I frequently get questions about the pros and cons of installing the NM groove in the gas cylinder piston. The alteration to the above pistons adds a .030/.040 wide groove running along the piston axis on the large diameter. The groove runs through the gas-port hole for the purpose of equalizing the gas pressure for a smoother more consistent and accurate action. The groove is ground to the actual GI national match drawing #9352724. The original GI drawing for the standard piston is #7267047 which does not specify a polished finish or the groove. If you plan to shoot NM ammo then the groove in the piston is useful. Otherwise, it was not intended for regular ball ammo (not enough power). The groove provides a more consistent pressure against the op rod by bleeding off some of the excess pressure inherent in high-power Match ammo. This results in a slight recoil reduction to help "keep on target" during rapids. It also, breaks the vacuum between the piston and the cylinder allowing the shooter to hear the piston slide down to confirm it isn't fouled. [center:54793b1221] [/center:54793b1221]
Not enough power huh? I have been running one of the TIN coated ones without the groove since I first became one of your dealers and I use a ton of low pressure cast bullets in my rifle. They still use IMR 4895 but only 30 grains. Enough to get me 2000 FPS. The piston without the groove was perfectly reliable. Just last weekend I put in one with the groove to see what it would do. Well, I started back at minimum load to see if it would work. It didn't at 1600 FPS but about 1900 it started having enough gas power for perfect and reliable functioning. The piston without the groove works all the way down to about 1500 fps with this load. These grooved pistons do soften the blow of the op rod to the receiver just a bit. It seems the higher the pressure the more blowby they will allow but down really low if the rest of your gas system is in spec they are not gonna hamper your shooting either within reason. I've installed them in every brand of gas system so far from chinese to SA and they work perfect in all of them. I've been way too busy to shoot much this winter but since I put the Sadlak grooved and coated piston in my rifle I am at about 520 rounds without cleaning it. That's roughly half cast lead 175 grain bullets and the other half barnes XLC coated bullets. Normally with a GI piston all I get before the piston fails the tilt test is about 2-300 rounds.
Great report WTA. Thanks. I'll pass that information on to Mike and add it to our files. We love feedback.
COOL! We've got our own range now on our property so there will be lots more testing to come. I just need to build the bern a few feet higher before I get back to the long ranges. I can go 350 yards across my property and I have permission to shoot from my neighbors land too so I can get to almost 1000 yards now. I just need to get the berm higher to catch any strays my son lets loose. I never miss the target ya know.
Thanks! I've been doing a lot of work on the site lately and really appreciate all of the comments I've received about it so far. It's not done yet.
Thanks. I just wish more people could find that page. The search engines are slow listing it lately. I have access to a lot more than is listed too. I have some really great suppliers that all drop ship if I need them to. If it's made by Leupold and you need it just holler. I've been doing some really good package deals on their scopes and whatever you need to mount it. LIke a Sadlak M14 mount or one to fit any other rifle too. You just can't go wrong with Sadlak mounts at all. They have some of the best service on what they sell in the industry.
