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It's a Grendel SAAMI chamber or its 264 LBC, Grendel II, etc. Any but the Grendel SAAMI chamber may use Grendel bolts or the .125 face depth bolts depending on how the manufacturer headspaced the chamber. Type I and Type II is an artificial construct started by Black Hole to distinguish between the .125 (Type I) and the .136 (SAAMI Grendel or Type II) in their nomenclature.
I am trying to confirm my Doubelstar barrel and bolt listed as "6.5 Grendel Type II" is the same as my Wolf Precision/Anderson upper with a supposed SAAMI .135 Bolt (lol) are the same spec. Or at least close enough to swap bolts and the like without fear of malfunction or worse.
I am trying to confirm my Doubelstar barrel and bolt listed as "6.5 Grendel Type II" is the same as my Wolf Precision/Anderson upper with a supposed SAAMI .135 Bolt (lol) are the same spec. Or at least close enough to swap bolts and the like without fear of malfunction or worse.
Bottom line, TNV: If it says "Grendel Type II", the odds are very high that it is not a SAAMI Grendel chamber. What you have there is essentially a .264 LBC with a wider throat. The Grendel II, and other variants like it, are reamed without the signature compound throat of the SAAMI Grendel.
Try not to confuse this with the term "Type I" or "Type II". As bwaites described above, that only refers to the bolts.
Irrespective of the chamber, though, you can use a caliper to measure the bolt face depth to see if both of your bolts are at .136" or at .125".
If it's true that we are here to help others, then what exactly are the others here for?
Bottom line, TNV: If it says "Grendel Type II", the odds are very high that it is not a SAAMI Grendel chamber. What you have there is essentially a .264 LBC with a wider throat. The Grendel II, and other variants like it, are reamed without the signature compound throat of the SAAMI Grendel.
Try not to confuse this with the term "Type I" or "Type II". As bwaites described above, that only refers to the bolts.
Irrespective of the chamber, though, you can use a caliper to measure the bolt face depth to see if both of your bolts are at .136" or at .125".
Ahhh now I think I get it. Never realized there was a difference in the chamber as well.
So, basically, even if the bolt face is the same on both bolts, one still has to worry about the chamber and headspace issues?
Chambering determines what chamber it has, and however the person reaming wants to set up bolt face depth is up to them.
I don't know of anyone who chambers SAAMI and uses a shallow bolt face depth where there isn't enough extractor lip mass, but you could do it.
I personally only look for manufacturers who use a SAAMI chamber with a Grendel bolt, the face depth being only one of many differences that separate Grendel bolts from others. There is also:
* Bolt length (Grendel bolts are longer than 5.56 bolts.)
* Extractor pin hole location
* Extractor shelf dimensions
* Metallurgy and processes
* Extractor metallurgy, processes, and dimensions
A manufacturer would be better off dropping any mentioning of confusing and undefined terms like "Type I" or "Type II". It makes it difficult for customers to understand what is even going on, especially since there are literally zero industry standards for those terms, whereas there is an industry standard for SAAMI and what has been tested extensively to work with 6.5 Grendel in the AR15.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
Chambering determines what chamber it has, and however the person reaming wants to set up bolt face depth is up to them.
I don't know of anyone who chambers SAAMI and uses a shallow bolt face depth where there isn't enough extractor lip mass, but you could do it.
I personally only look for manufacturers who use a SAAMI chamber with a Grendel bolt, the face depth being only one of many differences that separate Grendel bolts from others. There is also:
* Bolt length (Grendel bolts are longer than 5.56 bolts.)
* Extractor pin hole location
* Extractor shelf dimensions
* Metallurgy and processes
* Extractor metallurgy, processes, and dimensions
A manufacturer would be better off dropping any mentioning of confusing and undefined terms like "Type I" or "Type II". It makes it difficult for customers to understand what is even going on, especially since there are literally zero industry standards for those terms, whereas there is an industry standard for SAAMI and what has been tested extensively to work with 6.5 Grendel in the AR15.
Thanks for the information, as a newbie to the Grendel world this is good to know. Of the five items you listed, what should a new person should be looking for? Are there measurements or locations that I need to know.
Grendel bolt length is 2.810"
Face depth is .136" (-.003" allowable)
Metallurgy is guarded by different vendors, but generally a certain type of 9310 alloy with certain heat treatments, shot peening, MPI, destructive testing of a certain % per batch.
There is nothing the consumer can really do other than check 2 of these dims, so it's best to source parts from reputable manufacturers and brands.
Nobody has done more testing than AA, and AA tests things that most 5.56 manufacturers aren't even aware of, since 5.56 is so well-vetted over the last 6 decades.
We've had some vendors that entered the market with really good bolts, then on subsequent production batches, something dropped in QC or specs and they no longer were holding up, especially looking at bolts and extractors.
I know AA works hard to maintain their standards with bolts and extractors, which is an endless battle with machine shops, kilns, and finishers.
The AA Hard Use bolt has a totally different surface treatment than most bolts on the market, as well as some external features that distinguish it from the rest.
I've had zero problems with standard AA bolts over the years, running thousands of rounds on them.
I'm also having no problems with the first batch of Underground Tactical bolts that PF used, with their own sources extractors that were nitrided, but it appears that something changed for the worse with Underground. Don't know what happened, but such is life.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
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