SIG Cross - jam nut / extension removal?

[Greg M]

Does anyone know how to remove the jam nut and barrel extension on the sig cross barrel?

The jam nut has an odd shape. Is there a special tool that's needed to do this?

 

[BELLYCRAWL]

12 point 1 1/16" box wrench. If you have an action wrench that fits from the stock side that is great. If not, you will probably have get creative holding the extension when you reassemble and tighten back down, but taking it off is super easy. My 12 point Jam nut was super loose. I left the barrel nut on and took the 12 point to the jam nut and it came loose.

 

[Greg M]

12 point 1 1/16" box wrench. If you have an action wrench that fits from the stock side that is great. If not, you will probably have get creative holding the extension when you reassemble and tighten back down, but taking it off is super easy. My 12 point Jam nut was super loose. I left the barrel nut on and took the 12 point to the jam nut and it came loose.

Excellent! Thank you.

 

[Greg M]

For anyone following this thread, I spoke to Nick at Straight Jacket Armory (bought my replacement barrel there). He is going to make a video showing how to do this procedure. For those starting from scratch, here are a few helpful tips / tools I have found so far:

TOOLS
There are many options here. These are merely suggestions if you don't know where to start. If you are a pro, feel free to skip.

1. Barrel nut wrench ($34, here)
2. 1-1/16-Inch Crowfoot Flare wrench ($24, here)
3. Bench vise ($190, here), barrel vise jaws ($30, here), paper drywall tape to protect the barrel ($4, here). There are plenty of alternatives:
   1. High-end: Short Action Customs, Modular Barrel Vice ($425, here)
   2. Mid-level: Barrel Removal Tool - requires a bench vise ($175, here). As of 3/9/2023, I have not found anyone else carrying an "action wrench" for the Cross. See this other thread as well.
   3. Entry-level: Wheeler Barrel Vise ($84, here)
   4. Git 'er done: go to home depot, buy a block of oak, drill hole, saw in half through hole diameter, clamp it with what you have.
4. "GO" and "NO-GO" gauges ($90, here).
   1. You can save money by buying only a "GO" gauge and making it "NO-GO" by putting painters tape on the base to create the proper dimension.
5. Miscellaneous - torque wrench, grease, thread lock, Fix-It sticks, etc.

DISASSEMBLY (draft):
There are instructions in the Cross Rifle Operators Manual (click here), but it assumes you have a barrel removal tool shown on page 95. Unfortunately, the barrel removal tool is not readily available for purchase. Both SIG and the one vendor in the "TOOLS" section above are out of stock. This and the next section are for the mere mortals who have tools that can be easily purchased...

Caution:

1. Another Sniper's Hide member said he broke the dowel pin in his barrel extension by not first loosening the castle nut and then loosening the barrel nut (thread here).
2. Your's truly made the same mistake and broke a piece off the dowel pin guide in the aluminum receiver.

REASSEMBLY (draft)
Numbers in this section are from the Cross Rifle Operators Manual where available. Otherwise, I will note source information.

Torque specs:

1. Castle / jam nut: ?? (same question different thread here, here. 3/13/2023 SIG cust svc said this is armorer-level spec, need to ask armorer)
2. Barrel nut torque: 40 ft-lbs
3. Handguard screws: 17.5 in-lbs
4. Receiver top rail: 35 in-lbs
5. Stock assembly: 50 in-lb.

The lack of clear instructions on how to do a SIG Cross pre-fit barrel swap (including the elusive "just reuse the factory extension") has been really frustrating, so I am doing my best to share what I have learned.

 

[Josh Saintz]

For anyone following this thread, I spoke to Nick at Straight Jacket Armory (bought my replacement barrel there). He is going to make a video showing how to do this procedure. For those starting from scratch, here are a few helpful tips / tools I have found so far:

1. Barrel nut wrench ($34, here)
2. 1-1/16-Inch Crowfoot Flare wrench ($24, here)
3. Bench vise ($190, here), barrel vise jaws ($30, here), paper drywall tape to protect the barrel ($4, here). There are plenty of alternatives:
   1. High-end: Short Action Customs, Modular Barrel Vice ($425, here)
   2. Mid-level: Barrel Removal Tool - requires a bench vise ($175, here). As of 3/9/2023, I have not found anyone else carrying an "action wrench" for the Cross. See this other thread as well.
   3. Entry-level: Wheeler Barrel Vise ($84, here)
   4. Git 'er done: go to home depot, buy a block of oak, drill hole, saw in half through hole diameter, clamp it with what you have.
4. Miscellaneous - torque wrench, grease, thread lock, Fix-It sticks, etc.

A few cautionary tales:

1. Another Sniper's HIde member said he broke the dowel pin in his barrel extension by not first loosening the castle nut and then loosening the barrel nut (thread here).
2. Your's truly made the same mistake and broke a piece off the dowel pin guide in the aluminum receiver.

The lack of clear instructions on how to do a SIG Cross pre-fit barrel swap (including the elusive "just reuse the factory extension") has been really frustrating, so I am doing my best to share what I have learned.

I'm just curious, did he provide you a jam nut torque for the barrel into the barrel extension? This is the only information I need and I can't find anything definitive anywhere. Good on you for sharing all your information

 

[Greg M]

I'm just curious, did he provide you a jam nut torque for the barrel into the barrel extension? This is the only information I need and I can't find anything definitive anywhere. Good on you for sharing all your information

No, but I did not ask. I have read 45 ft-lb for the barrel nut. There seems to be some sort of torque specification manual (or something similar) because video authors spout off torque specs as if they are reading them from a spec.

If you find it please post here and I will do the same. It seems ridiculous to me that we have to scrounge around to find this stuff.

 

[BELLYCRAWL]

I've looked everywhere as well for jam nut torque, and I haven't found it either. I ended up using 75 ft-lb on the extension jam nut, but it was a guess. I was going to send Sig a request for that data since they checked headspace on my rifle when it went back to them...assuming they removed the extension. I need to follow up with them since fixing my own rifle.

 

[Greg M]

I've looked everywhere as well for jam nut torque, and I haven't found it either. I ended up using 75 ft-lb on the extension jam nut, but it was a guess. I was going to send Sig a request for that data since they checked headspace on my rifle when it went back to them...assuming they removed the extension. I need to follow up with them since fixing my own rifle.

Thanks for sharing...I am updating the thread as I learn stuff. I try to avoid having to "relearn" something every time I do it.

 

[Greg M]

@BELLYCRAWL Just spoke to SIG's customer service. They said the jam nut torque is an armorer-level spec. They won't share the value, but said I could get it if I spoke to an armorer.

 

[BELLYCRAWL]

Thanks for the update...I"m curious what the armorer says.

I think Sig has failed here because the manual clearly mentions: "changing the barrel" in section 7.3, pp. 94-100. When I changed the barrel on mine, to include the new factory affixed extension, my bolt did not headpace to the new barrel/extension.

I did find it odd that these barrels have a bevel on the outer portion of the barrel on the chamber section where a pin is inserted through the extension that one could assume makes contact on the beveled area not allowing the barrel to screw into the extension any further, thus setting headpace. Someone can correct me if I am way off but that is an odd design. In my case I could screw the original barrel "in" further causing me to second guess the purpose of that pin because it did not really impact headspace. I believe it was a straight jacket video that stated they had removed that bevel from their barrel offerings.

Regardless, for Sig to mention "changing the barrel" and fail to give the data for checking headspace and torqueing the extension jam nut, just seems odd. They don't even give a safety warning. The manual doesn't mention to use an armorer and I fear one who doesn't do a little more research may just put a new barrel on and "kaboom."

 

[Greg M]

@BELLYCRAWL You're welcome!

When I changed the barrel on mine, to include the new factory affixed extension, my bolt did not headpace to the new barrel/extension.

This does seem odd, assuming you properly torqued the barrel nut.

Yes, Straight Jacket did remove that taper. No, the pin does not stop anything...I spent a bunch of time looking at that myself.

FWIW - Nick (at Straight Jacket) gave me an easy method to set headspace.
To set the headspace:
Assemble the receiver, load your "GO" gauge, close the bolt, screw the barrel in by hand until it is snug, back it off a hair, set your jam nut.

To check the headspace:
Remove the GO gauge, insert the NO GO gauge, try to close the bolt. If the bolt will not close, you should have the proper headspace.

Still looking for Jam nut torque and will post it when I find it.

 

[Judd]

If you loosen the jam nut first you have to figure out a way to hold the action to get the barrel extension nut off.

I’m contemplating chambering it up with a shoulder up against the barrel extension nut. Sig not stocking the proper tool is very frustrating.

This barrel mess and not putting a R700 trigger hanger on this thing are my only complaints, unfortunately those are two bigger complaints.

 

[Greg M]

If you loosen the jam nut first you have to figure out a way to hold the action to get the barrel extension nut off.

@Judd After thinking about this overnight, I believe the way to do this is secure the receiver to hold things and loosen the barrel nut. Holding the action to loosen the barrel nut will stress the dowel pin and its alignment slot in the aluminum receiver. The male threads are machined into the receiver and (obviously) the female threads are the barrel nut. Holding the action doesn't make sense to me and could cause damage to the receiver.

 

[Judd]

I think it’s a terminology thing, meaning I think we’re saying the same thing. The wrench that Sig doesn’t have in stock goes on the bolt raceway and locks into the action lugs, that’s the action…or in the AR world receiver. Unless I’m missing your point…which is also quite possible .

Initially, I put it in a vice with soft jaws vertically…meaning barrel (which is off) to the sky and butt to the floor…clamping to that flat spot in the action/receiver just behind the barrel nut. I didn’t feel comfortable tightening it up enough to get the nut loose.

My next thought was making some wooden blocks with a V cut in them to hold that same spot, then it hit me I could measure (headspace and bolt clearance) all this up and make a shouldered barrel that would tighten to the face of the barrel nut and not worry with removing it…eliminating the need for the jam nut completely. Decisions, decisions...but I don’t like either.

 

[BELLYCRAWL]

@BELLYCRAWL You're welcome!


This does seem odd, assuming you properly torqued the barrel nut.

Yes, Straight Jacket did remove that taper. No, the pin does not stop anything...I spent a bunch of time looking at that myself.

FWIW - Nick (at Straight Jacket) gave me an easy method to set headspace.
To set the headspace:
Assemble the receiver, load your "GO" gauge, close the bolt, screw the barrel in by hand until it is snug, back it off a hair, set your jam nut.

To check the headspace:
Remove the GO gauge, insert the NO GO gauge, try to close the bolt. If the bolt will not close, you should have the proper headspace.

Still looking for Jam nut torque and will post it when I find it.

On the Cross, you don't need the barrel in the receiver or proper barrel nut torque to check headspace. Similar to an MSR, HS can be easily checked with just barrel and bolt.

I don't have an action wrench either for the Cross, which inserts into the barrel extension, which contains the locking lugs locking surfaces. A wrench would make things easier for sure, but I'll list my method below, but I'm sure there are other ways. Hopefully my typing communicates clearly.

I assemble barrel/extension/gauges & bolt just loose on the bench and basically know where I need to be in relation to where I am going to clamp my barrel in the vice and my extension into a bench vise (it will make more sense below) so that bolt handle isn't going to contact the bench vise when I make adjustments for final head space and torque.

As to torqueing things down, I clamp the barrel into a Brownells barrel vice with sheetrock tape. I position a small bench vice on another table with the Sig barrel extension clamped into soft jaws that way I can easily loosen the bench vise vs the barrel vice when I'm setting HS. I can insert a go gauge and bolt, spin the extension with gauge & bolt until contact is made on the gauge (back off a little if desired), lock down the bench vise soft jaws on the extension carefully not to move anything, and tighten jam nut (I guessed at 75 foot lbs). I then check with a no go gauge and GTG.

I do then insert the barrel/extension into the receiver and torque barrel nut (I think I used 60 or 70 foot lbs) to double check everything. I do have the ejector(s) removed (just the way I was trained/creature of habit), and reassemble the bolt ejector(s).

I have some history with Remages and Savages, and while they are easier with the bolt’s lug locking surfaces being part of the receiver/action, I like Sig's design. I will be buying a rear entry action wrench when I can find one to make this a little easier, but it can definitely be done without one.

I'm not saying my final assembly method is the only way, as I did experiment with the barrel/extension/receiver all together a couple of times, and it is easier to have the bolt body sliding down the receiver races. If someone is doing a home project, the way I do it has everything secure to my standard while I start adding torque.

Blessings,

 

[FisherT&C]

I wrote this up to assist anyone needing to swap a barrel out. I personally think they're a pain in the ass and do not care to do another one.
It would be a lot easier with a barrel extension wrench but they're rarely available and expensive.

 

[Hyintensity]

12 point 1 1/16" box wrench. If you have an action wrench that fits from the stock side that is great. If not, you will probably have get creative holding the extension when you reassemble and tighten back down, but taking it off is super easy. My 12 point Jam nut was super loose. I left the barrel nut on and took the 12 point to the jam nut and it came loose.

I just bought a Sig action wrench. I should have it in a few days.

Does the 12pt 1-1/16 Crows foot fit the extension jam nut well? Or is this the best fit that could be found?

Is the jam nut pattern a Sig factory patten nut, or is the 12pt the correct pattern wrench?

 

[Judd]

There are two nuts…it’s like an unemployed engineer was hired to design the system.

You need both the Avid barrel nut wrench and the 12 pt crows foot….there are two nuts.

Where did you find the action wrench for sale?

 

[Hyintensity]

I got the action wrench directly from Sig. $299.

So the 12pt 1-1/16 is the correct wrench for the barrel extension jam nut? I mean, it fits correctly and isn't just "good enough"?

It is a weird design and the manual leaves the jam nut and extension out of the conversation completely.

I called Sig and they basically blew me off.

 

[Judd]

Yes, it’s correct…not just good enough.

Thanks, I’ll call them tomorrow.

 

[Hyintensity]

Yes, it’s correct…not just good enough.

Thanks, I’ll call them tomorrow.

Perfect!
Thanks for the info!

FYI, the reaction rod is shown in red on page 95 of the Cross manual. I would reference the page to minimize confusion. Their reps don't seem very knowledgeable about their own products. The rep I got had zero clue about this tool.

Good luck and thanks for the help!

 

[Greg M]

I just bought a Sig action wrench. I should have it in a few days.

Where did you get it? Every place I found was "out of stock"

Does the 12pt 1-1/16 Crows foot fit the extension jam nut well? Or is this the best fit that could be found?

Is the jam nut pattern a Sig factory patten nut, or is the 12pt the correct pattern wrench?

The 12pt 1-1/16 crows foot is the correct tool for the job.

 

[Hyintensity]

I got it directly from Sig.

 

[Judd]

They are out again…just talked to them on the phone. He has no idea when they will be back in stock but mentioned if you are changing to all Sig parts they will swap it out if you sent it to them. Not what I’m looking to do (wanting to make it a 6 Gaymoor) so that doesn’t help me at all. He also warned about changing it without that part because they have seen where someone broke or messed up the threaded section of the receiver/action.

Sure seems like someone is missing a golden opportunity to make a bunch of these and sell them for a couple hundred bucks…shocked no one has jumped on this…it’s not like it’s a part that can be proprietary or anything.

Thanks for the head’s up Hyintensity.

 

[Greg M]

Sure seems like someone is missing a golden opportunity to make a bunch of these and sell them for a couple hundred bucks…shocked no one has jumped on this…it’s not like it’s a part that can be proprietary or anything.

Once I get my Cross back we are taking measurements of the extension and making this tool:

If you want one, please click "Like" on the post and I will reach out directly.

 

[Greg M]

I wrote this up to assist anyone needing to swap a barrel out. I personally think they're a pain in the ass and do not care to do another one.
It would be a lot easier with a barrel extension wrench but they're rarely available and expensive.

Straight Jacket created an instructional video for swapping SIG Cross barrels that may help folks as well.

 

[Hyintensity]

Straight Jacket created an instructional video for swapping SIG Cross barrels that may help folks as well.

Very helpful! Thx!

 

[Greg M]

Another "lesson learned" here...this tool:

1. 1-1/16-Inch Crowfoot Flare wrench ($24, here)

from my "instruction" post above is not capable of applying the required torque to loosen my castle nut. The jaws flex under torque and slip on the nut.

After searching a few places (Midwest Gun Works, Optics Planet, etc.), I went with a standard torque adapter from Snap-on (click here). It is a box-end attachment with a 1/2" drive, so I can use my torque wrench directly.

@Josh Saintz Barrel nut torque mentioned by Nick at Straight Jacket Armory is 55 ft-lb (click here).

 

[Hyintensity]

I cannot thank you enough for this information.

I literally just cut open the package from Sig with the action wrench in it.
I bought the 1-1/16" 12pt and armorers wrench suggested in previous posts.

I am now ordering the Snap On wrench before beginning this project.

I wish I could buy you a beer in appreciation.

Many thanks!

 

[Greg M]

I cannot thank you enough for this information.

@Hyintensity You're welcome... it increases the value of my mistakes when I am able to help others! Really glad to know you find it useful.

One thing - the 1-1/16" 12pt and armorers wrench is for the same purpose as the Standard Torque Adapter (1-1/16", 12 pt) from Snap-on that I recommended. I went with the Snap-On tool because it is generally a better way to apply torque. The one draw-back is that I will need to remember it is close-ended before applying my "barrel clamp" (I am using a vise with barrel jaws which makes it easier).

 

[Greg M]

One thing worth sharing, the castle/jam nut on the barrel has an internal shoulder with an ID larger than the threads. Not knowing this gave me pause when trying to remove it, since there were no more visible threads and it needs to be turned counter clockwise (viewing from breech of barrel). I was reluctant to apply a lot of torque not knowing there were additional "useful" threads on the barrel.

Also, adding a few pictures for those who are new to this rifle so you have an idea of how it goes together.

.

 

[Judd]

Barrel Removal Tool for Sig CROSS - Pro Firearm Tools

Sig Cross barrel removal and installation tool.

shop.taconesports.com

wrench…I got one yesterday and they were out after I checked out. They are showing 2 in stock right now.

 

[rabeck27]

This is how i do it. Clamp the barrel in a barrel vise, use an AR armorers wrench to loosen the receiver nut. Pull the receiver off the barrel. Flip the barrel around and grab the barrel extension with the vise. Use a 1 1/16 12-point box end wrench to loosen the jam nut. Swap the barrel, set headspace, tighten the jam nut using the crows foot mentioned earlier and then put it back in the receiver clamping on the barrel shank again. No need for any special action wrenches.

 

[mviv07]

I'm just curious, did he provide you a jam nut torque for the barrel into the barrel extension? This is the only information I need and I can't find anything definitive anywhere. Good on you for sharing all your information

120 ft-lbs for the jam nut between the barrel and extension. 45 for the receiver nut.

 

[mviv07]

For anyone following this thread, I spoke to Nick at Straight Jacket Armory (bought my replacement barrel there). He is going to make a video showing how to do this procedure. For those starting from scratch, here are a few helpful tips / tools I have found so far:

TOOLS
There are many options here. These are merely suggestions if you don't know where to start. If you are a pro, feel free to skip.

1. Barrel nut wrench ($34, here)
2. 1-1/16-Inch Crowfoot Flare wrench ($24, here)
3. Bench vise ($190, here), barrel vise jaws ($30, here), paper drywall tape to protect the barrel ($4, here). There are plenty of alternatives:
   1. High-end: Short Action Customs, Modular Barrel Vice ($425, here)
   2. Mid-level: Barrel Removal Tool - requires a bench vise ($175, here). As of 3/9/2023, I have not found anyone else carrying an "action wrench" for the Cross. See this other thread as well.
   3. Entry-level: Wheeler Barrel Vise ($84, here)
   4. Git 'er done: go to home depot, buy a block of oak, drill hole, saw in half through hole diameter, clamp it with what you have.
4. "GO" and "NO-GO" gauges ($90, here).
   1. You can save money by buying only a "GO" gauge and making it "NO-GO" by putting painters tape on the base to create the proper dimension.
5. Miscellaneous - torque wrench, grease, thread lock, Fix-It sticks, etc.

DISASSEMBLY (draft):
There are instructions in the Cross Rifle Operators Manual (click here), but it assumes you have a barrel removal tool shown on page 95. Unfortunately, the barrel removal tool is not readily available for purchase. Both SIG and the one vendor in the "TOOLS" section above are out of stock. This and the next section are for the mere mortals who have tools that can be easily purchased...

Caution:

1. Another Sniper's Hide member said he broke the dowel pin in his barrel extension by not first loosening the castle nut and then loosening the barrel nut (thread here).
2. Your's truly made the same mistake and broke a piece off the dowel pin guide in the aluminum receiver.

REASSEMBLY (draft)
Numbers in this section are from the Cross Rifle Operators Manual where available. Otherwise, I will note source information.

Torque specs:

1. Castle / jam nut: ?? (same question different thread here, here. 3/13/2023 SIG cust svc said this is armorer-level spec, need to ask armorer)
2. Barrel nut torque: 40 ft-lbs
3. Handguard screws: 17.5 in-lbs
4. Receiver top rail: 35 in-lbs
5. Stock assembly: 50 in-lb.

The lack of clear instructions on how to do a SIG Cross pre-fit barrel swap (including the elusive "just reuse the factory extension") has been really frustrating, so I am doing my best to share what I have learned.

Don't use a crowfoot wrench. The torque will exceed max allowable on the tool and you'll end up permanently damaging the tool and the gun.

Instead pick up something like this, with a torque mount so you can use it again when to set the proper torque on reinstalation

Snap-on Store

shop.snapon.com

 

[jackals]

I needed a Crowfoot and found these open box 12 Point 1-1/16 X 3/8 ones for $15 shipped at https://www.ebay.com/itm/125526155979 - 8 left at time of posting.