Originally Posted By: SnowmanMoHaving talked with Bill Alexander about his Grendel at the SHOT show, I might be bale to shed some light on this. By the way, he was very generous with his time and information to a young gun builder.
First of all, there is no such thing as Grendel I and Grendel II. When Bill Alexander submitted his print to SAAMI he had every intent of releasing the print to the public when SAAMI approved it. Somehow, that original print got out to the public. But the print had an error. When Mr. Alexander realized the error, he resubmitted the corrected print. But it was too late to put the genie back in the bottle. Now true to his word, Mr. Alexander did release the print to the public but it was too late.
Many of the manufacturers who got their hands on the first print, found that they had to use a 7.62x39mm bolt to work on their barrels. When you use an actual Grendel bolt, it is common to shear the lugs off of the bolt. This appears to be because the extra headspace allows the bolt to move rearward, gaining momentum and shearing off the lugs.
There is a go-no-go gauge that you can use to see what dimensions your barrel has been cut to. You can also use a cartridge and a disassembled bolt to see if you have a mix and match situation. Take your bolt down, pulling out the extractor and ejector, and drop a cartridge into the chamber and see if your bolt will drop in and that you are able to close it with a bit of drag. If it will not close you have the wrong combo. If it will close and rattle, you have the wrong combo.
So, as many of the other guys have previously stated, you might be best off buying the bolt with the barrel.
Hope the info helps.
There is no doubt that Bill Alexander is the authority on all things Grendel.
However, there may not "technically" be a Grendel I and Grendel II, there is a Type I bolt and a type II bolt in Grendel's history.
A Type I bolt, also known as the 7.62×39 bolt, has a bolt face depth of . 125” and is used with some Grendel variants. The Type II bolt is the bolt originally designed for the 6.5 Grendel and has a bolt face depth of . 136”