From: henryc@panix.com (Henry Chan)
Subject: Re: Stuff
Date: Mon, 17 Aug 1992 02:49:43 GMT
Organization: PANIX Public Access Unix & Internet, NYC

In article <kleung.15ke@terapin.com> kleung@terapin.com (Keith Leung Keith Leung) writes:
>
>     I would like to say  hi to everyone before I start.
>
>   I'm pretty new to this sub, and pretty new to paintballing.  I bought a
>Sheriden PGP to start off with.  I found that the gun is really nice to have
>if you need to move quickly since it's pretty small.  The only thing is, how

Notice that the PGP is also hefty from its all brass construction and steel
parts.  The gun is built rugged and you shouldn't need to dissasemble it beyond
cleaning the barrel and bolt.  In the eventuality your gun leaks air, you'll
need a sheridan dissassembly tool to access the 3 rubber seals and 1 lead seal
in the CO2 valve & chamber.

>can I make the gun more accurate?  I've added a 4 inch barrel extender on it,
>and it's chrono'ed at 290.  But, accuracy up to 100 feet away is a big problem.

The 4" barrel extender added 20-40 fps extra to your stock PGP.  Check to see
if the barrel extender is properly aligned with the barrel of the PGP.  A slight
imperfection at the seam between the barrel extender and the barrel can cause
balls to cut and break in the barrel (at the worst) to throwing/imparting a
spin on the paintball.  To check for this, take off the bolt and look down the 
barrel with a strong light shining down the other end.  If there is a lip 
causing the mis-alignment the solution can be as simple as turning the barrel
extender until the seam alignment is lessen to flex-honing out the joint.

Another area to improve accuracy is to check to see if the PGP bolt is bottom
vented or center vented.  A center vented bolt will have  a concentric CO2
exhaust port while the bottom vented will a channel located at 6 o' clock on
the bolt.  Center vented is supposed to be more accurate since the CO2 is
pushing at the center and back of the paintball thus giving equal expansion
and pressure on the paintball.  Bottom vented is theoretically more stressful
to the paintball.  The CO2 is concentrated on one spot, liable to cause the
paintball skin to break, putting uneven pressure on the ball (higher pressure
on the bottom and lower pressure on top) which could impart a significant
spin on the paintball affecting accuracy.  The PMI-1,DF are equipped with
center bolts but I'm not sure if the PGPs are similiiarly upgraded as well.
If not, you cn upgrade to an aftermarket center bolt such as Cooper-T.  The
Cooper-T bolt also has significantly less cocking pressure than the stock
PGP bolt and needs no tools for dissassembly.  You can reduce or eliminate
the cocking pressure on the stock PGP bolt by clipping a coil or two on the
bolt retention spring or by removing the bolt retention spring and detent balls
entirely.  The detent ball and spring locks up the bolt in thr firing position
to avoid gas leakage(gas loss could affect accuracy).  The firing bolt has two
friction dragging rubber O-rings which check the gas from leaking firing positio
n, so I think this part of the CO2 delivery system is over design.  You can
remove the detent ball & spring to decreade cocking effort and increase your
rate of fire with no adverse effects.

Try experiamenting with different brands of paintballs.  Not all paintballs
are create equal.  Switching from brand X to brand Y can bring out the true
accuracy of your gun.  Sheridan barrels are considered tightbore; meaning
paintballs do not roll out of the barrel easily.  Experts point to this as
one of the reasons for PGP's accuracy.  Large bore paintballs will perform
differently from small bore paintballs.

Considering all barrels equal, bolts equal then maintaining constant velocity
(not high velocity, APG editor thinks 280fps is optimum for accuracy) is the
next consideration for gun accuracy.  On a Constant AIr gun maintaining even
pressure and velocity isn't a problem until the tank is running low on air.
In a 12 gram gun, Co2 pressure and subsequent velocity starts to drop from 
the instant you pierce the CO2 cartridge.  You could spend $25-30 for a
Sheridan expansion chamber which vaporize liquid CO2 to gas and a pressure
valve for adjusting gas pressure to ensure constant and even velocity or
memorize how many strong shots you get from a 12 gram and adjust your sights
accordingly.
A gun shooting at 250 fps will have a different point of impact than a gun
shooting at a significantly different velocity.  You might want to waste a
12 gram and some paintballs to map out your gun over a chronograph and a
target.



>be a help if someone could tell me what I can do to keep accuracy up to 100+
>feet.  ( or atleast get fairly close ).  And please, don't tell me
>to get a better gun.  I think i'll just stick with  this PGP for now. 

The PGP has been around so long that you shouldn't have problems finding
aftermarket parts to spruce it up.  If you find yourself in a position needing
any of the aftermarket PGP goodies, such as direct feed, CA attachment, auto-
trigger, stock, and velocity adjustment kit then you are better off getting a
new gun which has all the features built in than upgrading the PGP.  Even the
semi-auto kit, for PGP, PMI-1,DF, -2, and Pirahna from Cooper-T Products is
marginal in terms of costs( within striking range of buying a $250 PMI-3).

>  ... Any help  would be greatly appreciated!
ask away  :-)


-- 
My friends, we can and we will, never, never, surrender to what is right.
--Dan Qualye speaking to Pat Robertson's Christian Coalition.