Shilen barrel chambered in 204 Ruger...barrel nut indexing shims

[RPR 6.5 slave]

I recently bought a Shilen heavy varmint barrel and I am experiencing some difficulty getting it assembled. It is an ar15 barrel and the indexing shims for the barrel nut are too small in diameter they will not fit past the gas block. Therefore I cannot properly align the gas tube. I have tried different hand guards and barrel nut combinations. The problem is the I.D of the guard to fit over the adjustable gas block. I found a hand guard to fit but you need to index the barrel nut. Has anyone out there experienced this and if so where do you find shims with an I.D. of 1.005 or slightly larger? Thanks for any help.

 

[Dusty Stevens]

Ive never heard of using shims to align a barrel nut. You torque it then back off to align it. If you use shims you would have to simply remove the gas block. I line them up with a bright light then install the gas tube/block

 

[Ggmac]

I recently bought a Shilen heavy varmint barrel and I am experiencing some difficulty getting it assembled. It is an ar15 barrel and the indexing shims for the barrel nut are too small in diameter they will not fit past the gas block. Therefore I cannot properly align the gas tube. I have tried different hand guards and barrel nut combinations. The problem is the I.D of the guard to fit over the adjustable gas block. I found a hand guard to fit but you need to index the barrel nut. Has anyone out there experienced this and if so where do you find shims with an I.D. of 1.005 or slightly larger? Thanks for any help.

Shims ? You aren't assembling as designed . Do as Dusty says . Make sure you lube the receiver threads and load and unload the barrel nut to seat correctly . Sometimes the action of load and unloading the threads will help in getting it MORE near the mark without undue sweat .
Load and unload refer to screwing the barrel nut onto the receiver NOT sticking a round in the mag !

 

[RPR 6.5 slave]

Shims ? You aren't assembling as designed . Do as Dusty says . Make sure you lube the receiver threads and load and unload the barrel nut to seat correctly . Sometimes the action of load and unloading the threads will help in getting it MORE near the mark without undue sweat .
Load and unload refer to screwing the barrel nut onto the receiver NOT sticking a round in the mag !

 

[RPR 6.5 slave]

View attachment 1099381

So I am not supposed to use barrel nut shims huh? I am not at the genius level some are at....but how would you get this to torque right and line up right without shims?

 

[RPR 6.5 slave]

So I am not supposed to use barrel nut shims huh? I am not at the genius level some are at....but how would you get this to torque right and line up right without shims?

As for the SMART_ASS comments from the peanut gallery.......thanks for nothing. I learned how to read at a very young age...you?

 

[akajun]

Your problem is than your using a barrel but for some type of specialty handguard that does nit have enough slots for the gas tube, hence the shims. It was probably designed to work with a a2 barrel as opposed to a bull

Your options are to have a small amount to turn off the barrel

Contact the handguard manufacturer and see if they have larger Id shims or can bore those out. In addition a good machinist could bore those out too but. E prepared to pay around $100 or so. Opening up thin wall shims will require making a device to hold them.

 

[BoydAllen]

Question from an admitted AR ignorant guy. How much interference is there at the gas block? Doing a quick search I found shims that have an ID of 1", which would make me think seriously of taking a file to the block, if they could be used.
https://www.wingtactical.com/firear...ries/aero-precision-ar15-barrel-nut-shim-kit/

 

[msalm]

Just face .002” off the receiver face and forget the shims.

 

[dfrosch]

Lap the face of your upper so you don't need to use shims. It'll help keep that heavy barrel from moving around too.

 

[RPR 6.5 slave]

Shims ? You aren't assembling as designed . Do as Dusty says . Make sure you lube the receiver threads and load and unload the barrel nut to seat correctly . Sometimes the action of load and unloading the threads will help in getting it MORE near the mark without undue sweat .
Load and unload refer to screwing the barrel nut onto the receiver NOT sticking a round in the mag !

You so smart....maybe you should teach.....learn more before you belittle others. It just makes you look like a fool.

 

[Ggmac]

You so smart....maybe you should teach.....learn more before you belittle others. It just makes you look like a fool.

Another that is awarded the IGNORE button .

 

[shortgrass]

You so smart....maybe you should teach.....learn more before you belittle others. It just makes you look like a fool.

By the posts you have made in this thread it appears that you are the one who is not very smart. Ask for help and then belittle those who try to help? What does that make you look like to others?

 

[shortgrass]

Another that is awarded the IGNORE button .

The "ignore" button,,,,,,, not a bad idea...……….

 

[DaveTooley]

RPR who? Another one bites the dust.

 

[akajun]

Lap the face of your upper so you don't need to use shims. It'll help keep that heavy barrel from moving around too.

This is a bad idea, you are changing the location of how the barrel sits in the upper in relation to the bolt carrier. If you ever true the upper face, it’s to simply true it up. While .002 probably wouldn’t hurt, look at the barrel but he’s using, there is a lot more needed to be taken off than .002.
Shims go on the muzzle end of the barrel extension so as not to interfere with this location.

 

[dfrosch]

This is a bad idea, you are changing the location of how the barrel sits in the upper in relation to the bolt carrier. If you ever true the upper face, it’s to simply true it up. While .002 probably wouldn’t hurt, look at the barrel but he’s using, there is a lot more needed to be taken off than .002.
Shims go on the muzzle end of the barrel extension so as not to interfere with this location.

The threads on an AR-15 upper receiver are 1.250-20 UNF, so each thread lead is about .050. Looking at his picture, the nut is octagon shaped with eight clearance channels for the gas tubes. So taking .006 off the face will allow indexing between each channel. He only needs about half of that. So if he lapped .003 off, it would index correctly with the same amount of torque.

Doing this would give the barrel extension a flat surface to seat against, which would reduce barrel vibration. It would also square the receiver face to the bore that the BCG rides in. This will allow the bolt to lock and unlock a lot more smoothly.

 

[tobnpr]

^^^
Bingo, we have a winner. Ideally it would be done on a lathe, but it could be carefully stoned off being careful to keep even pressure on the nut while doing so to keep the face perpendicular to the threads. They really should include a full set of timing shims with a product like that (similar to Precision Armament's for muzzle brakes) to get it to time.

 

[dfrosch]

I just use a lapping tool. Here's a link to mine:

https://www.midwayusa.com/product/810457/ar-stoner-upper-receiver-lapping-tool-ar-15

 

[akajun]

The threads on an AR-15 upper receiver are 1.250-20 UNF, so each thread lead is about .050. Looking at his picture, the nut is octagon shaped with eight clearance channels for the gas tubes. So taking .006 off the face will allow indexing between each channel. He only needs about half of that. So if he lapped .003 off, it would index correctly with the same amount of torque.

Doing this would give the barrel extension a flat surface to seat against, which would reduce barrel vibration. It would also square the receiver face to the bore that the BCG rides in. This will allow the bolt to lock and unlock a lot more smoothly.

I understand that and I get what your saying, however I was taught in armorers school that more than .003 can cause problems. In fact this subject was so continuous with the instructor he stated don’t ever lap/ true the face just replace the reciever if it’s out of spec. I talked to him after class and told him about my experiences with having to lap/ remove burrs with my homemade lapping tool because of accuracy problems. He stated that since this class was for police officers and not machinists that he did not advocate lapping as it reduced this gap between the bolt carrier and barrel extension . This area fills up with carbon due to the gas tube being right there. Go inspect the bolt carriers on a few guns, you’ll see the finish removed on a few on the forward face.
While shooting a highpower match or a little target session would probably be ok, a pd shoot or a police training class where 500-1000 rds shot in a day are common, it can start causing problems.
This guy doesn’t seem like a machinist, but it sounds like he needs one, hence the recommendation he not lap the upper.