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How I Built a .300 Whisper Suppressor

(and a .22 suppressor too)

By Rob Robinette

Warning: You must have a BATFE Form 1 with tax stamp to legally build a suppressor. National Firearms Act (NFA) rules apply and youcan do hard prison time for violating the law.

The first step in manufacturing a suppressor is getting permission from the Bureau of Alcohol Tobacco Firearms and Explosives (BATFE) byfilling out a Form 1 and sending in $200 for a tax stamp. It will take about 5 months to get the tax stamp so send it in early.

Since I had a combo lathe/mill at home that I used for making car parts I already had everything I needed to make a suppressor. I decided togo with an all aluminum "monolithic baffle" design for this .300 Whisper suppressor. The .300 Whisper uses .308 size bullets and is verygood at sending heavy 220 or 240 grain bullets at subsonic speeds downrange accurately. If I were building a suppressor for .308 supersonicloads I would use at the very minimum steel for the blast baffle (first baffle the bullet encounters). Subsonic .308 loads are very mild and athick aluminum blast baffle is fully adequate.

I used 1.5 inch outside diameter round aluminum bar for the baffle and 1.5 inch inside diameter aluminum tube for the baffle cover. I used6061 T6 aluminum bar and tube from www.metalsdepot.com The 1 foot long bar used here cost only $12. The suppressor is 8 inches long.

To manufacture a monolithic baffle suppressor the basic steps are:

Start with a solid round metal bar to make the baffle

Face both ends of the baffle on the lath

You may need to remove some material from the outside of the baffle so that it will fit inside your aluminum tube

Drill and tap one end of the baffle where the baffle will screw onto the threaded barrel

Drill the bullet path through the baffle

Mill out the gas chambers in the baffle

Face the ends of the seal tube

To finish the seal tube you can remove a small amount of material on the lathe or simply polish it up with some steel wool

Insert the completed baffle into a metal tube and seal. The seal can be a press fit, welded, epoxied or even duct tape!

Don't forget to inscribe or engrave the suppressor with:

Serial #

Model #

Manufacturer (your name)

Manufacturer's city & state

Suppressor http://www.robrobinette.com/suppressor.htm

1 of 15 1/30/2011 4:18 PM

Using the Grizzly lathe to drill the baffle's center hole.

Suppressor http://www.robrobinette.com/suppressor.htm

2 of 15 1/30/2011 4:18 PM

To prepare for tapping I drilled the thread end of the baffle.

Suppressor http://www.robrobinette.com/suppressor.htm

3 of 15 1/30/2011 4:18 PM

Drilling the bullet path the full length of the suppressor. For a .308 bullet I used an 11/32" (.344") long bit from Home Depot. For a

.223/5.56 use a 1/4" (.250") bit.

Suppressor http://www.robrobinette.com/suppressor.htm

4 of 15 1/30/2011 4:18 PM

Boring the thread end to the pre-tap size.

Suppressor http://www.robrobinette.com/suppressor.htm

5 of 15 1/30/2011 4:18 PM

Tapping the baffle--Do not try to use the lathe's power to do this. I used the tailstock to simply hold the tap for perfect alignment

with the bullet path. I pushed inward on the tailstock and turned the lathe chuck by hand to start the tap. I did the last half of the tap

using a standard tap hand wrench so I could feel when the tap hit bottom. I used a 5/8" x 24 threads per inch (tpi) tap to match the

thread on my .300 Whisper upper. For a normal .223/5.56 AR use 1/2" x 28 tpi.

Suppressor http://www.robrobinette.com/suppressor.htm

6 of 15 1/30/2011 4:18 PM

Drilling and milling the baffle chambers.

Suppressor http://www.robrobinette.com/suppressor.htm

7 of 15 1/30/2011 4:18 PM

Cleaning up the bullet path after milling.

Suppressor http://www.robrobinette.com/suppressor.htm

8 of 15 1/30/2011 4:18 PM

The finished baffle. I had to turn the baffle in the lathe to remove about 15 thousandths from its diameter to make it fit easily into the

tube. I intentionally left the baffle chambers odd shapes to disrupt the gas's path through the baffle.

Suppressor http://www.robrobinette.com/suppressor.htm

9 of 15 1/30/2011 4:18 PM

Suppressor http://www.robrobinette.com/suppressor.htm

10 of 15 1/30/2011 4:18 PM

I slid the completed baffle into the aluminum tube and welded both ends to seal the suppressor. It's now ready to be screwed onto a

rifle, inspected for barrel alignment and test fired. Please forgive the crude welding, I'm an amateur aluminum welder. You'll need an

AC TIG welder to do this kind of work. If I need to open the suppressor I can use the lathe to cut the welds to remove the tube cover.

The suppressor wrapped and installed on the .300 Whisper upper. The wrap helps reduce noise too.

Suppressor http://www.robrobinette.com/suppressor.htm

11 of 15 1/30/2011 4:18 PM

A .22 baffle made of 1 inch solid round aluminum bar

Suppressor http://www.robrobinette.com/suppressor.htm

12 of 15 1/30/2011 4:18 PM

The .22 baffle next to it's outer seal made from aluminum tube with a 1 inch inside diameter

Suppressor http://www.robrobinette.com/suppressor.htm

13 of 15 1/30/2011 4:18 PM

The .22 baffle inserted into the tube seal with a nice tight press fit.

Suppressor http://www.robrobinette.com/suppressor.htm

14 of 15 1/30/2011 4:18 PM

The .22 suppressor installed on the 10/22

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Suppressor http://www.robrobinette.com/suppressor.htm

15 of 15 1/30/2011 4:18 PM