Bolt Rings

[Specialized Armament]

Is the McFarland one piece bolt ring an improvement over the three ring system?

From Brownell's:

Stops Gas Leaks & Eliminates Sluggish Bolt Performance

Single spiral of spring steel loops around the bolt three times and leaves no path for gas leakage. Replaces conventional three-piece “piston ring”-style sets that can accidentally line up, causing a major leak from the gas expansion chamber in the carrier.

I thought the ring gap alignment myth had been debunked for years. That being said, what other problem has the part solved?

[rebelEMPIRE]

If and when the rings line up, the amount of gas pressure blow-by is not enough for concern. In your car engine, it's a big deal because you lose a lot of power if that happens, but in your BCG, you only need enough pressure to ensure proper cycling of your bolt and carrier. It's been proven by others that your Bolt can run on just one ring; the others are there as merely back up.

-rebelEMPIRE

[TehLlama]

I can see a definite application on a competition rig, or when running a part-time suppressed weapon on a hard schedule (with minimal gas port and heavy buffers), but the stock ones should be adequate unless you're tinkering with trying to use as little gas as possible.

[Muddyboots]

Take a look at Mike Panonne's book on the M4. He comments on the gap issue and alignment. If it is NO issue with the three ring set up, I can't see any need for a one piece ring that may not conform to the carrier as well as three smaller rings.

Muddyboots

[tpelle]

I'm thinking that the gaps in the rings pretty much close up when the bolt is in the carrier anyway.

[Quib]

Take a look at Mike Panonne's book on the M4. He comments on the gap issue and alignment. If it is NO issue with the three ring set up, I can't see any need for a one piece ring that may not conform to the carrier as well as three smaller rings.

Muddyboots

True, and a good point.

I think I’ve mentioned this here before:

- 3 rings provide redundancy.
- Loose one ring, you still have two.
- Loose two rings you still have one.
- With a one-piece ring, loose it, and you have none.

[5pins]

I'm thinking that the gaps in the rings pretty much close up when the bolt is in the carrier anyway.

That’s what I have always though. Just how big is the gap when the bolt is? I would think it’s pretty small.

[TehLlama]

I'm a bit amazed they didn't make the one-peice ones shorter to allow a single stock gas ring to be used for redundancy.

[Quib]

I'm a bit amazed they didn't make the one-peice ones shorter to allow a single stock gas ring to be used for redundancy.

I should probably keep this idea, and market it for myself. The next thing you'll see are these style rings on the market:

- Instead of a solid one-piece ring coiled similar to a spring, design three separate rings that instead of a gap, have a slight overlap.

These rings would eliminate the gap, still flex and give for variances in the bolt carrier while in operation, and allow for the removal of individual rings in the event that a ring failed.

[Army Chief]

Instead of a solid one-piece ring coiled similar to a spring, design three separate rings that instead of a gap, have a slight overlap.

Conceptually, this is a very sound idea, but I'm wondering about the potential for these sharp, angled edges to catch and foul themselves on the edges of neighboring/adjoining rings with even the slightest misalignment under normal rotation.

AC

[Quib]

Conceptually, this is a very sound idea, but I'm wondering about the potential for these sharp, angled edges to catch and foul themselves on the edges of neighboring/adjoining rings with even the slightest misalignment under normal rotation.

AC

I thought about that too.

The design though in one form, has already been in use for years. If you've ever disassembled and rebuilt a landing gear strut or a pneumatic or hydraulic actuator, you've probably had to replace Teflon back-up rings which are of the same design.

If designed correctly, with the correct angle at the meeting point, I think there's a possibility it might work. The drawing posted above was simply to get the basics of my idea across. The rings could be installed and designed in such a way, that rings passing each other do not snag one another at the overlap.

[5pins]

What is the inside diameter of the carrier where the gas rings ride?

[Quib]

What is the inside diameter of the carrier where the gas rings ride?

I measure .5375"

[5pins]

I measure .5375"

That doesn’t sound right. My new gas rings measure .5105. Did you measure inside the carrier where it steps down for the gas rings?

[Quib]

I measured as far in as my digital calipers would reach. Anything deeper would require a t-gauge which I do not have here at home.

ETA: I measured 4 separate carriers. All fell into the same window.