Practical Limitations of Variants

[keystone183]

Ok, so we all know that the gredel was designed with the compound throat to be able to shoot a variety of bullet weights. I know this may have been covered before but wading through the mass of discussions on the topic is daunting and this might help some others as well.

What do you give up in some of the variant chambers? I believe the GII enables you to shoot a longer bullet, but doesn't shoot the lighter ones as well? My main area of interest is the 264LBC and peoples experiences reloading both the lights and heavies. But having an idea of what each one does well, and not so well, would probably be very helpful.

[JASmith]

I understand there is not that much difference between the GII and the LBC chambers except for one has a slightly longer throat.

My sense is that most of these chambers shoot well enough for medium game out to 300 yards.

The chambers tend to sort out a bit only when one gets serious about accuracy with a particular bullet.

[sneaky one]

It's all up to the safe load data charts- use them as a start point. Use the oal device of your choice to check the jump to the Contact point.,, whether it be a compound throat or not- One must know where the bullet contacts the Lands, Lads! Oal's mean a Lot.

Yes, which bullets are you most interested in? We all can help you on a pathway -then.

Measurements are key on this pathway... Need to know all specs. to the rifling ,throats are so in different-

[Tamarac]

I too am interested in this. I just literally ordered a Grendel 2 barrel from Satern because of what I believed to be a longer throat. I'd like to load 123 gr SMK's and I'm more than willing to load them single shot, but yeah, I'm an accuracy geek.

[65Whelen]

The reason there a mountain of discussion is because there is no easy answer. No one size fits all. One thing I have found there is a lot of variation of free bore from barrel to barrel. I just finished measuring four different barrels from four different barrel makers and they had .160 difference of free bore from shortest to longest throat(with the Hornady 123 SST).

As Sneaky recommended, when you get your barrel, measure the chamber throat using the bullet or bullets you're going to use and seat to the appropriate COL. Finding the bullet weight that is most accurate in your rifle is trial and error. Lots of variables to work through: bullet manf., bullet weights, how much free-bore jump, powders, primers, brass, to mention a few.

I guess I wouldn't get all caught up in the general discussions. Get your barrel, measure it, decide what you want out of it. Then you can ask some specific questions that someone here probably has some first hand experience. JMHO

[LRRPF52]

The Grendel SAAMI chamber has been described as a machine gun chamber that will shoot with exceptional accuracy.

Sure, you can get every projectile to shoot well from any of the chambers with the right seating depth, but magazine feeding then become another affair, and a single load one when you have insane amounts of jump.

Benefits of the SAAMI chamber are numerous. The difficult part of it is on the manufacturing end, where a barrel smith or rifle builder really needs to pay close attention to what is going on with reamer life, but that should be the case with any reamer.

Any of the variant chambers will suffer from running the reamer ragged like any other chamber design, once you go below what will work with a SAAMI maximum cartridge.

We're seeing this throughout the industry in .308, .223, 5.56 NATO, you name it. If you have lazy people in charge of tooling and reaming, expect a lot of returns.

One of the main reasons we have variant chambers is because rifle builders didn't want to deal with licensing for Grendel reamers before the Grendel was a SAAMI certified cartridge, and the demand was such that rifle builders needed to respond to customer wants, so Les Baer did the .264 LBC-AR. You also had the Arne Brennan CSS chamber, which has a .295" neck versus .300".

In my own experience, as well as many others here, the SAAMI chamber just shoots no matter what bullet I load in it, from reasonable magazine COL's for the AR15, namely the 2.200-2.275" region. You don't want to start pushing much further than that since the AR15 magazine well itself is 2.395" without a magazine, and you need material to comprise the body of the magazine of course.

Production variances in magazines can't be held to extreme tolerances and be sold for under $20, so it makes zero sense to throat an AR15 for COL's much over 2.260" for factory ammo, and that's even pushing it when you look at 5.56 magazines and COL of that cartridge, which are shorter than 6.5 Grendel.

The Grendel is a very good balancing point at the end of the day, when looking at the constraints of the AR15 dimensions, while providing exceptional accuracy. Sure, you can throat a chamber so that you can load way out, but now we have a single-shot fed from a lead sled, which doesn't make a lot of sense if using the AR15 action.

The idea that a reamer should just be made with a longer throat so it lasts longer for production ignores things like the neck diameter, mouth location, side walls, etc. You have to replace reamers as a rifle builder, no matter what reamer you use. It doesn't make sense to cut corners in the mindset that you will get a few more barrels out of a reamer, when reamers cost $145, and that cost is distributed across ~200 barrels. You're talking about 72.5 cents per barrel.

As a customer, I'll spend that whopping 72.5 cents, plus inspection costs/skilled labor for a chamber done correctly, whether it's a .308 Winchester or a .223 Wylde. I don't want someone touching my barrel if their mind is nickel and diming the process to death like that.

The other thing is that if there is a chamber design for this cartridge, it was tested.

There is nothing inherently wrong with the .264 LBC-AR chamber, but it does have a tighter neck. There are pros and cons to a tighter neck. Most people who have the .264 LBC-AR chamber seem to be happy. The steel case might pose problems for some of the tight-necked chambers, since it has a coating and wider tolerances.

[danm]

One thing I can confirm is Wolf steel runs 100% in my .264 LBC.

[bwaites]

One thing I can confirm is Wolf steel runs 100% in my .264 LBC.

Who built it?

[danm]

Who built it?

Me and my gunsmith friend, Don Wood from Lewiston Idaho... 18" BHW 1:9"...

[bwaites]

Its a Black Hole barrel? That explains some things. They do a very good job with their barrels. They run a true .264 LBC reamer, at least from what my discussions with them led me to believe. Not everyone actually has one, there are multiple variants.

[LRRPF52]

Most people don't realize that the .264 LBC-AR is a specific chamber Les Baer had made for him, while many chambers are unknown with ".264 LBC" stamped on the barrel.

As long as someone knew what they were doing when they designed the reamer, and the smith cut the chamber correctly, if the reamer was meant to feed factory ammo, it is usually fine.

There are some custom chamber variants meant for bolt guns or specific loads that may or may not digest certain factory offerings.

I personally just get barrels from reputable sources, and companies that back up their products 100%. I then verify each chamber as to what it will actually do, I don't care if it comes from AA, PF, Brownell's, Lilja, doesn't matter, I'm checking where my seating depths are, and if factory ammo will chamber fully, then extract with minimal effort.

[danm]

Its a Black Hole barrel? That explains some things. They do a very good job with their barrels. They run a true .264 LBC reamer, at least from what my discussions with them led me to believe. Not everyone actually has one, there are multiple variants.

My first BHW barrel was for my .223 Wylde build and I loved it so when I built a 'Grendel' I went with them again... Weird, love it too!