AR-MPR: Phase II – Sizing Depriming Priming .223 Remington

In this video we’ll start the precision loading process by lubing, sizing, depriming, and priming cases. We’ll walk through the features of the Redding Big Boss II, show how to lube .223 cases, validate sizing die setup, and then size/deprime/prime the cases.

Next, we’ll cover charging the cases with the Redding 3-BR benchrest powder measure and the Hornady Auto Charge.


13 thoughts on “AR-MPR: Phase II – Sizing Depriming Priming .223 Remington”

  1. Your videos have been and continue to be fantastic. I am interested to see your take on primer sealants?

      1. yes I am.
        I shoot when I can and sometimes that means in varying degrees of weather, so I was interested to see your thoughts or if this step is needed

  2. As usual very nice video. I will go so far as to say that as far as an independent video producer for firearms related information, you’re as good as any I’ve seen and far better than most. One expects Brownells or Midway to put out a first rate video but you’ve raised the bar for a guy doing this stuff on his own. I don’t know what better compliment I can pay you. I’m still interested in seeing how the scope holds zero with the bridge mount. 😉

    1. Thanks Mark! Just installed a new ProMag mount- and I’ll let you all know how it goes. Is the theory that it will not hold zero from shot-to-shot, or will loose zero when in transport or if it’s banged around (the scope/mount) ?

      1. The way I had learned it was that sooner or later the quad rail will move. I don’t think this is a shot to shot issue but rather “it was on one day and the next day it wasn’t”. As I said, I’ve built a ton of these guns and was taught this early on but for no particular reason just didn’t experiment with it to see if it was fact or myth. That’s why I’m interested in seeing someone who has actually tried it and will report on it.

  3. I’m assuming those pieces of brass were fired from the AR-MPR? Not setting the shoulder back at all is quite unusual, it seems that you should be setting the shoulder back approximately .002-.003″, not setting the shoulder back could create problems of getting those rounds to go into battery. Not sure if you were going to cover this in your next video but it’s always wise to chamber a sized case to make sure the bolt will go into battery, especially if it prevents having to tear down a batch of rounds when you find they don’ chamber. Hope this helps.

    1. Yes, I agree- I’ve tested this adjustment, and it seems fine. It’s within a few thousandths of new Winchester brass, and based on the 5.56 chamber dimensions, I think it’s fine, but not what I expected either! The brass was fired in this rifle. I did the chamber test when I first set the die (like a headspace test, but with a sized brass case.

      I should also note that I measured the overall length of the case, and do not need to trim yet, but you should check after each firing. I just got the Hornady Lock-N-Load headspace comparator kit- I’ll check measurements with that as well. Expecting the same results.

      1. Gavin, for what it’s worth and I’m making a generalization across perhaps 10 different AR’s that I currently own. It seems like I can get 3 reloads on most military brass before I need to trim the case. For whatever reason most commercial brass (with the exception of LC) goes only a through a couple of cycles before trimming is needed. I of course, always measure the brass but have stumbled into this tidbit over many years and a bunch of AR’s. I typically load moderate to moderately warm rounds, most often 62 grain bullets. This also assumes the head spacing to be within spec. I’ve only had it happen a couple of times but sooner or later piecing together an AR from a variety of manufacturers will eventually lead to one being out of spec on the head space. This of course should be checked on every build.

        1. Thanks Mark- It’ll be interesting to see how many firings this Winchester brass needs before trimming… I have 600 pieces now, so for precision shooting, it’ll take a while to cycle through all that a few times. But I do have about 20lb of powder on the shelf, so I need to keep things going! 🙂

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