My FN5.7 rifle is near finished.

[22_boomer]

I've been playing with the little 5.7X28 cartridge for some time and finally decided to build a gas operated semi-auto rifle for it. I got a used SS barrel from Mark D and shortened it from 23" to 18". The barrel was already chambered in 5.7X28 so all I needed to do was add a gas port, gas block and gas tube. I had built a special AR bolt for the rifle back when I first started testing the 5.7 round and at that time, the rifle operated strictly as a straight pull bolt action. I bought a load of FN brass from ab_bentley and have now put hundreds of rounds through the rifle.

I still like the side mounted charging handle. The small band on the barrel in front of the handguards is a sling mount location. The magazine is The 20 round FN FiveSeven pistol magazine. I plan to make a special magwell adapter for the magazine but right now the adapter is actually fixed to the mag -- although the mag can be removed to be used in a pistol.

When I first started to sight the rifle in I was using the 30gr Hornady blems sold by Midway over 10.2 grains of H110. The first shot is on the left and the next four are together on the right. I'm not sure why that first shot was so far off but it was most likely just me.

One of the FN rounds with the Hornady blem 30gr bullet in on the target. The rifle shot great the whole afternoon and I thing I have a good replacement for my 22 magnum.

Edit to add: Compared to those really beautiful wood stocked rifles that are shown here, my rifle is like having to look at the back-end of a pack mule all day (flies optional) but it does shoot really nice and throws the brass into a nice little pile.

[MarinePMI]

Nice work!!!

[RareBear]

I have always thought the AR15s looked like something you would walk out of a hardware store with . It looks like this project is really coming together for you. Congrats. Did the rifle require a larger diameter than normal gas port, I'm just guessing due to the small powder charge?

[22_boomer]

Originally Posted by RareBear

I have always thought the AR15s looked like something you would walk out of a hardware store with . It looks like this project is really coming together for you. Congrats. Did the rifle require a larger diameter than normal gas port, I'm just guessing due to the small powder charge?

Please forgive me for not explaining this before -- I only shoot hand loads in this rifle! The 10.2 grains of H110 under a 30gr bullet makes the rifle operate just like a standard AR. The gas port doesn't need to be oversized just moved back to the AR pistol length gas system position and the carbine buffer has no weight in it. The bolt and carrier need to be modified to allow them to function with the narrow FN pistol magazine. The commercial FN ammo uses a very fast burning powder that doesn't generate enough gas to fully operate the gas system I have. I was thinking about doing a second setup with a shorter gas system and putting the bolt carrier on a weight loss program so I can shoot the commercial stuff. The nice part about my rifle is the brass comes out almost like it went in although the case does need a touch of resizing. You're right about the AR looking like something from a hardware store -- it just looks like a tool, nothing more.

[nvreloader]

22 Boomer

A very nice sweet handling rifle, way better than the 22 Mag RF round, just over 2600+ fps for the QL SWAG. Another "Reloadable Rim Fire" round with More performance etc.
Don

[22_boomer]

Originally Posted by nvreloader

22 Boomer

A very nice sweet handling rifle, way better than the 22 Mag RF round, just over 2600+ fps for the QL SWAG. Another "Reloadable Rim Fire" round with More performance etc.
Don

Hey Don, thanks a bunch for that info! I don't have a chrony and figured I should just be happy that the rig works. 2600fps was actually more than I expected -- and to think I can reload over and over!

Charlie

[johno]

Don't compare apples & oranges.

That is a great build up and I would be a very happy camper to own that one, your going to have a lot fun with that.

Johno

[22_boomer]

Originally Posted by johno

Don't compare apples & oranges.

That is a great build up and I would be a very happy camper to own that one, your going to have a lot fun with that.

Johno

I was kinda joking about the 22 magnum replacement. I like the 22 magnum but wanted something small, about the length or size of the 22 mag, that was reloadable and would feed nice and easy in the AR platform. I have a gas operated AR in the 22 Reed Express but I don't like the Starline brass that much so I buy 7.62X25 Sellier&Bellott ammo, shoot that stuff and reform and reload to the 22RE. All the military ammo in the 7.62X25 is corrosive berdan primed -- darn!

[LT17]

It may look "functional" and I prefer a nice bit of walnut but you can't argue with that accuracy or the efficiency. Outstanding stuff.

[nvreloader]

22 Boomer
The best (ballistic efficient) powder (as you have your rifle set up now) is Norma 123, (when you can find it) 9.4 grs= 3000+fps @ 34.1% with 34500+ psi, and 98% load ratio. QL SWAG
As usual START LOW and work up.
Don