Page 6 of 11 FirstFirst ... 45678 ... LastLast
Results 51 to 60 of 109

Thread: Issue with rifle surfaced during training course, report

  1. #51
    Join Date
    Dec 2008
    Location
    North Carolina
    Posts
    431
    Feedback Score
    37 (100%)
    Ok did some tests sans bolt catch. I backed the bolt catch pin far enough out to remove the bolt catch:




    I noticed a wear mark on the top rear of the mag well that looked odd. I don't know if this is a normal wear spot so I snapped a picture. I can feel a slight dip where the mark is so it isn't just surface finish removal:




    I then fully loaded 3 PMAGs and 3 BCM mags. I made sure the rifle was plenty wet with slip2000. I loaded the first 30rd pmag, made sure it was fully seated by striking the bottom a couple times and tugging. I pulled the CH to the rear, paused, let go, round fed fine. Also note I had the rifle angled down pointing towards the ground (about 45degrees). I did this with other two pmags and switched to holding the gun parallel with the ground, they all fed fine. I then used the first BCM mag and holding it parallel to the ground it fed fine. I tried the second BCM mag and help it upward at about a 45degree angle towards the ceiling (about the angle you hold the rifle when reloading), it hung up like it's been doing:



    I used the last BCM mag again holding it upward and it hung up. I then went back to the PMAGS (topped them off) and did all three of them. 2 out of 3 PMAGS failed to feed when holding them upward toward the ceiling:





    On a side note the PMAGS I used were previously lent to a friend who used them in a a VTAC class with a S&W M&P rifle. They worked fine and he didn't have any issues at all.

    So is it safe to say that it isn't the bolt catch at this point? Does this indicate there is something "bigger" wrong with the rifle, like lower/upper tolerances, feed ramps, etc? Remember when at the class I used the instructors lower on my upper and it fed fine when I tried out a few different fully loaded mags.

    I guess next thing to try is a stronger buffer spring. I don't have any spares, can someone advise a good choice for that?

    Thanks for all the help guys.

  2. #52
    Join Date
    Jun 2008
    Location
    Edmonds, WA
    Posts
    1,845
    Feedback Score
    1 (100%)
    Did you actually measure the buffer spring to make sure it is within spec?

  3. #53
    Join Date
    Dec 2006
    Location
    Commonwealth of Virginia
    Posts
    3,749
    Feedback Score
    2 (100%)
    This is starting to sound like an out of spec receiver. Try someone else's lower and upper to see if it happens again and to which receiver.

    If it happens to your upper, try another lower. If it happens again, then your upper may be the suspect.

    If it happens to your lower, do the same. If it happens again then your lower is suspect.
    We must not believe the Evil One when he tells us that there is nothing we can do in the face of violence, injustice and sin. - Pope Francis I

  4. #54
    Join Date
    Dec 2008
    Location
    North Carolina
    Posts
    431
    Feedback Score
    37 (100%)
    Ok guys. No I didn't measure the spring. Can you advise me how to do that and I will.

    I will try to get a few guys to bring their ar's to work to try what you said, swapping them to try and figure out if its the upper or lower.

  5. #55
    Join Date
    Dec 2008
    Location
    North Carolina
    Posts
    431
    Feedback Score
    37 (100%)
    37 to 38 coils, right at 3 inches completely compressed...

  6. #56
    Join Date
    Oct 2008
    Location
    Houston, Texas
    Posts
    4,167
    Feedback Score
    1 (100%)
    there was a tolerance on the lengths of the spring, I cant remember what it was off the top of my head. I think carbine buffer springs are suppose to be around 11-11.5 inches uncompressed? Rifle buffers are longer around 14.

    edit: I measured some of my carbine buffer springs that are known to be reliable. They were 10.5", 11", 10.75"
    Last edited by ForTehNguyen; 10-03-10 at 12:45.

  7. #57
    Join Date
    Dec 2008
    Location
    North Carolina
    Posts
    431
    Feedback Score
    37 (100%)
    Uncompressed it is 10.8 inches. I slipped the spring over a wooden dowel and measured that way....

  8. #58
    Join Date
    Aug 2010
    Posts
    14
    Feedback Score
    1 (100%)
    I regards to the lower being out of spec.. I found this sticky in the NFA section. Has some specs on what the lower should be.

    4. Check all the pin holes to see if they are in spec. Trigger/hammer holes are .154” and takedown holes are .248”. The tolerances are +/- 0.001”. Anything more than that is out of spec. I don’t care what any blueprints say. You can take 100 lowers and measure them yourself. You will come up with these numbers.

    5. Measure the magazine well. A good magazine well will measure .900” at the front and back and .970” at the slot. If you are less than this, you may have magazine drop free problems.-scottryan

  9. #59
    Join Date
    Apr 2009
    Posts
    637
    Feedback Score
    0
    Re-install the bolt catch and try your test again. If it functions the same then the bolt catch is eliminated as being a contributing factor. If it gets worse then the bolt catch may be adding to the problem. Personally I think the issue will be resolved with an extra power buffer spring.

  10. #60
    Join Date
    Jan 2008
    Location
    AZ-Waging jihad against crappy AR's.
    Posts
    24,902
    Feedback Score
    104 (100%)
    Off the top of my head the proper length (per the TM) is 10 1/16 to 11 1/4 inches. I think the issue here is the lower receiver.



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

    Semper Paratus Arms AR15 Armorer Course http://www.semperparatusarms.com/cou...-registration/

    M4C Misc. Training and Course Announcements- http://www.m4carbine.net/forumdisplay.php?f=141

    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

Page 6 of 11 FirstFirst ... 45678 ... LastLast

Bookmarks

Posting Permissions

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