Jump to content

Upper receiver machining


Recommended Posts

I know you all like looking at how stuff's done, so here's another pictorial

 

Todays project: Machining a Mega Machine upper receiver

 

I have a few of these uppers, and the problem with them is that they're too thick at 10mm wall thickness, which prevents me fitting one of my World Famous® Charging Handles.
To make the very best of this, the ideal solution is to remove material from the sidewalls of the receiver, 4mm to be precise, which brings the wall thickness down to .250"
That should be Billety enough for anyone!
76E10499-4CB0-4378-9251-7BB2C40258ED_zps
Machined vs unmachined sides
56F14B6A-6965-4ADC-A563-04615F149DB1_zps
Doing this however leaves the upper too slab-sides, so reprofiling of the upper and lower facets is required
B5AF1CD7-4BBF-4A26-A750-625AC494CED0_zps
7B19F01D-15BF-46C1-9C5E-57B7601BA506_zps
678771A8-7A42-41AB-9AC2-1DC76F8B89CF_zps
EEBFE2ED-A1A1-4250-9482-9D32CD674FEB_zps
After this the charging handle slot needs machining to suit the handle.
The Mega uppers are already partially machined for sidecharginbg, but it is far from suitable.
The slot requires lowering, lengthening and widening
657BDF5E-33AB-4FF3-BD4F-F63A26089262_zps
Chamfered.
This will be finished by hand later
1516EBE6-F920-4DF3-837B-43E390A32667_zps
D0DCC26F-A5B6-4FFF-96F4-4AD5F9B3D9D9_zps
39C67622-C6C8-4DF0-87B7-E470A2DECC8D_zps
After all machining is done, it's off to the bench for finishing.
The first step is to remove the machining marks
F304CF70-A6D4-4907-A5EC-75469C4E70A4_zps
49B9B715-47C9-43B0-A4CF-BECF4F3208CF_zps
A1B92B8F-DC54-4136-B138-8D4ECE176036_zps
Reprofile the rear edges to blend and match
4FDA2D1A-0E34-4B1D-8CF5-56CC3E289E96_zps
8C3378A3-8901-4465-A8DE-9851056A8D61_zps
Finally after all radiusing and deburring and a clean
EC221F6A-8185-4C7D-B67A-B0F6749D9B52_zps
5CCC1352-835A-4EF1-8F0B-E0FD35AF6977_zps
2EE5F82E-4742-42EB-B6BA-37C3320E82DD_zps
The finished item
512A707A-FCDB-4535-AFFB-6985D387B696_zps
Tomorrow we blast and Cerakote®
ETA:
Cerakoted them yesterday, so here's the finished item
68E42618-B658-438B-9EF7-75573219A731_zps
0C4FA3DB-ED07-4B91-9E6A-6BC42152DCDE_zps
E21B07D3-D0A8-44A3-A4EA-4BDAD85C6ECC_zps
A4A552B8-F3D7-4DC6-84A7-134B73D419F0_zps
And here's some pics of a barrel I fluted and crowned yesterday
C2E9DFBB-C4C9-4796-83AF-4F6CDA633621_zps
6A563CE6-C486-4FFF-B1FD-6D20F707320C_zps
C1030925-6AB0-411A-8BCF-AAD4A65F552A_zps
F4163A76-A276-48E3-8191-4F7FCA6A3F64_zps
Link to comment
Share on other sites

Very impressive, brads...out of interest, how long did that receiver take to complete?

 

Cheers

 

All in, probably about 90 minutes each, but I was doing 6...and with all the other things like drilling and tapping bolt carriers, as well as other jobs, today turned into another 12hr day

Don't know where the times goes some days

Link to comment
Share on other sites

  • 3 weeks later...

what is the barrel spec, length, calibre ? Looks lovely and short. Would be a beautiful 300 blackout truck AR

 

 

 

Craig

It's a .22lr, 12" made from a Sassen blank

That said, I've done plenty of .300Blks/Whispers and .223s in 12" configs

I did the first one in 2005 when the only option was .300 Whisper

Link to comment
Share on other sites

These are Swedish military findings regarding barrel length and 5.56mm 62gn SS109 ammo

It should be relevant for all 62gn/SS109 ammo types


Barrel length SS109/M855 V4 bullet velocity

210 mm (8.3 in) 723 m/s (2,372 ft/s)

240 mm (9.4 in) 764 m/s (2,507 ft/s)

270 mm (10.6 in) 796 m/s (2,612 ft/s)

300 mm (11.8 in) 825 m/s (2,707 ft/s)

330 mm (13.0 in) 843 m/s (2,766 ft/s)

360 mm (14.2 in) 866 m/s (2,841 ft/s)

390 mm (15.4 in) 878 m/s (2,881 ft/s)

420 mm (16.5 in) 892 m/s (2,927 ft/s)

450 mm (17.7 in) 906 m/s (2,972 ft/s)

480 mm (18.9 in) 915 m/s (3,002 ft/s)

508 mm (20.0 in) 922 m/s (3,025 ft/s)


As for Blk, well subsonics will be below 1150fps, but with a 125gn .30 for example, you'll be getting about 2100-2150fps with a 12" barrel

Link to comment
Share on other sites

Before I sold my Blackout I was running 200gn bullets at 1080fps from a 12" 1:7 with what I'd describe as .22lr accuracy but with a touch more range.

As Bradders says, supersonics in the 125-135gn range ran around 2100fps but I found them more accurate at 1800fps.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Privacy Policy