5 replies to this topic

[DX-Robert]

So, I bought an SM 500 recently and have put a CPVC barrel on it, but it only gets 75-85ft, depending on what goes in it (slug darts have actually been doing better than slingshot darts so far). It seems disappointing to me, though, because this gun has the loudest pop I've ever heard in an air gun so small. Surely more range can be squeezed out of it?

So, my question to SM 500 modders is this: can the opening in the back of the barrel where the trigger valve plate rests be widened safely? Even when using a flashflight, I can't see the edge of the rubber ring that rests against the opening. if it is wide, the opening could be widened quite a bit. But, if the rubber ring is not wide enough, I will wreck the gun if I widen the opening. There is no way to access this part by opening the gun - it is only accessible from the barrel after sawing the muzzle off.

A picture won't help because if you could see what I need to see, then this question would be moot. If you've modded an SM 500 before, you will have seen the firing plate/rubber ring and the size of the opening. I rarely ask modding questions, but I don't want to do something undocumented to a rare gun without some advice.

[Blue]

I have modded a sm500 and I too was very disappointed with ranges, mine only got high 60's-low 70's though. The tank was opened up for the mod, and if my memory is correct there is no obvious flow widening you can do. Also, with an open sm1k and sm5k tank here there is very little that can be done for the flow for them, and they were made at the same time. A pump replacement might help, or pump plugging, but the poor design of the tank will lead to a quick break like my sm1k since the tiny little nub holding the plug in place has to handle all the added pressure to the trigger pull.

[Merzlin]

If I remember correctly, the dump valve diameter is already quite large in comparison to the size of the tank. Unfortunately, that leads to inevitable tank failure from tons of use, but there really isn't much you can do to enlarge that hole any bigger than it already is.

I don't know the pump shaft diameter either, but I'm sure it wouldn't harm replacing the pump and then leaving the quick release valve functional. If anything, I'd try to lengthen the life of the blaster, since SM500's are way cool as it is.

Edited by Merzlin, 16 September 2010 - 02:58 PM.

[Draconis]

You may need to reexamine your dart fit for this application, especially since the slugs are working better than the slingshots. How long of a barrel are you using? Is it normal CPVC or Flow Guard Gold?

[DX-Robert]

7" of the usual Home Depot CPVC, although it is a "thinwall" version from Eastern CT that makes a perfect fit with white foam. In a springer, the fit is actually too loose for any other type of micro except the '06-'07 Frost King foam, which is why I shoot white. But, I guess since it's an air gun, it really likes those loose-fitting slugs. I found out today that it also likes BB and fishing weight darts, just not the slingshot ones.

There definitely is a feel that it lacks power. I tried an in-line clip on it since 3/4" CPVC fits in the white barrel - it worked pretty well except that each shot went about 45ft. Also tried an RSCB with similar range reduction.

[Blue]

7" of the usual Home Depot CPVC, although it is a "thinwall" version from Eastern CT that makes a perfect fit with white foam. In a springer, the fit is actually too loose for any other type of micro except the '06-'07 Frost King foam, which is why I shoot white. But, I guess since it's an air gun, it really likes those loose-fitting slugs. I found out today that it also likes BB and fishing weight darts, just not the slingshot ones.

There definitely is a feel that it lacks power. I tried an in-line clip on it since 3/4" CPVC fits in the white barrel - it worked pretty well except that each shot went about 45ft. Also tried an RSCB with similar range reduction.

The gun is not a powerful gun by any means, the main attraction is the comfyness and looks of the shell.