Modern Sporter - Build Discussions

greg olmstead said:
The only torque transferred would be how much resistance there is on the threads between them and the barrel nut.

Using good grease on the threads will eliminate most of it. Most of the index pin failures associated with the reaction rod are due to faulty index pins or improper use of the tools.

A reaction rod keeps all the stress out of the upper eliminating flex on the upper. Think about it. How would aluminum be stronger than the hardened stainless steel of the index pin?
I'd rather have to replace an index pin that shears vs an upper that flexed and cracked.
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Absolutely not, it's the complete opposite. Using a reaction rod concentrates ALL the torque on the barrel index pin and upper index pin slot. That's why so many break using a reaction rod, and why pretty much none break using an upper fixture. The "reaction rod" tool design was used before Geissele marketed it. It's only used out of convenience and speed, nothing to do with actual engineering concepts or torque mechanics. Just because something is being used by big companies, does not necessarily mean it's a good idea or is the best or proper solution, it just means it's what they use.

7075-T651 is very, VERY strong, the index pins aren't breaking in half, they're shearing out of their hole because the aluminium is mechanically stronger than the press fit and hole depth relationship of the index pin under side torque.

An appartus that keeps the upper fixed but not the barrel extension is a superior way of torquing the barrel nut than an appartus that keeps the barrel extension fixed. The optimal upper appartus would spread the torque evenly through the upper and not concentrate it to select areas. The worst offender being the old Teflon vise blocks that kept the upper fixed through the takedown and pivot pin holes. That was one stupid design.

If you think otherwise, you just don't understand the torque mechanics at play here. It's okay. But before putting statements out there that people can base their decisions on, be sure you know what you're talking about.


It's like that Aeroshell 33/64 "barrel nut grease" thing that's been bouncing around the Internet for who knows how long. That's absolutely not what Colt uses, Colt has been using DuPont G-N Metal Assembly Paste on the barrel nut threads for like... a very long time. Someone somewhere some time ago got a hold of some probably expired datasheet, and spread the data like gospell on the Internet and now everybody believes it. It's a lot harder to come by than Aeroshell tho so maybe that plays a part in this. It's more hazardous too. Aeroshell has been sufficient for home gamers and has been "deemed" acceptable over time. People haven't seemed to run into problems using it so... if it works... heck people have put everything under the sun on the threads, from motor oil to red bearing grease to metallic anti-seizes, with no particular ill effect. Use whatever you want or have on hand and you'll more than likely be fine.

But just because everybody says the same thing doesn't mean it's true.


The nicest available appartus to install a barrel would be the Magpul Bev block, because it keeps both the upper and barrel extrension mechanically fixed together during torque. It eliminates all the stress points that every other appartus style compromises upon. It's a very clever design and one that should have been marketed decades ago.

Geissele has built a reaction rod version for manufacturers that has integrated rotating bushings that keep the upper fixed to the rod. It's the only reaction rod design worth buying IMO. It's double the price of the normal reaction rod so it hasn't spread in popularity like the lesser model has. It's still not as good a design as the Magpul Block IMO.
 
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So much fuss over reaction rods and proper installation. You can literally tighten a barrel nut with hand-strength only (holding the upper in one hand, wrench in the other) and it will hold adequately and not come loose. Dont fret over exact torque or using a vise. Use a quality grease like Aeroshell, but copper/silver anti-seize is just fine.
 
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HotSoup said:
So much fuss over reaction rods and proper installation. You can literally tighten a barrel nut with hand-strength only (holding the upper in one hand, wrench in the other) and it will hold adequately and not come loose. Dont fret over exact torque or using a vise. Use a quality grease like Aeroshell, but copper/silver anti-seize is just fine.
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I know right... there's a tongueless guy in a cave in the middle east making guns with a grinder and files. It's not rocket science.
 
alberta tactical rifle said:
THAT certainly is the best way to go. We have seen several thou difference in headspace with generic barrel/bolt set ups. In theory any bolt should headspace correctly with any barrel, but in the real world there are tolerance differences. Even different gages will result in differing headspace factors.
Best plan is to cut the chamber and employ the bolt that is going to be used in that rifle, this reduces any possibility of too much or too little headspace.
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I’m another rookie, first build. I’ve got a good 6 months to figure things out. Big question, how does one go about matching the bolt to barrel? Buy the bolt you want and send it to the barrel manufacturer? I’m thinking about an MRA barrel but at this stage I just want a good idea of what I need to buy, without buying something expensive that doesn’t work.
 
Yes me too. So curious to know what ATRS "OFFICIALLY" recommends or what do they use in house?


KePet said:
Not trying to complicate things. It’s just that some of us already own BEV blocks. If possible, why not use a tool that you already own. I’m not above buying a reaction rod - probably the cheapest part that I’ll be buying for this build - I just didn’t realize when I made the comment that a BEV block wouldn’t work.
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This too has been my understanding of the Bev so again curious as to what the official in-house tools are used by ATRS??? This is a tad disconcerting, though maybe I wasn't reading the fine print in regards to what will/not work. But....I have at least six months to wait for all this to get figured out. Tool share and build party for group two in YYC anyone?



Dietz said:
Absolutely not, it's the complete opposite. Using a reaction rod concentrates ALL the torque on the barrel index pin and upper index pin slot. That's why so many break using a reaction rod, and why pretty much none break using an upper fixture. The "reaction rod" tool design was used before Geissele marketed it. It's only used out of convenience and speed, nothing to do with actual engineering concepts or torque mechanics. Just because something is being used by big companies, does not necessarily mean it's a good idea or is the best or proper solution, it just means it's what they use.

7075-T651 is very, VERY strong, the index pins aren't breaking in half, they're shearing out of their hole because the aluminium is mechanically stronger than the press fit and hole depth relationship of the index pin under side torque.

An appartus that keeps the upper fixed but not the barrel extension is a superior way of torquing the barrel nut than an appartus that keeps the barrel extension fixed. The optimal upper appartus would spread the torque evenly through the upper and not concentrate it to select areas. The worst offender being the old Teflon vise blocks that kept the upper fixed through the takedown and pivot pin holes. That was one stupid design.

If you think otherwise, you just don't understand the torque mechanics at play here. It's okay. But before putting statements out there that people can base their decisions on, be sure you know what you're talking about.


It's like that Aeroshell 33/64 "barrel nut grease" thing that's been bouncing around the Internet for who knows how long. That's absolutely not what Colt uses, Colt has been using DuPont G-N Metal Assembly Paste on the barrel nut threads for like... a very long time. Someone somewhere some time ago got a hold of some probably expired datasheet, and spread the data like gospell on the Internet and now everybody believes it. It's a lot harder to come by than Aeroshell tho so maybe that plays a part in this. It's more hazardous too. Aeroshell has been sufficient for home gamers and has been "deemed" acceptable over time. People haven't seemed to run into problems using it so... if it works... heck people have put everything under the sun on the threads, from motor oil to red bearing grease to metallic anti-seizes, with no particular ill effect. Use whatever you want or have on hand and you'll more than likely be fine.

But just because everybody says the same thing doesn't mean it's true.


The nicest available appartus to install a barrel would be the Magpul Bev block, because it keeps both the upper and barrel extrension mechanically fixed together during torque. It eliminates all the stress points that every other appartus style compromises upon. It's a very clever design and one that should have been marketed decades ago.

Geissele has built a reaction rod version for manufacturers that has integrated rotating bushings that keep the upper fixed to the rod. It's the only reaction rod design worth buying IMO. It's double the price of the normal reaction rod so it hasn't spread in popularity like the lesser model has. It's still not as good a design as the Magpul Block IMO.
Click to expand...
 
If you believe that you can adequately tighten a barrel nut by hand, you clearly have no concept of what 50 ft/lbs is.

After twisting an upper using a Bev block, I stick to the giessele now. Not sure if the Bev block was faulty or not, but I know the snap-on torque wrench is accurate.
Both work, I just prefer the reaction rod, although I do follow your logic with holding the upper since that's where the torque is being transferred to.

Dietz said:
I know right... there's a tongueless guy in a cave in the middle east making guns with a grinder and files. It's not rocket science.
Click to expand...
 
purplezuk said:
If you believe that you can adequately tighten a barrel nut by hand, you clearly have no concept of what 50 ft/lbs is.

After twisting an upper using a Bev block, I stick to the giessele now. Not sure if the Bev block was faulty or not, but I know the snap-on torque wrench is accurate.
Both work, I just prefer the reaction rod, although I do follow your logic with holding the upper since that's where the torque is being transferred to.
Click to expand...

If you believe you can’t adequately torque a barrel but without specialty tools, you clearly aren’t that creative or able to understand the method of grease-tighten-loosen-repeat until complete.

It can, and has been done. Is it ideal... nope, we have luxury tools for that very reason. But they’re simply that, luxury.
 
Grease - tighten - loosen?? Been professionally pulling wrenches for 15 years in dealerships.... this is a new one to me. Lubrication doesn’t affect torque, but it does affect clamping force. Torque values are there for a reason, and accuracy will be affected with improper values.
You’re building at minimum a 2000$ rifle, spend 40$ on the only tool you really need to build it properly. We aren’t assembling these in a cave where our lives depend on it
 
Yes well put!!! But....so what is the tool really needed, or "THE" tool.


purplezuk said:
Grease - tighten - loosen?? Been professionally pulling wrenches for 15 years in dealerships.... this is a new one to me. Lubrication doesn’t affect torque, but it does affect clamping force. Torque values are there for a reason, and accuracy will be affected with improper values.
You’re building at minimum a 2000$ rifle, spend 40$ on the only tool you really need to build it properly. We aren’t assembling these in a cave where our lives depend on it
Click to expand...
 
koesdibyo said:
If you believe you can’t adequately torque a barrel but without specialty tools, you clearly aren’t that creative or able to understand the method of grease-tighten-loosen-repeat until complete.

It can, and has been done. Is it ideal... nope, we have luxury tools for that very reason. But they’re simply that, luxury.
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It's not a luxury, it's a requirement to do a job properly. Can you install a barrel nut without a torque wrench? Yes. Can you install one properly? No.
 
Well, you can buy a reaction rod and own the tool or you can hire someone to do it correctly for likely around 40$.

If anyone would like pictures to understand why the bev block won’t work, I can send one.
Shaun also has the pictures now as well
 
To answer the BEV block question:
48982694_281965642672775_2903341666679128064_n.jpg

48429924_766271343730207_1794129219609952256_n.jpg
 
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