300 Blk PDW Zero

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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300 Blk PDW Zero

Post by 2jwagner » Mon Aug 12, 2019 6:44 pm

Before you comment, please spare me the question of "why?"... There is good reason for what I'm about to state and ask...

I am building a 300blk pistol. 10.5" Faxon barrel and superlative adjustable block is really all that matters for my question lol.

The purpose of this build is strictly a home defense sub gun. I am going to be using 194gr Lehigh Maximum Expansion rounds only. I ran ballistic data matched to the specs of that round, and after playing with numbers I came to the conclusion of zeroing at 20 yards.

Ballistic data as follows @ 20 yd zero:
(FPS)(Ft. Lbs)(Traj)(MOA)
0 Yards = 1000, 431, -2.6", 0
25 yards = 992, 424, +0.4", -1.5,
50 yards = 984, 417, +1.2", -2.2,
75 Yards = 977, 411, -0.3", 0.4
100 yards = 969, 405, -4", 3.9

With this data, I can easily operate in and around 0 to 100 yards within a spread of less than 4". The likelihood of my using this past 10 yards is extremely unlikely, but at least I'll know what it can do. I actually like a 15 yard zero better with this round since it has a tighter overall spread, but the trajectory between 25 and 75 yards isn't as tight as with a 20 yard zero.

My question is this... How can I zero this thing at 20 from a 25 yard range? I've seen zeroing 50 yards at 25, 36 at 25, 100 at 50, etc. Just wondering if there's math behind it that I can use to zero 20 from 25. It's kinda dumb - I already know!

Also, with an adjustable gas block, does the setting(s) of the block affect the ballistic data? What about the suppressor?

Thank you 8)

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Re: 300 Blk PDW Zero

Post by bearcatrp » Mon Aug 12, 2019 8:40 pm

Suggest you chrono the round once it’s built. Data from the manufacturer isn’t always accurate. Then run your numbers in a ballistic program. Go from there. Myself, I zero at 50 yards. Not much difference at closer range or at 100 yards..

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Re: 300 Blk PDW Zero

Post by dellet » Mon Aug 12, 2019 8:53 pm

"Zero" .4" high at 25 yards.

Then confirm any other known distances you can shoot.

1.2" @ 50
-.3" @75
-4" @100

If those are correct, any other distance on the table should also be
300 Blackout, not just for sub-sonics.

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Re: 300 Blk PDW Zero

Post by popper » Sun Sep 08, 2019 10:52 pm

Got a 10 RD zero and shoot. You said home defense, not 75 yds. 2" won't make a difference.

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