Does anyone have any idea if a 223 bolt can be opened up slightly in a small lathe to function with a 6.8 SPC case?
6.8 SPC bolt from 223/5.56 bolt
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Originally posted by bj139 View PostDoes anyone have any idea if a 223 bolt can be opened up slightly in a small lathe to function with a 6.8 SPC case?
The bolt and extractor would need to be thinned in their thinnest areas and the face depth looks to be different. Just find a cheap 6.8 somewhere."The best we can hope for concerning the people at large is that they be properly armed."
-- Alexander Hamilton, The Federalist Papers at 184-188
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Sorry 'bout that unwanted advice I gave earlier. I guess I didn't read your post closely enough.
Good luck. Video please."The best we can hope for concerning the people at large is that they be properly armed."
-- Alexander Hamilton, The Federalist Papers at 184-188
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One of the overarching concerns would be the removal of surface hardened material. These bolts are heat treated, and grinding / milling / cutting will only compromise the surfaces in one of the areas where hardness is most needed.
Is it really worth the cost of a new bolt to see if you can do this? I'm not familiar with your machinist skills, bj139, but even if you are successful in hogging out the bolt face, are you certain you want a compromised bolt?
ETA:
If you're really convinced this is something you want to try, at least follow the lead of people's opinions you might better respect.
If it's true that we are here to help others, then what exactly are the others here for?
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Originally posted by bj139 View PostNow I've got to try it.
I was asking if anyone knew about doing it not that it should not be done.
The naysayers will always say it should not be done.
Make sure you make a video when you fire the gun for the first time."In any war, political or battlefield; truth is the first casualty."
Trump has never had a wife he didn't cheat on.
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NF,
Practical machinist was one of the sites that said any good smith could open up the bolt.
I would not try this with the Grendel because too much material must be removed (0.032") but with the SPC only 0.022" must be removed.
I bought 2 group buy Grendel bolts so I have 2 extra 223 bolts just gathering dust.
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IMG_20170802_132336 (Medium).jpg
I'm getting some mileage out of this photo. I posted it another thread yesterday.
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From my experiences with 2 6.8 SPC ARs, even when running boxed SSA ammo with an adjustable gas block, the 6.8 SPC is pretty hard on every part of a bolt.
I have an early 'snowflake bolt' that would be somewhat comparable to what you're suggesting. It's face stretched to 11mm in fewer than 1000 rds and I started having extraction issues.
I've run superbolts or something similar since then. Strangely, right now I have a 9 yr-old snowflake bolt in a 16" 6.8 RRA after wearing out the lugs on an ARP bolt (Top in the photo below). Not going to buy another until I see how my new Grendel build performs. Might re-barrel the RRA for 65Grendel or another 223...
Those side walls are gonna be mighty thin if you carve them out...
The worn snowflake bolt below (middle) has a 1.37mm wall at its thinnest point adjacent to the bolt face.
3Bolts:
Top: ARP Superbolt
Middle: Snowflake
Bottom (black): new 223
3Bolts (Medium).jpg
Not saying it can't be done. Just saying build a 300BLK pistol instead."The best we can hope for concerning the people at large is that they be properly armed."
-- Alexander Hamilton, The Federalist Papers at 184-188
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That middle bolt looks awfully thin. Are you sure thats not a 6.5 Grendel bolt?
Here is a photo from a site selling SPC bolts of an SPC bolt. They are out of stock.
SAA_PH_Bolt_68_s__66157.1489091630.jpg
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Originally posted by bj139 View PostThat middle bolt looks awfully thin. Are you sure thats not a 6.5 Grendel bolt?
Here is a photo from a site selling SPC bolts of an SPC bolt. They are out of stock.
[ATTACH=CONFIG]10791[/ATTACH]
The takeaway is "what will the sidewall thickness be when a standard 223 bolt is drilled out and how will it hold up?"
Modern SPC bolts now have a greater outer wall circumference so the walls can be thicker - similar to the ARP bolt up top.
"...SPC bolts of an SPC bolt?" (?) Not following..."The best we can hope for concerning the people at large is that they be properly armed."
-- Alexander Hamilton, The Federalist Papers at 184-188
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How about this, "Here is a photo of an SPC bolt from a site selling SPC bolts."
I may just buy this below. Notice how much thicker the bolt web is than yours.
Last edited by bj139; 01-15-2018, 12:44 AM.
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Originally posted by bj139 View PostHere is a photo of an SPC bolt from a site selling SPC bolts."The best we can hope for concerning the people at large is that they be properly armed."
-- Alexander Hamilton, The Federalist Papers at 184-188
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