Liberty barrel evaluation and repair by Precision Firearms

[woohoo]

Why don't you re-check the SAAMI drawing? I just did and could not find the feature you describe. The 0.5 degree reduction in diameter from .2644" to .2677" starts at 1.5478" and ends at1.7025" for a run of 0.1277 inches. That should not produce a 'ring-like' appearance. k.

I don't need to recheck it, I've known what it looks like for 5-6 years.
IF any part of the throat is .264 or larger there will be NO lands. The groove in the barrel is .264. If the reamer removes material .264 or larger it will remove all of the lands making a smooth bore...freebore.
Your numbers are wrong, the area where the lands slope a .5 degrees starts at .2644 and they get taller to .2617. Notice the .2644", that is larger than .264 and will remove all of the lands.

[JASmith]

I don't need to recheck it, I've known what it looks like for 5-6 years.

With all the respect owed to a well-known and respected gunsmith, this comment suggests that one may have lost the desire to learn new things.

Based on looking at and reading the drawings, I concur with your observation:

IF any part of the throat is .264 or larger there will be NO lands. The groove in the barrel is .264. If the reamer removes material .264 or larger it will remove all of the lands making a smooth bore...freebore.

Your numbers are wrong, the area where the lands slope a .5 degrees starts at .2644 and they get taller to .2617. Notice the .2644", that is larger than .264 and will remove all of the lands.

I was truly hard-pressed as to why you could say my numbers are wrong when yours agree with my memory and those on the drawing -- until I re-read my post and realized I had misstyped! BTW, tapering out from .2644 to .2677 and then starting a 1.5 degree slope down to bore diameter would create an interesting picture! Many thanks for calling my attention to the error. I have just corrected the typographical error.

I am still hard pressed to find a feature in the drawing that would evoke the appearance of a ring "just before where the lands start" as described in post #17.

I will concede that the observer may have confused the neck-freebore transition with where the lands start, which would explain the differences and why we don't seem to be on the same page in this discussion.

[woohoo]

With all the respect owed to a well-known and respected gunsmith, this comment suggests that one may have lost the desire to learn new things.

Based on looking at and reading the drawings, I concur with your observation:





I was truly hard-pressed as to why you could say my numbers are wrong when yours agree with my memory and those on the drawing -- until I re-read my post and realized I had misstyped! BTW, tapering out from .2644 to .2677 and then starting a 1.5 degree slope down to bore diameter would create an interesting picture! Many thanks for calling my attention to the error. I have just corrected the typographical error.

I am still hard pressed to find a feature in the drawing that would evoke the appearance of a ring "just before where the lands start" as described in post #17.

I will concede that the observer may have confused the neck-freebore transition with where the lands start, which would explain the differences and why we don't seem to be on the same page in this discussion.

I look down about 70 barrels a day on average. I'm sorry you are confused about what would look like a ring. Let this guy shoot his barrel and see how it shoots before you worry the s*** out of him by not knowing what would look like a ring and what would not. If you don't understand that a reamer larger than the bore would remove ALL of the lands you'll need to find someone that has more time than me to explain it to you.

[JASmith]

I look down about 70 barrels a day on average. I'm sorry you are confused about what would look like a ring. Let this guy shoot his barrel and see how it shoots before you worry the s*** out of him by not knowing what would look like a ring and what would not. If you don't understand that a reamer larger than the bore would remove ALL of the lands you'll need to find someone that has more time than me to explain it to you.

Are you deliberately misrepresenting my comments?

This guy should be worried given that the operation was described as a "scraping" rather than retouching with a finishing reamer.

Add to that his observation of an unexpected feature that cannot be be explained by the SAAMI drawings, and he should be worried.

Yes, someone who looks down 70+ barrels a day and has developed a reputation for excellent workmanship should understand this.

[montana]

Let's keep it classy gents.

[woohoo]

Are you deliberately misrepresenting my comments?

This guy should be worried given that the operation was described as a "scraping" rather than retouching with a finishing reamer.

Add to that his observation of an unexpected feature that cannot be be explained by the SAAMI drawings, and he should be worried.

Yes, someone who looks down 70+ barrels a day and has developed a reputation for excellent workmanship should understand this.

Fortunately for me I understand reamer design very well.

OK, everyone that owns a AA Grendel barrel pull your barrel out and look down the chamber.
You should see, A big long ring(chamber), A tapered ring (shoulder), a shorter smaller diameter ring(neck), a short steep tapered ring that looks more like a step(cone), a short slightly smaller rig (typical freebore but in the Grendel this is the start of the compound throat that is larger than .264 dia.). Then the lands start sloping up a .5 degree.

If your lands start at the end of the 45 degree cone then the throat part of your chamber is small in diameter and short throated. No part of a .264 diameter bullet can protrude outside the case mouth without slamming into the lands.
What do you see?

I don't care what Satern calls it, anything put in there to correct a small diameter throat will be done with a rotary reamer of some sort. A throater, A reamer, whatever.

[JASmith]

Thanks for the suggestion -- the ring described i post #17 is now very likely to be placed in its proper context as folks pick up your challenge

[woohoo]

This is a description by Sputnik in post #17-" By looking into the chamber, it appears they scraped/removed all or part of the compound throat as I see a small "ring" around the throat just before the lands begin; where it looks like it was removed or slightly "bored out""

This is your reply-
Sputnik,

From all that has been said, it appears that your velocities and especially your pressures will most likely be in line with the norms expected of factory ammunition.

The ring you observed is troubling in that there is no feature described in the SAAMI drawing that would evoke a feature like that. Furthermore, I am told that the way to fix a tight chamber is to run a finishing reamer through it. That operation should not produce the ring you describe.

Regarding accuracy, you probably will find acceptable woodland hunting accuracy with some bullets. Chances are the rifle will like one or two a lot more than others.

We know from Chapter 8 of Volume 1 of the Grendel Reloading handbook that the compound throat was developed to accommodate a variety of bullet styles while maintaining good accuracy in an AR.

We also know from both public and private statements that several, more conventional, throat designs were tried during the early development. Some of these provided excellent accuracy with some bullets, but not so good accuracy with others. Some of these earlier designs look a lot like the "alternative" chambers floated by others, including the chamber suggested as being the one Satern is now advocating and selling.

Bottom line, e caveat emptor.

Compare your scraped Satern throat with the one in your PF Neptune V. They should look alike. If not, at least one of them is not a Grendel chamber. What you conclude is worth bothering with is up to you, but folks need to know who produces barrels that meet the standards and who does not.

Now what I said JA, is "yes there will be a "ring"". It will not be as long as a .264LBC "ring"(freebore) but there will be one there. The part I quoted you on several post ago, the one in red above is what I was disagreeing with. The SAAMI Grendel chamber shows it clearly, it will remove a short section of lands creating a "ring". In another thread weeks ago I gave the length of that ring(freebore).

[JASmith]

This is a description by Sputnik in post #17-" By looking into the chamber, it appears they scraped/removed all or part of the compound throat as I see a small "ring" around the throat just before the lands begin; where it looks like it was removed or slightly "bored out""

This is your reply-
Sputnik,

From all that has been said, it appears that your velocities and especially your pressures will most likely be in line with the norms expected of factory ammunition.

The ring you observed is troubling in that there is no feature described in the SAAMI drawing that would evoke a feature like that. Furthermore, I am told that the way to fix a tight chamber is to run a finishing reamer through it. That operation should not produce the ring you describe.

Regarding accuracy, you probably will find acceptable woodland hunting accuracy with some bullets. Chances are the rifle will like one or two a lot more than others.

We know from Chapter 8 of Volume 1 of the Grendel Reloading handbook that the compound throat was developed to accommodate a variety of bullet styles while maintaining good accuracy in an AR.

We also know from both public and private statements that several, more conventional, throat designs were tried during the early development. Some of these provided excellent accuracy with some bullets, but not so good accuracy with others. Some of these earlier designs look a lot like the "alternative" chambers floated by others, including the chamber suggested as being the one Satern is now advocating and selling.

Bottom line, e caveat emptor.

Compare your scraped Satern throat with the one in your PF Neptune V. They should look alike. If not, at least one of them is not a Grendel chamber. What you conclude is worth bothering with is up to you, but folks need to know who produces barrels that meet the standards and who does not.

Now what I said JA, is yes there will be a "ring". It will not be as long as a .264LBC "ring"(freebore) but there will be one there.

... and my comment about now highlighted in bold green type tells us we are in agreement that comparing chambers and throats is a good thing to do.

Should he discover a difference, then safety and performance considerations suggest follow-up action is needed.

If they appear the same, then I will stand corrected and we will need to work out how to discuss these differences of interpretation and description.

[PrecisionFirearms]

For those wanting to send in their barrels for us to repair:

FIRST and MOST IMPORTANT: We will do these in batches of 10 or more, unless there is a long time between orders. We will not be doing these for at 4 weeks due to work volume and catching up from the move, my health, SHOT show, and the NRA Great American show.

Second: Send the barrels to our address at 74A Dupont Rd, Martinsburg WV 25404. Include Your Contact info, Email address, and phone number.

Mark Hostetter
Precision Firearms
pf15@pf15.com

[woohoo]

further-
The minimum 264LBC reamer has a .061" freebore, mid spec .080 and the largest .099".
The minimum Grendel SAAMI chamber has a .023" freebore. If the reamer is .001" larger in diameter than the minimum size the freebore is .080". If the reamer is the largest allowable spec in the Grendel the freebore is .137" That'll leave a ring.
Edited 2- I was off on the calculations, that's what I get for doing it on paper instead of a calculator. each .001" change in dia lengthens the freebore .057" using .5 degree as the angle

[Sputnik]

Whoa, gentlemen...please lighten it up. Sorry I caused this. How about this. Everybody is right. Also, Since this is really getting technical with all kinds of numbers and angles and such...Kinda space-like: Since I have a Neptune, and this Liberty comes from Satern (I know it is spelled differently), so I am going to name my chamber Uranus! Behold the ring around...

[woohoo]

Those lands appear to be in the area of 30:70 (land to groove) lands apx .050" wide. Compare that to the freebore(ring). I would shoot it and see how it does. The bullets shouldn't jam the lands so it shouldn't cause excessive pressure.
As for the compound throat, I think it would be pretty tough to tell the difference between a .5 and 1.5 degree slope with the naked eye.

[Sputnik]

Thanks, JASmith and Woohoo. I concur with the shoot it and see. The ring was not there before, and the "fix" seems to be remove the compound throat. So I guess that is what that looks like. The factory ammo removes easily, the lands no longer touch the projectile. Just hoping my ring doesn't work like a speed bump.

[45r]

My liberty barrel will let a 123 SST drop out of the chamber seated to 2.233 but will hold one seated to 2.245.
I think my barrel will be fine and drop a factory 123 SST round after some more shooting.
Some of the group buy barrels are probably OK.
I polished the throat a lot and now all I see is a few small scratches on a 123 sst when seated to factory spec and they seem to be made by a little roughness in the throat on one side.
That is probably what is holding the round from dropping at factory length.
My barrel shoots good and I must have got lucky.
A little JB's or Iosso on a patched 6 mm brush and some elbow grease might make some of the barrels work out and others might not see a need to change their chamber.