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Posted: 10/19/2008 1:26:04 PM EDT
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I finally got around to installing the gas piston conversion I got from Brownells. I would have liked to have installed it on my lightweight, but the piston block will only work on barrels that are .750 under the FSB. So, that left me with either a new build or slapping it on my Sabre Defense M4. Funds being what they are, I went with the Sabre install. Everything was pretty straightforward--removed the front sight, dimpled the barrel for the set screws and ran an end mill down the middle of my MI #20 handguard to provide clearance for the tube. I only had to remove about 1/8" of material and open up the end. One of these days I'll actually get to the range and shoot it.     
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CMMG--thanks for the feedback. I was worried about weakening the rail too much, so I stopped as soon as I had a bit of clearance. I'll take it down a touch more before I take it to the range. By the way, I've read about increased wear in the buffer tube due to carrier tilt with some of the earlier piston conversions. Are there design features in your kit that mitigate this issue? Thanks |
| tyler2you, thanks for the post, the pictures answered a question I've asked CMMG but never got a reply to. The gas block for the system is a slit design, so it at least looks like it will work on a barrel with a fixed flash suppressor, being two piece it can clamp onto the barrel instead of sliding over the end. If I'm wrong on this please correct me before I order one!! Thanks |
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It's actually listed as an optional procedure in the install instructions. It provides a little more security for the piston assembly by giving the set screws a place to set into the barrel. The way I did it was to install the 2 halves of the gas block, align perfectly, and then use a transfer punch through the set screw holes to punch a mark. I took off the assembly and put the barrel in the v block in my mini mill vise. I used a small ball end mill to dimple about 1/16" into the barrel on the punch marks. Put the 2 halves back together, apply red loctite to the 4 corner screws, line everything up and tighten, then install the set screws to lock it down. You could also use a drill press. Takes a little time, but I think it's worth the effort. Good luck. |
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Oh, ok. I'm guessing the set screws are under the block, out of view in the photos. This looks like a pretty slick system. Like its competitors on the market however, it won't fit under a rail system, which kinda limits its use a little. I hear Adams Arms is contemplating a low profile block which would fit under a rail, but no photos of the prototyps have been released that I'm aware of. I don't see why a low profile block can't been done, it would actually seem to be easier to do, but then I'm not an engineer. But, with everybody and his brother running long rails, you would think the market would have shown "them" that low pro blocks is what will sell. Anyway, I look forward to hearing your range report, I'm going to try and post one on the 6.8 gas piston I had KKF build for me, weather permitting, in a week or so. |
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