Grendel II chamber

[45r]

The throat on the Grendel has a very slight taper of .2644 down to .2617 for a distance of .1547 and then another very slight taper for a distance of .1088.
The 264LBC reamer and other type reamers like it the front leading edge is doing all the cutting for the most part and if it wears down a little it doesn't make much difference.
A lot longer length is cutting the throat on a Grendel reamer.
It wears down faster and with the taper being .0027 deep(that's less than .0014 on each side) it doesn't cut the throat long enough and you end up with a shorter than normal throat.
The compound throat should be perfectly centered to get the benefit of centering the bullet in the cone.
The 264LBC type reamers are a cheaper way to cut barrel chambers since they are more tolerant with wearing out and being centered in the bore.
Both types can be accurate.
The Grendel is better for 85 to 123 grain bullets.
The Grendel reamers should not be used when they get worn out if you want to avoid short throats.
Worn reamers leave burrs on the downwind side of the lands a take a 100 to 200 rounds to smooth out the roughness.
The chamber cast picture of the Precision Firearms barrel shows what the Grendel throat looks like when done right.
If all Grendel chambers were cut like that barrel we would be happy I think.

[JASmith]

I disagree that the exact dimensions of the throat are part of the spec. When you have a custom rifle built and if the gunsmith is a good one they always want to chamber to a dummy round. this is so they can set the throat. The throat is cut in a separate process. lets go pull a ruger, remington and tikka rifle off the shelf, in 308 winchester. would you expect there to be the exact or close measurement base to lands on those different rifles off the shelf?? with the talk that is around here about sammi this and that why even bother to measure the others?!?!here is a link to the reamers gre tan rifles has on hand

http://www.gretanrifles.com/reamers.jsf

notice that all calibers have a neck diameter AND a throater you can spec in particular look at 6mm there are 3 different throats you can spec, with 6.5 there are 4 different choices in throat you can spec. Not all gunsmiths do it this way, for example a company like GAP rifles you must send or use one of their reamers which doesn't allow the neck and throat options, its fixed to whatever reamer that is because they do the whole thing in one process. things aren't always what they seem.

There is a lot wrong with this post -- and it shows either serious ignorance on the part of the poster or deliberate falsification.

Go here for the SAAMI spec: http://www.65grendel.com/forum/showt...endel-Drawings and you will see the throat is part of the specification.

Second, only some manufacturers use a separate throater. I have a reamer that does the complete chamber.

One problem with a separate throating operation is that one can get the throat off-center from the chamber, so not all barrel makers do that.

This poster has erroneously or falsely claimed that the throat is not part of the spec until he has become "blue in the throat." Is he a subscriber to the Goebbles doctrine that a lie repeated often enough becomes the truth?

[nincomp]

I have been away from the forum for a while and missed much of the bru-ha-ha about chamber issues. I know that people are rightfully upset about non-SAMMI chambers in their rifles. My question is : "How do they shoot." Are there any accuracy problems?

If this has already been answered, please send me the link.

[hidesert cowboy]

I've had 2 rifles built by GAP, both AR10's, and I was asked each time which bullet I would be shooting. With the .308 Winchester, I told them the 155gr Scenar, and they cut the throat to that bullet. With my .260 Remington, I told them the 139gr Scenar, 142gr SMK, and 140gr VLD. They cut each throat to the specific bullet ogive shapes I was planning to shoot, and both of those rifles shoot those bullets amazingly well. They are custom rifles with custom throats optimized for gas gun magzine-fed COL.

The Grendel SAAMI chamber is not a custom chamber. It's meant to address various bullet shapes at lower operating pressures, where you can't rely on 60,000psi to slam a VLD into the lands quickly like the .260 Remington does, with corresponding barrel life and weapon weight considerations.

The Grendel chamber really does handle a wide variety of projectile shapes well in extensive testing, as well as the customer pool. No matter what I load in mine, it shoots them consistently into ~ 1 MOA. Some are .79 MOA, while others 1.2 MOA like the 129gr SST, which is known to not shoot well in a lot of different chambers, whereas the new 123gr SST shoots amazingly well after Hornady upgraded their bullet-making equipment and reduced the jacket variance significantly, starting with the A-MAX line.

A lot of this is about egos getting in the way of providing a superior product to the customer in my opinion. Different makers can't check their egos at the door when they go to work, so the customer pays the price for it. Little do they know that they are just recreating chambers that didn't work well with a wide variety of projectile shapes when the Grendel was being tested.

For anyone to claim that their chamber will shoot better than the Grendel indicates that they have done more testing than the company that brought it to market, after a very strenuous testing regimen before releasing it to the customer. From that point, credibility goes downhill quickly.

If you look at the comparison that rick0shay posted above, a 2.350" COL can't be loaded in magazines anyway, so a single-loaded projectile that already fits well within the SAAMI Grendel will give you 30-50fps more MV if you single load it to 2.350". Just another attempt by the detractors of the Grendel to try to drag it down. They have found useful idiots who will believe their negativity, and wallow around in the mud together-relationships built on goals of ruining a fine product, and pull in totally new people to the AR15/hunting market who don't know the background.

What I would say to those who don't know the characters involved and the chips they bear on their shoulders against the Grendel is this:

Just enjoy the cartridge. If you have a variant chamber, there will be several of the over 100 projectiles available for 6.5mm that you will find that shoot well in your rifle when hand-loaded. Several of the factory loads should shoot well also. Just demand that factory ammo will feed and function safely in your chamber if you plan to shoot factory ammunition, which is something the Grendel was meant to do from the start.

A lot of this has to do with the frustration people feel when not able to shoot in the winter, and that is changing now for many with Spring coming. I feel for those of you who have been screwed over out of the performance I have personally enjoyed with my Grendel since 2009, which included reliability and accuracy-no issues or complaints. That's what is hard for me to see going on, when I know the potential of the system.

so the gap rifles you mentioned you still call them 308 and 260 but the throats are specific to the bullets you shoot are they not still 308 and 260 chamberings?? I am not defending liberty barrels in fact I returned my barrel for a shilen. The problem centered around not being able to chamber factory ammo and that is a valid problem.

[WildBill3/75]

I have been away from the forum for a while and missed much of the bru-ha-ha about chamber issues. I know that people are rightfully upset about non-SAMMI chambers in their rifles. My question is : "How do they shoot." Are there any accuracy problems?

If this has already been answered, please send me the link.

Mine shoots exceptionally well. Sucks to be limited in COAL though. my chamber measures around 2.230 with 123amax....so there is no way around jamming.

If you are talking about "Grendel II" I dunno nor do I want to personally find out.....264 LBC chambers from what I've seen shoot pretty good.

[bwaites]

so the gap rifles you mentioned you still call them 308 and 260 but the throats are specific to the bullets you shoot are they not still 308 and 260 chamberings?? I am not defending liberty barrels in fact I returned my barrel for a shilen. The problem centered around not being able to chamber factory ammo and that is a valid problem.

The problem is that if you buy a FACTORY standard .308 Winchester (to use the full name), you expect that it will function with ANY factory ammunition, and it will. Has anyone here ever heard of a rifle that did not do so?

When you order custom rifles, the fact that it is being made specifically for you allows you to customize the barrel to what you WANT, not what the standard is.

If the standard accepts all .308, then your rifle may or may not do so. (I've seen a few AR10's that were so loose they almost could have accepted a 30-06, it seemed!)

Is it still a .308, yes. Is it still a .308 Winchester, NO, most emphatically NO. It won't accept all the factory .308 Winchester out there, thus it is not a .308 Winchester. Anyone who sold such a rifle WITHOUT specifying the difference would be liable for whatever happened when someone shoehorned a factory round in there and had a "kaboom".

It's not about defending anyone, its about the standard that is the 6.5 Grendel. That standard calls for a very specific compound throat. If the chamber does not have that throat it is not a 6.5 Grendel, it is a variant, just like a .223 Wylde chamber is a varianat on the .223, or any of the .308 tight necked variants that precision shooters like.

[nincomp]

For what its worth, several years ago, Clymer Tools and Reamers had the dimensions of numerous SAAMI and wildcat reamers online. They clearly labeled each print as SAAMI or as a variation such as Palma chamber, etc. At least the person buying the reamer knew what they were getting.

[LRRPF52]

so the gap rifles you mentioned you still call them 308 and 260 but the throats are specific to the bullets you shoot are they not still 308 and 260 chamberings?? I am not defending liberty barrels in fact I returned my barrel for a shilen. The problem centered around not being able to chamber factory ammo and that is a valid problem.

The .308 AR10 I had built pulls 168gr and 167gr factory ammo, and dumps powder everywhere. If you light one off, it craters or blows the primers.

The .260 Rem will never see a factory round if I have anything to say about it. I only fire hand-loaded ammunition through my .260 Remington. Every .260 Rem gas gun I've seen, as well as 6.5 Creedmoors, spit out brass with either:

* ejector swipes
* thrashed extractor rims
* Cratered primers
* flattened primers
* pierced primers

Here is what JP has posted on their website about the .260 Rem in a gas gun:

You must find or load ammo that is compatible with the rifle, not expect that the rifle can be made compatible with the particular ammunition that you have chosen.

Every factory load I have shot through my 6.5 Grendel has fired, extracted, ejected, fed, and chambered correctly without these pressure signs, and it's fun to shoot. I honestly got into the Grendel thinking that I would only hand-load for it, but I ended up shooting a lot of factory ammunition in it from AA, Precision Firearms, and Hornady. What's not to like?

It makes it much easier for me to take it out shooting than my .260 Rem, which a very kind forum member has sent me an improved firing pin for to address primer piercing and cratering issues of the 60,000psi SAAMI .260 Rem. When you drive long bullets with slow powders and those pressures, and have a gap between the firing pin and the hole, the primer likes to fill in there. I've already bent & ruined at least 2 firing pin retaining pins with my .260 Remington AR10. Hopefully this new pin will solve the cratered primer issue.

When I describe the AR10's I have had custom built, I usually explain that the chambers were cut for specific bullet profiles. My .260 Rem will shoot all the bullets I had it throated for into very tight little clusters. Guess what? Trying to get the 140gr A-MAX to shoot that way has never worked, no matter what powder and combo I have tried. 139gr Scenars first 5rd group I ever shot looked like this:

[hm2 clark]

I Kinda understand that there is a difference between 5.56 and .223. Still, both chambers and bulllets will shoot in the guns I buy. Is that the kinda distenction we are drawing here?

[bwaites]

.223 chambers MAY exhibit high pressure signs with 5.56 ammo, which is loaded to higher pressures. The 5.56 chamber has significantly more leade than the .223, unless the .223 is a variant cut for long bullets. A .223 AR will often exhibit pressure signs with Black Hills 5.56 77gr ammo, for instance. Across the course shooters often have their ARs throated for longer bullets even than 77 grainers.

[LRRPF52]

.223 Remington is SAAMI MAP rated to 55,000psi, whereas 5.56 NATO is a 62,000psi cartridge and chamber. Two different animals from a pressure containment standpoint.

The original .222 Remington is rated to 50,000psi MAP, and that is what the AR15 was built around when it was just a prototype in Armalite's solicited development for the High Velocity Small Caliber Rifle contender for the Army.

[Tedward]

Then came Bill Wylde and improved the whole thing, right??

[bwaites]

You don't see Wylde chambers in target rifles, but its a great compromise in the AR.

[Tedward]

Yes I was referring to AR's, not a bolt gun. I have a Loather Walther Wylde and it shoots 1/2" groups all day. When I got my Loki, 556, it couldn't hold 1" groups at 75 yards and I was very disappointed in the AR platform. That is when I ventured into the Wylde and then was looking for another caliber. After lots of reading and this forums info, I picked the Grendel over the 6.8 and 300 BO. The Grendels accuracy and reach is where its at plus being able to hunt with it in VA.

This entire throat debate is the worse 3 months dealing with the Grendel I've had. I think there are a lot of questions, or was, and asking unknown questions makes answers and responses seem so defensive like some people are trying to hurt the cartridge and I really don't think that is anyone's intentions, or at least mine.

[nincomp]

NOTE: I started this post several hours ago, and in the meantime, some of these questions have been answered. Sorry.

I Kinda understand that there is a difference between 5.56 and .223. Still, both chambers and bulllets will shoot in the guns I buy. Is that the kinda distenction we are drawing here?

Kind of... .the leade and throat combination of the SAAMI .223 Rem was designed light short bullets. The leade and throat of the 5.56x45 are considerably longer. This allows longer bullets to be used, and in fact the specification of the round reflects that. It is completely possible to get a 5.56 x 45 cartridge that won't work in SAAMI-chambered .223 Rem rifles Worse, if the bullet "jams hard" into the throat, chamber pressure can get very high, possibly breaking a bolt or worse. It is not uncommon to see the warning "For .223 Remington ammo only" marked on a rifle.
Fortunately, it seems that most of the 5.56x45 ammo is toward the low end of tolerances and fits in the smaller chamber.

The Wylde chamber has a leade-throat combination designed to safely fire any in-spec military 5.56x45 ammo as well as .223 ammo. The Wylde leade-throat combination is longer than the .223 Rem. The very fact that the Wylde chamber exists indicates that there is a chance of danger with a .223 Rem chambering a military round. I suspect that many barrels marked .223 Rem actually have a chamber close to the .223 Wylde.

In some respects, Grendel ammo is like the 5.56 x 45 ammo. It usually works in the variants, but not always. Some may remember that some of the first Hornady Grendel ammunition did not fit in some of the variants but worked fine in rifles with the standard Grendel chamber. Many have tried to forget the finger pointin', name callin' and mud slingin' that occurred at the time. To my recollection, one of main problems was that the variants did not have a generous radius on the transition from the shoulder to the neck like the Grendel. The ammo was on the high side of the Grendel spec. The previous runs of ammo had been closer to the low end of the specifications and worked just fine in the variants.

Take a look at the case-to-shoulder and the shoulder-to-neck transitions on the SAAMI drawing of the Grendel chamber and ammo. Each of the transitions has a specific radius. Look at the reamer drawings for the variants. No radiususes, er radios, aw crap... They ain't rounded, dagnabit!

When a near- maximum sized case with a nice round shoulder-to-neck transition is put in a chamber that has a sharp transition, it won't go in all the way. From the outside, it looks like a headspace issue. Nope.

WARNING, CAUTION, AND OTHER SCARY WARNINGS.
DO NOT SMACK THE END OF A LOADED ROUND WITH A HAMMER TO SEE IF IT WILL FIT THE CHAMBER. THIS FALLS UNDER THE CATEGORY OF "STUPID STUFF."