Lehigh NFPJ conversion- issues?

[4gun-drill]

I recently purchased a Knight UL 45 that I’m trying to get sorted. I ordered it with the bare 209 ignition and as ordered the rifle is fine. I’m getting good primer crush with the factory setup and I like the factory bare 209 system. However, based on research here it appears that many prefer the Lehigh system. So, I separately ordered a FPJ bolt from Sportsman’s and Lehigh conversion and plug to try out. However, it seems that I’m getting some contact making it difficult to fully close the bolt. Initially the bolt was closing about 80% or so and then it would get difficult it’s probably closing 80-90% now. Basically where you would normally start to feel primer crush the bolt starts to get tight the problem is that it’s a stripped bolt and no primer inserted. I covered the Lehigh insert with layout fluid and cycled the bolt a handful of times and don’t see any obvious contact. The one thing I thought it may have been was that the insert was contacting the hex on the breechplug so I cut the hex back about .010” in my lathe. It may have made a small improvement but not much. What’s interesting is it’s only doing this with the new Lehigh breechplug. With the factory knight plug it closes fine. The nose of knight plug was also cut back at the factory about .025-.030”, but I don’t think the Lehigh plug is making contact there. I guess another question is why Knight would have cut it back? I emailed them to ask but have not heard back from them.

I know I have seen threads in the past when others have ran into similar problems. I spent last night looking for those threads but didn’t find any. Anyone have any tips or have a thread you could point me toward?

 

[GM54-120]

Does it function with the Knight bare primer bolt and Lehigh plug?
Does it function with the Knight FPJ bolt (no adapter) and Lehigh plug?

On mine if i use a FPJ bolt and the adapter the face of the adapter hits the hex on the plug. You need to take about .030" off the face of the adapter (plug side not bolt side). Removing material off the face of the adapter wont hurt a thing. Just dont remove any on the bolt side.

The NFPJ Lehigh adapter is intended for Extreme/Elites ect but it can easily be made to work with FPJ Ulites and Moutnaineers too. Both my bolts will close with just the bare bolt bodies and Lehigh plug. No adapter in the FPJ bolt but as soon as i tried adding the adapter it hit the hex on the Lehigh plug.

 

[52Bore]

Try pulling out the bolt release on the side while closing the bolt.

 

[4gun-drill]

Thanks for the replies! I think I have it figured out now.

-With the bare primer bolt, it worked fine with 2 Knight plugs and 3 Lehigh plugs.
-With the FPJ bolt (tried 2 UL bolts and 1 Extreme bolt) it was fine until I inserted the Lehigh adapter.
-I had not though of pulling out the bolt release, that’s a great idea. However, it did not resolve this particular situation.

In my initial troubleshooting I had removed about .005 off the nose of the breechplug. I didn’t THINK this was the issue but I figured it was worth a shot. My best idea was along the same idea as GM54-120 and that the adapter must be hitting the HEX on the breechplug. Instead of removing material from the face of the adapter I chose to remove material from the HEX. I took a total of about .020” off the face of the HEX with no real improvement. Because I felt the interference was minimal I thought .020” should have been enough if that was the problem. I ended up slathering everything in ink (a second time) from a marker, reassembled everything and ran the bolt 10-15 times. The interference is best described as “bite”. The bolt appeared to be closing all the way, but not under its own weight. Same with unlocking the bolt, there was some bite between barrel and bolt cam, and it took a little pressure to get it to snap open. This was with a stripped bolt and no primer. I still didn’t see any contact / rubbing that was evident in the ink. Standing at my bench somewhat perplexed I looked at the inside of the adapter and saw the issue. The nose of the breechplug WAS contacting the inside of the Lehigh adapter. The ink had not rubbed off the breech plug, but just enough transferred to let me see where it was hitting. I took about .003” off the nose of the breechplug and that appears to have resolved my situation.

One other thing I noticed about the UL FPJ bolts (two) that I purchased from Sportsman’s is that they provide way more crush, an additional .005” or so, over the bolt that came in my UL. Fortunately this Lehigh plug pairs well with it and gives me a good amount of crush on my primers.