How to Safely Change AR Muzzle Devices and Barrel Nuts Using a Magpul BEV Block

If you like working on AR-type rifles and plan to replace a muzzle device or change a barrel nut to install a free-floating handguard or to swap barrels, you are going to need to apply a lot of torque. Torque and aluminum are not friends and this is certainly the case with the upper receiver for AR rifles and pistols.

What not to do?

I actually want to take a minute and tell you two things not to do. First, do not simply clamp your lower in a vise and go cranking on whatever on the upper. Remember that the upper is connected to the lower by two steel pins going through relatively soft aluminim. Not a good combination.

Number two, there are work fixtures that look like a rectangle that allow you to remove the upper from the lower and then pin the upper to this block that is then held by a vise. I’m not fond of this either because then your two aluminum connection points on the receiver take up all the stress and they weren’t designed to do so.

Please do not do either of those or you may regret it. The odds are that you will regret it. I word it this way because you may get by once or twice but these methods are risky so don’t do them.

So what do I recommend?

At this point, it comes down to two options that engage the barrel extension, which can handle the torque of any AR upper operation you may need to perform. The first is the Geisselle Reaction Rod. It’s pricey but it does the job and you can get a relatively good price on an AR tool kit from them on Amazon.

Geissele Automatics (09-109) AR15/M4 Armorer’s Package (Sports)


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The second approach, which is what I use, is to secure the upper in a vise using a Magpul Barrel Extension Vise (BEV) block. It’s a very well designed block that engages via the barrel extension with its own steel lugs that are designed for strength but also to not harm the extension.

This is the top of the BEV block. You can see the front engagement lugs, the rear protrusion is for the bolt carrier and I would recommend keeping that O-ring oiled. The hole just under the front lugs is for a cross pin to secure it to the upper.

The BEV block uses a bolt carrier with the bolt removed to further secure it in the upper. You could remove the bolt from the bolt you normally use. I have a bolt carrier body that I keep in my toolbox for just this purpose.

The following photo shows it partially inserted in the upper.

This next photo shows it fully forward with the bolt carrier assembly installed. It does not have a cross pin installed at that point. Even without the pin it can handle the rotation stress. The pin just keeps it all in position and is not load bearing.

At this point you are good to go to change muzzle devices, barrel nuts or whatever else you may need to do without risking damage caused by torque. It’s a solid tool and I highly recommend it.


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TEKTON 24335 1/2″ Drive Click Torque Wrench (10-150′.-Lb./13.6-203.5 Nm) (Tools & Home Improvement)

Calibrated to an accuracy of +/ 4%, the TEKTON 1/2 in. Drive Click Torque Wrench lets you work with confidence, eliminating guessing and the common tendency to overtighten fasteners. Correctly tightening fasteners to a vehicle or equipment manufacturer’s torque specifications ensures parts are properly secured without being damaged. Simple and easy to use, this wrench has a reversible ratcheting head that drives fasteners in both directions and measures torque in the clockwise direction. To measure torque, set the desired value on the handle scale (foot pounds or Newton meters) and begin tightening the fastener. When the preset torque value is reached, a reliable mechanical operation inside the handle produces a click you can hear and feel, alerting you to stop applying force. Built for consistent performance and years of dependable service, the mechanical design doesn’t need batteries, and the allsteel construction has no plastic parts to break or wear out.

IMPORTANT: This wrench is shipped precalibrated and ready to use. To help maintain calibration, store at its lowest setting of 10 ft.lb./13.6 Nm when not in use. Be sure to read and understand the operator’s manual, including all safety information, before first use.

Specifications:

  • Range – ft.-lb.: 10-150 ft.-lb.
  • Range – Nm: 13.6-203.5 Nm
  • Increment: 1 ft.-lb. (1.36 Nm)
  • Accuracy: ± 4 percent
  • Length: 18-3/8 inch
  • Ratchet: 24 tooth
  • Country of Origin: Taiwan

Includes:

  • (1) 1/2 in. drive torque wrench
  • (1) Storage case
  • (1) Operator’s manual with torque conversion chart


Features: 
  • Wrench emits click that can be heard and felt when the preset value is reached
  • High-contrast dual-range scale is easy to read, even in low light
  • Reversible ratchet head drives in both directions and measures torque in clockwise direction
  • Durable all-steel construction has no plastic parts to break or wear out
  • Ships pre-calibrated to +/- 4% accuracy and ready to use
List Price: $40.00 USD
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