AR-Stoner 6.5 Grendel barrel short chambered.

[explorecaves]

Are you assuming that the bullet is usually at full diameter out to well beyond the nominal seating depth? I think only poorly designed round nose bullets have that feature. So a bullet diameter freebore gives lots of room for alignment grief, especially when manufacturing tolerances are considered. The gentle taper you see in the SAAMI spec gives a mechanism for the slop resulting from those tolerances to be minimized.

One of the results is that the bullet need NOT touch the lands to be well-centered. The accuracy enjoyed by many Grendel shooters who use factory ammunition or handload without loading to the lands testifies to this. Further, the accuracy lasts long enough that folks frequently enjoy more than 5,000 (yes, five thousand) shots before accuracy starts to slip from order .3 MOA to .6 MOA. LRRPF52 is one of these folks so we should expect that he has a pretty good handle on what makes the Grendel tick.

It really is time to re-read Page 8 and following in Volume 1 of the Grendel Reloading Handbook.

Absent that and other documentable information, we will continue to talk past each other.

It seems to me that this is actually the correct technical answer. I'm assuming the compound throat was designed around Bill A's original favorite load, the 123 Lapua Scenar. The challege was to then shoot with reasonable accuracy the VERY wide range of 6.5mm projectiles available (part of the beauty of a 6.5).

You could even say the 6.5 Grendel SAAMI chamber is DESIGNED to headspace on the very shallow first angle of the compound throat. Understandably, this is CONFUSING to those who have heard all their shooting lives: "Don't jam into the lands! Don't jam into the lands!" In standard throats this is prudent advice. A compound chamber upends the conventional wisdom.

I think the concerns of those trying to learn are valid. But both Satern and AA know and knew what they are doing. Satern, for example, takes pride in very precise measurements, in having a "line-to-line" fit of bullet to barrel, so I'm guessing they will seem a hair tighter (and shoot a bit faster).

Let the newer shooters simply understand that a slight kiss into the lands of the shallow first angle of the compound throat is both per spec and is OK with the SAAMI 65G chamber.

John

P.S. Knowing the various personalities and agendas involved in this thread, there JUST might also be a titch of pot stirring, as well.

150+ posts to follow JA's advice and summarize the information in the book…. No wonder it is hard to find information in this forum at times.

[BjornF16]

There are two types of people - those who say:

Wow - higher than normal velocity! Where do I get one?

And those who say...

Whoa - there's no free lunch. Higher velocity means higher pressure.


Are the pressures unsafe? No problems reported.
How high are they? No one has measured.

Lesson learned: know your chamber, even if you don't reload.

Question:

How was the 50K psi rating determined and with what type of equipment and or labs?

Answer:

Operating pressure is 50,000 psi

It is derived from the requirement for a complete durability cycle within the AR weapon system. Determination was from old fashioned fatigue analysis of the design and trials of the weapons. Ultimately the fielded rifles have the biggest effect as the fleet durability is what matters.

Additional info:

And finally hand loading. LR is correct that the the Grendel must be approached with caution. If you simply load it up and then look for flat primers you have already killed your parts. The MAOP is a very mild 50,000 psi, proof is 67,340 psi. I cannot see the difference on the case or the primers when firing the two. That said it is quite capable of meeting the performances we built in while remaining durable. I have test mules that have run over 8000 rounds and are still ticking along. But a small case will bite without much provocation. I know how my throat works and we set up the loads and OAL to suit. Anyone ever notice that the 100 Berger could be loaded out longer than the factory set up? We set the jump to control the pressure. Same with the 123 Scenar. Sub a 120 SMK and then set to the lands minus a bit and the pressure will skyrocket with very little load adjustment. Tiny case = sensitive.

And finally:

...5R barrels within a specific pressure level will allow faster velocity that is why the competition guys love them (they shoot good groups as well). Good lapping will also help for the same reason by allowing the bullet to move easily down the bore. For a given load they will drop the pressure and consequently the velocity. Bring them up to spec and they are fast.

Polygonal form rifling (BHW makes excellent examples of this and fine barrels) extends the logical progression of 5R. It will drop the pressure slightly more and so you get a slight reduction in velocity.

So the "results" using the term in the broadest sense.

5R unlapped Liberty, most pressure fastest, variable throat and bore fouling so pressure jumps the most and the ES is up.
5R lapped, Very consistent bullet moves a little easier drops a bit of MV nice ES
Polygonal, Smooth, lowest engraving force and least bore resistance, slowest. (good barrel for hand loads that might well allow some improvement over factory velocities)

...Satern 5R demonstrates that it is a superb barrel as always.

[LongRanger]

My first AR build was a Grendel. I've built two Grendel AR15s and one Grendel bolt. I haven't had any issues. Both of the AR barrels are Satern (cut rifled, hand lapped).

As you have ascertained in reading the 34 pages of "hell", the issue is the Liberty barrel (AR Stoner and possibly Brownell's). It does look as if it is a matter of a "rough throat". It is interesting that Satern also produces the Liberty barrels...I look forward to Satern's assessment of their Liberty barrels that exhibit the issue.

There is no doubt the Grendel is not the typical chamber design...perhaps the compound throat lends itself to these issues if not lapped/polished.

I seriously doubt that the issue is with Hornady factory ammo. I don't believe the issue exists with any other barrel brand.

I am the original poster for this thread and after reading through hundreds of posts and having my experience with using Tubb's final finish throat and barrel polishing bullet kit; I am agreement with BjornF16 that the problem at least appears to be that the AR Stoner/Liberty barrels just have a rough throat that causes the bullets in some factory ammo to be tight when chambered. The results that I had where on my AR Stoner barrel, my after polish OAL measurement using a Hornady 123 gr A-Max bullet increased from my initial measurement of 2.246 inches to 2.300" tells me that the Tubbs barrel polishing kit took out some roughness in the throat. I have not had the time to check this new barrel for accuracy as I had to go back offshore to work on an oil rig in the Gulf but I am guessing that like all other barrels that I have used the Tubb's polishing system on I will be seeing around 0.5" MOA when I get back home to shoot for accuracy. I will also be using the Tubb's system to polish out a second AR Stoner Grendel barrel that I purchased at the same time and have changed my mind about sending it back now that I have a better understanding of throats and where the lands actually begin in the barrel. That second barrel has an OAL of 2.236" when measured using a Hornady 123 gr A-Max bullet. My concerns with these barrels have been relieved both due to my experience and those from dozens of other peoples posting about their experiences. I am only speaking for what I have done with one barrel and intend to do with the second barrel and am not making any hard recommendations for what anyone else should do with theirs.

[mperry1945]

I am starting to feel good about my barrel. These new revaluations about this situation and how a rough compound throat effects it all is promising. But for me it isn't over until the Fat Lady (Satern) sings.

[NugginFutz]

Ok - so which is it? Grendel designed to be loaded into the forcing cone / lands, or set with the OAL designed to jump? Bill A, as quoted by BjornF16 would seem to point to the latter, while Hanka's recent observation suggests the former.

I'm getting seriously conflicted, here. And, yes, I understand that the response will vary according to who you ask...

[bwaites]

WOW!! I see a lot of people bench racing their barrels and nowhere near enough people shooting!


C'MON folks, go shoot your rifles! Get out there. Shoot!


Satern knows how to make barrels, trust that they have done a good job and go shoot!


My two Saterns shoot .25MOA groups, and they have since day one. I didn't have 25 shots down the tube before I started seeing itty, bitty groups.


GO SHOOT!

[adrenaline junkie]

Ok - so which is it? Grendel designed to be loaded into the forcing cone / lands, or set with the OAL designed to jump? Bill A, as quoted by BjornF16 would seem to point to the latter, while Hanka's recent observation suggests the former.

I'm getting seriously conflicted, here. And, yes, I understand that the response will vary according to who you ask...

its not supposed to be stuffed. Satern, llija, AA, Shaw, etc, none of the other barrels mentioned are forcing into lands/cones. Only the liberty barrels are.

XC has been bragging for months about how much "faster" his barrel is, now we have a definitive answer. Pressure increase from being in the lands/grooves.

Is that unsafe? Is it good? Is it neccesary? Those are what we are waiting for Satern to respond to, and remedy if necessary. Im guessing that theyre not pushing that far into the lands/cone, so wgile pressure is spiked, its not extreme, like up in the 65k range or anything with factory loads . Handloaders will do like they usually do, and seat their bullets to depths that they feel safe and accurate with, with the knowledge that they might not be able to load out as long as some other barrels can.

[XcountryRider]

It's NOT jamming into the lands.

[Tedward]

its not supposed to be stuffed. Satern, llija, AA, Shaw, etc, none of the other barrels mentioned are forcing into lands/cones. Only the liberty barrels are.

XC has been bragging for months about how much "faster" his barrel is, now we have a definitive answer. Pressure increase from being in the lands/grooves.

Is that unsafe? Is it good? Is it neccesary? Those are what we are waiting for Satern to respond to, and remedy if necessary. Im guessing that theyre not pushing that far into the lands/cone, so wgile pressure is spiked, its not extreme, like up in the 65k range or anything with factory loads . Handloaders will do like they usually do, and seat their bullets to depths that they feel safe and accurate with, with the knowledge that they might not be able to load out as long as some other barrels can.

You can sit and wait for Satern but they are not members of the forum. It will be second hand info so do what bwaites said and go shoot, him and Hanka know the cartridge and are not the manufacture so have interest whether you do or not so wait or keep waiting or shoot.

your choice.

[Drifter]

You can sit and wait for Satern but they are not members of the forum.

Satern knows their way on to this forum:

http://www.65grendel.com/forum/search.ph...hid=879843

[XcountryRider]

Satern knows their way on to this forum:

http://www.65grendel.com/forum/search.ph...hid=879843

Hes not going to post on the forum.

[NugginFutz]

Satern knows their way on to this forum:

http://www.65grendel.com/forum/search.ph...hid=879843

The link doesn't work, now.

[Drifter]

Hes not going to post on the forum.

I simply corrected the lie from the previous post.

[BjornF16]

Satern IS a member of the forum...they currently have a grand total of 5 posts.

http://www.65grendel.com/forum/showthrea...#post25311

[Lead Chucker]

I agree, go shoot. The bullets are not in the lands. Last night i measured 123gn Amaxs in my Satern from bolt face to where they just meet resistance in the throat. That measurement was 2.236". I loaded that bullet today to what i have been loading them to for two years 2.260". I chambered it easy with the side charger & it loaded & locked the bolt with ease, then ejected with ease, no sticking or hardness at all. No mark on the bullet or ogive from rifling marks at all. So checking the COL by just inserting a bullet by hand real easy your coming up against the compound throat or cone or what ever just enough to feel it but your not in the lands. So if i feel the bullet just touch at 2.236" and load to 2.260" & im not touching the lands in anyway with easy extraction. How else can you explain it?

[XcountryRider]

I simply corrected the lie from the previous post.

I don't think it was a lie thats kind of harsh don't you think?

[NugginFutz]

I see it as Tedward being under-informed, rather than intentionally misleading. A fair distinction.

[dmsims21]

We need a ton of new threads started with pics of rifles built with the Lilja and Liberty barrels. They should also include pics of targets.

[Tedward]

I see it as Tedward being under-informed, rather than intentionally misleading. A fair distinction.

Thanks and true, i have no reason to misinform or inadvertently tell falsehoods.

More guns and targets like swiss cheese. My Lilja should be here tomorrow. Lots of cool stuff getting put together this week ahead.

[NugginFutz]

Agreed - dmsims21 has hit the nail on the head. Let's see some range reports, along with the obligatory build pictures and targets for bragging rights! Just be safe about how you work up your loads, etc. No ER reports necessary or wanted.