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Posted: 6/21/2026 7:17:49 PM EDT
[Last Edit: flcracker][Edited]
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My 12" Saiga 12 SBS is a project that I began 20 - 25 years ago when I bought it for $500 in factory/import condition from a dude in 1980s conversion van behind a Denny's restaurant. I've done every step of the parts count, FCG, and folding stock conversions along with all of the other work myself, except when I sent off the BCG for professional polishing. Tromix puck, Tac-47 Auto Plug, upgraded spring, etc.. It's on the ragged edge of almost running properly - cycles slugs & heavy buckshot but not standard loads. But it wasn't a whole lot better before I cut the barrel so I figure it's been under-gassed all along. Today I removed the gas block to check out the gas ports. The pins came out easily but the block was a whole different story. It was not gong to budge without encouragement. After soaking each end of the gas block with Kroil and letting it stand vertically overnight in each position, I gently heated it with a torch and persuaded it off with a 2# crack hammer & a piece of 1"x1/8" flat SS bar stock. I've got all 4 holes, but they're pretty undersized. A 1/6" (0.0625") bit passes with a little wobble, but a 5/64" (0.0781") bit will not fit. Attached File Attached File Attached File I've seen many posts on the Saiga forums suggesting that the holes should be enlarged to 3/32" (0.093"). I'm leaning towards going one step at a time, enlarging it to 5/64" then trying it before going any further. However, I've seen several posts suggesting that a 12-in barrel will almost definitely require the 0.093" holes and I should just go ahead and drill them to that size since I'm using the auto plug to bleed off excess gas. Before I start drilling, I'd welcome any suggestions - especially if Mr. Rumore cares to chime in! Most appreciated would be suggestions regarding which drill bits to purchase for the job. |
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The larger you open the holes up, the more fouling you will get building up in front of the puck. You'll end up with pieces of plastic wad fouling, powder, lead bits, and all sorts of trash getting through those holes. It's best to keep them as small as possible, while still cycling the lowest power ammo you want to shoot. If the fouling gets bad enough, the puck won't be able to return completely, and the bolt will be held back, out of battery. This can happen in as few as 25 shots of crappy ammo with large gas ports. The ammo makes a huge difference as well, as far as how much fouling it produces. Some rounds will run WAY cleaner than others. Tony Rumore Tromix |
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Thank you all for your guidance. I decide to proceed conservatively. I purchased even-numbered wire gauge bits from Grainger starting with the largest that would pass all four of my gas port holes (#50/0.0700"). This confirmed that my ports were factory-standard 0.0730". Inserted wood dowel to protect opposite wall of barrel. Leaving that bit in a hole to provide an alignment guide and dipping bit tips in cutting oil, I reamed the holes with a #48 (0.0760"), a 5/64" (0.0781"), and #46 (0.0810") bits. Cotton patches confirmed no burrs in barrel. Reassembled and ready for function testing tomorrow. If no joy, I'll take it to the max 3/38" (0.0938"). Attached File |
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