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+--- Thread: upper to barrel fit up (/showthread.php?tid=9948)
upper to barrel fit up - Squatch - 10-06-2015
Does anyone know what kind of clearance there is between a quality billet upper and a high quality barrel (satern, pf, bhw, lilja)? It should be less than .01 of an inch right?
upper to barrel fit up - am4966 - 10-06-2015
It'll vary on the mfg, if they build upper on the tighter side of MIL spec or at MIL spec. I wouldn't worry, get your barrel and upper. Then prefit them if too loose send back and ask for new one.
upper to barrel fit up - LRRPF52 - 10-07-2015
Depending on the extension and the extension tunnel on the upper, they can be wobbly or too tight, to the point that you need to heat the upper and freeze the barrel to get a thermo-fit, which when I find that combo, I'm happiest.
Otherwise, it's bedding time for the extension and upper.
upper to barrel fit up - devildogandboy - 10-09-2015
new guy here, this is the reason i joined the forum today! i posted in the trouble shooting section about my receiver/barrel fit being way too tight and 37L1 was kind enough to link me to this thread. i'm going to try the hot/cold method that LRRPF52 recommends!
i think i'm really going to like this place! thanks guys!
Bruce
upper to barrel fit up - LRRPF52 - 10-09-2015
JP uses the thermo fit method on their SCR rifles, which are high end billet receivers with under-sized tunnels intentionally.
John Paul told me about it personally back in 2007 when I called up about an order.
Whatever method used, we're trying to make the upper and barrel behave more like one unit, as opposed to 3 different components (upper, barrel extension, barrel).
That's where you start to see extreme accuracy kick in with the AR15.
upper to barrel fit up - devildogandboy - 10-10-2015
LRRPF52 Wrote:Depending on the extension and the extension tunnel on the upper, they can be wobbly or too tight, to the point that you need to heat the upper and freeze the barrel to get a thermo-fit, which when I find that combo, I'm happiest.
Otherwise, it's bedding time for the extension and upper.
just one quick question before i do this method, if i wish to change barrels later i would heat it up and remove barrel? no problems?
Bruce
upper to barrel fit up - Kikn - 10-10-2015
How are you heating up the receiver? Oven, torch, Zippo lighter?
upper to barrel fit up - devildogandboy - 10-10-2015
Kikn Wrote:How are you heating up the receiver? Oven, torch, Zippo lighter?
whichever method is recommended, i have a propane torch if that works.
Bruce
upper to barrel fit up - LRRPF52 - 10-12-2015
devildogandboy Wrote:whichever method is recommended, i have a propane torch if that works.
Bruce
Open flame is strongly recommended against. You'll hear a lot of people say, torch away, no problem, but you're now messing with the temper of the alloys. I personally use the oven for heating uppers that need thermo-fit, and the freezer for the barrel.
For removal, I modified the AR15 armorer kit T handle that inserts into the upper receiver, so I can knock out barrels with a hammer. Even Loc-tited barrels pop out easily, like they weren't glued in the first place.
upper to barrel fit up - devildogandboy - 10-12-2015
LRRPF52 Wrote:Open flame is strongly recommended against. You'll hear a lot of people say, torch away, no problem, but you're now messing with the temper of the alloys. I personally use the oven for heating uppers that need thermo-fit, and the freezer for the barrel.
For removal, I modified the AR15 armorer kit T handle that inserts into the upper receiver, so I can knock out barrels with a hammer. Even Loc-tited barrels pop out easily, like they weren't glued in the first place.
i appreciate the info against the torch and i was kind of leery of it to begin with. i ordered a heat gun that should be here tomorrow. i'll try that and if that doesn't cut it i'll use the oven. i read elsewhere that only the threaded area needed to be heated and not very hot at all. i'll keep you informed how it goes.
thanks guys for the input!
Bruce
upper to barrel fit up - LRRPF52 - 10-12-2015
Just hang it in the oven at 350 for 20 minutes while the barrel is in the freezer.
Rush to the bench and install.
One thing I do before installing a barrel is make sure that the feed ramps in the upper match the extension. This is harder to do with a thermo-fit job, so you can approach it by taking a lot of measurements, or blend once installed. I prefer not to blend installed barrels for several reasons.
upper to barrel fit up - am4966 - 10-12-2015
Lap Receiver face or make sure it's straight, that helps with accuracy too.
upper to barrel fit up - devildogandboy - 10-12-2015
am4966 Wrote:Lap Receiver face or make sure it's straight, that helps with accuracy too.
never thought about this but after doing a little reading i ordered the Brownells lapping tool. put this upper on hold for a few more days now!
you guys are being a big help for this senior citizen LOL, i really appreciate tthe help.
Bruce
upper to barrel fit up - devildogandboy - 10-13-2015
okay, my receiver lapping tool from Brownells should be here Sat and i'll get that done. this morning just playing around with the heat gun i was able to slip the barrel nearly all the ways in, just shy by about 3/16" and then i removed it. this should work well when i'm ready, i'll just heat the reciever a bit more and the barrel might go all the ways in. i'll keep psoting as i go along.
Bruce
upper to barrel fit up - devildogandboy - 10-17-2015
okay, to keep everybody up on the assembly of tight barrel/receiver fit i received the heat gun on Monday and it was suggested to true-up the face of the receiver before hand. placed an order with Brownells and recived the receiver lapping tool today(Sat) and put that baby to use on the Aero upper. it really didn't take all that long to get it trued-up, maybe 15-20 minutes of using 220 grit compound since that is all i had on hand and cleaning and inspecting my progress every 20-30 seconds or so. got to i think it came out really good as there is a bright shiny area all around the face. be sure to keep the tool clean so no grit gets into the receiver itself.
i then got out my new heat gun and heated the receiver around the threaded spigot area and tried fitting the barrel to it, still too snug so i heated a bit longer and tried again with the barrel going on all but the last 3/16". i heated again this time about 30 seconds and tried to push the barrel on with no success. i had my dead blow mallet laying near and gave the receiver a couple whacks with it and everything is in place as it should be, with the feed ramps aligned and barrel to receiver fit looking good also. i couldn't be happier at this point. i just hope the handguard(due here tue-wed) goes well and i have no ftf's or fte's when it's time to shoot.
thanks guys for the helpful suggestions, i really apprecite the help!
Bruce
upper to barrel fit up - customcutter - 10-18-2015
Sounds like you've got a great fit on the barrel and upper, glad you got the upper lapped also. That should help with accuracy.
upper to barrel fit up - devildogandboy - 10-18-2015
customcutter Wrote:Sounds like you've got a great fit on the barrel and upper, glad you got the upper lapped also. That should help with accuracy.
LOL if i ever get it out shooting we will find out! i'm looking forward to working up some loads.
Bruce