The latest project gun I’ve acquired is a Century Arms CETME Sporter in .308. This rifle served as the basis for Heckler and Koch’s HK-91 and G3 series rifles, and has been used all over the world as a formidable battle rifle, and I’m excited to have it in my collection.
My first order of business is to make it a usable suppressor host. The first hurdle was to remove the pinned/welded muzzle brake, which proved to be more difficult than I thought. I was initially going to take it to a gunsmith to have it cut and rethreaded 5/8×24 so it could use standard 30 cal muzzle devices, but the one I regularly use doesn’t have a lathe large enough to fit the whole rifle in & I wasn’t looking to pay to have the barrel removed & re-pressed into the receiver. I also measured the barrel profile and found that it’s only 15mm, which is about 1mm too thin to accept the 5/8 threads. I then resolved to make do with the existing 15×1 HK standard threads on it.
In order to get the pin out, I had to dremel off the top of the weld about 3/4″ up from the base of the device, and used a magnet to pull it out. It turns out that the brake was also welded to the barrel at the base, so I cut through all the brake ports at the 6 & 12 o’clock down to the muzzle crown inside, and then using a large screwdriver as leverage to snap the brake in half. The threads underneath looked pretty good, just some carbon fouling near where the brake ended and was timed. A CNC Warrior thread adapter is on the way, and for now I’ll be timing a Killer Innovations brake on it until I can verify that the threads and adapter are concentric to the bore to avoid a baffle strike. I’m also debating between getting a 51T Flash Hider in 15×1, or a 5/8×24 Brake to use on the adapter.
Over the course of my research I’ve found that HK91/G3 locking pieces do NOT fit in the CETME, so I’ll have to figure out another way to increase the lock time in order to decrease the added recoil impulse due to the suppressor back pressure. H&K used different angled lock pieces in order to modify this lock time in the G3, however these parts are not compatible with the CETME bolt, and none of these variants exist. A heavier recoil spring or different rollers may be a platform fix, but I intend to try and solve the problem from the ammunition end by handloading lighter loads for .308.
I think the end dream for this rifle is to make a G3SG/1 inspired DMR rifle, with an M-LOK handguard and PRS2 stock, but we’ll see as time goes on. Before I go too far, I should probably hit the range with it.