Go Back   The AK Files Forums > General Forums > Gunsmithing & Build It Yourself

Notices

Reply
 
Thread Tools
Old 08-01-2008, 08:55 AM   #1
slowshooter
Member
 
AKaholic #: 9816
Join Date: Nov 2007
Location: San Diego, CA
Posts: 70
Default headspace and oversized barrel pins

My headspace battle with one build continues. This board has helped with several issues faced, and now I need more advice on an AMD65 with headspace problems. I bought the oversized (0.281") pins and high quality J-sized bits. Turns out that the bit fit in the barrel pin hole without any need to drill, so I just pushed in the oversized pin. It was a tight fit going through the trunion, noticeably easier going past the barrel and then a tight fit at the other size of the trunion. I shot it five times, and from shot 1 to shot 5, I saw the headspace change from not being able to fit the no go gauge to being able to close on the field gauge. (At least I'm getting proficient at using headspace gauges.)

What's the largest safe hole that may be made for the barrel pin?
slowshooter is offline   Reply With Quote
Old 08-01-2008, 10:53 AM   #2
Random Chaos
Member
 
AKaholic #: 1747
Join Date: Feb 2004
Location: GA
Posts: 66
Default

Here's a thread where I had the same problem and a couple of experienced builders worked me through it. I ended up drilling mine to .311 with a .316 pin.

http://www.akfiles.com/forums/showthread.php?t=29979

hth
Random Chaos is offline   Reply With Quote
Old 08-01-2008, 11:53 AM   #3
7.62x39
Senior Member
 
AKaholic #: 463
Join Date: Nov 2003
Posts: 629
Default

I use 19/64ths which is .297
7.62x39 is offline   Reply With Quote
Old 08-03-2008, 09:49 PM   #4
slowshooter
Member
 
AKaholic #: 9816
Join Date: Nov 2007
Location: San Diego, CA
Posts: 70
Default

Thanks for the link and the information. So all I need to do is remove the barrel and find the drill-end of the bit that does not fit completely in the barrel groove, replace the barrel in the trunnion, headspace, and drill with the next-size down bit?

It sounds so straightforward.
slowshooter is offline   Reply With Quote
Old 08-06-2008, 10:27 AM   #5
Random Chaos
Member
 
AKaholic #: 1747
Join Date: Feb 2004
Location: GA
Posts: 66
Default

It did fix the problem. You have guesstimate how large a hole and pin you will need. I bought two sets of drill stock and drill bits, The smaller set did not work, the larger set was a perfect fit. You want to redrill the hole large enough so that the barrel cannot move. My problem was that the barrel channel was elongated on the front to back axis of the barrel. I've never seen anything like it. If you want any of the drill stock, please let me know and I'll send you a pin size length.

Rick
Random Chaos is offline   Reply With Quote
Old 08-10-2008, 03:08 PM   #6
slowshooter
Member
 
AKaholic #: 9816
Join Date: Nov 2007
Location: San Diego, CA
Posts: 70
Default guidance before drilling

The 0.310" bit (5/16") shows a little bit of light between it and the barrel groove when I try to put it in. Just checking: I should drill the hole to 0.310" and chop down an 'O' size bit (0.316") for a barrel pin?

Thanks,
slowshooter is offline   Reply With Quote
Old 08-11-2008, 10:29 AM   #7
Random Chaos
Member
 
AKaholic #: 1747
Join Date: Feb 2004
Location: GA
Posts: 66
Default

I tried to respond to your pm but I cannot get my pms to work...

explain this to me - "The 0.310" bit (5/16") shows a little bit of light between it and the barrel groove when I try to put it in". When I did mine I was concerned that the barrel pin bottomed out in the barrel channel in order to stabilize any for and aft movement of the barrel. The .316 pin does sound fine, it will be a tight fit, use some anti-sieze and youe'll be fine.
Random Chaos is offline   Reply With Quote
Old 08-11-2008, 10:53 PM   #8
slowshooter
Member
 
AKaholic #: 9816
Join Date: Nov 2007
Location: San Diego, CA
Posts: 70
Default

Since the barrel is moving forward as I fire, I figured the barrel pin hole would need to be slightly larger than it is now to hold it in place. I tried the chuck end of different bits until I found one that would nearly fit into the barrel groove. The drill bit has a diameter that is slightly larger than the length of the barrel groove, so it will not fit in perfectly. It is hard to tell how closely the bit fits the groove, so I held it up to a bright light and saw a bit of light between bit and the bottom of the groove. There also is some light on the sides of the bit.

The thinking is that once the new barrel pin hole is drilled and the oversized pin installed, there should be no movement.

Should I be going down a size with the plan to use a barrel pin of 5/16ths? The next smaller drill bit size I found at McMasters was 0.008" smaller.
slowshooter is offline   Reply With Quote
Old 08-12-2008, 08:25 AM   #9
Random Chaos
Member
 
AKaholic #: 1747
Join Date: Feb 2004
Location: GA
Posts: 66
Default

Ok, I understand what you were saying... I would not go any smaller because if you can see light around the chuck end of the bit you are probably close to the size of the hole. How does the .316 pin look in the channel? Can you still see light in the channel around pin? I'm just curious if the .316 pin fits better. The light could be caused by the hole simply being out of round. I'd go ahead and drill it and press the pin in. Let me know if you need the .316 stock.

Rick_at_ricklewisdotnet remove underscores, at, dot
Random Chaos is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 02:56 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
©2015 The AK FIles