The Geissele Reaction Block is designed to aid in the assembly of lower receivers. Once the armorer has installed the buffer tube, the lower receiver can then be slid into the Reaction Block at the 12, 3, 6 and 9 o’clock positions. This allows the armorer to rotate the lower receiver by 90° increments in the block simply by loosening the provided nylon screws, removing the lower receiver and sliding it back in at its desired orientation. The Reaction Block provides an ultra-stable platform for performing an array of lower receiver operations as well as making the installation of the buffer retainer nut quick and easy. This is all possible while keeping both hands of the armorer free to work, saving both time and frustration. Specifications for Geissele AR15/M4 Reaction Block: Manufacturer: Geissele Color: Black Gun Model: M4, AR-15 Condition: New Country of Origin: USA Package Contents: Geissele AR15/M4 Reaction Block
6 reviews for Geissele AR15/M4 Reaction Block
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Ken C. –
I was completing two new rifle builds and wanted to upgrade my tools. OP had the Reaction Block on sale and after looking at some reviews on YouTube, I decided to give it a try and I'm glad I did! It was perfect for the trigger install and trigger guard install (using the Wheeler Guard Install Kit), as well as my Troy ambi magazine and bolt release lever. I could position the buffer tube and lower at 90 degrees, which made working on different parts of the lower much easier. The screws on top are polymer, but they held up well and didn't scratch the tube. I still used my vise block for some of the work on my lower, but the Reaction Block got a lot of use as well!FIVE STARS!
Ken C. –
I was completing two new rifle builds and wanted to upgrade my tools. OP had the Reaction Block on sale and after looking at some reviews on YouTube, I decided to give it a try and I'm glad I did! It was perfect for the trigger install and trigger guard install (using the Wheeler Guard Install Kit), as well as my Troy ambi magazine and bolt release lever. I could position the buffer tube and lower at 90 degrees, which made working on different parts of the lower much easier. The screws on top are polymer, but they held up well and didn't scratch the tube. I still used my vise block for some of the work on my lower, but the Reaction Block got a lot of use as well!FIVE STARS!
Frank –
If you plan on doing alot of builds this is worth every dollar. It makes castle nut torqueing and staking very easy. It also makes installing the pistol grip a breeze along with most of the lower parts.
Andy –
If you are happy having a crooked buffer tube when torquing the castle nut then this isn't for you. If you're only going to be building one rifle maybe this isn't for you. But… if you work on a lot of AR15s this is a must for a perfectly aligned buffer tube to lower receiver. This tool or a similar one to hold the buffer tube will prevent that last tiny bit of rotation when applying torque. If you are a detailed oriented builder/machinist, fabricator then you know what I am talking about.
painlez –
The geissele Reaction Block is well engineered & produced to the highest standards, like all Geissele products. It is not inexpensive but I guarantee you will get your money's worth over the long haul!!! It is sturdy and functions as described…
Rob –
This is an excellent item that holds the buffer tube when tightening the castle nut. I like it because all the stress and torquing stress is on the buffer tube and not the lower receiver. This is especially helpful when you are trying to remove a stubbornly tight castle nut.