AR15 pump Kit.

[Meketrefe]

The UMOS system is a good way to get a pump upper retrofit. Nothing that a good local gunsmith could not easily do but these seem to work really smoothly, are readily available, and have several advantages over other pump action options:

- Compatible with existing standard lowers.
- Can use alternative calibers and bolts like 6.8SPC, 6.5LBC/Grendell, 7.62x39...etc...
- It is 100% reversible preserving original bolt, receiver and barrel to be re-purposed in those places where auto-loaders are compliant in any configuration.
- It can take an cam pin roller adapter that makes it super smooth.
- I have not tried one but folks who are using them love the fact that one can have a softer or cut buffer spring that assists with the action making it super fast if needed.

The UMOS, or Universal Manual Operating System is a novel retrofit kit for AR-15s that utilizes existing barrels, bolt carriers, and receivers, to convert a semi-automatic rifle into a pump-action centerfire wunderkind. As an added bonus, converting the rifle to manual operation has quite a few benefits.

• Manually operated rifles are not “banned” or “controlled” in most states, allowing you to have detachable magazines and other “naughty” bits
• You can create a ridiculously quite subsonic build
• Hunt with an “AR” in states that ban semi-autos.
• Have a familiar stroke for manual 3-gun divisions.

Compatible with carbine, mid-length, and full rifle barrels, the kit itself weighs in at 21.5 ounces (which is not bad, considering it replaces the gas block, handguards, etc.) and consists of six parts, with six screws holding it together tightly:

1. Barrel nut,
2. Barrel bushing,
3. Main tube,
4. Operating rod,
5. Pump
6. Pump key

There are a few limitations, namely the barrel is not free-floated as the tube affixed to the gas block journal, completely plugging covering the gas port. Bentwood says this may affect accuracy but match grade barrels will maintain their groups when used appropriately. Bentwood tested splits and the best were coming in at .39 seconds between shots.

The kit retails for $350 with the sight base an extra $20. It is 100% made in the USA of T6 aluminum and machined Acetal Nylon. It is currently available direct from Brentwood or currently through two California dealers:.

[GUNSICK]

Looks nice. I wonder how well the oprod would hold up over time. I'd like to see a bushing where it goes through the upper also.

[Meketrefe]

Looks nice. I wonder how well the oprod would hold up over time. I'd like to see a bushing where it goes through the upper also.

I think the large bushing works as a guide. but what you are saying makes sense and should be very easy. If a piston bushing does not fit having one cut and drilled takes minutes.The std bushings are cheap and can be opened up as needed too...

[Wildman]

Looks interesting. I just ordered that Troy par to try. I wonder how this compares

[Meketrefe]

Looks interesting. I just ordered that Troy par to try. I wonder how this compares

It is compatible with lowers, uppers and standard parts. The troy is not.

These are the benefits....

- Compatible with existing standard lowers.
- Can use alternative calibers and bolts like 6.8SPC, 6.5LBC/Grendell, 7.62x39...etc...
- It is 100% reversible preserving original bolt, receiver and barrel to be re-purposed in those places where auto-loaders are compliant in any configuration.
- It can take an cam pin roller adapter that makes it super smooth.
- I have not tried one but folks who are using them love the fact that one can have a softer or cut buffer spring that assists with the action making it super fast if needed.

[thughes]

No slide lock/release? I am concerned about out of battery/partially out of battery issue with this rig. I wonder if there are detents/spring-loaded ball integrated into the maintube/pump (or some other mechanism) to at least provide a tactile "feel" for when the bolt is completely closed in full battery?

[Meketrefe]

This is not different than an autoloder on that respect. If an autoloader doesn't go into battery the AR will not fire.
While there is pressure in the chamber and bolt nobody will be able to open no matter how hard one pulls. The extractor would break before it opens.
Think the spring makes this easier even a milder spring with almost no weight.

[thughes]

Didn't think about the spring.....good point.

(my Mossy 500 don't have one a dem dare buffer spring thingies)

[PY-Tactical]

The proper name of the company making this is Bentwood Gun Smithing in Henderson, Nevada, not "Brentwood,"

[dsdmmat]

I would like to get a couple of these just for fun.

[PY-Tactical]

Wish that action rod wasn't exposed as that. Seems that would be susceptible to bending damage in transport or dropping.

[BuellSix8]

Like a manual piston system.... Exposed OP rod is ok. Just like some build their ARs with Gasblock and some gas tube showing. Not taking into battle.... That's when you unbury the OTHER upper and swapem lol

[Meketrefe]

when I get a chance I am going to machine one with my own design and dimensions just for fun. It is quite simple. Nothing fancy. Just something the average working man can do with some
common tools. You see the bushing for the rood can ride inside a regular tube and for the outside handle one can use either slots or an entire unit that telescopes down the tube. Pretty
much like an antenna does. All one needs is a slot on the outer tube so it doesn't rotate and keeps the pushing rod nice and straight and true.
The inside bushing could be made of nylon or aluminum, just like the outer one. One of those carbon fiber handguard/tubes would be perfect to make it
smooth and keep everything light.
No rocket science.