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1/27/2021 12:46:26 AM
Posted: 5/20/2018 6:10:06 AM EST
3.75 inch 300aac Blackout Gas Operated AR15.  I make the official claim as of this date to have the shortest 300blk functioning semi auto AR15.  Of course with my luck someone already has one shorter.

First test fire

3.75 inch 300blk first test fire


Second Test fire

3.75 inch 300blk


does it work without the suppressor?

3.75 inch 300blk unsuppressed
Link Posted: 5/20/2018 6:28:32 AM EST
Pretty cool.
Well done
Link Posted: 5/20/2018 6:37:41 AM EST
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Quoted:
Pretty cool.
Well done
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Thanks.  It took a really long time, thinking, studying, crunching numbers, and making wild guesses, to get it to operation.  A friend asked me why.  I told him Because I can.
Link Posted: 5/20/2018 7:16:35 AM EST
I prefer my 6".  Shown next to a 8" 5.56.  Yours is pretty cool though.

What handguard do you plan on running?





Link Posted: 5/20/2018 7:18:42 AM EST
Wow that fireball. Lol
Link Posted: 5/20/2018 7:24:25 AM EST
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Nice.

I do not know yet.  It will have to be a somewhat custom handguard, or something I make myself.
Link Posted: 5/20/2018 7:25:53 AM EST
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Wow that fireball. Lol
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There are 2 reasons I held the gun like I did.

One was so you could get a decent view of the gun.  The other was the singed hairs on my hands from test firing when I held it around the magwell.
Link Posted: 5/20/2018 9:43:41 AM EST
cool deal! always fun to do something different.
Link Posted: 5/20/2018 1:39:57 PM EST
Okay, that’s pretty bad ass
Link Posted: 5/20/2018 1:43:21 PM EST
what ammo were you using?  Handloads?

I have a 6.25" that I like
Link Posted: 5/20/2018 2:03:17 PM EST
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Quoted:
what ammo were you using?  Handloads?

I have a 6.25" that I like
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Yes, handloads.

I have never fired a factory 300blk round.  I need to pick some up at some point.
Link Posted: 5/20/2018 3:06:31 PM EST
Bring out the chronograph/ballistics gel for the next video and shoot some groups.  It would be nice to see how practical it is vs just a silly range toy.
Does it have any hope of stabilizing the bullet with such little barrel?  And assuming it does group less than 20MOA, how hard does it hit?
Link Posted: 5/20/2018 3:33:17 PM EST
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Quoted:
Bring out the chronograph/ballistics gel for the next video and shoot some groups.  It would be nice to see how practical it is vs just a silly range toy.
Does it have any hope of stabilizing the bullet with such little barrel?  And assuming it does group less than 20MOA, how hard does it hit?
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It is a one in 10 twist, so I am currently limiting to around 200gr bullets or lighter.  At this point I have not shot it for groups yet.  However I have fired several rounds at a large piece of cardboard and 155gr cast, 140gr tracers and 200gr cast have all left mostly circle holes.  There have been a few that were slightly out of round but not enough to where I, at this point am overly concerned.

This was not built for any real purpose other than I wanted to see if it could be done.  Not really practical.  I guess in theory it could make a cool PDW, but not a first choice for that.

I have a few subsonic loads that I like for reliability, but as I said still got to get them on paper.  I have managed to push a super load to 1300fps using the 140gr tracer.  But I think I can get it faster than that.  I am hoping close to 1500fps. But only testing will tell.
Link Posted: 5/21/2018 11:46:38 PM EST
Link Posted: 5/21/2018 11:58:39 PM EST
Looks like there is gas coming out of the gas block. Are you bleeding some of the gas off at the gas block?
Link Posted: 5/22/2018 4:06:45 AM EST
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Quoted:
Looks like there is gas coming out of the gas block. Are you bleeding some of the gas off at the gas block?
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Technically, yes.  On purpose? No. I have to anodized the block and do some other things to tighten the seal.  Still in prototype mode.
Link Posted: 5/22/2018 4:28:13 AM EST
Neat....but where are you going to put your vertical pistol grip?
Link Posted: 5/22/2018 4:34:33 AM EST
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Neat....but where are you going to put your vertical pistol grip?
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I am adding a handguard system to it.  just have not figured out which one.  May make something myself.

I have to mill down the gas block in order to fit a handguard on it.
Link Posted: 5/22/2018 9:00:06 AM EST
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Neat....but where are you going to put your vertical pistol grip?
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And what about the light, bipod, and BUIS?
Link Posted: 5/22/2018 9:11:05 AM EST
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Quoted:
And what about the light, bipod, and BUIS?
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Quoted:
Quoted:
Neat....but where are you going to put your vertical pistol grip?
And what about the light, bipod, and BUIS?
And bayonet, and laser, and ir strobe, and door stop, and m203.??
Link Posted: 5/22/2018 10:04:43 AM EST
Great, job.
I think you may be surprised on accuracy. Ron from RMW XTREME a few years ago built a DI 45 ACP with a 3.5" barrel and that one was also just to see if it would work. And every time I shoot it I am amazed at the accuracy, no it is not a precision gun but out to 40-50 yards it hits a 6" steel target 99% of the time as long as I do my part.  I think as long as it is built well and you keep loads within reason bullet wise it should be good to 50yds. I would be interested in what kind of velocity you get with different loads and if you can hit 850-950 fps it should suppress well.
Link Posted: 5/22/2018 10:09:39 AM EST
Hahaha nice!

Thats a mega can too
Link Posted: 5/22/2018 11:22:28 AM EST
Nice!!  I just built a 7.5” one to use with a Sandman-K. Maybe I will rethink it and build shorter.
Link Posted: 5/23/2018 3:10:33 PM EST
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Thats a mega can too
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Yeah, I'm curious as to why you made the can so long. The gas block looks adjustable, so can I assume you're looking to be able to shut off the gas entirely to get crazy quiet?
Link Posted: 5/23/2018 4:59:08 PM EST
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Quoted:
Yeah, I'm curious as to why you made the can so long. The gas block looks adjustable, so can I assume you're looking to be able to shut off the gas entirely to get crazy quiet?
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Quoted:

Thats a mega can too
Yeah, I'm curious as to why you made the can so long. The gas block looks adjustable, so can I assume you're looking to be able to shut off the gas entirely to get crazy quiet?
The can, was my first form 1 suppressor I built over 10 years ago. Before I really understood completely suppressor dynamics. It is designed around 9mm bore but designed to handle 300 Winchester magnum.
Link Posted: 5/23/2018 5:01:15 PM EST
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Quoted:
Great, job.
I think you may be surprised on accuracy. Ron from RMW XTREME a few years ago built a DI 45 ACP with a 3.5" barrel and that one was also just to see if it would work. And every time I shoot it I am amazed at the accuracy, no it is not a precision gun but out to 40-50 yards it hits a 6" steel target 99% of the time as long as I do my part.  I think as long as it is built well and you keep loads within reason bullet wise it should be good to 50yds. I would be interested in what kind of velocity you get with different loads and if you can hit 850-950 fps it should suppress well.
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I have done some rudimentary accuracy, and while not spectacular.  I believe I can improve it some.

As far as suppression.  With a 3.75 barrel, it will have an issue getting very quiet.
Link Posted: 5/23/2018 5:42:39 PM EST
Link Posted: 6/4/2018 6:16:10 PM EST
https://youtu.be/cmZSFBy9CZ8
Link Posted: 6/4/2018 6:50:11 PM EST
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https://youtu.be/cmZSFBy9CZ8
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That is 5.56/.223.  Which was my inspiration.
Link Posted: 6/4/2018 11:16:03 PM EST
Just thought it was relevant to the topic. Pretty cool to see the tip of the bullet.
Link Posted: 6/4/2018 11:51:04 PM EST
you pronounce boolit weird.

sweet gun. looking forward to seeing what you come up with to finish the handguard.
Link Posted: 6/5/2018 3:07:47 AM EST
I would love to hear more about your tracer loads.
I asked a question about such a thing a couple years ago and got zero replays

Tracer subs would be super cool.
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