View Full Version : chased threads barrel still resists
February 04, 2009, 13:18
I chased the threads in the receiver and on the barrel, but the barrel still resists being screwed in all the way by hand. I can screw it in about half way and then it binds up. I can turn the tap into the receiver by hand until it bottoms out and I can spin the die onto the barrel without a problem. I have tried using Never-Seez and that didn't help.
This is one of the new Coonan receivers. I am using Ratas' receiver wrench and barrel vice. This is my seventh build and the first time I have encountered this problem. Any constructive suggestions?
February 04, 2009, 13:58
buy a pitch mike .....taps and dies have varrying forms on the pitch ...measure over the major od (2plcs) and see if there is taper ....for starter
snap guage the ID of the receiver THDs too ...(2plcs)...more likely taper there
February 04, 2009, 14:32
These are the same tap and die I used on the previous six builds and experienced no problems.
February 04, 2009, 14:48
johnny the taps and dies will give a different pitch if there is taper in the hole .....taps only cut to depth .....
the major and minor controll the pitch dims and firmness of mating fittment .......
FYI some inserts we use on cnc have the major OD cutter in front of the 60° point....they may not have had the special tooling ...ill just bet there is taper if ya measure front to back of rec thds ....o1o can make a big difference ..in thread form and fit between the 2 parts . ........:wink:
February 04, 2009, 14:58
So, if the hole in the receiver IS tapered, what is my solution? Has anyone else attempted to run a barrel into the new Coonan receivers? If so, did you encounter any problems?
February 04, 2009, 15:03
Here it starts.
February 04, 2009, 15:17
well buddy after you check for taper ..may just need to carefully sand the top of the "point " ...as its may be too tall for the mating valley on the BBL thds ...check taper first though ..
is there any swaging/galling/deformation marks on the top of the thread form on the bbl ,at the point where it binds ????..or does it look like its trying to scrape the top "V" off ....???
"without hands on "could be something else but i doubt it ... have cut ALOT of threads hehe .thats just my first thought .....
February 04, 2009, 15:46
It looks like the peaks in the receiver are a bit too tall and they are removing the finish from the valley in the barrel threads. With added leverage it will screw on and off with no apparent problem other than that just stated.
February 04, 2009, 15:51
close your barrel die a tiny bit
February 04, 2009, 16:22
Perfect!! And it spins on and stops at about 11:15 on the dial. Couldn't ask for more. That was a constructive suggestion and one I should have thought of myself. Thanks.
North Texas Ed
February 22, 2009, 09:00
For what it might be worth to others, just yesterday I hand threaded an L1A1 kit barrel into a new Coonan receiver. Other than needing a thinner breeching washer than the one in the kit, I had no problems at all. Stops at about "10:45" with the old washer. Threads to about "2:00" without any washer.
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