is it worth buying a " headspace'd bolt" to match a barrel?

[_Will_]

I was looking at buying a Criterion M118LR hybrid barrel for my 20" Aero M5 308, right now it has the factory 416R stainless steel barrel which isn't very consistent. (Great cold bore shots, but when it heats up POI shifts to 3-4 MOA with match ammo FGM 168grs @ 100 yards) I know Criterion offers a headspaced bolt with their barrels, just wondering if it's worth it? From my understanding is they look for a bolt like a JP that is "matched" to your barrel. It seems like from watching videos they just use a standard GO/NO gauge set of gauges and look for a bolt on the tighter end. The price jump is pretty high, barrel is already $389+199 for a JP bolt. $588.00 with my discount 15% off (First responder/military) it's $499. Seems like a bit of $$ for something that might not be an issue?

Checked the obvious things like loose barrel nut, shooter (myself) to rule out the obvious things. Let my buddy have a go, same result. Produces fantastic cold bore shots.. then with different strings, POI go will from center mass, 3 o' clock, then 1". It's kinda of a head scratcher.

on my 16 " Recce" build with a Criteron Core I'm using a standard Toolcraft BCG with good results. Seems much more consistent. I attribute that to the Criterion barrel and also being 223.

Thoughts?

 

[bfoosh006]

Is it worth it ?... if you want to hedge your bets towards accuracy, yes, I think it is worth it.
And match ammo isn't cheap. You could spend that 200 bucks on ammo, just trying to make a barrel shoot to your desired results.

I would suggest you lap the upper receiver face true, and shim / loctite in the new Criterion barrel.
I have had good results True and Gluing barrels in.
Part 3 of the video series ... about the 50 second mark.

 

[redneckbmxer24]

Yes. You’re not just paying $200 to get a headspaced bolt, you’re getting the best bolt money can buy too.

 

[muad]

The only time I ever did this was with my 20" Lothar Walther Varmint Tactical barrel (.223 Wylde chamber). I'm not sure if the "matched" bolt made the difference or not, but this has been the most precise barrel I have ever owned in the AR platform - and I've owned a lot of "big" names (Krieger, LaRue, White Oak, etc.)

This rifle was built as a precision hunting rig for "longer" range varmints (~400y max), and it was used as my test rig when I was doing ammo evaluations (aka Range Reports).

That all said, I've built dozens of other ARs that were plenty precise using high quality, non-matched components.

I'll agree with the above, if you're trying to gain every advantage in a precision rig, a matched bolt seems to add value.

What would be interesting is to buy the matched bolt, shoot some groups, then swap in another new bolt and see if there is a measurable difference - down range that is.

 

[Rocketvapor]

Measure your bolt.
LUG length minus FACE depth.

 

[supercorndogs]

Do you reload or shoot factory ammo? I wouldn't because I headspace my ammo to my rifle. If you shoot factory ammo I am still not sure I think tightening up headspace .001 or .003 is going to make much diffrence. Not as much diffrence as buying quality parts anyway.

 

[whatsupdoc]

JP bolt is no better than a Toolcraft or RCA bolt.

Never tested the difference in a large frame AR but on a very accurate small frame AR with a heavy Kreiger barrel
i swapped between a JP bolt and a Colt bolt and there was ZERO difference in 100 yard group sizes.

 

[hlee]

A complete JP 308 enhanced high pressure bolt (no carrier) has a msrp of $228.95. Criterion isn’t exactly trying to screw you on it…

 

[Redlion]

I am very satisfied with my 18" Criterion 6.5 Grendel barrel with matching JP bolt. I would recommend.

 

[Cascade Hemi]

Headspace does not effect accuracy. Tight headspace does not increase accuracy. You can headspace your own bolts with a set of gages. I like JP bolts, I wouldn't pay someone to headspace a bolt to a barrel.

 

[themightytimmah]

For peak accuracy, that $200 is better spent elsewhere. I’ve seen triggers, stocks and barrels do more to improve practical accuracy than anything else.

ARs are hard to hold and shoot compared to a bolt gun and mechanical accuracy (those great groups people post online usually come off a rest) often takes a back step to real world accuracy when shot prone or off a bipod.

 

[Ernest 5.56]

I was looking at buying a Criterion M118LR hybrid barrel for my 20" Aero M5 308, right now it has the factory 416R stainless steel barrel which isn't very consistent. (Great cold bore shots, but when it heats up POI shifts to 3-4 MOA with match ammo FGM 168grs @ 100 yards) I know Criterion offers a headspaced bolt with their barrels, just wondering if it's worth it? From my understanding is they look for a bolt like a JP that is "matched" to your barrel. It seems like from watching videos they just use a standard GO/NO gauge set of gauges and look for a bolt on the tighter end. The price jump is pretty high, barrel is already $389+199 for a JP bolt. $588.00 with my discount 15% off (First responder/military) it's $499. Seems like a bit of $$ for something that might not be an issue?

Checked the obvious things like loose barrel nut, shooter (myself) to rule out the obvious things. Let my buddy have a go, same result. Produces fantastic cold bore shots.. then with different strings, POI go will from center mass, 3 o' clock, then 1". It's kinda of a head scratcher.

on my 16 " Recce" build with a Criteron Core I'm using a standard Toolcraft BCG with good results. Seems much more consistent. I attribute that to the Criterion barrel and also being 223.

Thoughts?

Here is some info that might help with what you are trying to accomplish. It's definitely not a bad thing to have a high quality Bolt. A lot of companies recommend JP It might be worth asking criterion and see why they recommend JP. As far as I know proof does as well.

The Ultra-Accurate AR — Secrets of AR Accuracy Revealed « Daily Bulletin

In our Shooters' Forum, one member recently asked: What makes an AR accurate? What parts on an AR can really affect accuracy -- such as free-floating handguards, barrels, bolts, bolt carriers? He wanted an honest, well-informed answer, not just sales pitches.

bulletin.accurateshooter.com

10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually re-formed in a non-consistent way, as they are loaded into the chamber.

 

[Cascade Hemi]

Here is some info that might help with what you are trying to accomplish. It's definitely not a bad thing to have a high quality Bolt. A lot of companies recommend JP It might be worth asking criterion and see why they recommend JP. As far as I know proof does as well.

The Ultra-Accurate AR — Secrets of AR Accuracy Revealed « Daily Bulletin

In our Shooters' Forum, one member recently asked: What makes an AR accurate? What parts on an AR can really affect accuracy -- such as free-floating handguards, barrels, bolts, bolt carriers? He wanted an honest, well-informed answer, not just sales pitches.

bulletin.accurateshooter.com

10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually re-formed in a non-consistent way, as they are loaded into the chamber.

Your bolt and barrel extension will never have .015" of forward gap with a loaded cartridge in the chamber.

 

[jthor]

For accuracy, I personally believe so.
Do you intend on shooting M118LR out of if?
Just curious. I just did a bunch of experimenting with M118LR to make it shoot better.

 

[AR shooter]

I can't say that it will help. I have a 204 Shilen with a head spaced bolt and it does real good. I've also built a dozen from 308 to 224 Valkyrie and used Tool Craft or Brownells bolts that shoot just as good. I'm thinking about a 7mm 08 and might try X caliber. They don't guarantee accuracy without a head spaced bolt. That makes me a little nervous.

 

[Rocketvapor]

I think you can send them YOUR bolt.

OR use the measurements from your AR-15 bolt.

Just tell them you have a 0.154" headspace bolt.

What's the Headspace for a JP bolt?

 

[Ernest 5.56]

https://criterionbarrels.com/media/what-is-headspace-and-why-should-it-be-checked/?v=7516fd43adaa#:~:text=Not%20only%20is%20headspace%20essential,levels%2C%20or%20failure%20to%20function.

 

[_Will_]

Do you reload or shoot factory ammo? I wouldn't because I headspace my ammo to my rifle. If you shoot factory ammo I am still not sure I think tightening up headspace .001 or .003 is going to make much diffrence. Not as much diffrence as buying quality parts anyway.

Typically reload on my Hornady Lock n Load. Shooting 168 HPBT or 175s.

 

[_Will_]

For accuracy, I personally believe so.
Do you intend on shooting M118LR out of if?
Just curious. I just did a bunch of experimenting with M118LR to make it shoot better.

I doubt i'll be shooting M118LR out of it, I mainly roll my own " match grade loads" using 168 HPBT's or 175's ELD's. Isn't the M118LR just a longer throat for longer to accommodate 175 grs?

 

[ThicketCricket]

For accuracy, I personally believe so.
Do you intend on shooting M118LR out of if?
Just curious. I just did a bunch of experimenting with M118LR to make it shoot better.

Find anything interesting? I shoot a lot of m118lr. I got an aero m5 upper and proof barrel with a similar issue. Cold it shoots lights out then heats up and spreads out. I shimmed and thermal fit the barrel too.

 

[jthor]

Find anything interesting? I shoot a lot of m118lr. I got an aero m5 upper and proof barrel with a similar issue. Cold it shoots lights out then heats up and spreads out. I shimmed and thermal fit the barrel too.

Can’t really do anything about the temp sensitive RL15 it has in it, Mk316 fixed that issue.
I wrote a whole write up and AAR on it for the Air Force Rifle Team, but M118LR is super inconsistent in seating depths, at least the military M118LR is. You gotta uniform the seating depths which will also crack the tar seal on them.

I’ve cracked the seals on them in the past to make them somewhat decent by seating them .010” deeper. However, with this last lot/can I was measuring BTO on every round and noticed there were 2 different lots of 175s used.

BTO
Lot 1 would measure: 2.123”-2.108”
Lot 2 would measure: 2.102”-2.096”
so that was an ES of .027”

Once separated and seated separately their BTO measurements were within .002” of each other when I was measuring every 20 or so rounds. I chose a seating BTO, in my case of 2.086”, so I was at least seating the shortest rounds by .010” to break the tar seal on it.

This is on my 308 trainer with a 26” barrel. Previously I was getting ES’s of almost 60 FPS. So going forward I’m measuring every rounds and matching sure seating depths are uniformed

 

[ThicketCricket]

Very interesting and good to know. Much appreciated!