Type 1 or type 2 bolts

[R Johnson]

What are the advantages of one over the other?

[KentuckyBuddha]

http://www.youtube.com/watch?v=DZncepUMgBg#t=23

[LRRPF52]

What are the advantages of one over the other?

The terms "Type I" and "Type II" are to my knowledge a creation of BHW to help them determine the difference between .124" bolt face recess, and .136" recess.

When Alexander Arms did the engineering for the bolts, there was actually some precedent for a bolt design based on the 7.62x39 cartridge, and that was done by Colt with the 7.62x39 Sporter II in the 1980's. Colt's engineers and R&D department (the most knowledgeable ones on the AR-15), decided to approach the thicker extractor rim with a deeper bolt face depth, since compromising on the extractor wouldn't help matters any. That is the advantage to the deeper bolt face depth.

The challenge then becomes ensuring that the reduced mass of the bolt between the face and the walls is strong enough for a durable part meant for use in a self-loading rifle, but the 7.62x39 is a cartridge that doesn't reach 5.56x45 pressures, so it is doable.

Other manufacturers in the industry have just gone with a .124" bolt face recess on after-market (non-Colt) 7.62x39 guns, and the trail of broken extractors is lengthy. Some people are able to get away with it, but many have proven susceptible to snapping off at the extractor claw, especially in 7.62x39 AR-15's that are run hard with a diet of steel-cased Russian ammo.

[GLShooter]

So basically it is all semantics on the TYPE I vs the 7.62X39? Since BHW standard 264 LBC is now the deeper Type II all should be well in the neighborhood. I did see where the Model 1 version is using the original 7.62X39 bolt so I guess the differentiation is still needed to some extent. I have seen Grendel variants using both sizes on the market. I suspect that consistency could be an issue and if a fellow had a batch of the 7.62 bolt head chambered rifles he might want to simplify his parts supply and stick with the 7.62 size vs going to the deeper improved offerings.

Ona side note I have an OLD, 1990's era, Olympic Arms 7.62 bolt that is 0.137 in depth. Now that was a shocker when I measured it!! LOL

Greg

[LRRPF52]

The original 7.62x39 bolt is the Colt, and the only way to tell if someone followed that work is if they copied their bolt face depth and used a similar extractor.

The only easily-identified standard among 7.62x39 and 6.5 Grendel bolts is the .136" Grendel bolt face. It makes replacement or sourcing of bolts easy when everyone is on the same sheet, but when you get into variant calibers in the AR15, there doesn't seem to be any binding set of conditions like we generally see with the 5.56 NATO guns.

[GLShooter]

The original 7.62x39 bolt is the Colt, and the only way to tell if someone followed that work is if they copied their bolt face depth and used a similar extractor.

The only easily-identified standard among 7.62x39 and 6.5 Grendel bolts is the .136" Grendel bolt face.

Kind of what I figured. I know that Satern was offering bolts of both depths last year.

Greg

[R Johnson]

So has Bill Alexander ever offered a Grendel with a .125 bolt?

[bwaites]

So has Bill Alexander ever offered a Grendel with a .125 bolt?

No, the bolt was actually developed for the Beowulf, long before the Grendel was developed. AA has never used the shallower bolt. However, there were some early CSS rifles that may have used them.

[Bronz]

So just to be sure. If I have a Saber upper I woukd need an type 1 AA bolt and/ or a AA Heavy Use bolt.

[LRRPF52]

AA doesn't have a "Type I" bolt. They have made bolts with a deeper face from the start, at .136". BHW refers to .124" depth bolts as "Type I", even though the industry precedent for 7.62x39 is a deeper bolt face.

[GLShooter]

So just to be sure. If I have a Saber upper I woukd need an type 1 AA bolt and/ or a AA Heavy Use bolt.

Yes the AA bolt will meet your needs if your upper is a Grendel. It will have the deeper bolt face not the 0.124/.0.125 of the others.

Greg