Who actually uses the SAAMI reamer on AR barrels?

[LRRPF52]

The SAAMI chamber is designed to handle a wide range of different 6.5mm projectile shapes and lengths considering the AR15 magazine well limitations on COL, and the resultant jump to the lands if you use long VLD bullets with a conventional chamber that was also meant to handle short tangent type bullets.

It does that extremely well, and we see this consistent behavior moving forward. Think of it like this...

If I wanted to shoot a 95gr varmint bullet loaded out as long as possible for the AR15 mag well, the throat would have to be set up for that.

Now let's say I want to shoot a 123gr Scenar, with a very Secant ogive with a long nose to it, the jump to the lands would be very long, and accuracy would likely suffer. What if there was a way to have both? That's what $10,000 in reamers and relentless Research, Development, Test, and Evaluation resulted in: a compound throat that will handle extreme ranges in projectile shape.

This is a particularly important issue with the 6.5mm from a short case in the AR15 running at sustainable pressures. A lot of other cartridges have much shorter ogives and little COL variance with a fairly standard ogive profiles and lengths. With most 6.5mm's, even dating to the late 1800's, we see an unusually long projection of the bullet from the case. This is true with the 6.5x55 Mauser, 6.5x54 Mannlicher-S, and the 6.5x52 Carcano.




6mm Lee Navy, 6.5mm Arisaka, 6.5mm Carcano, 6.5x54 Mannlicher-Schönauer, 6.5x54R Mannlicher, 6.5x55 Mauser (first 6 left to right).

Those legacy cartridges had a lot to do with driving the types of projectiles that were made for the 6.5mm bore of course, and the unusually high SD's and BC's of the 6.5mm attracted the more perceptive shooters and hunters to them. With around 150 different 6.5mm projectiles already out there, the shortest possible case with the most case capacity that would still fit in the AR15 and stagger in a magazine seemed like a promising idea.

To capitalize on the wide range of bullets that would naturally attract everyone from varmint slayers to competitive shooters, and medium game hunters in between, the challenge was really about finding a throat that could step up to the task, without having to deeply seat one type of bullet in the case as much. After lots of hair-pulling, frustration, testing, more testing, and thoughts of ditching the whole matter entirely, the compound angle became the solution, and it worked very well.

In my personal shooting and hand loading with this cartridge, I have seen consistent performance no matter what bullet type I shoot through it, ranging from 90gr TNT, to 129gr SST, and a lot of bullets in between. While those of us who are working on new projectiles being introduced to the market work up and test loads, we continue to see the same type of exceptional accuracy performance, which is a testament to the success of the compound throat design.

Yes, you can get excellent results with other chambers that work really well with certain projectiles seated to depths appropriate for those projectiles. The .264 LBC-AR is an example of that, and was designed around the 123gr SMK loaded to reasonable Grendel magazine allowable COL. The neck is a little tighter at .295", and not as forgiving as the Grendel's .300" throat when it comes to fouling and neck variations, but the guns shoot well if built by someone who knows what they are doing.

My .260 Remington has a custom throat for Scenar and VLD profile bullets loaded from an SR25 magazine, and it shoots them amazingly well as it was designed at 2.800" COL. It hasn't, and never will see a single round of factory ammunition because most of the lighter and 120gr hunting bullets, or older target bullets with tangent ogives will jam into the rifling and spike the pressure.

I had a .308 AR10 built the same way, with the 155gr Scenar specifically in mind. Any other factory ammo will pierce or blow primers, and bullets get pulled when trying to manually extract an unfired cartridge.

Since the SAAMI compound throat reamer has the double angle to the throat, it takes a sense of attention-to-detail and pride in one's work as a rifle builder to maintain accountability of what is going on with the reamer, but that is true of many chamberings, .223 vs. 5.56 for example, or any of the .308 and 7.62 NATO variants, and back to the .260 Remington or 6.5 Creedmoor.

If you are mass volume manufacturer who makes money off of volume and lower quality, then we're already talking about a product that needs a dedicated call center with customer service reps ready to handle upset patrons who are having problem after problem with just their worn reamer-cut 5.56 and 7.62 NATO barrels. Several companies come to mind, but none of them have the call center.

So the idea that this is something particular to the 6.5 Grendel has not been my experience at all with almost every caliber of rifle I have. What I have seen with off-the-shelf guns over the years is that headspace is rarely correct, concentricity is absent, threads and shoulders are not true, chambers don't match what's listed on the barrel or receiver (.223 vs. 5.56 especially), and other basic errors are commonly present. We're in a rare time in history with increasing demand for just the basic specs to be correct, while capacity of the industry to deliver that is diminishing, no matter what caliber or product you are looking at.