Custom Dynamax Full Shroud Finished

[Fisherdude]

Dynamax Full Shroud Project:
My shroud was fabricated from black delrin rod and a length of ¾ inch steel electrical conduit.  Machining was done on my 7 X 12 mini lathe.  My shroud extends about 6 inches beyond the end of the barrel creating a hollow void making the barrel appear longer.  I like the fact that it is easy to remove if I ever need to retrieve a lost patch or something.  It simply threads on and off.

Piece #1
Piece #1 is the transition between the rear of the barrel and the conduit.  At the rear, it should aesthetically match the breech and at the forward end it must match the OD of the conduit. 
 I started with a piece of delrin about 3 inches long and drilled/bored it to just slide over the OD of the barrel without having to force it on.  Then I turned the OD to match the OD of the conduit. 
Next, I turned about a 1 inch section on the front end to just slide into the conduit leaving about 1 1/2 inch on the rear to taper back to match the receiver.  Actually, I intended to taper it back, but I forgot and just cut a step.  It looks OK that way so I didn’t remake the piece.
The Dynamax has a sliding tab at the base of the barrel that secures the magazine in place.  For the shroud to fit properly, a notch has to be cut into the rear of piece #1 to accommodate this tab.  A milling machine would have been nice to accomplish this, but since I didn’t have one, I used a Dremmel tool to cut the notch manually.
Piece #2
Piece #2 is what holds the forward end of the conduit centered with the bore.  When assembled, it keeps the shroud firmly in place but allows it to be removed when desired.
I made piece #2 out of delrin.   Piece #2 is an internally threaded (1/2 X 20) section about 9/16 long with an OD that will just slide into the conduit. This is pretty easy to make on a lathe by turning the OD to match the ID of the conduit and then boring it out 29/64 for a ½ X 20 tap.
Piece #3
Piece #3 is the delrin end cap.  It finishes off the shroud.
The end cap is also machined from Delrin with an OD/ID that matches the conduit.  The hole in the end should be as small as possible to just allow the pellet through without touching anywhere.  I use a hole about 0.0070 greater than pellet diameter.  For this end cap, I epoxied a small section of 5/16 OD copper tubing into it that extends back about 1 inch into the hollow of the conduit.  The copper tube isn’t required, but in my opinion it increases the path length some of the air will have to travel to get out.  It also adds an aesthetic look to the end of the shroud that I like.
Piece #4
Piece #4 is optional. 
For this build, piece #4 is a delrin disk about 3/8 inch thick that is center bored about 0.070” greater than pellet diameter and turned to just fit inside the ID of the conduit.  During assembly, I put this about center of the void at the front of the barrel to partition the forward volume. 
ASSEMBLY
Piece #1 is simply slid over the barrel into final position.  It will be held in place by the conduit.
Piece #2 is threaded onto the end of the barrel all the way then I backed it out ¾ turn.  I then slipped the shroud completely over the barrel and piece #1 and drill/tapped two 6-32 eighth inch set screws through the conduit into the side of piece #2.  I chose locations so that when I turned he shroud it would tighten up against piece #1 the set screws would be on the underside of the shroud.
Next, piece #4 (if used) is inserted into the front section of the shroud wherever you want it and secured from underneath with another eighth inch 6-32 set screw.
Finally, the end cap (piece #3) is installed.  Again I used a small 6-32 set screw to secure the end cap.
The assembled shroud was then spray painted flat black and installed onto the rifle.
Afterthoughts:
The Dynamax is a great shooting rifle.  It deserved better than a noisy muzzle break.  Metal ¾ inch conduit is actually more like 7/8 ID.  To me this is the ideal size.  Any larger (such as 1 inch Al) and I don’t think you could get much of a scope on it without having to use a riser.  Steel also holds paint better than aluminum.  I haven’t seen any detrimental effect on accuracy.

[ronbeaux]

Slick!

[eddielee70]

looks great.  glad you got the rifle shooting again after the fedex man damaged it.  I miss that tack driver now.

[ozzi]

Dynamax Full Shroud Project:
My shroud was fabricated from black delrin rod and a length of ¾ inch steel electrical conduit.  Machining was done on my 7 X 12 mini lathe.  My shroud extends about 6 inches beyond the end of the barrel creating a hollow void making the barrel appear longer.  I like the fact that it is easy to remove if I ever need to retrieve a lost patch or something.  It simply threads on and off.

Piece #1
Piece #1 is the transition between the rear of the barrel and the conduit.  At the rear, it should aesthetically match the breech and at the forward end it must match the OD of the conduit. 
 I started with a piece of delrin about 3 inches long and drilled/bored it to just slide over the OD of the barrel without having to force it on.  Then I turned the OD to match the OD of the conduit. 
Next, I turned about a 1 inch section on the front end to just slide into the conduit leaving about 1 1/2 inch on the rear to taper back to match the receiver.  Actually, I intended to taper it back, but I forgot and just cut a step.  It looks OK that way so I didn’t remake the piece.
The Dynamax has a sliding tab at the base of the barrel that secures the magazine in place.  For the shroud to fit properly, a notch has to be cut into the rear of piece #1 to accommodate this tab.  A milling machine would have been nice to accomplish this, but since I didn’t have one, I used a Dremmel tool to cut the notch manually.
Piece #2
Piece #2 is what holds the forward end of the conduit centered with the bore.  When assembled, it keeps the shroud firmly in place but allows it to be removed when desired.
I made piece #2 out of delrin.   Piece #2 is an internally threaded (1/2 X 20) section about 9/16 long with an OD that will just slide into the conduit. This is pretty easy to make on a lathe by turning the OD to match the ID of the conduit and then boring it out 29/64 for a ½ X 20 tap.
Piece #3
Piece #3 is the delrin end cap.  It finishes off the shroud.
The end cap is also machined from Delrin with an OD/ID that matches the conduit.  The hole in the end should be as small as possible to just allow the pellet through without touching anywhere.  I use a hole about 0.0070 greater than pellet diameter.  For this end cap, I epoxied a small section of 5/16 OD copper tubing into it that extends back about 1 inch into the hollow of the conduit.  The copper tube isn’t required, but in my opinion it increases the path length some of the air will have to travel to get out.  It also adds an aesthetic look to the end of the shroud that I like.
Piece #4
Piece #4 is optional. 
For this build, piece #4 is a delrin disk about 3/8 inch thick that is center bored about 0.070” greater than pellet diameter and turned to just fit inside the ID of the conduit.  During assembly, I put this about center of the void at the front of the barrel to partition the forward volume. 
ASSEMBLY
Piece #1 is simply slid over the barrel into final position.  It will be held in place by the conduit.
Piece #2 is threaded onto the end of the barrel all the way then I backed it out ¾ turn.  I then slipped the shroud completely over the barrel and piece #1 and drill/tapped two 6-32 eighth inch set screws through the conduit into the side of piece #2.  I chose locations so that when I turned he shroud it would tighten up against piece #1 the set screws would be on the underside of the shroud.
Next, piece #4 (if used) is inserted into the front section of the shroud wherever you want it and secured from underneath with another eighth inch 6-32 set screw.
Finally, the end cap (piece #3) is installed.  Again I used a small 6-32 set screw to secure the end cap.
The assembled shroud was then spray painted flat black and installed onto the rifle.
Afterthoughts:
The Dynamax is a great shooting rifle.  It deserved better than a noisy muzzle break.  Metal ¾ inch conduit is actually more like 7/8 ID.  To me this is the ideal size.  Any larger (such as 1 inch Al) and I don’t think you could get much of a scope on it without having to use a riser.  Steel also holds paint better than aluminum.  I haven’t seen any detrimental effect on accuracy.

wow very interesting, I would like to make it but I need a picture of each part is, so I can more easily understand it,,

[Ivanders]

Verry nice craftsmanship.
Just one question (i'm a newby) Would a bsa R10 shroud not fit the dynamax 1on1?

[lloyd-ss]

Nice project and it sounds (literally) like it is working well.  On piece #2, I can't tell if you cut any length-wise grooves on that part to allow some of the air to make a U-turn and expand into the long space that surrounds the barrel.  If you did, great, if not, doing so might knock a little more noise off the rig.
Thanks for sharing your work.
Lloyd-ss