AR-MPR Phase II – Seating Bullets

In this video, we’ll use the Hornady OAL Gage measurements from our first Phase II loading video: AR-MPR: Phase II – Determining Max COL with OAL Gage and measure the dimensions of the cartridge and magazine to determine the optimal bullet seating depth for the bullet and rifle in question. We’ll then use the Redding Big Boss II and Redding Competition Seating Die to seat the bullets.

Next, we’ll validate the precision of the seating using the Hornady Concentricity tool.

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6 thoughts on “AR-MPR Phase II – Seating Bullets”

  1. Hey Gavin, cool video. I was wondering, because the limiting factor for OAL is the magazine to ensure proper feeding what benefit do you get by using the OAL Gauge Measuring tool? I watched the video a few times and couldn’t figure it the reasoning.

    1. I always start with the OAL gage to find out where the rifle’s chamber is at for max COL. Since we’re loading long here (compared to .223 specs) we need to make sure:
      1. We are as close to the lands as possible
      2. We have enough bullet clearance for proper magazine feed

      Either of the above could potentially limit/imact COL, so it’s important to measure both, and load to which ever requires the shorter COL measurement.

      Hope that helps to clarify.

  2. Gavin; like all the other’s, I’m learning more with each video you put out. My comment is more about the work bench you’re now using. The rail (track) system looks nice with giving you increased mounting flexibility, but I noticed during the bullet seating the entire press (Redding Big Boss) flexed. Was this caused in part because of the wood block mounts, or were they just not torqued down enough? Also could this, the flexing, be the cause of your concentricity results in the next video?

  3. I recently bought the redding 308 taper crimp die. How do I know how much crimp to put on the round. I am new to reloading (11 months) everything I have loaded so far has been pistol calibers.

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