+- 6.5 Grendel Forum (https://65grendel.com)
+-- Forum: 6.5 GRENDEL DISCUSSION FORUMS (https://65grendel.com/forumdisplay.php?fid=3)
+--- Forum: 6.5 Grendel ARs and Other Semi-Autos (https://65grendel.com/forumdisplay.php?fid=8)
+--- Thread: 12.7 group buy Faxon gas block troubles (/showthread.php?tid=16068)
Pages:
1
2
12.7 group buy Faxon gas block troubles - grayfox - 04-25-2018
Well, this 12.7 faxon build is getting frustrating. I have tried 2 0.750 gas blocks, one of them a BCM, and neither one fits, both "seem" too small. Apparently the nitriding process on this barrel has thickened the journal > 0.750. I tried heating the GB and no help. Then chilling the barrel and heating the GB, and I got one to slide partially on but it immediately became stuck, naturally out of position, and I cannot get it off.
I am used to chilling the barrel and/or heating the upper for the BCM uppers, but never have I had this kind of trouble with the gas block.
Heating both did not loosen up the gb... now trying to freeze them both.
If I have to take this to a GS to fix that's going to jump my costs, delay my build, and raise my ire.
Yeeeeesh.
I am certainly thinking faxon has major QC issues in this setup.
I've done 2 other faxon builds and did not have any gb trouble, actually, no troubles at all, with them.
This one is different.
12.7 group buy Faxon gas block troubles - jonny rotton - 04-25-2018
the first one i tried was too small too. i tried another one that i had and it fit fine. try another one!!
12.7 group buy Faxon gas block troubles - grayfox - 04-25-2018
I tried 2, different mfr's... that's my limit.
Took it out of the freezer, applied a rubber mallet and some oak 2x3 I have on hand and beat the GB off of the barrel.
Guess I will head out to find some lapping compound and try that on either the barrel or one of the GBs.
12.7 group buy Faxon gas block troubles - ClutchAutomatic - 04-25-2018
That's one reason why I like the clamp on adjustable design.
12.7 group buy Faxon gas block troubles - Kswhitetails - 04-25-2018
Mine was really tight. Diamond head set screw. I was rather surprised that there is no damage to the finish on the barrel after three installments, impressed with the seemingly hardened metal. Lap the gb, be glad for the good better than factory fit. I was surprised with the increase in work required to put this build together, guess I’m just happy with the silver lining that it’s a better build because of it.
12.7 group buy Faxon gas block troubles - grayfox - 04-25-2018
I'm going to hit autozone tonite after dinner and get some lapping compound. Not sure I want to go the clamp-on route, even the "low profile" blocks have only a little clearance on the bottom. They probably work fine, just I haven't gone there as of yet and don't want to write off these 2 gb's I have on hand...
So, yeah, ksw one of the gb's will get the treatment.
I've got everything else, except the red-dot is still inbound (tomorrow hopefully). But the rest I've got here.
12.7 group buy Faxon gas block troubles - ClutchAutomatic - 04-25-2018
True that, I've got a large handguard that can fit a suppressor in it.
12.7 group buy Faxon gas block troubles - grayfox - 04-25-2018
I inspected the barrel extension lugs and chamber, and cleaned the interior, not sure if I saw any burrs, maybe some steel "flashing", so I used some JB compound to polish them up a bit, everything there, so far, looks ok - I used a dental pick to probe around places where my finger couldn't get to. But I won't know on that (brass scoring) until I can send something downrange.
12.7 group buy Faxon gas block troubles - Lastrites - 04-25-2018
Nitriding should not add any thickness during the application, something else has got to be off, did you happen to measure the journal?
12.7 group buy Faxon gas block troubles - BCHunter - 04-25-2018
Measure the journal and ID of the gas block. On my Odin the gas block was out of spec, .743"
I was at the same point was trying to tap it on with wood and gunsmith 2 oz hammer. When the light went off and said something was not right.
12.7 group buy Faxon gas block troubles - Popeye212 - 04-25-2018
Try freezing the barrel only. If you freeze both it's possible both will contract. Frozen barrel heat the gas block. Heat will make the gas block expand and may fit on the COLD barrel. My .02
12.7 group buy Faxon gas block troubles - Bigs28 - 04-26-2018
Use clamp on.
12.7 group buy Faxon gas block troubles - grayfox - 04-26-2018
As a brief re-hash, it was difficult logically to conclude, IMO, that 2 gas blocks from 2 diff mfr's would both be too small, by the pretty much same amount if I judge from their similar almost-fit onto the barrel, sticking in the same spot, refusing to spin - both acted much alike -- what was the common item in this? the barrel's journal. I tried the barrel freeze/GB heat combo to get the gb on and it resulted in the GB going part-way on, then sticking in place, misaligned as well. That's where this thread commenced. The problem was that the barrel and GB were stuck together. I know that nitriding is not SUPPOSED to change the dimensions any, but well, here we sit. All my previous builds have gone barrel/gas block just fine, no problems. Either something was out of spec or the gremlins finally caught up to me!!
Now, to continue, I placed the entire barrel/stuck gb in the freezer to chill them, then with help of a rubber mallet and block of oak I was able to knock the gb down and off of the barrel.
Off to the Autozone and pick up some lapping compound. Using that compound and a 12-ga mop I lapped several times inside the gb. But I also did some lapping on the journal. Now finally at last I got the 2 to fit, still very snugly. The journal looks a little "bronzed" rather than the original dark choco-black, but they fit together, so that's my ultimate aim.
Rifle is now completely assembled but I am still waiting on my red dot... then out for the test firing (to see whether I will also have brass gouging or not...)...
12.7 group buy Faxon gas block troubles - BCHunter - 04-26-2018
Thank you for sharing your experience, it is always good to see solutions to problems.
When I had this issue it was easy to determine the gas block was out of spec, and was exchanged with the manufacturer. I was relieved that it was the easier of the 2 to exchange!
Look forward to the range report.
12.7 group buy Faxon gas block troubles - grayfox - 04-26-2018
I have to say this is a new one for me. I was quite frustrated, glad now to get thru it.
We'll see what tomorrow brings!
12.7 group buy Faxon gas block troubles - Kswhitetails - 04-26-2018
If you posted it I apologize, I missed it. What does your journal measure? I’m seeing.7495 at the front of the block.
12.7 group buy Faxon gas block troubles - grayfox - 04-26-2018
I need to admit that when this all was going down, I was so frustrated that I did not measure them in the "before" state. This morning I checked the gb not used, and it is 0.7490 with my digital caliper.
The barrel journal is 0.750-0.7505 and this is after lapping was done on it. The installed gb I will measure when I take it back apart following test fires.
I'm projecting that the installed gb is now (after lapping) in the range of 0.751/ 0.7505 since it slides on but is still pretty tight to the journal.
I may also need to admit (DANG those gremlins!!!) that both gb's may have been < 0.750............. but it does look to me as though the journal was >0.750 in its "before" stage -- educated guess is all I have here since I didn't measure it before lapping.
I have done 7 builds previously from 5 mfrs and did not have this issue in any of them, nitrided as well as ss, and with several gb mfrs.
Guess I'll have to chalk this up as tolerance stacking -- and not be so surprised next time <sigh>.
12.7 group buy Faxon gas block troubles - aephilli822 - 04-26-2018
next time (or for the next guy) wooden dowel with hacksawed slot and piece of emery cloth spun on a drill works fast
these guys do it on double rifles
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=printthread&Board=1&main=10915&type=thread&PHPSESSID=
12.7 group buy Faxon gas block troubles - Kswhitetails - 04-26-2018
Heh, no worries, I never measured mine either. I was excited it was such a tight fit, that meant I didn't need to bed it. What was fun was the first time I put it on, I used red loktite (hereafter:LT), and just dropped it in the hole. When I screwed in the set screws, it hydraulically forced the red LT between the barrel and block. Okay, I thought, even better fit. Good.
15 mins later: (&^%#$^%%$**&^) - I forgot to put the hand guard nut on first! OOOOOPH. Let me tell you, this was devastating. You thought it was tight before? Hydraulically press some adhesive between it, and see how you do... ROFL There are now marks in the GB that seem to say, "WTH man, you can't install a GB without tearing it up?!?"
https://www.larue.com/products/larue-tactical-12-0-handguard-lt15-12/#fndtn-panel7 - check out the pics. Notice there are two pieces, the handguard nut, AND the barrel nut, - oh and the spacer, OH and the keeper... heh, instructions, who needs em??
(The LaRue hand guards are a fun one, guys, seriously strong, but make SURE you put all the necessary peices on before you LT ANYTHING)
I can laugh about it now, but I was actually considering using a dotco and a wheel to slit the GB at the set screws... I FNG'd it bad! I wound up using a heat gun to putty the LT, and a rag and a pipe wrench to turn the GB off. It wasn't going to slide. It took an hour, and lots of sweat and cuss words. I am ashamed. But on the up note, that journal is still lew looking. Like, no lie, the finish is brand new. I can't believe it. I'm sold on QPQ done right.
Here's a pic from last night, when I measured the journal, see the pretty tool marks?
![[Image: 41717261581_f50aabf774_b.jpg]](https://farm1.staticflickr.com/972/41717261581_f50aabf774_b.jpg)
Untitled by ., on FlickrThe Dotco may still come out at some point. On the fourth installation of said GB (don't ask) The rear screw finally gave up and went to heaven giving up in the allen hole. (The allen was seated, I'm positive of that. The pieces that broke off did so all the way down into the bottom of the hole, and show fatigue - that's what I get for using a cheapo GB i guess - freakin chinese screws...) I immediately tried to back it out with a screw remover, but failed. The GB was still warm from the previous oops, and now it resides firmly on the barrel with a nasty ability to shrug off attempts and cackle me as I think about making another attempt at removal. Guess I don't have to worry about it ever coming off on it's own...
Next time I want it off, I'm going to by buddy at the machine shop to beg him to let me use his end mill...
--- 2% rule?
12.7 group buy Faxon gas block troubles - grayfox - 04-26-2018
Trials and tribulations, brother!!
Those aren't tool marks, they are the toothmarks of vanquished critters...LOL!
Tell your grandkids about the monster boar you had to take down in hand to hand!!!!!