BadBoyBilly Posted March 21, 2015 Report Posted March 21, 2015 (edited) So I finally got all the parts that I needed to build my .308 (buttstock was on backorder for 3 months). So I started to assemble the upper and ran into an issue. The gas block will not go onto the barrel shoulder. I tried greasing it up but it only goes on a couple mm's and then jams up. So I said ok maybe I ordered the wrong dimension on the gas block or barrel shoulder. I double checked and everything is .750 Barrel: http://www.brownells.com/rifle-parts/barrel-parts/rifle-barrels/308ar-barrels-prod69784.aspx?avs|Make_3=AR xzzx308 Gas Block (part # 100-011-111): http://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/ar-15-m16-low-profile-gas-block-prod26994.aspx So I thought ok maybe when the products were packaged up with the wrong product labels. So I had another barrel for an AR15 project that had a .750 barrel shoulder. I took the gas block and it slid right on the barrel with little effort. This to me proved it's not the gas block but the barrel. I then took out a set of digital calipers and measured the barrel and the diameter of the gas block. Both come to an exact .750 So now that I confirmed the parts are in fact both .750 but the barrel shoulder seems to be a little thick, what do you guys recommend? I'm afraid if I force it on too hard it's going to get stuck because it takes a LOT of effort to get it off when it gets jammed. I dont want to sand it because it will obviously ruin the finish of the barrel..... Edited March 21, 2015 by BadBoyBilly
BadBoyBilly Posted March 21, 2015 Author Report Posted March 21, 2015 So I ended up coming across some other threads online and it looks like other people who ran into this situation bought the "clap on" style gas block with gives a little bit more clearance when installing. I might go that route since it's a fairly inexpensive part.
MikedaddyH Posted March 21, 2015 Report Posted March 21, 2015 Another option would be to apply heat to the gas block then pound it on with a rubber mallet. Your are talking about .001" or .002" correct?
washguy Posted March 21, 2015 Report Posted March 21, 2015 Emery cloth Yep...Ive had to do that on a few of them...get you some sandpaper and wrap it around your finger and go to town...sometimes the anodizing /coating inside will make it tight....back away from the barrel with anything...lol.....after sanding clean it up then grease it up should slide on.... :) Wash
ChaseFan9 Posted March 21, 2015 Report Posted March 21, 2015 Heat up the gas block a little (NOT red hot) to make it expand and slip it on, or else sand down the inside lightly. Some gas blocks are supposed to be that tight to keep it all aligned and in the right place
Robocop1051 Posted March 21, 2015 Report Posted March 21, 2015 you guys are putting way too much thought into this. It's a lot simpler than you think. Back the screws out completely. Put a penny or a dime in the gap on the gas block. Reinstall the screws, into the coin. As you tighten the screw into the coin, the gb will expand. Slide it on,remove the coin.
Robocop1051 Posted March 21, 2015 Report Posted March 21, 2015 I had to do this with all my PRI gas blocks.
guruofhotrod Posted March 21, 2015 Report Posted March 21, 2015 So I ended up coming across some other threads online and it looks like other people who ran into this situation bought the "clap on" style gas block with gives a little bit more clearance when installing. I might go that route since it's a fairly inexpensive part. I think the OP may have the "set screw" type block
BadBoyBilly Posted March 21, 2015 Author Report Posted March 21, 2015 Yes correct it's the set screw type. Ok the issue I have with the heat method is that if I ever need to take it off, I'm going to have to heat it up again to take it off. So i'm kind of leaning towards sanding the inside of the gas block since I dont feel like buying another gas block. Sounds like emery cloth and sand the inside of the gas block with my finger? What grit should I use?
BadBoyBilly Posted March 21, 2015 Author Report Posted March 21, 2015 (edited) OK exact measurement (as much as I could get them) with digital calipers Gas block - .7510 Barrel Shoulder - .7510 It's probably not going on because one needs to be SLIGHTLY smaller than the other so they can mate. Edited March 21, 2015 by BadBoyBilly
guruofhotrod Posted March 21, 2015 Report Posted March 21, 2015 I'd get some 220 or 320 wet/dry, put a little WD40 on it and have at it <thumbsup>
washguy Posted March 21, 2015 Report Posted March 21, 2015 Badboy Just take a lil out of the inside...grease her up...slide her on....it aint rocket science or govt work try fit....sand try fit.....it should be rather tight...put a lil oil on the barrel right before the gas port... dont use any heat. :) Wash
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 Thanks guys. Never had this problem with any of my builds before. I'll head to Home Depot tomorrow and pick up some stuff to sand with. Dumb question, if I sand off the melonite finish on the inside of the gas block, won't it rust?
FaRKle! Posted March 22, 2015 Report Posted March 22, 2015 I'd just tap it on with a rubber mallet.If you have to remove it you can always re-heat it back up or remove the gas tube and tap it off from the rear. I've had to do that before. If you can get it on without sanding, do it since sanding will only make the sealing of the block to barrel worse.
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 Farkle, Its an EXTREMELY tight fit. I tried with a rubber mallet and it didnt go anywhere. I was hitting it very hard.
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 Guys I ended up finally getting it on. Instead of using grease I used light gun oil. Really good even wacks on both sides of the gas block, it SLOWLY went on. I banged it back off and wiped it clean. I got off a lot of excess coating that came off in the process and now it goes on a lot easier.
Robocop1051 Posted March 22, 2015 Report Posted March 22, 2015 The gas block in the link on the OP was a clamp on. I misunderstood. Glad it all worked out
washguy Posted March 22, 2015 Report Posted March 22, 2015 Guys I ended up finally getting it on. Instead of using grease I used light gun oil. Really good even wacks on both sides of the gas block, it SLOWLY went on. I banged it back off and wiped it clean. I got off a lot of excess coating that came off in the process and now it goes on a lot easier. Like I said in post #14 use some oil.....lol good going... :) Wash
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 (edited) Well I finished my very first AR 308 Build! Edited March 22, 2015 by BadBoyBilly
unforgiven Posted March 22, 2015 Report Posted March 22, 2015 Great job brother I like the look. <thumbsup>
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 (edited) Thank you sir. I just need glass, muzzle attachment and a bi-pod. I'm going to check the headspace tomorrow to make sure it's safe to shoot =) Edited March 22, 2015 by BadBoyBilly
BadBoyBilly Posted March 22, 2015 Author Report Posted March 22, 2015 Headspace is good. She's safe to shoot!
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