A little about o-rings

by Tom Gaylord
Writing as B.B. Pelletier

An assortment of o-rings.

This report covers:

  • History
  • Flexibility is key
  • O-ring failure
  • O-rings as a face seal
  • O-ring-assortments
  • Hardness
  • Some o-ring facts
  • The seats or channels they sit in help o-rings work!
  • O-rings used other ways
  • Summary

An o-ring is a donut-shaped elastomer (pliable) seal that performs sealing functions for hydraulics and gasses. Airguns use o-rings a lot, and for different purposes. They help us enjoy our hobby with a minimum of fuss. But what do we know about them?


The first patent for an o-ring was by the Swedish inventor, J.O. Lundberg. It was granted in 1896. Not much is known about him, but Danish machinist, Neils Christensen who came to the U.S. in 1891, patented the o-ring in this country in 1937. No doubt his work originated from his development of a superior air brake that Westinghouse, a leader in air brake technology since George Westinghouse invented the first fail-safe railroad air brake in 1869, gained control of. In World War II the U.S. government declared the o-ring a critical mechanical seal technology and gave it to numerous manufacturers, paying Christensen a stipend of $75,000 for his rights. Long after the war was over and he had passed away his family received another $100,000 read more

My fair Daisy: Repairing a Daisy 717 pistol

by B.B. Pelletier

Blog reader Vince has been disassembling and repairing so many guns lately that I believe no gun will ever leave his house without some part of it being removed, replaced, repaired or refined. He’s a master at fixing just about any gun that crosses his path. Sit back and read as Vince shows you the ins and outs of fixing a Daisy 717 pistol.

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by Vince

A diamond in the rough, that’s what I thought when I looked at the beat-up Daisy 717 in a hole-in-the-wall gun shop not far from my parents’ house just about 2 years ago. Sure, it was a bit ugly, but (as the proprietor demonstrated) it pumped up and went pfffft when you pulled the trigger. So, I let him talk me out of $10 for it.

$10 is a minimal investment for a gun that now sells for $149.

Turns out that going pfffft was about the only thing it did well. Putting pellets on paper in the same spot certainly wasn’t in its repertoire! I fiddled with it on and off for some time. I oiled it and cleaned the barrel, and it got a little better — but not great. It really struggled to do under 1″ at 10 meters for 5 shots, which is about twice the group size I can get from my Marksman 2004 (now known as the Beeman P17).

Barrel, anyone? Fair chance that’s the ticket. For all I know, some ding-dong used to shoot BBs through this thing. Like I probably would have done as a kid. But there’s a complication. I’m aware that Daisy still makes the 717, but they also make the 747 with a superior Lothar Walther barrel — a gun that appears to be identical in every other respect.

I got the parts diagrams and price lists for both pistols, and lo! Barrel aside, everything is indeed the same between the two. Well, except for the metal shells that are stamped 747 instead of 717. But certainly everything else.

Now I had to decide — $18 for the Daisy barrel, or $793 for the Lothar Walther? Ha! Only kidding! The LW barrel is only $50, still a bit steep for me, especially when I’m worse at pistol than I am at rifle. Is it worth the extra bucks? Will Wobbles the Pistol Pointer really be able to tell the difference?

I went to the expert: Mr. B.B. himself, who told me, “Absolutely go for the better barrel. It ain’t MY money!” Well, he didn’t phrase it quite like that, but he certainly did recommend the Lothar Walther. After kicking it around for about 18 months, I finally got off my keister and ordered it. For good measure, I also ordered a new valve assembly for $3. TWO DAYS LATER, I got them. I’m serious — I ordered Thursday, they showed up Saturday.

The replacement parts have arrived.

It wasn’t until I took the above picture that I noticed something. Seems that the new barrel assembly comes WITH all new valve guts, making that extra $3 superfluous. Not even worth sending back. Oh well, live and learn.

Anyway, down to business. The 717 comes apart rather easily, beginning with the three screws you can get to after lifting the pump handle.

Disassembly is a piece of cake.

The cover just lifts off. No little parts go “sproing.”

Before you do anything else, note how the trigger fork engages the valve.

From here, you can either lift the barrel and grip assembly away from the right-hand cover, or you can pull the grip off (rearward and downward) first. It’s not particularly difficult either way.

It didn’t take much to pop this apart.

While you’re at it, you might want to replace the o-ring on the bolt. A standard #006 seems about perfect. (Original old, squished o-ring on left, #006 on right.)

With a little coaxing the barrel slides out the back.

Now, you’re ready to put everything back together. Oil the o-ring on the new barrel assembly and put it all back together in reverse order. When you put the grip back in place, make sure you put the trigger fork over the valve stem as I pointed out in the above photos.

Everything is now all back together, and I’m itching to start punching one-holers. But, there’s a problem. I pumped the gun and heard a very light sssssssss from somewhere. It doesn’t take long to figure out that it’s coming from the muzzle, which means that my brand new valve is leaking. Grrrrrrrr.

Again, I take it apart and pop out the valve.

I took out the valve, again. (I cheated. This is the old barrel. When I originally did this, I neglected to take pictures, so I’m showing these steps using the old barrel as a model.) read more