Post by 22boomer on Jul 12, 2014 8:47:59 GMT -5
This is way off base but I thought it might make for some different reading matter. I have two AR uppers in FN5.7X28 one of wwhich is gas operated and the other is a manually operated. These are not the AR57's you see but are more like a standard AR setup. The gas operated 5.7X28 shares parts with a 4.6X30 that has the cartridge necked down to a more common .17 caliber so becomes something like a 17X30 varmint rifle. Right now I'm playing with the 5.7X28 with a light power charge and both lead and copper jacketed bullets. below is the manual rifle.
The reason for the manual operation is the light powder charge to try and copy the average 22 magnum round. 22 magnum ammo is impossible to find here except at scalpers prices and I refuse to do that. The barrel is a GM 22 magnum 1:14 twist barrel that was shortened to 18" and had an AR barrel extension added. With between 6.0gr and 6.5gr of H110 the 45 grain Lyman type lead bullets shoot just OK with groups from 3/4" to 1.5" at 50 yards but I never was very good with cast bullets. Below is an average 10 shot group at 50 yards with the manual rifle.
I have not had a chance to shoot any copper jacketed bullets yet.
Below is the gas operated 5.7X28 rifle and the 17X30 rifle. the gas blocks at the front of the handguards are only to hold the handguard caps in place -- the real gas blocks are under the handguards at the pistol gas system position.
The 5.7X28 gas operated AR.
The 17X30 gas operated AR.
All the rifles use the same FN 20 round pistol magazine which is plenty adequate for me.
In my opinion, these rifles would not be a fair replacement for something like an AR in 22 Reed Express or the 22TCM since the 5.7X28 and 17X30 require major mods to the AR bolt and carrier but since I already did it the manually operated AR was done for shooting really light loads that would not operate the normal gas system -- plus, I don't have to look all over the place for the ejected brass. By the way, I also did light loads with cast lead bullets using a standard .223 AR barrel in the manual upper but the barrel was a 1:7 twist and just didn't give me the accuracy I wanted. I did shoot full power commercial .223 rounds in the rifle and it shot really nice. Right now once fired brass for the 5.7X28 is easy to find and not expensive. The 4.6X30 that's converted to 17X30 is another story.
The reason for the manual operation is the light powder charge to try and copy the average 22 magnum round. 22 magnum ammo is impossible to find here except at scalpers prices and I refuse to do that. The barrel is a GM 22 magnum 1:14 twist barrel that was shortened to 18" and had an AR barrel extension added. With between 6.0gr and 6.5gr of H110 the 45 grain Lyman type lead bullets shoot just OK with groups from 3/4" to 1.5" at 50 yards but I never was very good with cast bullets. Below is an average 10 shot group at 50 yards with the manual rifle.
I have not had a chance to shoot any copper jacketed bullets yet.
Below is the gas operated 5.7X28 rifle and the 17X30 rifle. the gas blocks at the front of the handguards are only to hold the handguard caps in place -- the real gas blocks are under the handguards at the pistol gas system position.
The 5.7X28 gas operated AR.
The 17X30 gas operated AR.
All the rifles use the same FN 20 round pistol magazine which is plenty adequate for me.
In my opinion, these rifles would not be a fair replacement for something like an AR in 22 Reed Express or the 22TCM since the 5.7X28 and 17X30 require major mods to the AR bolt and carrier but since I already did it the manually operated AR was done for shooting really light loads that would not operate the normal gas system -- plus, I don't have to look all over the place for the ejected brass. By the way, I also did light loads with cast lead bullets using a standard .223 AR barrel in the manual upper but the barrel was a 1:7 twist and just didn't give me the accuracy I wanted. I did shoot full power commercial .223 rounds in the rifle and it shot really nice. Right now once fired brass for the 5.7X28 is easy to find and not expensive. The 4.6X30 that's converted to 17X30 is another story.
