Bushmaster 308 ORC Followup

After changing a number of components, the rifle appears to be working properly again. The items that were changed include:

Swap from AR-15 collapsible stock tube to Vltor AR-10 collapsible stock tube

Replacement of cutdown aluminum buffer body containing two tungsten weights (weighing 3.8oz) with steel buffer body containing two tungsten and one steel weights, resulting in a weight of 7oz.

Replacement of stock short action spring with Tubb CS flat wire spring

Addition of o-ring on extractor spring.

Individually, these changes only reduced the number of malfunctions; all were required to (seemingly) eliminate them.

Very observant viewers may notice a little bolt bounce; this may be reduced with the replacement of the one steel weight with yet another tungsten weight, but I’ll be doing more testing to see how reliable it is before I say for sure that that’s the setup I want to use. I’m more concerned with consistent extraction and ejection at the moment, and high speed video seems to show that the weapon is working properly in that regard.

The video is pretty boring, but here it is:



Filed under Firearms

3 responses to “Bushmaster 308 ORC Followup

  1. FrankSL

    Glad that you were able to sort out the issues.

    How many frames per second does that camera take?

  2. MarkM

    Mid length gas on a .308 is what Bushmaster catalogs it.

    The extractor upgrade makes sense, why the buffer and spring helps, don’t know. I suspect having a good grip on the case uses up some of the energy, all the upgrade slows bolt speed.

    It implies either the bolt is too light, the timing too soon, or the gas impulse too much. Semi autos tend to prefer one load because of nonadjusting gas ports, it would be interesting to know what this gun has. AR10’s not being milspec leaves that without a reference point.

  3. MarkT

    I just recently purchased one of these but have not had the chance to shoot it yet. Many thanks for posting your experiences with it and your solution to the reliability issue .

    I was just wondering why you chose to use a AR10 buffer tube and not a modified AR10 spring and slash CAR-10 XH heavy buffer? That way you could still use the AR15 buffer tube. Would it have made a difference?

    Also, did you try using an adjustable gas block? I am wondering if just swaping out the gas block (and adjusting the gas) would have solved the problem.

    Thanks for an excellent blog.

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