300 BO Pistol Build

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8 years 1 week ago #47733 by jtallen83
300 BO Pistol Build was created by jtallen83
Just test fired a 300 BO pistol build today. Need some tweaking but it is basically ready for the suppressor to get out of jail. Had to borrow BUIS and a BCG from another AR but no failures once the adjustable gas block was dialed in.
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Anderson upper and lower, Faxon 10 1/2 inch barrel, MI GenIII 9 1/4 inch rail, SLR adjustable gas block, LaRue tactical MBT trigger, Mech Armor CQB charging handle, KAK buffer tube and stabilizing brace. A friend did the custom Cerakote work, even did some mags for me to help ID the dedicated 300 BO stuff.

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8 years 1 week ago #47734 by Libertarian623
Replied by Libertarian623 on topic 300 BO Pistol Build
Looks good JT. I like the stabilizing brace. I am contemplating a 458 SOCOM pistol upper from RRA right now.

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8 years 1 week ago #47735 by jtallen83
Replied by jtallen83 on topic 300 BO Pistol Build
For a .458 I might go the Sig brace route. The KAK shockwave is real stiff while the Sig braces I have are softer with a bit of give to them. Just in case the brace would inadvertently make contact with some part of your body during recoil the Sig brace would be more forgiving. The Sig braces have more surface area on the end as well.

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8 years 1 week ago #47736 by jtallen83
Replied by jtallen83 on topic 300 BO Pistol Build
Second time out I tried several different sub loads and had failure after failure. Appears to be under gassed as it got better the higher I turned it up but the gas block maxed out before the issues stopped. Hope I have time for an autopsy before I go back to Florida this weekend.........

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8 years 1 week ago #47737 by Libertarian623
Replied by Libertarian623 on topic 300 BO Pistol Build
JT- Where are the rounds from? Do they meet spec(light/heavy). Remember you may have to put some stout loads through it , with heavy oil to get that upper broke in. Maybe chrono the rounds to see where your at. Just throwing ideas at it.

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8 years 1 week ago #47738 by jtallen83
Replied by jtallen83 on topic 300 BO Pistol Build
Loads are Remington UMC 220's and 120's, Freedom munitions 208 A-Max and S&B 200 gr. I did notice the 220's were the closest sub to function with full ejection just no lock back or reload happening. Other than double checking the gas system for leaks/alignment issues I may wait and see what it does with a standard BCG and the Tubbs flat wire spring for the 300BO, my original intention for the pistols configuration. Since the 120's functioned fine I will get several boxes and use them for break in on the new BCG, that and hope my SDN-6 is out of jail before Christmas!

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8 years 1 week ago #47740 by Siscowet
Replied by Siscowet on topic 300 BO Pistol Build
Like the handguard.

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8 years 1 week ago #47745 by Libertarian623
Replied by Libertarian623 on topic 300 BO Pistol Build
I second that Sisco , JT that is a very nice design for the handguard.

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8 years 1 week ago #47746 by jtallen83
Replied by jtallen83 on topic 300 BO Pistol Build
MI's new barrel nut and torque plate system are interesting, seemed to work well and no worry about lining up the gas tube, just torque it and go.
www.midwestindustriesinc.com/product-p/mi-ss9g3.htm

They just updated their website so it isn't real organised yet.

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7 years 11 months ago #47806 by jtallen83
Replied by jtallen83 on topic 300 BO Pistol Build
The Drilling has commenced. Installed the d. wilson standard BCG and the Tubbs flat wire 300 BO buffer spring. The original port size was the .075 stated by Faxon. I drilled six times total with a trip to the range for testing after the new spring, BCG, and checking the gas system, then after each drilling of the port. The .081 trip showed evidence of progress. Still no lock back on the last round in the mag but the heavier 220 subs are now being fed after each firing. The lighter subs are not feeding a new round but they are not stovepiping and the hammer is being cocked, getting close! I'll open it up a couple sizes too near .085 tonight and test again.

The following day;

Got it! .0935 #42 bit finally got it to function with the 200 grain subs. It ran on the UMC 220 grain subs at .089 but still wouldn't lock back or load the next round with the S&B 200's or the Freedom Munitions 208's so I went another size up. This is with the SLR gas block wide open so now I can tune the block down for everything else I need it to do. The NFA tracker website predicts I will have my first stamp show up mid January, hope congress will drop silencers from the NFA about then, and give me a tax credit for the three stamps I applied for!

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