating 18+ inches?
Link Posted: 11/28/2008 4:34:35 PM EDT
[#22]
Yes, several.
Link Posted: 11/28/2008 7:06:27 PM EDT
[#23]
Can you post it/them?
Link Posted: 11/28/2008 11:07:50 PM EDT
[#24]
Quoted:
Yes, several.


best answer in this thread


Link Posted: 11/29/2008 8:30:18 AM EDT
[#25]
Link Posted: 11/29/2008 10:12:11 AM EDT
[#26]


Another impressive load by SSA; the 110 gr TSX is a great choice for hunting almost all medium to large game in the lower 48 states where you don't want fragments of metal in your meat...
Link Posted: 11/29/2008 11:12:48 AM EDT
[#27]
Wow, great pic, thanks Doc!  I'd trust that to drop game up to 400 lbs.

Now you just gotta test the 115 Remington MC!

BTW, what length barrel was used and what distance was the gel shot from?
Link Posted: 11/29/2008 11:27:29 AM EDT
[#28]
16", 2592 fps MV, 100 yds
Link Posted: 11/29/2008 11:29:12 AM EDT
[#29]
The Remington 115 gr FMJ is not particularly of any interest, as none of the organizations we test for use it or desire it tested...
Link Posted: 11/29/2008 11:40:01 AM EDT
[#30]
Link Posted: 11/29/2008 12:44:50 PM EDT
[#31]
No clue as to barrel maker, you would have to ask Art about that one.
Link Posted: 11/30/2008 11:52:07 AM EDT
[#32]
All test were preformed with a (believe it or not) a Shaw 1-10 twist with a Spec II chamber. We did it that way to give the best representation of most of the currently configured barrels are.

Art - SSA
Link Posted: 3/8/2009 10:26:24 AM EDT
[#33]
Below is some new 6.8 mm test data we recently completed:

6.8 mm Hornady 110 gr OTM, vel=2613 fps from a 16” 1/11
BG:  pen=17.7”, NL=3.5cm, Max TC [email protected] from 3.5-20cm, RD=0.50”, RL=0.37", RW=80.0gr
Glass:  pen=14.0", NL=0.5cm, Max TC [email protected] from 0.5-24cm, RD=0.32", RL=0.51", RW=74.5gr

6.8 mm SSA 115 gr OTM (SMK), vel= 2520 fps from a 16" 1/11
BG:  pen=15.0”, NL=5cm, MAX TC [email protected] from 5-28cm, RD=0.49”, RL=0.26", RW=53.5gr
Glass:  pen=12.8", NL=0.5cm, Max TC [email protected] from 0.5-19cm; RD=0.48", RL=0.20", RW=32.7gr

While both the Hornady 110 gr OTM and SSA 115 gr SMK OTM offer acceptable terminal performance, the Hornady projectile is more consistent.

In addition, since we had a bit of gel left over, single shots of the following loads were made:

6.8 mm Remington 115 gr FMJ, vel=2436 fps from a 16" 1/11
BG:  pen=15"+, NL=7cm, Max TC [email protected] from 7-32cm, RD=0.40x0.15” (bullet flattened), RL=1.09”, RW=96.3gr



6.8 mm Hornady 110 gr VMAX PT, vel=2522 fps from a 16" 1/11
BG:  13.8", NL=0.5cm, Max [email protected] from 0.5-20cm; RD=0.54”, RL=0.22”, RW=55.5gr



6.8 mm Speer 90 gr TNT JHP, vel=2610 fps from a 16" 1/11
BG:  13.8"+, NL=4.5cm, Max [email protected] from 4.5-24cm; RD=NR, RL=NR, RW=NR



A review of common 6.8 mm projectiles is available at:  http://www.m4carbine.net/showthread.php?t=19884
Link Posted: 3/8/2009 10:59:09 AM EDT
[#34]
Quoted:
Below is some new 6.8 mm test data we recently completed:

6.8 mm Hornady 110 gr OTM, vel=2613 fps from a 16” 1/11
BG:  pen=17.7”, NL=3.5cm, Max TC [email protected] from 3.5-20cm, RD=0.50”, RL=0.37", RW=80.0gr
Glass:  pen=14.0", NL=0.5cm, Max TC [email protected] from 0.5-24cm, RD=0.32", RL=0.51", RW=74.5gr

6.8 mm SSA 115 gr OTM (SMK), vel= 2520 fps from a 16" 1/11
BG:  pen=15.0”, NL=5cm, MAX TC [email protected] from 5-28cm, RD=0.49”, RL=0.26", RW=53.5gr
Glass:  pen=12.8", NL=0.5cm, Max TC [email protected] from 0.5-19cm; RD=0.48", RL=0.20", RW=32.7gr

While both the Hornady 110 gr OTM and SSA 115 gr SMK OTM offer acceptable terminal performance, the Hornady projectile is more consistent.

Wow!  I have mags loaded with the Hornady 110gr VMax and SSA 115gr OTM, but I may have to get some of the hotter Hornady OTM instead.  I like those velocities.

Link Posted: 3/9/2009 9:22:33 AM EDT
[#35]
Thanks for posting this,  Gary  
Link Posted: 3/9/2009 8:16:58 PM EDT
[#36]
Link Posted: 3/15/2009 9:34:03 PM EDT
[#37]
Thanks for those shots. I've really wanted to see how the TNT performed.
Link Posted: 3/16/2009 6:05:28 PM EDT
[#38]
 Gotta love the loads Art puts out
Link Posted: 3/17/2009 7:51:14 PM EDT
[#39]
Quoted:
Quoted:I don't know about ya'll but if I need to put a hole in something 400m away I'll just reach inside the safe and pull out a bolt gun chambered for a full powered rifle cartridge


...then I guess we'll see you later.



My M4 is perfect for 400m. I don't need a "rifle" round until 800m or so.
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