Not trying to start a fight....

[BluntForceTrauma]

While the 6.5 Grendel has the SAAMI 6.5 Grendel, 6.5 CSS, 264 LBC, 6.5 PPCX, 6.5 BPC and maybe more chambers now.

There is only one 6.5 Grendel chamber, particularly for newbies: the SAAMI 6.5 Grendel.

As with any cartridge, all other chambers are wildcats and you should know why you want it and what you're getting into before you go down that road.

So let there be no confusion.

[Sticks]

So where does the .125 and .136 bolt face come into this - I still see that as an option among the various barrel/upper manufacturers.

[1075 tech]

So where does the .125 and .136 bolt face come into this - I still see that as an option among the various barrel/upper manufacturers.

See Post #27 on the previous page. Paul talks a little about bolt development. My (limited) understanding is that the .136 bolt face was designed to give the extractor more strength. Less prone to breakage.

[1075 tech]

After reading all this, and many other threads here, I am glad that I chose the Grendel. A couple of years ago, I had only heard of the Grendel from a passing mention of it when my brother was talking about his 260 bolt gun. I had my LR-308 and a 5.56. I wanted another AR-15 platform but was undecided on caliber. The 308 was too heavy for hunting, obnoxiously loud, and my older shoulders just didn't like getting punched any more.

The 5.56 was fun to shoot, but I wanted something with more punch for hunting. I mentioned to a guy at my LGS about wanting something better than 5.56 and was thinking about 300 AAC or 6.8. He suggested I look at the Grendel.

I came across this forum while doing a little research. I joined the forum and haven't looked back. Sold the 308, and have 2 Grendels.

[BluntForceTrauma]

So where does the .125 and .136 bolt face come into this

The short answer is that 0.125 bolts, sharing the same boltface depth and extractors as standard 5.56 bolts while only increasing the inside diameter, are a shortcut for those who can't be bothered to do the proper engineering a bolt for the 7.62x39/65G case rim requires.

The 7.62/65G rim is thicker. This is because the combat lineage of the cartridge called for a thicker rim to grip as a reliability feature for the relatively violent extraction of the AK.

To account for this in an AR where the 5.56 has a thinner rim (this can be seen by studying SAAMI drawings or looking at the actual cases) one can either eat into the meat of the extractor hook, or deepen the boltface depth by a corresponding amount.

[Mike Wood]

Thanks for the info BFT, 1075, LRPF, etc. Good to read

[ahillock]

This photo is from one of the proponents. Notice anything?

Yeah, why does the 6.8 get fancy ballistic tip while the others are FMJ? The testing couldn't have been this lopsided, could it?

[JASmith]

It does seem curious -- especially since tipped bullets and match hollow points were available for all the calibers mentioned. The only one I would have hesitated on is the .277-6.8 back when the cartridge was developed and initislly hyped, but it is there in the picture.

[LRRPF52]

Yeah, why does the 6.8 get fancy ballistic tip while the others are FMJ? The testing couldn't have been this lopsided, could it?

In that photo, you actually have SMKs in the 6mm, 6.5mm (a moly coated SMK), a VMAX varmint rapid expansion bullet in the 6.8, I think they used a 110gr 7mm TNT, and a 125gr in the .30 cal variant. It's been a while since I've read the details on the different projectiles used in the 7mm and .30 bore experiments.

The rigging of the tests and attempts to pull the wool over the eyes of ballisticians who had decades of experience in the business went over predictably though, and from the start, they ignored the AMU Commander's attempts to provide them with the optimal caliber studies documentation and results. It was a very amateur effort from the start, that ballooned out of control at an opportune time during the kick-off of GWOT.

It would have been a great little cartridge in .257 bore. The 6mm is nice too. Once you get above there, you run out of room for decent ogive length, as you can see in the photos.

[stanc]

Yeah, why does the 6.8 get fancy ballistic tip while the others are FMJ? The testing couldn't have been this lopsided, could it?

It does seem curious -- especially since tipped bullets and match hollow points were available for all the calibers mentioned. The only one I would have hesitated on is the .277-6.8 back when the cartridge was developed and initislly hyped, but it is there in the picture.

There were more than one series of tests done, from the initial development of SPC variants, up through later evaluations by law enforcement and military.

- There is nothing in that photo which tells us when the photo was taken.
- There is nothing in that photo which tells us if the bullets which are shown were of the types that were used in any test series, or which test series they were used in.

I was privy to some of the e-mails between Murray and Holland. My recollection is that tests of the 6mm through 7.62mm SPC candidates were done with Sierra MatchKings in all calibers, with the Hornady 115gr BTHP being developed after 6.8mm had been selected as the optimum choice.

The 110gr VMAX was created at an even later date, and did not exist during the development testing that led to selection of 6.8mm for the Special Purpose Cartridge. Therefore, it could not have been used in testing to determine which caliber would be chosen for the SPC.

[LRRPF52]

There were more than one series of tests done, from the initial development of SPC variants, up through later evaluations by law enforcement and military.

- There is nothing in that photo which tells us when the photo was taken.
- There is nothing in that photo which tells us if the bullets which are shown were of the types that were used in any test series, or which test series they were used in.

I was privy to some of the e-mails between Murray and Holland. My recollection is that tests of the 6mm through 7.62mm SPC candidates were done with Sierra MatchKings in all calibers, with the Hornady 115gr BTHP being developed after 6.8mm had been selected as the optimum choice.

The 110gr VMAX was created at an even later date, and did not exist during the development testing that led to selection of 6.8mm for the Special Purpose Cartridge. Therefore, it could not have been used in testing to determine which caliber would be chosen for the SPC.

They submitted a varmint bullet to the FBI Ballistics lab and called it an OTM. FBI Head ballistician was not impressed.

The lightest 7mm SMK available is the 168gr .284 SMK. I don't recall them loading that heavy of a bullet in the 7mm, although I do remember the claim that SMKs were used across the board. The lightest .277 SMK is a 135gr, and that was not submitted to the FBI lab. In fact, it ticked the FBI lab off so much, they said there was no way that cartridge would ever be signed off on for domestic LE use in the US.

There are other events that happened that I won't discuss in the open as a professional courtesy to those involved, but it was really, really bad.

[stanc]

They submitted a varmint bullet to the FBI Ballistics lab and called it an OTM. FBI Head ballistician was not impressed.

The lightest 7mm SMK available is the 168gr .284 SMK. I don't recall them loading that heavy of a bullet in the 7mm, although I do remember the claim that SMKs were used across the board.

Actually, the lightest 7mm SMK available is 130gr. https://www.sierrabullets.com/store/...HPBT-MatchKing

However, that's unimportant. Murray and Holland were not restricted to bullets which were available COTS. Since the 115gr SMK was custom made for the 6.8mm version of the SPC, I see no reason to think that Sierra would not also have made SMKs of appropriate weight and dimensions for the 6mm, 6.5mm, 7mm, and 7.62mm SPC candidates.

There seems to be two issues being conflated in this thread: The bullets used in 6/6.5/6.8/7/7.62 SPC development and testing, and the bullet(s) used in later tests of 6.8 SPC by law enforcement. The photo you posted is at least partly responsible for the confusion, because it shows a bullet (the .277 110gr VMAX) which did not exist during the time period that the different caliber versions of the SPC were developed.

[ahillock]

In LRRPF52 we trust.