Welcome to the Home of the 6.8 SPC - 68forums.com.

Advertise Here
Page 1 of 2 12 LastLast
Results 1 to 10 of 13
  1. #1

    Default 6.8 SPC II vs. 6.8x43

    Everything I can find so far on these is a little confusing. It sounds like (depending on who you listen to) that these are the same caliber. Is this true or I am totally off base?

  2. #2
    68Forums.com Team Member
    Join Date
    Sep 2008
    Location
    NH some of the time...
    Posts
    7,759

    Default

    they are the exact same thing you can shoot the same ammo in those two and the 6.8 SPC
    Molṑn Labé
    http://www.dtic.mil/ndia/2008Intl/Roberts.pdf
    "I figure we are gunman because we are better then most, and it beats branding cows or digging copper" -Appaloosa
    Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them.-Thomas Paine

  3. #3
    68Forums.com lifer
    Join Date
    Dec 2010
    Location
    Albuquerque, NM
    Posts
    2,394

    Default

    it is confusing, as the 6.8 is a 6.8x43 I believe....however when the 6.8 first came out it had a chamber that wouldn't allow for higher pressure rounds, then the SPC II came out which allowed for the higher pressures, the newest...6.8x43, according to AR Performance website, the 6.8x43 chamber corrects the 80 degree angle found in the SPC II chamber
    Last edited by elkbow; 01-23-2011 at 09:40 AM.

  4. #4

    Default

    Thank you all very much

  5. #5
    68Forums.com Industry Partner
    Join Date
    Jul 2007
    Location
    holding
    Posts
    11,114

    Default

    Quote Originally Posted by elkbow View Post
    it is confusing, as the 6.8 is a 6.8x43 I believe....however when the 6.8 first came out it had a chamber that wouldn't allow for higher pressure rounds, then the SPC II came out which allowed for the higher pressures, the newest...6.8x43, according to AR Performance website, the 6.8x43 chamber corrects the 80 degree angle found in the SPC II chamber
    That is the main reason I designed the DMR chamber which has evolved into the "6.8x43", I just dropped the "Remington" and "SPC" part of the name. The only other difference is the leade is .2775 instead of .2781 like the SPCII has. I forgot the new SPCII has a .114 freebore and the 6.8x43 has a .095 freebore.
    Last edited by constructor; 01-24-2011 at 03:12 AM.
    SIX5 -6.5mm on a 6.8 case
    Nexgen the lightest 308 AR coming mid 2014
    http://www.msrhunt.com/

    The 6.8 is the #1 choice for hunting deer and hogs with an AR15

  6. #6

    Default

    For the record, the SPC II chamber does not have an 80 degree angle by design. There is one drawing out in the web that shows an incorrect dimension, from a transcription error, that is not actually used on any barrels that I know of, for which if you compute the angle you get approximately 80 degrees. All of my reamers, and all the reamers I've ever seen, and all the reamers now in use by E.R. Shaw and anyone else I know of have the correct 45 degree angle. NO BISON ARMORY BARREL HAS EVER HAD AN 80 DEGREE FORCING CONE ANGLE.

  7. #7
    68Forums.com Industry Partner
    Join Date
    Jul 2007
    Location
    holding
    Posts
    11,114

    Default

    Quote Originally Posted by carnaby View Post
    For the record, the SPC II chamber does not have an 80 degree angle by design. There is one drawing out in the web that shows an incorrect dimension, from a transcription error, that is not actually used on any barrels that I know of, for which if you compute the angle you get approximately 80 degrees. All of my reamers, and all the reamers I've ever seen, and all the reamers now in use by E.R. Shaw and anyone else I know of have the correct 45 degree angle. NO BISON ARMORY BARREL HAS EVER HAD AN 80 DEGREE FORCING CONE ANGLE.
    Sorry Ben but you're wrong, most SPCII chambers have the 80 degree cone because Shaw makes most of the 6.8 barrels, Shaw sent me 2 carbide SPCII reamers to regrind because they lost my 6.8x43 reamers and Tim _W still has one of them that has not been reground, they were dated 3/09 as when PTG made them they both had the 80 degree cone angle. All of the SPCII chamber reamers with the 80 degree cone angle originated from PTG, Clymers is correct. Dave may have changed his SPCII design when you called him last year but I have prints from PTG that show a 80 degree cone angle. I think the whole thing started when Randall Roush sent a drawing for a reamer to Dave in late 05 and it was just passed down. There is a huge thread in the arfcom archives where Art asks Randall about the dimension on the prints back in 2006. Art said several companies had sent him chamber drawings with the wrong dimension. In the same thread Tim Hicks says Art was sending him the new SPCII chamber design. I posted the links to the exact post over a year ago when Vernon and I were going back and forth about this same thing.

    This is a PDF made from the original drawing by PTG, the number 8584 in the corner is a print number on file with ptg and matches the number stamped on the reamer. Right click on the pDF and then click properties it will give you the date that the PDF was made, in this case back in 06 shortly after Art designed the SPCII chamber and gave it to Tim Hicks. The numbers in question is the 1.6964 and 1.701 which is .005 more or less, the number should have been 1.710 in order to get a 45 degree angle on the cone, the line must travel .015 up and .015 over to make a 45 degree angle. The 45 degree on the print is just a note the numbers in the boxes must be correct in order to get a 45 degree angle. This same drawing was used by Tim_W in the 2008 performance report and stored in his offsite files. It is the same drawing shown in the archives on arfcom. Anyone that is a team member on arfcom can view the archives, it could be on p 40 #84 titled "6.8 upper & SSA combat loads" it is a high reply count thread where Art and randall are going back and forth for weeks about things.
    Attached Files
    Last edited by constructor; 01-24-2011 at 01:42 AM.
    SIX5 -6.5mm on a 6.8 case
    Nexgen the lightest 308 AR coming mid 2014
    http://www.msrhunt.com/

    The 6.8 is the #1 choice for hunting deer and hogs with an AR15

  8. #8

    Default

    Harrison, I have a reamer that Shaw sent me over a year ago and the cone angle is correct. I have a drawing from PTG that shows the correct cone angle. My barrels have always had the correct 45 degree cone angle. The drawing you mention I have and it shows an obvious transcription error, as the angle is shown as 45 degrees, but the dimensions, if worked out, come to 80 degrees. This is not a design error but a drawing transcription error. The DESIGN of the SPC II is not an issue.

    Notice that I wrote that the cone angle of 80 degrees is NOT BY DESIGN. The 80 degree error on the reamers you write of and the drawing is in error. For the record, do you have any close-up photos of these reamers with calipers showing the dimensions to prove that you actually have them? The correct drawing shows 1.7113" - 1.6964" = 0.0149". The incorrect drawing shows 1.70185" - 1.6964" = 0.0055". This is very easy to show, and in fact, here's a shot of my reamer:



    Notice that it is a PTG reamer dated March 2009. Next up, the correct angle:



    The calipers are set to 0.015" and you can see the cone has approx that dimension. I'd do better but I don't want to waste a lot of time on this. But one last photo:



    That shows the cone with the calipers set to 0.0055", which is very very small. It is obvious that the dimension of the cone is nowhere near this.

  9. #9

    Default

    Here's the drawing I have from PTG. The cone dimensions are correct:

    PTG 6.8.pdf

    Also, right-clicking and going to properties doesn't help. It doesn't show when the original document was created, only when your local copy was created. If you download both your file and mine you will find that the date of download is the "created" date in the properties.

  10. #10
    68Forums.com Industry Partner
    Join Date
    Jul 2007
    Location
    holding
    Posts
    11,114

    Default

    No I regrind all of my reamers to my design because I don't want the 80 degree cone angle. I know that the SPCII was not designed with a 80 degree cone but the error was made on the print and they were ground to the print because I received 2 that way. That is the whole reason I designed the DMR chamber in 07 sometime.
    There is no doubt you have had the reamers ground correctly now, that looks like a 45 degree angle to me but Shaw was using PTGs reamers for a long time and they did have a 80 degree cone I have seen the chambers with a borescope and I have seen the reamers. I still have a chain of emails where one of the girls at PTG argued with me about the dimensions for days.
    This is the pdf you posted last year, it was made 5/14/2010 by clicking the properties the date will show. I also know the old dates stay on the reamers I have a few of those as a matter of fact one has the same date as in the photo you just took.
    ETA other links- This is a link to the 2008 performance report, about 2/3 of the way down 2 chamber reamers are shown, a SAAMI with a 4192 print number and the familiar SPCII with the 8584 print number, both originated from PTG. Some manufactures may know about the mistake, most probably don't have a clue. I saw a new stainless 16" barrel made by Shaw early this last year, it came into the shop for beadblasting, it had a SPCII chamber with the 80 degree cone. The old SPCII reamers may get replaced by the new SPCII reamers that is a good thing for the cone angle but now the new SPCII has a .114 long freebore instead of the original .105 combined freebore. Also you can't back up that created date on the PDFs, the one I have from 06 has been around and used since 06. The one you have is different from the one Art designed in Jan of 06.
    http://68forums.com/forums/showthrea...ng-Report-2008
    Attached Files
    Last edited by constructor; 01-24-2011 at 03:34 AM.
    SIX5 -6.5mm on a 6.8 case
    Nexgen the lightest 308 AR coming mid 2014
    http://www.msrhunt.com/

    The 6.8 is the #1 choice for hunting deer and hogs with an AR15


 

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •