New receiver overtimes

[zetabird]

Just got my new coonan today and went to throw the barrel on it but I can hand tighten it all the way to just past 12 it's a metric type 3 with an stg barrel, that would mean I would need a timing washer between the barrel and receiver correct? If so what size should I start with

[FUUN063]

Well, first off, try another barrel or two. Maybe the one you have has had the shoulder turned back. Or, maybe not and there is a problem with the receiver. If there is, then send it back. Dan has a great customer survice if there is a problem. Otherwise, yes, a breaching washer will be needed if that's the route you go.

Leland

[zetabird]

Well right now I only have the one barrel so another one. Try is out of the question so where's the best place to get Breeching washers from, I've been asking around town today with now luck even the electric shop that rebuilds motors only has thicker ones, there was a member on here that had them but I found a thread saying it might not be the best person to order from right now

[MAINER]

How many degrees past 12 o'clock are you estimating? You will require a .0052" washer to get to the 11 0'clock position from the 12 o'clock position or .0078" for a 10:30 position. . I torque a barrel from 11 o'clock, others like 10:30, your choice. Each additional 5.7 deg. past 12 o'clock is another .001" in thickness required.

GP is listing Breeching washers on his site.
http://www.arizonaresponsesystems.co...a1barrel.shtml

[zetabird]

its not off by much only a few degrees past 12

i guess im probaly looking for about a .052 or .053

[MAINER]

I'm estimating 10 deg. past TDC?

Given that 5.7 deg. of rotation results from a .001" difference in thickness.
40 deg. back to 11:00 = .007"
55 deg. back to 10:30 = .0096"

Another way of determining thickness needed is to turn the barrel to desired position and measure the Receiver-shoulder gap with automotive type feeler gauges.

I'm thinking that I would get a washer of .010" and thin it until I was happy with the position, somewhere between 10:30 and 11:00.

An L1A1 Breeching Washer is way too thick for your purpose here. One of the members like Mountainman or Adam 7.62 might have thin tbarrel timing washers or something close or make your own?

If you can't find shim material, try:
http://www.mcmaster.com/#standard-shims/=humfga

[zetabird]

thats what my next step was i just need to get a washer thats gonna start me closer, the thinnest one i found in town was .040 ish and id rather not spend that much time fileing at it

[gunplumber]

I don't recommend trying to find some paper-thin washer. I recommend setting the shoulder back more and using a standard breeching washer. This means you'll also need to modify your rear handguard support and gas tube nut, or use an inch pattern. And your wrench flats will be skinnier.

I've built quite a few Coonans this last month and had zero problems. I'd definitely want to check another barrel - if that barrel was clocked to recent DSA receiver, that's about about where it would hand-tighten to an in-spec receiver.