Ion Breech Section > Tech index > SP Ion > Parts of an Ion > breech section
This page encompasses the SFT o-ring, feedneck, barrel, and detents. Most of these are just minor features of the marker, but deserve some explanation 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.
SFT o-ring SFT o-ring SFT o-ring

The SFT o-ring can infrequently be the caused 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).

Warning 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.

The feedneck is the circular port above the marker, into which the hopper is inserted. The stock feedneck on the Ion is oversized and fitted with three o-rings to allow an adjustable fit into different sized hoppers. One or more of the o-rings can be removed to allow a snug fit onto the hopper.
Many aftermarket clamping feednecks are available, from a myriad of manufacturers, in a variety of styles. My personal recommendation is the SP Q-Lock, which features a large cam-operated lever to tighten the neck, and is available in multiple colors. I'm not going to list any more because there are simply too many out there (nearly every online store carry several brands to choose from).
Tech The feedneck threads on the Ion are the same throughout all SP markers (Shocker Sport, Shocker SFT, Impulse, Nerve) except the Shocker NXT. SP markers share feedneck threads with the Evil Omen and ICD Bushmaster. The threading is close to a standard 13/16-32 thread size, however slightly different dimensions are often used to compensate for anodizing thickness and other considerations.

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 breech.
5. Allow threadlocker or epoxy substantial time to cure. 12 hours at a minimum, 24 hours recommended.

The barrel threading on an Ion is the same as the Nerve, Impulse, SP8, Epiphany, and Shocker NXT markers. This threading is generally referred to as Impulse threads because the Impulse was the first marker to use it. There are many aftermarket barrels available, both from SP and otherwise. I won't go into a comparison about barrels becuase they're all essentially the same, except in different lenghts, colors, materials, and with different porting.
Tech Here's some approximate technical specifications on the threading style:
Barrel thread spec
Aftermarket breech sections are available which function with Autococker threading (from Lucky paintball and NDZ).

Serial Number:
Each Ion's factory serial number can be seen at the very front of the breech section. The numbers are small, so be sure to get a good look at them before you use the number for anything (such as warranty registration).
Seen above is Ion number 120027.

Located on each side of the breech are the detents. These consist of a small, rubber nub that sticks into the breech by a slight amount. The purpose of the detent is to prevent multiple paintballs from rolling down into the barrel while the bolt is open (while the marker is idle).
The Ion uses two identical detents in its breech. The detents aren't threaded (as they often are with other markers). To remove them, use a knife or other tool to pry the detent away from the breech, then pull it out.

Replacement stock detents are $2 each from SP. Aftermarket detents are also available:
NDZ spring detents: These function much like traditional spring and ball bearing-based detents from other guns, unlike the stock rubber nubbins. These come with three sets for $10 from most NDZ retailers.
NDZ detents
Kila magnetic detents: Similar two-piece design to the NDZ detents, except using magnets for repulsion instead of a spring. These allow for adjustable force control and can't be blown out. Available from Kila and their retailers.

Aftermarket Breech Sections:
A couple aftermarket breeches are made, should you need to replace your current one.
New Designz Ion breech section: Threaded for Autococker barrels and SP feednecks. NDZ spring replacement detents included. Available in multiple colors for $55 from NDZ retailers. Available in impulse threads soon.

Lucky Ion breech section: Threaded for Autococker barrels and SP feednecks. Not guaranteed to function with Kila detents. Available in multiple colors for $54 from Lucky.

Vision Daughterboard:
Located around the underside of the marker is a small circuit board, which houses the anti-chop eye hardware for the Ion. Please refer to the Daughterboard page in the related liks at the bottom of the page.

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.
Ions use Impulse/Nerve threaded barrels only.
Detents are an anti-double feeding device, aftermarket detents are available.

Related Links:
Daughterboard & Vision system