Looking for a bolt to match to a 16" Proof AR barrel (.223 Wylde).
I was thinking JP, but figured I'd post in case there's a better option.
I was thinking JP, but figured I'd post in case there's a better option.
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Proof AR Barrel - Which Bolt?
- Thread starter Army of One
- Start date
Misleading. Proof specifically states they are headspaced for JP bolts. Don’t risk it loosing accuracy or not working properly. My smith commented on how tight the headspace was on both my AR10 and 15 with Proof CF and JP high pressure bolts.
Any bolt that headspaces will be fine. I don’t use JP bolts on any of mine and they headspace and shoot just fine although mine are large frames. I have many different BCG and barrels for AR15 and have ‘t found one yet that won’t headspace. I’m sure it happens but I doubt its common.
I’ve been using an Aero hp nitrided bolt. I understand JP’s reputation and it’s well deserved. That said, with my proof barrel I’m afraid to try anything else because of what I’m doing with the Aero.
Headspaces fine?
I guess I've been lucky. All my AR-15 bolts (5.56 and 6.8 types) meet drawing.
Typical of my bolts.
What are the measurements on the JP bolt? or a Rubber City bolt?
Are my bolts OK @ 0.278 - 0.124 ?
Do you want a TIGHT headspace, or maybe 0.002" over GO for an AR-15 ?
(asking for a Friend
)
I understand some accuracy guarantees can depend on using the correct brand of bolt.
Late Edit: When a vendor headspaces a gas gun to a specific bolt do they set it to the GO dimension, Go + a thou, Go+ 2 thou?
What are the bolt dimensions of the bolt they used?
What if you don't send a bolt or buy theirs? What dimension do they use?
Do they tell you? Do you care
Can you replace the bolt in the future and not change headspace?
I understand most factory ammo is 'short' and reloaders adjust cases to the chamber/bolt they have.
Maybe a barrel maker can clear up this "headspace to a specific brand of bolt" question.
I guess I've been lucky. All my AR-15 bolts (5.56 and 6.8 types) meet drawing.
Typical of my bolts.
What are the measurements on the JP bolt? or a Rubber City bolt?
Are my bolts OK @ 0.278 - 0.124 ?
Do you want a TIGHT headspace, or maybe 0.002" over GO for an AR-15 ?
(asking for a Friend
)I understand some accuracy guarantees can depend on using the correct brand of bolt.
Late Edit: When a vendor headspaces a gas gun to a specific bolt do they set it to the GO dimension, Go + a thou, Go+ 2 thou?
What are the bolt dimensions of the bolt they used?
What if you don't send a bolt or buy theirs? What dimension do they use?
Do they tell you? Do you care
Can you replace the bolt in the future and not change headspace?
I understand most factory ammo is 'short' and reloaders adjust cases to the chamber/bolt they have.
Maybe a barrel maker can clear up this "headspace to a specific brand of bolt" question.
Last edited:
I checked mine with a Clymer no go with ejector removed. She no go lol. Hornady match ammo chambers, I’ll ASS U ME it’s fine.
The Mil-Spec allows 0.156" down to 0.153" from the rear of the lug (contact with extension) to the bolt face.
0.156" gives a tighter headspace than the other end of the tolerance 0.153".
An in spec bolt would give a range of 0.003". I imagine that high quality bolts will be held to a much tighter tolerance.
Would that be 0.156" to 0.155" or 0.155" to 0.154" or maybe 0.154" to 0.153"?
How about 0.154" +/- a half thou? (Tighter than Mil-Spec).
When headspaced, a barrel/extension/bolt could be set up for exactly GO for the caliber or to allow for a higher fire rate set up for GO + a couple thou. Bolt lugs will "wear in" some. Maybe some makers will set really tight on the Go and hope for wear.
The range of acceptable headspace might be 0.006", Go to No-Go.
Whatever the tolerance on the quality bolts are, setting to a tight GO dimension might cause cycling issues.
(unlikely with short factory cartridges)
Setting longer, closer to the No-GO dimension, still in spec, could shorten life.
If you used a 0.153" bolt (loose) and set total headspace to GO, swapping in a 0.156" bolt (tight) would result in GO minus 0.003.
That doesn't sound good.
If you used a 0.156" bolt (tight) and set total headspace to GO + 0.003", swapping in a 0.153" bolt (loose) would result in GO Plus 0.006".
That doesn't sound good.
Barrel makers KNOW what headspace they WANT likely based on the expected usage of their barrel.
Knowing the bolt dimension, and the total headspace they WANT is necessary to send out a unit with the desired headspace.
Someone KNOWS what the dimensions are (and tolerance) of a JP or RCA bolt.
I bet it's NOT a 0.003" (Mil-Spec) range.
0.156" gives a tighter headspace than the other end of the tolerance 0.153".
An in spec bolt would give a range of 0.003". I imagine that high quality bolts will be held to a much tighter tolerance.
Would that be 0.156" to 0.155" or 0.155" to 0.154" or maybe 0.154" to 0.153"?
How about 0.154" +/- a half thou? (Tighter than Mil-Spec).
When headspaced, a barrel/extension/bolt could be set up for exactly GO for the caliber or to allow for a higher fire rate set up for GO + a couple thou. Bolt lugs will "wear in" some. Maybe some makers will set really tight on the Go and hope for wear.
The range of acceptable headspace might be 0.006", Go to No-Go.
Whatever the tolerance on the quality bolts are, setting to a tight GO dimension might cause cycling issues.
(unlikely with short factory cartridges)
Setting longer, closer to the No-GO dimension, still in spec, could shorten life.
If you used a 0.153" bolt (loose) and set total headspace to GO, swapping in a 0.156" bolt (tight) would result in GO minus 0.003.
That doesn't sound good.
If you used a 0.156" bolt (tight) and set total headspace to GO + 0.003", swapping in a 0.153" bolt (loose) would result in GO Plus 0.006".
That doesn't sound good.
Barrel makers KNOW what headspace they WANT likely based on the expected usage of their barrel.
Knowing the bolt dimension, and the total headspace they WANT is necessary to send out a unit with the desired headspace.
Someone KNOWS what the dimensions are (and tolerance) of a JP or RCA bolt.
I bet it's NOT a 0.003" (Mil-Spec) range.
Last edited:
The JP BCG is milspec(at least in dimension, not sure on material), the JP Enhanced is not milspec.
It will replace a mil spec bolt, but the above explanation was a good point to the JP potentially having a much tighter tolerance set while still existing within the mil-spec’s range.
This isn't going to matter to most users, buying quality parts.
Mostly this is not knowing, just relying on brand for a proper fit (whatever that fit is )
For those that load for precision and bump to fit the chamber it might matter for bolt swaps or loading for multiple guns.
Maybe just luck but MOST of my bolts seem to be 0.154" +/- about a half.
I shoot a long barrel 22 Nosler with a 5.56 size bolt and swap bolts to a 6.8/224V sized bolt for 22 NOSGAR.
I Bump to minus 0.002" with either bolt.
I'll be replacing one barrel this winter and will check with the maker on a more specific dimension.
Mostly this is not knowing, just relying on brand for a proper fit (whatever that fit is
)For those that load for precision and bump to fit the chamber it might matter for bolt swaps or loading for multiple guns.
Maybe just luck but MOST of my bolts seem to be 0.154" +/- about a half.
I shoot a long barrel 22 Nosler with a 5.56 size bolt and swap bolts to a 6.8/224V sized bolt for 22 NOSGAR.
I Bump to minus 0.002" with either bolt.
I'll be replacing one barrel this winter and will check with the maker on a more specific dimension.
My 18" Proof barrel is matched to a BCM bolt carrier group and gives me reliable 0.5 MOA accuracy with a handload using SMK 77gr bullets/TAC powder.
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