As are many of you, I am a tinkerer. It is in the blood and a lifelong hobby. Lately I have been experimenting with the Impact in .30 caliber and have shot over 3000 rounds in the past year testing, tuning, and generally having fun ringing steel. Throughout this year I have went through a few OEM rubber C-3 bumper o-rings, and disintegrated as many homemade nylon C-3 bumpers as well.
General specs are 7mm o.d. × 3mm i.d. × 1.5mm thick. This isn't the exact size of the OEM washer, but close. This is roughly the size I turn out my washers, with the white nylon washers being the most prevent test subject lately. I have tested various thicknesses, including one made out of a credit card once at .75mm thick, and lastly, a black delrin plastic washer at 1mm. However, not all plastics are created equal. Here's what I found:
The OEM C-3 o-ring works well, until it doesn't. When it breaks down FPS gets erratic and drops off as the rubber cracks, letting you know that it needs replacing. As far as longevity goes, the OEM C-3 o-ring does not last long before it needs replacing. Replacing that o-ring and going to a solid plastic or delrin washer gains only 5 fps across the board from 50 grain pellets on up to 65 grain slugs. (Tested and verified again tonight.) This slight gain in fps is due to the non-cushioning properties of the hard plastic material between the hammer and hammer stop, whereas the OEM rubber o-ring bumper has some "give" as the three pieces smash into each other. Changing the rubber o-ring out for the same is not too hard and may save on wear and tear of parts if something should become loose in the interim.
Here's where the C-3 experiment got interesting... I tried standard white nylon washers for the bumper. After FPS speed testing various thickness nylon washers, from 4mm down to .75mm, and finding no FPS changes, I made one out of a credit card and left it in the gun. This washer didn't last long though and was smashed into plastic dust, with no changes in velocity and the same tight E.S. across the board (so I didn't know that it was gone). When I discovered it was missing I made another one out of white nylon again, 1.5mm thick, thinking that the credit card was just cheap plastic anyhow. But because of the constant smashing of the hammer and hammer stop, the white nylon washers did not last either! I figure a 1.5mm thick washer lasted just about as long as the OEM O-ring did. When I discovered that it too was missing it had just about desintigrated into nothing. It was about .2 mm × .2 mm and barely hanging onto life as a small donut around the valve stem.
What is interesting between these two different types of C-3 bumper washers is that when the hard washer wears out you don't notice an erratic change in point of impact or a drop in the FPS as you do with the rubber o-ring. It is just as solid of a hammer strike as when they were new. (Please note that my ImpactX in .30 caliber is loud and so I don't hear these smaller nuances of the change in tone that you >12pfe guys do.)
For my latest experiment today, I turned a piece of actual hard black delrin down to 7mm o.d. and cut some 1mm thick washers to see how long these will last before turning to dust. Everybody has said that true delrin plastic is strong and we will see. It is definitely a harder plastic and machined easily compared to the softer white nylon, or even soft black nylon. I'll let you know what happens with the delrin washers in another 500-1000 rounds...
So far my takeaway from this experiment is twofold. The Impact performs well either way, even with literally no cushion between the hammer and stop. And, if you have replaced the o-ring with a washer, don't assume that the thing will last for a lifetime. Your plastic C-3 bumper may not be in there now even, so you should probably check...
Please post up your results as well.
General specs are 7mm o.d. × 3mm i.d. × 1.5mm thick. This isn't the exact size of the OEM washer, but close. This is roughly the size I turn out my washers, with the white nylon washers being the most prevent test subject lately. I have tested various thicknesses, including one made out of a credit card once at .75mm thick, and lastly, a black delrin plastic washer at 1mm. However, not all plastics are created equal. Here's what I found:
The OEM C-3 o-ring works well, until it doesn't. When it breaks down FPS gets erratic and drops off as the rubber cracks, letting you know that it needs replacing. As far as longevity goes, the OEM C-3 o-ring does not last long before it needs replacing. Replacing that o-ring and going to a solid plastic or delrin washer gains only 5 fps across the board from 50 grain pellets on up to 65 grain slugs. (Tested and verified again tonight.) This slight gain in fps is due to the non-cushioning properties of the hard plastic material between the hammer and hammer stop, whereas the OEM rubber o-ring bumper has some "give" as the three pieces smash into each other. Changing the rubber o-ring out for the same is not too hard and may save on wear and tear of parts if something should become loose in the interim.
Here's where the C-3 experiment got interesting... I tried standard white nylon washers for the bumper. After FPS speed testing various thickness nylon washers, from 4mm down to .75mm, and finding no FPS changes, I made one out of a credit card and left it in the gun. This washer didn't last long though and was smashed into plastic dust, with no changes in velocity and the same tight E.S. across the board (so I didn't know that it was gone). When I discovered it was missing I made another one out of white nylon again, 1.5mm thick, thinking that the credit card was just cheap plastic anyhow. But because of the constant smashing of the hammer and hammer stop, the white nylon washers did not last either! I figure a 1.5mm thick washer lasted just about as long as the OEM O-ring did. When I discovered that it too was missing it had just about desintigrated into nothing. It was about .2 mm × .2 mm and barely hanging onto life as a small donut around the valve stem.
What is interesting between these two different types of C-3 bumper washers is that when the hard washer wears out you don't notice an erratic change in point of impact or a drop in the FPS as you do with the rubber o-ring. It is just as solid of a hammer strike as when they were new. (Please note that my ImpactX in .30 caliber is loud and so I don't hear these smaller nuances of the change in tone that you >12pfe guys do.)
For my latest experiment today, I turned a piece of actual hard black delrin down to 7mm o.d. and cut some 1mm thick washers to see how long these will last before turning to dust. Everybody has said that true delrin plastic is strong and we will see. It is definitely a harder plastic and machined easily compared to the softer white nylon, or even soft black nylon. I'll let you know what happens with the delrin washers in another 500-1000 rounds...
So far my takeaway from this experiment is twofold. The Impact performs well either way, even with literally no cushion between the hammer and stop. And, if you have replaced the o-ring with a washer, don't assume that the thing will last for a lifetime. Your plastic C-3 bumper may not be in there now even, so you should probably check...
Please post up your results as well.
