This page encompasses the SFT o-ring, feedneck, barrel, and ball detents. Most of these are just minor features of the marker, but deserve some explaniation nonetheless.
Seal-Forward (SFT) O-ring:
The seal-forward o-ring (or SFT o-ring for short) is a ring placed in the front of the breech, right behind the barrel, which seals with the bolt during firing. The purpose of this o-ring is to prevent any of the air pressure that fires the paintball to leak up into the feedtube (also known as blowback into the feedtube). When blowback occurs, efficiency decreases due to more air being required.
The SFT o-ring can infrequently be the cause of paint breakage problems in the barrel. This can either be due to low-quality paint, dirty SFT o-ring (or the o-ring clogged with paint from previous chops), cold weather problems, or due to severely enlarged paintshells. These are explained in further depth in the Troubleshooting section (see the Related Links).
When replacing the SFT o-ring, I suggest you always use a clean, new 17/90 o-ring. This is more "stiff" than the o-rings that are used throughout the bolt assembly (which are 70 durometer instead of 90, see the page for o-ring information for details on this). Some users have found that a softer 17/70 o-ring can help with barrel breaks, however I don't personally recommend doing this. If a 17/70 is used, it is likely that it will pop out of position, which then jams the bolt and forces you to disassemble the marker to remedy the problem. This is why a 17/90 is used in the first place, and I recommend using it.
Feedneck:
The feedneck threads on the Nerve are the same throughout all SP markers (Ion, Impulse, Shocker SFT, Shocker Sport) except the Shocker NXT. This feedneck shares threads with the Evil Omen and ICD Bushmaster. The stock feedneck on a Nerve is the Smart Parts clamping cam-operated Q-Lock model, which not very many people choose to disregard in favor of another feedneck.
The threading is close to a standard 13/16-32 thread size, however slightly different dimensions are often used to compensate for anodizing thickness.
Feedneck Installation:
1. You must first remove the current feedneck. They are loctited from the factory, so a lot of force may be required. I suggest using a hairdryer or other heat source heat up the connection between the body and the feedneck. Heat it until it is too hot to touch, wrap the hot material in a layer of clothing and untwist. If you don't want to deal with the hairdryer, you could also try vicing down the feedneck and unscrewing the body from it, however this will most likely scratch the current neck.
2. Clean the threads in the body, remove as much of the old threadlocker as you can.
3. Apply threadlocker to the threads of the new feedtube. DO NOT apply thread locker to the threads in the body. I recommend red loctite, in liquid form (no loctite sticks). You can also use a strong epoxy, or a standard metal-to-metal epoxy.
4. Align the new feedtube with the body and gently screw them together. Go slow to avoid cross-threading; if there is resistance, you're most likely beginning to crossthread the neck, back it off and try again. Screw the feedneck down ONLY hand-tight; don't simply screw it down as hard as you can. If you screw it in too tight the feed tube will shatter during the game if enough force is applied, and may even damage the threads in the body (hundreds of dollars to replace).
5. Allow threadlocker or epoxy substantial time to cure. 12 hours at a minimum, 24 hours recommended.
Barrel:
The barrel threading on a Nerve is the same as the Ion, Impulse, SP8, Epiphany, and Shocker NXT markers. This threading is generally referred to as Impulse threads becuase the Impulse was the first marker to use it. There are many aftermarket barrels available, both from SP and otherwise, however all Nerves come stock with the multiple-insert Freak system base so you may not find the need to switch barrels.
Here's some approximate technical specifications on the threading style:
Ball Detents:
Located on each side of the body are the ball detents. These consist of a small, round housing that holds a spring and plastic bearing. The purpose of the ball detent is to prevent multiple paintballs from rolling down into the barrel while the bolt is open (while the marker is idle).
The detents used in the Nerve are both "short" versions. Even though the marker uses the Vision system, the Nerve does not use a "Vision" detent. The detents can be removed for cleaning or replacement using a 1/8" allen wrench. A common problem is for the ball to come out of the housing and get lost; when this occurs you will have to replace the detent (individual parts aren't available). Another common problem is for the detent allen wrench hex to strip out; if this occurs, use a hacksaw or rotary tool (dremel, etc) to notch a mark in the head so a flathead screwdriver can be used for removal.
SP ball detent threading is unique to SP markers, but there are a few aftermarket varieties available.
· New Designz detents: Replacement metal detents made by NDZ. Higher tolerances mean these detents will be more reliable than the stock ones, and are available in multiple colors. Cost is $12 per detent.
· Kila Magnetic Suspension v2 detents: Magnetic piston design, made to be impossible to "blow out" as a regular ball-based detent would. Features adjustable magnetic repulsion force. Rebuildable if necessary. High quality manufacturing makes these very good products. Cost is $25 per detent; available in multiple colors. Get them from Kilaproducts.com.
· Eclipse ball detents: Wire-nubbin detents sporting the Eclipse logo. No longer available.
· Hybrid detents: Piston based ball detents from Hybrid technologies.
· Replacement stock detents cost $10 each.
Vision Eye Cover:
Located on the left side of the body is a small piece of metal called the eye cover. The function of this part is to shield the anti-chop eye component underneath, and to prevent outside light from interfering with its operation. Please refer to the Vision system in the Related Links at the bottom of the page.
Overview:
· The SFT o-ring is located right behind the start of the barrel, it is a 17/90 o-ring.
· SFT o-ring can be the cause for some barrel breaking problems.
· All SP markers use the same feedneck threads, as well as the Omen and Bushmaster; aftermarket feednecks are available.
· Nerves use Impulse/Ion/Nerve threaded barrels only; they are unique to these markers.
· Ball detents are an anti double feeding device, aftermarket detents are available.
· Vision eye cover protects the eye element from damage.
Related Links:
· Vision system
· Troubleshooting (chopping problems).
· O-ring information