M4-177 flat top piston

[Crimson Starling]

I bought an m4-177 about a month ago and was wondering what speed could be had from them when slightly modified.
Before anyone gets their panties in a bunch, I'll let you know that I do have my PAL license. First thing I did was to plug the
hole in the back of the valve that Crosman drilled for the Canadian market. I fired some pellets through the Chrony and got
a 575 fps average for 7 grain hobbies and a 530 fps average for Crosman pointed pellets. I then made a flat top piston out of
aluminum and 1/4-28 threaded rod at work ( I am a machinist ). This piston closely resembles the one sold by Scopes and Ammo, the
only difference being a section of UHMW nylon I added to the back piece to keep the aluminum from rubbing in the tube. I fired some
more pellets through the Chrony and got some interesting numbers. The Hobbies now went 620 fps average for a 45 fps increase but
the Crosman pointed pellets only went 550 fps for a 20 fps increase, I pumped the gun ten times for each shot. Since the Crosmans
are heavier I thought that might have something to do with the low numbers so I grabbed some RWS pointed pellets that weigh
8.2 grains, which is heavier than the Crosmans 7.9 grains and should go slower. Well, they went 570 fps on average, making me wonder
if the slower speed of the Crosmans might be due to the smaller diameter of the pellet allowing air pressure to slip past it as it goes down
the barrel. I must add that the rifling in this barrel looks rough and poorly cut and I could only see this after extensive cleaning with a
brush and solvent as well as a dozen patches. This was the dirtiest Crosman barrel I've encountered so far.

 

[REM700J]

So the big question is will the Gods of fun ruining claim these are an ar varient and call it restricted lol. Nice job though all joking aside.

 

[weasel1]

Any chances of some pics? I'd love to know how to take this apart and see what I can do with that valve.

 

[ShotgunNut]

I have one of these. I used it to ease my pain of waiting for a PAL approval. I also have a problem with an invasive black squirrel problem where I live. These guns, unless modified are not sufficient for pest control at all. In fact it is very inhumane and Crossman shouldn't be advertising pellet ammunition for air rifles 500 fps and less. To kill a squirrel you need corner it in a tree and land about 10 head shots before it dies of shock.

When I took mine apart I didn't find a hole drilled but I did notice that where the barrel mates with the pump cup is a very loose fit and allows a lot of air to escape with each shot.

I also have to note; these pellet guns come with excellent rail mounted iron sights. They work very well. If you can't find iron sights for less than $100, buying one of these m4 - 177's is always an option.

 

[weasel1]

It does have awesome sights. I've never used peep sights before and I find that I am quite accurate with these. Could you provide a little help in getting mine apart? I'd like to see if I have that little hole or not.