SpudFiles

I'm going to build another bbmg this week over spring break, and want it to be a bullpup style, similar to this-
http://www.spudfiles.com/forums/davidva ... 14559.html

It will probably be in either 1" or 1.25" pipe, most likely 1" as i want it to be small and compact. My issue is with the plunger, and how to design it.

one idea I came up with is plugging the front end obviously, but then inserting an o-ring and have the plunger rod go through it. This way when its time to reload i can simply pull back on the rod and reload-- dunno how easy this would be to implement though. I'm thinking of using a 3/16" rod for this, so would I want an o-ring with a 3/16" ID, or one slightly smaller?

Unless you are using insanely high pressure I do not think that you need to worry about orings. I just used a pvc cap with hole drilled in the center and it worked fine at 800 psi;to reload, the front just came off and the entire plunger assembly came out then I just poured in the bbs.

yea, but I'd rather have an o-ring for as much air efficiency as possible, since this will not be run off of a compressor, but a closed air source, and probably not super high pressure.

JDP12 wrote:yea, but I'd rather have an o-ring for as much air efficiency as possible, since this will not be run off of a compressor, but a closed air source, and probably not super high pressure.

if you are worried about air efficiency, why build a BBMG... the most inefficient type of cannon on this site. lol

im not worried about that much of efficiency, I want a BBMG. I suppose I could not worry about the o-ring, just wondered if it would help.

You can take my design that you linked above, and you can actually glue an oring on the threaded cap.. that way when you slide the cap over the barrel, the oring seats against the barrel and you get a decent seal.