nheiny13 Posted December 27, 2015 Share Posted December 27, 2015 I just got a Rainier Arms forged upper with a barrel extension opening that is 1.004" and a Stretch 16 fluted melonite barrel with a barrel extension of .995". I know that some use loc-tite to snug up the loose fit. I was wondering if using loc-tite is as good as getting an upper to barrel fit that is a tight fit to begin with? Are there any forged uppers that are know to have a tighter barrel fit than others? Thanks for the help Link to comment Share on other sites More sharing options...
Dan Sierpina Posted December 27, 2015 Share Posted December 27, 2015 At the suggestion of Jim Lambert of Firebird Precision, on loose barrel / upper recievers I used copper RTV on them. I'd prefer a better mechanical fit, but tolerance stack up does exist. I purchased 2 Rainier uppers that did not have the forward assist, and they were not oversize like that. A 1.0000 gage was snug in the bore. The Black Hole Weaponry barrel extension was not sloppy. Link to comment Share on other sites More sharing options...
bmiller Posted December 28, 2015 Share Posted December 28, 2015 I had the same problem last summer. I ended up using red loctite. Rifle is cured of wandering zero. Link to comment Share on other sites More sharing options...
sschultz Posted December 28, 2015 Share Posted December 28, 2015 There is .009 difference in your parts.what I do is buy a piece of shim stock and cut to fit around the extension then freese the the barrel and heat the upper. Wrap the shim stock around the extension and slide the parts together. You can use a little bit of anti seize on the parts. Link to comment Share on other sites More sharing options...
jameslee1223 Posted December 28, 2015 Share Posted December 28, 2015 ^^^ this. I just did this to my double duty AR. My groups tightened up considerably. Consistently getting .7 MOA groups from a pretty plain non-match barrel. Link to comment Share on other sites More sharing options...
JonF Posted January 6, 2016 Share Posted January 6, 2016 I had the same issue with a 2A armament upper receiver and voodo0 barrel. Had to use some .001 or .002 shim stock to fill the gap. Seemed like it would be easier to service than a bedding compound or locktite. Link to comment Share on other sites More sharing options...
Jsp Posted January 7, 2016 Share Posted January 7, 2016 The BCM4 receivers are very snug. Barrel in the freezer and heat the reciever and it'll still be tight. Link to comment Share on other sites More sharing options...
openclassterror Posted January 7, 2016 Share Posted January 7, 2016 Dang, that is a LOT of clearance. The Mil-Spec print for barrel extensions calls out a MINIMUM diameter of .9985. We manufactured them for a while during one of the shortages. That is WAY out of spec on BOTH parts. If they were my parts I would have returned them, if possible. Shimming is possible, but that is ridiculous. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted January 8, 2016 Share Posted January 8, 2016 Dang, that is a LOT of clearance. The Mil-Spec print for barrel extensions calls out a MINIMUM diameter of .9985. We manufactured them for a while during one of the shortages. That is WAY out of spec on BOTH parts. If they were my parts I would have returned them, if possible. Shimming is possible, but that is ridiculous. Tom, there are a lot of billet receiver sets that were pushed out the door during the last panic. Quality control was not very high on the list of the people with the CNC's. Link to comment Share on other sites More sharing options...
reptoid Posted January 8, 2016 Share Posted January 8, 2016 Dang, that is a LOT of clearance. The Mil-Spec print for barrel extensions calls out a MINIMUM diameter of .9985. We manufactured them for a while during one of the shortages. That is WAY out of spec on BOTH parts. If they were my parts I would have returned them, if possible. Shimming is possible, but that is ridiculous. What he said....... .995" is way small on a part (barrel extension) that is suposed to be a "precision part" Link to comment Share on other sites More sharing options...
nheiny13 Posted January 8, 2016 Author Share Posted January 8, 2016 Well I tried strip of .003 & .004 shim wrapped around the extension but I couldn't get either to fit into the upper and I didnt feel like going back to Grainger for thinner shims. so I applied 640 loctite and torqued the barrel nut down pretty good. Link to comment Share on other sites More sharing options...
co-exprs Posted January 8, 2016 Share Posted January 8, 2016 All of the JP barrels I have removed were shimmed to fit. Link to comment Share on other sites More sharing options...
blairmckenzie1 Posted January 8, 2016 Share Posted January 8, 2016 Sounds like Nate got his issue resolved, so I will thread drift slightly. I have the exact opposite problem. I have a very tight barrel fit. Is it ok to use a soft face hammer to get the last quarter inch of the extension into the reciever? Link to comment Share on other sites More sharing options...
sschultz Posted January 8, 2016 Share Posted January 8, 2016 Try a little heat or freeze the barrel before install Link to comment Share on other sites More sharing options...
Amerflyer48 Posted January 8, 2016 Share Posted January 8, 2016 what sschultz said. I used the wife's hair dryer on my Aero upper when I set the BHW into it, surprised by the amount of heat it put out just put snout of dryer on threads (muzzle to muzzle ?) on low fan high heat for a few mins. and then while heating exterior of upper gently slid the barrel in until it seated then torqued the barrel nut or if you have grille gloves a warm oven would do but id just set oven to warm for a few minutes wouldn't want to overcook an upper if you are already "stuck" the Upper will expand with a little heat before the steel barrel catches up so all is not lost and hammering isn't something I usually do during an assembly process disassembly on the other hand I have a nice collection of hammers etc. John Link to comment Share on other sites More sharing options...
openclassterror Posted January 8, 2016 Share Posted January 8, 2016 Sounds like Nate got his issue resolved, so I will thread drift slightly. I have the exact opposite problem. I have a very tight barrel fit. Is it ok to use a soft face hammer to get the last quarter inch of the extension into the reciever? As long as the crown is protected by a muzzle device of some kind (flash hider, etc), tapping it in the last 1/4 in or so with a dead-blow is perfectly acceptable Link to comment Share on other sites More sharing options...
DEP44 Posted January 24, 2016 Share Posted January 24, 2016 You guys rock! Armed with .0005, .001 and .002 shim I went to install my 18" 308 JP barrel on an Aero upper. The sloppy hand fit pointed me to this thread. I tried .001 first and there still was play, .002 didn't go. Put the barrel in the freezer and heated up the receiver with the wife's blow dryer. tiniest bit of grease on the receiver and the barrel slipped right in. 5 Minutes later I couldn't pull the barrel for the life of me. Thanks!!! Link to comment Share on other sites More sharing options...
DBTN Posted January 24, 2016 Share Posted January 24, 2016 I did the same thing last week using a .001 shim on my new build. Don't know if it will help but I should not hurt. We shall see. I had not even considered such a thing until reading this thread. Link to comment Share on other sites More sharing options...
striped1 Posted January 24, 2016 Share Posted January 24, 2016 What are you using for shim stock? SS? Low Carbon? Link to comment Share on other sites More sharing options...
DBTN Posted January 24, 2016 Share Posted January 24, 2016 I used stainless purchased at Grainger. Link to comment Share on other sites More sharing options...
DEP44 Posted January 24, 2016 Share Posted January 24, 2016 I used SS. Link to comment Share on other sites More sharing options...
bradhall Posted January 26, 2016 Share Posted January 26, 2016 Never dealt with shims, seems like around a $50 expenditure, you all have any tips on where to find it? My barrel is 0.998 and receiver is 1.000. Link to comment Share on other sites More sharing options...
sschultz Posted January 26, 2016 Share Posted January 26, 2016 I spent $5 on shims. Link to comment Share on other sites More sharing options...
fedupflyer Posted January 26, 2016 Share Posted January 26, 2016 (edited) Brownells has a shim kit for around $20. http://www.brownells.com/gunsmith-tools-supplies/sight-scope-installation-tools/scope-shims/kit-no-ac-24-steel-shim-stock-prod589.aspx Edited January 26, 2016 by fedupflyer Link to comment Share on other sites More sharing options...
Chip3 Posted January 26, 2016 Share Posted January 26, 2016 http://www.mcmaster.com/#shim-stock/=10unzj5 McMaster carries a wide range of shim stock. They have $20 kit similar to Brownells but with a lot more stock included. Also for the ultimate lightweight 3gun build they have titanium shim stock! Link to comment Share on other sites More sharing options...
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