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Posted: 5/22/2006 10:41:38 AM EDT
6.8 SPC Resource/FAQ Page
6.8 SPC Reloading Resources (including recipies) --------------------------------------------------------------------------------------------------- Since the other thread was about to hit the "40 page limit" wall.. Links to Other Discussions/FAQs Original 6.8 Thread (Archived - Members Only) 6.8 Thread Part II (Archived - Members Only) Zak's FAQ 6.8SPC.com (Randall's FAQ/List of Links) 2004 NDIA Small Arms Symposium Presentation on the 6.8 SPC (Power Point File) Wikipedia Entry for 6.8 SPC Links to Reloading Data Zak's Reloading Data Hodgdon's 6.8 SPC Reloading Data IMR's 6.8 SPC Reloading Data Preferred Muzzle Thread Pattern: 5/8-24 Dimensions of the 6.8 SPC Case (courtesy of J-A-R and kalwasart) Case length = 1.686" -.020 Base to neck = 1.414"-.008 Base to Shoulder = 1.310" should be 1.301 -.008 Neck I.D. = .277" -.003 Neck O.D. = .306"-.008 Shoulder O.D. = .401"-.008 Base O.D. = .421"-.008 Wall Thickness at Shoulder = .016" Wall Thickness at Base = .032" Web Thickness = .200" Head spacing = 1.350" -.007 Trim To Length = 1.676" (from Hodgdon Powder Co) Note from Art (kalwasart): You will have to work to the bottom of the spec otherwise the case will not work in a DPMS or CMMG weapon. Primer Used Remmington & Silver State (prior to July 2006) use Large Rifle Primers Horady & Silver State (July 2006 and after) use Small Rifle Primers Case Capacity = 34.8 grains of water Chamber Pressure = 55,000 psi MAP (via conformal transducer) Typical Muzzle Velocities (115gr projectile) 24" Barrel: 2800 fps 16" Barrel: 2500-2625 fps 12" Barrel: 2475 Weight Comparisons: 28 Rounds 6.8 SPC (115gr OTM): 1.06 lbs 30 Rounds 5.56 (62gr FMJ): .76 lbs 20 rounds 7.62x51 (150gr FMJ): 1.07 Ballistic Coefficients of various 6.8 SPC (.277) Bullets Barnes Triple Shock TSX-BT 110gr: .323 Hornady 110gr Ballistic Tip (V-Max): .370 Hornady 110gr OTM: .352 Hornady 115gr OTM (cannalured): .340 Nosler 150gr Ballistic Tip: .496 Remmington 115gr FMJ: .292 Remmington 115gr OTM: .344 Remmington 115gr HPBT Match: .333 Remmington 115gr Core-Lokt Ultra Bonded: .295 Sierra Match King (SMK) 115gr OTM: .324 (2400fps+), .317 (2400->1800fps) Sierra Pro Hunter 110gr SP: .314 ( 2800->2000fps), .308 (2000-1600fps) Sierra Varminter 90gr OTM: .203 (2800->2200fps), .219(200->1800fps) Speer 90gr TNT OTM: .275 X-Treme TMJ 115gr (used in the SS TMJ Load): .203 All info on Vendors and who supplies what for rifles, parts, ammo, and reloading can be found in the 6.8 SPC FAQ link at the begining of this post. SAAMI Specs for Round & Chamber (courtesy of Art & Randall)  Photos of Rifle moved to a later post, this post will be reserved for 6.8 SPC Data/Information |
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Posted: 5/22/2006 11:09:45 AM EDT
[#1]
VERY nice rifle Forest, I may have to copy that build when i get my 6.8 AR up and running...
I have used AA2520 in my 223 AR for heavy bullets with much success, have yet to try it in the 6.8. I will try it there too! |
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Posted: 5/22/2006 11:15:51 AM EDT
[#2]
Ok decision making time...age old question 6.8 opr 6.5G, the only reason i can find to lean towards a grendel is the larger spread in available bullet weights, so is it possible to squeeze a nosler 140 in a 6.8 and still be at mag length without serious risks? My end result is going to be 115gr for paper punching and the 140 for god's furry creatures.
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Posted: 5/22/2006 11:17:43 AM EDT
[#3]
Please do not put 6.5 vs 6.8 stuff in this thread.
You can definitely go 130, but I'm not sure about 140. In either case, the velocity will be low. My advice is to choose a better bullet in the 110-120gr range, such as the Barnes TSX. |
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Posted: 5/22/2006 11:24:49 AM EDT
[#4]
I've run 150's before without issue, but not enough to know that they are 100% accurate, reliable, etc.
Stephen 
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Posted: 5/22/2006 12:24:55 PM EDT
[#5]
I agree with Zak, we have been testing the Barnes 110 grain TSX with the following results. 2,715 FPS 16 inch barrel. A gun writer has tested it with a bench rest 6.8 and gets under .400 of an inch max spread at 100 yards. I think it will be great hunting round. we will be offering it in about 2 weeks. Art - SSA |
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Posted: 5/22/2006 12:59:41 PM EDT
[#6]
I'VE USED THE SEARCH ENGINE BUT COULDN'T FIND ANY DATA, HAS ANYONE HAD ANY SUCCESS IN THE SUBSONIC REALM FOR THIS CALIBER? WHAT POWDERS WERE YOU USING? MAGNUM PRIMERS? ALSO, WHICH BULLET 130GR, 140GR? ANY HELP WOULD BE GREATLY APPRECIATED.
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Posted: 5/22/2006 2:07:53 PM EDT
[#7]
Agreed on the 110gr-120gr advice. Art, are you going to offer a load with the Hornady 110gr OTM? Hopefully in the next couple of weeks LMT will ship the MRP 6.8SPC barrels & bolts. I have 2 MRP's that have been waiting a long time for this.  Just wish LMT had released an equivalent SS barrel to their 5.56MM first.
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Posted: 5/22/2006 2:22:17 PM EDT
[#8]
As far as the velocity issue with a heavier bullet - I am planning on a 24 inch if not 28 inch barrel so i should get a little better speed out of it. My main concern was if seating that deep could cause a problem with safety or not.
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Posted: 5/22/2006 9:59:50 PM EDT
[#9]
Tag
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Posted: 5/22/2006 10:06:33 PM EDT
[#10]
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Posted: 5/23/2006 4:25:58 AM EDT
[#11]
My CMMG mid-length upper cut to 14in w/can!
  
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Posted: 5/23/2006 5:17:44 AM EDT
[#12]
Hornady is not interested in selling to us their projectiles, as they make their own loads with their OTM. Their OTM is a good projectile but their velocity is around 2,525 - 2,550 FPS. With the Barnes TSX we are nearly 200 FPS faster at the same weight of 110 grains = more energy and the TSX has excellent glass penetration something I would think the RMP would want. Art - SSA |
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Posted: 5/23/2006 5:42:37 AM EDT
[#13]
New 6.8 Configuration, just need to take the pic............
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Posted: 5/23/2006 10:06:22 AM EDT
[#14]
User Info IM User Email User Reply Quote
-------------------------------------------------------------------------------- Ok decision making time...age old question 6.8 opr 6.5G, the only reason i can find to lean towards a grendel is the larger spread in available bullet weights, so is it possible to squeeze a nosler 140 in a 6.8 and still be at mag length without serious risks? My end result is going to be 115gr for paper punching and the 140 for god's furry creatures. I know two furry creatures (deer) that were killed cleanly with the 110 Barnes TSX, in fact being a 270 fan for 20 years I was very inpressed with the 110 gr. all copper bullet. I will always think of the 270 fondly though it may forever rest comfortably in the safe on the Michigan opener. My new best deer gun is an AR 6.8 w/110 TSX. Art is squeezing an additional 100 fps than I was getting with handloads so it's all good . |
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Posted: 5/23/2006 7:58:30 PM EDT
[#15]
Accurate doesn't provide data for the 6.8, but they do have data for AA2520 in .223 with projectiles from 40 to 80gr. Accurate Arms rifle load data |
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Posted: 5/24/2006 6:10:48 PM EDT
[#16]
Finally was able to chrono 3 handloads and 4 factory loads(at 100yards) today in my M1S/ER Shaw 6.8mm 20" A4. Bushnell 3200 Elite 10X, Olyarms "multi" lower, RRA NM 2stage trigger, CAA G27 grip, A2 stock, Samson FF. Sorry if pix are too big.
    My rifle seems to like 100gr SIE spitzer and SSA 115gr xtreme. I know I need to practice proper breathing more. I was using a front rest, no rear. |
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Posted: 5/25/2006 4:59:04 AM EDT
[#17]
I"m no expert on 6.8, but just wanted to note that if you don't know, there is a point where barrel length is not adding velocity. With the low powder charge of the 6.8, and with powders like IMR 4198, I'd be pretty certain that anything over 20-22" is not helping velocity much at all Once the powder is burnt up, acceleration of the bullet stops, and any length of the barrel the bullets still has to travel will be drag and slow it down. Ideally, the optimal barrel length is when the bullet exits just before the powder is burnt up. There would be a point where the powder is still burning, but not enough pressure is created to accelerate the projectile. |
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Posted: 5/25/2006 5:37:54 AM EDT
[#18]
You are correct if you are keeping only with one powder. To get max preformance from a longer barrel (24 - 28) you would need a slower burning powder taylored to the weight of projectile you are using. Art - SSA |
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Posted: 5/25/2006 5:42:00 AM EDT
[#19]
If you replaced "powder is still burning" with "gas is still expanding" you would be much closer to right. The 6.8 SPC will continue to pick up velocity at 48" of barrel, much less 28". David |
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Posted: 5/25/2006 8:29:32 AM EDT
[#20]
It's the gas that propels the projectile. The powder just creates the gas. The projectile does not stop accelerating until the gas is fully expanded. Here is my velocity series in case you missed it back in August. |
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Posted: 5/25/2006 6:30:48 PM EDT
[#21]
I was thinking it was a given that the powder produced expanding gas which propelled the projectile. I didn't specify expanding gas becuase I thought we were all already on the same page.
I'm surprised that there is a powder that would continue to propel the projectile as much as 48". (Not doubting you, just surprised) I did miss the series Randall. I've just become interested in the 6.8 as I consider it for a short to medium range caliber for use with my .30 cal suppressor. |
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Posted: 5/25/2006 10:32:10 PM EDT
[#22]
Fun with quickload.
Below is a completely arbitrary 6.8 load I ran just to demonstrate the pressures remaining in the bore behind a bullet at REALLY long barrel lengths. There is some debate as to what pressure threshold is required of a bullet to overcome bore friction and therefore what pressure level the bullet would actually start to decelerate in the bore. Numbers vary from 7500 on military 224 caliber bullets to probably less than 1000 PSI on 45 caliber lead bullets. Quickload does not seem to allow for bore friction properly as they will accelarate a bullet forever where the pressure would obviously be too low to sustain accelaration. Cartridge : 6.8 mm Rem SPC Bullet : .277, 130, Sierra SPBT 1820 Cartridge O.A.L. L6: 2.283 inch or 57.99 mm Barrel Length : 150.0 inch or 3810.0 mm Powder : Hodgdon H335 Charge : 27.5 grains or 1.78 grams Estimates of the progress of combustion: Travel (in) Velocity (FPS) Pressure 0.00003 1.2 3823 0.00013 2.8 4085 0.00037 4.9 4444 0.00083 7.6 4883 0.00164 11.1 5450 0.00291 15.4 6164 0.00482 20.9 7039 0.00753 27.5 8099 0.01125 35.5 9366 0.0162 45.3 10866 0.02263 56.8 12609 0.03081 70.5 14612 0.04102 86.5 16880 0.05358 105.1 19409 0.06882 126.5 22178 0.0871 150.9 25156 0.10879 178.5 28297 0.13432 209.4 31540 0.16408 243.5 34815 0.19854 281.1 38045 0.23816 321.9 41157 0.28343 365.9 44067 0.33486 412.9 46715 0.393 462.8 49039 0.4584 515.3 50997 0.53163 570.1 52564 0.61331 627 53724 0.70406 685.7 54485 0.80452 745.8 54858 0.83223 761.6 54894 0.84747 770.2 54903 0.85583 774.8 54906 0.8604 777.4 54906 0.86538 780.1 54906 1.05142 876.5 54494 1.16715 930.8 53955 1.16715 930.8 53955 1.21291 950.7 53660 1.25987 970.5 53327 1.30808 990.4 52958 1.35759 1010.2 52554 1.40845 1030.1 52118 1.46072 1049.9 51651 1.51445 1069.7 51156 1.56969 1089.6 50634 1.62652 1109.4 50087 1.68499 1129.3 49516 1.74517 1149.1 48923 1.80713 1168.9 48310 1.87093 1188.8 47678 1.93665 1208.6 47027 2.00437 1228.5 46361 2.07417 1248.3 45680 2.14614 1268.2 44985 2.22036 1288 44277 2.29692 1307.8 43559 2.37593 1327.7 42830 2.45748 1347.5 42093 2.54168 1367.4 41347 2.62864 1387.2 40595 2.71848 1407.1 39836 2.81133 1426.9 39073 2.9073 1446.7 38306 3.00654 1466.6 37536 3.1092 1486.4 36763 3.21541 1506.3 35990 3.32534 1526.1 35215 3.43915 1546 34441 3.55702 1565.8 33668 3.67913 1585.6 32896 3.80568 1605.5 32126 3.93686 1625.3 31360 4.07291 1645.2 30597 4.21404 1665 29838 4.36049 1684.9 29084 4.51252 1704.7 28335 4.6704 1724.5 27591 4.83442 1744.4 26854 5.00486 1764.2 26124 5.18206 1784.1 25401 5.36635 1803.9 24685 5.55809 1823.8 23978 5.75766 1843.6 23278 5.96546 1863.4 22588 6.18192 1883.3 21906 6.40749 1903.1 21234 6.64266 1923 20571 6.88795 1942.8 19918 7.14389 1962.6 19276 7.41108 1982.5 18644 7.69014 2002.3 18022 7.98174 2022.2 17411 8.28657 2042 16811 8.6054 2061.9 16222 8.93904 2081.7 15645 9.28835 2101.5 15079 9.65427 2121.4 14524 10.03778 2141.2 13981 10.43996 2161.1 13450 10.86195 2180.9 12930 11.30498 2200.8 12423 11.77036 2220.6 11927 12.25953 2240.4 11443 12.77401 2260.3 10971 13.31546 2280.1 10511 13.88566 2300 10063 14.48654 2319.8 9627 15.12017 2339.7 9203 15.78881 2359.5 8790 16.49491 2379.3 8389 17.24111 2399.2 8000 18.03028 2419 7623 18.86556 2438.9 7257 19.75035 2458.7 6903 20.68834 2478.6 6560 21.6836 2498.4 6229 22.74053 2518.2 5908 23.86398 2538.1 5599 25.05923 2557.9 5300 26.3321 2577.8 5012 27.68896 2597.6 4735 29.13683 2617.4 4468 30.68345 2637.3 4212 32.33735 2657.1 3965 34.10796 2677 3729 36.00572 2696.8 3502 38.04223 2716.7 3285 40.23034 2736.5 3077 42.58439 2756.3 2878 45.12036 2776.2 2689 47.85611 2796 2508 50.81166 2815.9 2336 54.00947 2835.7 2172 57.47478 2855.6 2016 61.23611 2875.4 1868 65.32566 2895.2 1728 69.77992 2915.1 1596 72.75652 2927.4 1517 |
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Posted: 5/28/2006 8:11:12 AM EDT
[#23]
I thought I should post my new Noveske 6.8 12.5 results here....A full shoot and look report here ar15.com/forums/topic.html?b=3&f=12&t=282555&page=1 and here ar15.com/forums/topic.html?b=6&f=18&t=199255
I am quite pleased I did not take too much of a velocity hit compared with my 18" at an average at 2575 fps or so. Same loads below with the 12.5" upper as my 18" load out. Took the Noveske out a few days back and finally chrono'd some data with both the hand loads and the Remington Express stuff. The gun HATED the Rem. Express stuff btw. Using 29.0gr of H322 and a 110gr V-Max with Rem brass, got the following 5 shot worth of data. 2408 2400 2416 2403 2422 Average: 2410fps Best Group Size 3/4"  The next string is with the Remington factory 6.8 SPC 115gr MC R68R2 2290 2220 2309 2291 2291 Average: 2280fps Group Size: 4.5"! I am a bit worried on the Remington Express accuracy...I need to obtain some Rem Exp. Match stuff to see how it performs. I will also try some Hornady I have laying around as well. I DO need to use factory loads so thus far the factory lots are concerning...Overall, the handloads are at 3/4" and this is what I have come to expect from this upper. A night shoot to follow to look at the KX3. I need to run more hand loads first, I ran out!   |
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Posted: 5/28/2006 8:26:08 AM EDT
[#24]
Victor- That target style looks VERY familiar as we have the same style at WEGC. Is that where you shoot? Perhaps you have seen me if you are a WEGC member. I drive the blue (rusted) ford ranger. |
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Posted: 5/28/2006 9:03:14 AM EDT
[#25]
So this might look familar to you then...  It's not the WEGC though...After hours, several of the local and fed folk get to test out some gear. Lot's of fun!  Also, a report on the 6.8 TAP from the Hornady folks I had not seen before. (Bottom of the page) Sorry if this has been repeated, I have not kept too close an eye on THREE PAGES of 6.8 data, wow!  www.policeone.com/police-products/firearms/accessories/ammunition/articles/126691/
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Posted: 5/30/2006 7:46:24 AM EDT
[#26]
Art-SSA
Back over 30 days ago a topic of CMMG upper and SSA ammo became a sort of heated topic. You had made an offer of ammo to try in my CMMG upper. You had sent several e-mails with notes w/ the ammo is on the way. After over 30 days, I purchased some on my own, to try in the CMMG upper. I purchased only 2 boxes of SSA ammo to run in my upper. I did notice that the cases had a hard time extracting and a few signs of high pressure were present w/ 2 blown primers. Not sure why. But, I will return to my hand loads and stick with other loadings. A little over a hundred FPS will not make a difference to me. I wish that I could have run some new production ammo, but after this small test it is not worth the risk of blowing an upper up or something else. I will no longer be able to test your ammunition. Thanks for the offer. I am sure that it may run fine in other uppers. As stated, This is my own finding and info has been posted.Thanks
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Posted: 5/30/2006 8:15:03 AM EDT
[#27]
Has anyone worked up loads using the Remmington 115gr FMJ projectile? I just bought a box of them from Midway. I figure I'd start loading with these as they are half the price of the 110gr Horady's I also picked up.
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Posted: 5/30/2006 8:39:35 AM EDT
[#28]
I have worked up some loads w/ the Remington FMJ. I use 26.5 grains of RL10X and seat them out to a working length in my PRI mags. They shoot close to my 110 grain Hornady load, so it works out real well. I can use both w/ out having to re-zero when I just want to plink. I will leave my optic set for the Hornady V-Max load. Hope this helps, need more info, just e-mail.Thanks
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Posted: 5/30/2006 2:25:20 PM EDT
[#29]
I thought you had gotten the ammo, sorry I should have followed up on it, I will have it out tomorrow. We have been working with a custom gun manufacture these past few weeks and it is very interesting the differences in chambers and the proformance variances you get from each. He is currently re-chambering a gun for us that is known to have pressure issues and we should have it back in a couple of days. Art - SSA |
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Posted: 5/30/2006 5:24:33 PM EDT
[#30]
I am using the 110 V-max backed by 29 grns H322 seated to .280. I have put 25 rnds through my Model 1 20" 6.8. Smallest group so far has been 1". I know this is a cop-out but he trigger pull is horendous. Has anyone had any luck with the RRA two stage trigger? What is the pull like?
Matt |
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Posted: 5/30/2006 7:10:28 PM EDT
[#31]
I have a RRA two stage in most all my rifles. They are clean and well worth the money if you like a good trigger. It does aid in tight groups and long range shots. If the cash is tight, take a mil-spec trigger and drop in a yellow spring kit from Brownells, "Part#452-000-007 @ $9.95. It isn't as nice as the RRA two stage, but it's nice for the money, put a little polish on your sear ingagement area and work it for about 15 times and remove and oil, that helps. Hope this helps, enjoy!
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Posted: 6/2/2006 9:16:05 PM EDT
[#32]
Yeah Forest, I have shot a lot of the FMJs from Remington.
I have a 16" and a 20" rifle. The 16 is more accurate with every load I have tested ---except with the FMJs. The best I have gotten from my 16" is 1.455" with 27.0 RL-10X The same load shot .798" in my 20" All were 5 shot groupes The best I have shot was with Sierra Pro hunters in the 16" and H-322 powder. I got one 5 shot groupe of .345" 5 shots SUPER accurate with the 110 Sierras. The next best was the Hornady factory load with 115 V-max at .552" and 3rd was the Barnes X 100 grain (discontinued) with 27.8 gr Rl-10X It was .602" hope this helps |
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Posted: 6/2/2006 10:47:07 PM EDT
[#33]
Why would having a shitty trigger pull be a cop out? Makes a huge difference in accuracy. At 29 grains you are right at the max, try backing off a bit besides getting a new trigger! I think people are forgetting the concept of the 6.8 SPC. Really do not think it was ever intended to be a match round shooting 1/2 moa groups. I thought it was intended to be a round with better terminal ballistics than the 5.56 utilized in the same package. I may be wrong though........ |
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Posted: 6/3/2006 7:16:17 AM EDT
[#34]
Yes but I can get sub 1 moa out if my 5.56 so I want that with my 6.8. I know it is possible it is just going to take some fine tuning. I tried 28.5 and then bumped up to 29, groups got significantly smaller. Nosogns of extreme pressure. So I bumped it to 29.2. Groups opened up again. I have been reloading for about 15 years now so I know how to read the limitations of the brass and gun combo.
Going to try some match kings soon. (Damn my Midway dealer account) Matt |
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Posted: 6/3/2006 7:27:00 AM EDT
[#35]
I think 29.0 is right on. That's what I use. I did the same, went a hair higher than 29 grains of H322 and the groups opened up. No pressure signs for me either. I know of someone here who uses over 29 grains and gets great results... As for the SMK's, good luck. they tumbled at 600 yards and went subsonic at that distance for me. Now the same charge under a Hornady 115 OTM was fine at 600 yards... That's just me and my gun, you may have better luck! ETA: Art, if you ever feel like sending me ammo to test I'll try some any day! My gun does very well with the SSA, better than the Hornady factory 115's. |
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Posted: 6/4/2006 6:57:30 AM EDT
[#36]
Art,
Didn't you say you were working on a 6.8 SPC load that could reach approx. 2800 FPS from a 16" barrel? Any news on that? Also, I think I remember you writing that SSA would start to keep the neck diamater (or some other relevant dimension) on the lower end of the tolerance to compensate for "out of spec chambers." Do I remember correctly or has my memory failed me yet again  ?Thanks. Justin |
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Posted: 6/5/2006 4:48:14 AM EDT
[#37]
You are correct on all counts. We have taken the dimensions right down to the bottom of the spec with regards to head spacing, shoulder height, neck size and AOL. Of course there is ammo out there at distributors and dealers that do not reflict the changes because it was produced a while back. We do have a round that gets 2,800 FPS and thats the Barnes Triple Shock at 110 grains. But we are running into the same problem - tight chambers that in some guns are driving up pressures. PRI or Barrett's have no problems after that only God knows. So what do we do, -- down load --. We will be testing it this week in a Model 1 and we have some ammo on its way to a CMMG custom who will be testing it for us in his personel weapon, I will post the results. A nice article in this months SWAT Magazine testing the Barrett 468, whereas all our three loads out perfomed all other factory loads. Art - SSA |
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Posted: 6/5/2006 10:41:18 AM EDT
[#38]
There was some earlier discussion on using the 6.8 SPC on game larger than deer.
I do not know if a link has been posted to this article yet. It is from Buckmasters Gun Hunter Magazine about using the 6.8 SPC on caribou from a Model 700 bolt gun. http://www.gunhuntermag.com/features/060124Wind.htm
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Posted: 6/5/2006 11:41:32 AM EDT
[#39]
Caribou are as easy to kill as deer. My uncle and cousin have had good results shooting them at 200+ yards with .223s.
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Posted: 6/5/2006 1:34:56 PM EDT
[#40]
My barrels are made with one of the first 6.8 SAAMI spec reamers and I have not had any complaints. My reamer print is the one that everyone on the web uses as their reference. The problem only seems to be the chrome lined shaw barrels you get from Model 1 and others. I guess CMMG is having similar problems now too as I see the warning on their site. The other thing is that it only seems to be the plated bullet that has problems, but of course, that's the cheapest load and so it's probably the most popular as well... |
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Posted: 6/5/2006 2:27:20 PM EDT
[#41]
<center><table width=85% border=0><tr><td width=100% class=textQuote><hr height=1px color=black noshade>Quoted:
My barrels are made with one of the first 6.8 SAAMI spec reamers and I have not had any complaints. <hr height=1px color=black noshade> Nope your barrel runs very well on their 'Combat' TMJ load. Edited to add: Not recently - see range report starting about page 9 |
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Posted: 6/5/2006 3:22:38 PM EDT
[#42]
Your chamber reamer drawing is to SAAMI, I agree.
Bolt face to shoulder you give a dimension of 1.2956. SAAMI cartridge for the same dimension is - 1.3012 minus .008 Head spacing chamber 1.346 min Head spacing cartridge 1.3500 to 1.3430 By the above you can see there is a problem. If i could learn how to link the SAAMI drawing on this web site I would. I know how to scan but from there I am lost. After a lot of testing we know how to get the most from the 6.8, lengthen the headspacing (keep it to the higher side of the tolerance) the shoulder will follow along with it and increase the free bore. Then you can throw a brick thru it at 2,650 FPS with no problems. Tight chambers (and or rifling) are increasing pressures with all projectiles from verious companies in some weapons. No less than two gun writers with their own hand loads were surprised at the differing results they were getting in different weapons. One writer had three different weapons two of which could handle the hotter hand loads and the third weapon could not and these were the top of the line projectiles. But being politically correct they did not but that info into their articles. If you like I can fax you the SAAMi drawing we have. Art - SSA |
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Posted: 6/5/2006 3:39:50 PM EDT
[#43]
Oh man, we got BIG problems then. I have not verified my drawing, reamer or gauges as I trust that PTG should have made it the right way. It almost sounds like the dimensions "as published" are reversed. In other words, they published chamber dims as cartridge dims and then published cartridge dims as chamber dims. Any smart reamer/ammo maker would catch this as you obviously have, but I wonder why SAAMI has not corrected their specs... I IM'd you about the drawing and I will post/host it for you. |
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Posted: 6/5/2006 3:49:05 PM EDT
[#44]
Art, Thanks for clearing that up. Will you be offering this loading? |
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Posted: 6/6/2006 5:00:13 AM EDT
[#45]
As a ammo manufacture we normally do not concern ourselves with chamber dim's we work to published numbers as I am sure barrel manufactures do. We only got into it because the problems that were being reported. I have talked directly to SAAMI'S top tech man and you would not believe the answer I got, "With a little force you can close a bolt gun and with semi's you may have a bit more of a problem" -- DAAAAAAAAA. He had no answer when I mentioned that it would also drive up pressures. He was going to Remington to see what they think as they were the ones who developed the cartridge and submitted it to SAAMI. Remember SAAMI is made up and controled by the big boys which includes Remington. Any changes now would admit error and that may cost them money. I have not heard back from SAAMI in 6 weeks. We now make our cartridges to the bottom of the spec and down load so all guns can handle our rounds. We do have a Combat load with higher velocities but we have to control who gets those rounds. Knowledgable gun manufactures that make full auto weapons have no problems because they as a rule open up the chamber for better feeding during full auto and they inadvertently corrested the problem. Not all dim's are in error just those two, of course they are the two must important ones. Art - SSA |
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Posted: 6/6/2006 12:14:31 PM EDT
[#46]
PLEASE, somebody get this shit fixed... I don't want to become a 6.5G taint.
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Posted: 6/6/2006 4:41:23 PM EDT
[#47]
I found a brass trim to length of 1.676"
What is max allowable 6.8SPC brass length? |
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Posted: 6/6/2006 4:50:55 PM EDT
[#48]
You want the SAAMI spec or the reamer spec? The chamber gauge I sent out today will let you know how long the brass can be in the barrel I made for you. If you own other barrels, they may be different. It's not uncommon to see 0.025" to 0.050" longer dimensions in the chamber than what SAAMI specifies for brass trim length. This is usually done for legal reasons, so you don't put LONG brass in the chamber that would wedge against the bullet and cause pressures to rise. If you watch what you are doing, 0.010" clearance is completely acceptable in brass trim length. |
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Posted: 6/6/2006 5:42:22 PM EDT
[#49]
randall,
is the 6.8 kreiger stub barrel youre cutting down to me cut to the right chamber specs? I plan on running my loads a little on the warm side and it'll see some F/A |
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Posted: 6/6/2006 6:00:38 PM EDT
[#50]
Thanks Randall! I've been playing with my Lyman universal trimmer tonight and some Silver State and Remmington Brass (Silver State is for the 'good stuff' the Remington is the brass I'm using to learn on that I don't mind messing up). Both are over the 'Trim to' spec of 1.676 so I was wondering how long is 'too long'.
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