Ultralight Ultralight Rifles

[StupidLightweight]

Makes me wonder if a Smith can easily replace a standard sloppy extension with an oversized one? They're just a press fit right?

The extension is threaded onto the barrel, but yes, a 'smith could easily replace a sloppy one with an oversized extension. Heck, with a barrel vice, torch, and the right tools, likely anyone could.

 

[HighUintas]

According to experts I've spoken with, the best way to rigidly attach the barrel to the upper receiver is a two part process. They use an oversized barrel extension and cool the entire barrel in the freezer. They then heat the upper receiver and quickly join the two. Once the barrel extension warms up and expands the receiver contracts, the two are rigid.

If you're a manufacturer, this is easy. What I do as a garage gunsmith is epoxy the barrel into the upper receiver. If you ever need to take it off, a torch on the upper receiver gets it hot enough to pop the barrel off.

Did you do this on all your ULUL builds? What accuracy increase have you seen? And have you tried different epoxies or do you think any epoxy would work that's used for bedding?

 

[Thegman]

According to experts I've spoken with, the best way to rigidly attach the barrel to the upper receiver is a two part process. They use an oversized barrel extension and cool the entire barrel in the freezer. They then heat the upper receiver and quickly join the two. Once the barrel extension warms up and expands the receiver contracts, the two are rigid.

If you're a manufacturer, this is easy. What I do as a garage gunsmith is epoxy the barrel into the upper receiver. If you ever need to take it off, a torch on the upper receiver gets it hot enough to pop the barrel off.

I wonder if release agent on both the receiver and barrel extension would allow the barrel and a small amount of epoxy to be removed more easily, with the epoxy still acting as a shim?

 

[StupidLightweight]

I've only done it on a semiauto upper with an accurate 16-inch pencil barrel. I then removed the barrel and gave it to a buddy on a different upper. Again, it wasn't tough.

On bolt-action uppers, I've not done this because I swap barrels often. I do believe the accuracy increase would be worth it, and a good shooter could likely tell. I'm not a good enough shooter with lightweight guns to detect a half-MOA difference, so the quick-change barrel feature outweighs the accuracy benefits.

You could use release agent, but I wouldn't worry about it. Again, heat will cause the expose to break loose if and when you decide to remove the barrel. For these builds, I'd make the barrel as permanent as possible. Realistically, most will never shoot one out. I'd file the extension rough, maybe take a Dremel to the inside of the upper receiver, degrease both, and then use a thin coat of Devcon to eliminate all slop.

 

[JBradley500]

This video is what made me stop worrying about bedding barrel extensions to the upper.

Smyth Busters: Should You Bed an AR-15 Barrel? | Brownells

To bed or not to bed? Steve and Caleb weigh in on whether your AR-15's barrel needs to be "bedded" into the receiver.

www.brownells.com

 

[BREAKCONTACT]

I don't really think it's worth the effort, but if someone wanted to, you can get metal shim stock as thin as 0.0005", so with micrometers you could shim a barrel to a thermal fit.

 

[Trackselk]

This video is what made me stop worrying about bedding barrel extensions to the upper.

Smyth Busters: Should You Bed an AR-15 Barrel? | Brownells

To bed or not to bed? Steve and Caleb weigh in on whether your AR-15's barrel needs to be "bedded" into the receiver.

www.brownells.com

I had basically planned on shooting it, and then bedding if the accuracy wasn't MOA or better. The fit for my shaw and bca could definitely be tighter. My Faxon was significantly tighter, but I wanted lighter. Since I already bought the loctite, I'll give it a go if necessary and report back. The guy in the article I linked above also lapped the face, and messed with the gas tube, so just bedding it might give us some real data. A lot easier than changing the extension for sure. I might try the oversized extension also but don't really want to pay $ to lose my gun to the Smith for weeks.
One of the biggest advantages to this platform is cutting the Smith out of the equation IMO. I'd buy a barrel vise and other necessary tooling first, which I probably have. I wonder if the wheeler action rod is strong enough for removing the extension(i doubt it)? Off to Google...

 

[Trackselk]

Did a little reading, looks like all we need for install is a extension tightening tool for $35 from Brownells, and a tool to hold the barrel nut. In my case, the crows foot for the Jag Composites nut that I use, fits securely in the vise.
Please correct me if I'm wrong, but looks like our strait pulls have another advantage. I don't think we need the index pin at all, as it's there to keep the gasport and front sight at 12 o'clock.
So, pull the pin with visegrips, remove the extension (probably requires a barrel vise?), and torque the new one back on, verify headspace with go and nogo gauges, and you're good to go right?
*One problem with the video I watched where they use the barrel nut as the 'counter torque holder' is that the Jag nut only takes 30 ft/lbs, so I guess I'll have to add a barrel vise to the list, which leaves us with a few tools in addition to a vise, tool to tighten nut, torque wrench or strap wrench, and tool to hold the upper, which I think most of us already have.

-barrel vise
-extension tool ($35 from brownells)
-go and nogo gauges

Install:
Start at the lowest torque (120), Check headspace, and then tighen more if necessary up to max (155). Red loctite. Forget about index pin (hooray!).

Edit: looks like the pin will make clocking the extension much easier, but it may be out of position with a new extension. So, I think you can make an alignment mark for the proper position after the extension is torqued in place. All bets are off if the headspace isn't correct...time for a gunsmith to machine it all to fit. Or better yet, just ream it with the chamber and throat you want if the chamber is too small. I've heard of guys doing this operation themselves also, but I wouldn't trust myself on the precision front with no experience...

*most online sources call for 150 ft lbsof torque...

 

[KyleR1985]

I think you guys are underselling how hard pin removal and barrel extension removal can be at times.

And headspacing new components.

But I’m ready for someone here to cut through the crap and prove me wrong.

I’ll be doing it eventually because I can’t get the barrel I want for less than 4-500 bucks so I’m going to have to improvise.

I’m not above paying that much for a barrel. But it’s unbecoming of a rifle thay looks like this

 

[Trackselk]

Think of ALL of the weight savings that we'd get with no index pin

 

[KyleR1985]

Think of ALL of the weight savings that we'd get with no index pin

I’ve been sitting here trying to figure out how to incorporate a barrel nut inside the receiver nut so I can headspace any barrel I want

 

[Trackselk]

I’ve been sitting here trying to figure out how to incorporate a barrel nut inside the receiver nut so I can headspace any barrel I want

That would take some significant machining and redesign, but you got me thinking. If the headspace is too little, a simple shim between the extension and barrel would lengthen it. And, maybe we could simply have any machinist shave down an extension that's too long, just need precise ability to measure how much shorter the chamber needs to be (scotch tape method on case head, multiple layers?)
I wonder if the right size shims are easily sourced?

Maybe a shim between the barrel and receiver would work to increase the headspace also?

Oh! And you could use the "face truing" kit for the upper to reduce the headspace very slowly and precisely. So, I think we can manage headspace at home either direction if the right shims are available.

 

[hereinaz]

I am as DIY and cheap as others, this may have jumped the shark a bit for me, lol. No way I am gonna jump into the barrel/extention game.

Putting in my order for the BCA pencil barrel soon.

 

[Trackselk]

Am I crazy to think that we could tackle small headspace (too long) adjustments with this kit?

AR Receiver Lapping Tool | AR 10 & AR 15

www.wheelertools.com

Edit: as a bonus we fix any out of true issues with the face at the same time.

 

[Trackselk]

I am as DIY and cheap as others, this may have jumped the shark a bit for me, lol. No way I am gonna jump into the barrel/extention game.

Putting in my order for the BCA pencil barrel soon.

Yeah, what's worse is the fact that I went down this rabbit hole before I even had a need for it!

 

[Tailwind5sw]

Am I crazy to think that we could tackle small headspace (too long) adjustments with this kit?

AR Receiver Lapping Tool | AR 10 & AR 15

www.wheelertools.com

Edit: as a bonus we fix any out of true issues with the face at the same time.

I got the laping tool a while back it is amazing how much some receivers are off on the front edge, I use it on every upper now. The pin is needed to clock the bolt to the extension besides the gas port . Still need it.

 

[Trackselk]

I got the laping tool a while back it is amazing how much some receivers are off on the front edge, I use it on every upper now. The pin is needed to clock the bolt to the extension besides the gas port . Still need it.

Thanks for the report! I was thinking as long as the barrel doesn't rotate, then we could visually line the extension up correctly for the bolt, and then tighen the barrel nut. If the barrel twists during the tightening, then with a little back and forth, it would be easy enough to give it enough lead to land in the right spot. I wouldn't bother if a new, tighter extension left the pin hole at 12, but good chance that it no longer will, and then you need a solid jig to drill a new pin hole in a steel barrel precisely.
Basically, I think it allows us to do this at home without precision drilling. Easy to tap in a new pin if the old hole is at 12 though.

*adjusting headspace would also lead to the pin being off of 12, unless you found some magic combination of new extension +barrel

 

[BREAKCONTACT]

Am I crazy to think that we could tackle small headspace (too long) adjustments with this kit?

AR Receiver Lapping Tool | AR 10 & AR 15

www.wheelertools.com

Edit: as a bonus we fix any out of true issues with the face at the same time.

Negative, headspace has to do with barel to barrel extension dimentions, nothing with barrel to upper reciver.

 

[Trackselk]

Negative, headspace has to do with barel to barrel extension dimentions, nothing with barrel to upper reciver.

Oh yah, duh, good catch!

 

[Trackselk]

Negative, headspace has to do with barel to barrel extension dimentions, nothing with barrel to upper reciver.

-Deleted my last dumb question, I got it figured out