Help on 7.5" SBR Upper

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Help on 7.5" SBR Upper

Postby DARYLU » Sun Sep 03, 2017 7:34 pm

Hi All;

I've done my best to search. Maybe I've missed it.

I have a Bowers VERS 458 suppressor on a 16" Bushmaster upper. It's a beast to carry with a lot of weight out front. I love the suppressor though.

So, I'm thinking I really want to put a 7.5" upper on my SBR lower. This is primarily an Ohio Deer hunting gun in the brush - but I'd still like to get out to 150-200 yards if possible.

I've searched high and low on the net and not found a 7.5" complete upper. I found a couple sources for barrels - but they are sold out.

Can anyone shed some light on this combination or point me to a direction on how I can get this done?

Thanks
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Re: Help on 7.5" SBR Upper

Postby Texas Sheepdawg » Mon Sep 04, 2017 2:28 pm

You could try Franklin Armory or BK GunNStuff
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Re: Help on 7.5" SBR Upper

Postby plant_one » Mon Sep 04, 2017 11:09 pm

franklin armory produces a 7.5" upper in 450 bushmaster

i have a barrel i was considering cutting down for my pistol. so i called them about how the round functioned at 7.5" barrel length.

i'm not quoting them verbatum, but the gist of it is the barrel being that short absolutely neuters the caliber.


from what i've been able to gather, the numbers down to 13" are still pretty keen, but they start to fall rather spectacularily from there down.


https://matchgrademachine.com/velocity- ... bushmaster

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Re: Help on 7.5" SBR Upper

Postby DARYLU » Wed Sep 06, 2017 7:23 pm

Thank you... this is excellent information. I could not find the 7.5" in stock anywhere - and they are a 3 month lead time +/-. But, I found a 9.5" in stock at Columbia River Arms and have that on its way to try.

My purpose for the 450 is not full power - but it is the only cartridge approved for Deer in Ohio that has a currently manufactured semi-auto rifle available. So, at the numbers on the chart - even 100 to 200 FPS less - it is still much more than the 44 Magnum which is also very suitable. If the 450 SBR is good out to 150 to 200 yards - that would really be a bonus. We seldom get a shot at much more than 75 yards. I'm working toward a nice little package with the suppressor.
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Re: Help on 7.5" SBR Upper

Postby Al in Mi » Thu Sep 07, 2017 3:51 am

you might check with Cole at Deadshot Barrels, He had some short ones listed on GB last winter.
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Re: Help on 7.5" SBR Upper

Postby Hoot » Thu Sep 07, 2017 4:42 am

QuickLoad predicts that a 250 FTX bullet (factory) drops to 1719 fps using H110 as the propellant and 1739 fps using W296 charged to max recommended chamber pressure in a 7.5 inch barrel. Not my cup of tea but still plenty lethal.

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Re: Help on 7.5" SBR Upper

Postby DARYLU » Thu Sep 14, 2017 9:56 am

Thanks for the help so far. I'll report what my current findings are. I had the factory-built Bushmaster 16" 450 upper. I was using the Bowers 458 can. I could not get a consistent group. Now, I changed many variables at once - but that's just the way it is. First, I got a Columbia River Arm/Black Hole Weapons 9.5" 1:18 barrel. I lapped the Bushmaster upper to square up the face.
All loads were Hornady Brass, CCI #41 small rifle primer, 2.225" COL, taper crimp to .476/.477. The suppressor seemed to have little effect on velocity - but I did need to adjust the scope about 3" left after putting the suppressor on. Shots at 1" circle at 50 yards. 2-3 shot groups.
Factory ammo: 1,974 FPS under 1"
37.0 Lil Gun 2,033 FPS under 1"
35.4 Lil Gun 1,978 FPS under 1"

All cycled fine. One load did not eject at 1,928 FPS - that was probably my error in adjusting early loads. Everything 1,975 & up cycled fine. I have a rifle stock and spring on this.

So, I think the crimp helped for sure from .480 to .476/.477. Maybe a better barrel. Maybe truing up the upper receiver.
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Re: Help on 7.5" SBR Upper

Postby Al in Mi » Thu Sep 14, 2017 10:26 am

impressive shorty set up there, post pics when you can!!!
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Re: Help on 7.5" SBR Upper

Postby DARYLU » Fri Sep 15, 2017 6:47 am

OK, here are some pictures. The brown targets are 50 yds. The other target is 100 yards. I should have stopped when the second round touched the other on that. That load is the 250FTX with 37.0 Lil Gun.

Configuration as shot. Bowers 458 can - sounds about 22 mag or so. Original Bushmaster 16" upper with Columbia River Arms 9.5" barrel change out. Yankee Hill Machine SBRed lower - entry level with magpul rifle stock.
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Re: Help on 7.5" SBR Upper

Postby plant_one » Fri Sep 15, 2017 11:04 pm

nice


can you run a few shots w/o the can and see what the numbers look like?

with numbers like that, if unsuppressed is even close thats a whole new take on this cartridge.

at 9.5" i beleive i could strap that thing onto my pistol lower and ccw it :o :mrgreen: 8-) .
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