Tailstock Misalignment?

[Henryrifle]

If you look at the lands where they ramp up to the rifling with a good borescope like a Hawkeye, this is easier to see that the cut is not perpendicular--it's skewed off to the side. I am guessing this is tailstock misalignment? I don't think it was a failure to dial the barrel in correctly. All 5 of the lands look like this.




Thanks for looking and commenting,
Hank

 

[LVLAaron]

You answered your own question.

The lands are ramped.

All lands look the same? It's not misaligned.

 

[SBS]

5R barrel, lands not same height on both sides before chambering.

 

[Henryrifle]

Wait. Yes, all lands look the same. So, what does it mean when the lands are cut more on one side than another?

 

[LVLAaron]

It's due to the shape of the land.

Draw a profile of the land, it looks like
/-|

So when you cut a taper across the ramp, you get the shape in your pictures.

 

[Henryrifle]

Aaron, I want you to be right and it's true that I've cut way more 4-grooves than 5Rs but I don't remember ever seeing that wierdness before. It literally looks like the land was cut off center.

Hank

 

[LVLAaron]

Your reamer cuts the lands on a taper... from the bore, to the top of the land.

In that barrel, one side of the land is ramped... two angles... you get what you see. It's correct, and if they all look the same, you did a good job.

Get some play dough and a razor blade... test it out on your kitchen counter. You'll see the same thing.

 

[LVLAaron]

Tada

 

[Henryrifle]

Thanks! Just have to say that is really messing with my brain and I've only had 1 Scotch--not even finished!

Thank you for the demonstration,
Hank

 

[LVLAaron]

Haha no problem. I'm about 3 deep and just happened to have play-doh in my desk drawer.

 

[DaveTooley]

You're premise is all barrels are perfectly shaped inside. Button and hammer forged are anything but. Cut rifled barrels come the closest but the cutter that cuts the groove be can off radius. Which shows up as an uneven line transitioning from land to land at the end of the freebore. 5R has it's own unique shape and even a standard 4 groove can be be slightly off.
Best to check concentricity and then shoot it.

 

[SKWERLZ]

If you look at the lands where they ramp up to the rifling with a good borescope like a Hawkeye, this is easier to see that the cut is not perpendicular--it's skewed off to the side. I am guessing this is tailstock misalignment? I don't think it was a failure to dial the barrel in correctly. All 5 of the lands look like this.

View attachment 1462409
View attachment 1462410

Thanks for looking and commenting,
Hank

I had a similar question with my first barrel attempt, a 5-R 338 barrel that’s almost identical in the throat at your and got a similar answer.
It’s an awesome shooting barrel but I was sure nervous!

 

[JPB3]

The Hawk Hill barrels were the truest I've seen in this regard, sides of lands were perpendicular to the grooves and top of the lands were parallel to the grooves.

A view through a scope after chambering was pure bliss..

Alas, they have been sold.. Time will tell with the new owners

 

[clowdis]

On 5R barrels the groove is cut deeper on the driving side and on standard barrels the rifling is cut to equal depth on both sides. The top of the lands are not cut on any barrels that I know of other than Shilen ratchet rifled barrels. So unless you have a Shilen ratchet barrel that means you have a problem with your setup, maybe a loose guide bushing or some chatter with your reamer.

 

[Henryrifle]

@clowdis thank you for your feedback. By guide bushing I think you mean reamer pilot bushing. If so, your assessment is spot on. I recently, for the last dozen or so barrels, started drilling and pre-boring prior to reaming.

For this barrel, a 284/Shehane, I pre-bore about 1.5" of chamber. That doesn't leave much for the reamer to do other than about .5" of chamber, neck and freebore.

As such, I have not tried to fit the optimum pilot busing to the reamer, and, while not in this barrel, I've reamed without a pilot bushing installed at all.

Lastly, I am using a pressure flush system running at 150 PSI during all phases of the chambering except the last plunge where I turn the pressure way down ~40 PSI because I use a micro reamer stop and that can result in a big mess at high pressure. My reamer holder is a Manson floating reamer holder.

Does that, perhaps, add some missing detail?

Thank you,
Hank

 

[LVLAaron]

On 5R barrels the groove is cut deeper on the driving side and on standard barrels the rifling is cut to equal depth on both sides. The top of the lands are not cut on any barrels that I know of other than Shilen ratchet rifled barrels. So unless you have a Shilen ratchet barrel that means you have a problem with your setup, maybe a loose guide bushing or some chatter with your reamer.

I fail to see how there's anything wrong with his setup. I even demonstrated how it works with arts and crafts.

 

[clowdis]

Hank,
5R barrels can sometimes be notorious for causing reamers to chatter. If you're preboring that helps a lot but if you don't have a bore bushing on your reamer the tip may begin vibrating when it engages the rifling. A sure way to check is to put a bushing on your reamer and go in and ream the chamber by hand until you hit the shoulder. Then inspect the throat again and see if that cleaned up the lands. Go slow, check often. I don't see anything wrong with your setup as such, but I always use a bushing even when I prebore and I haven't had this problem. I just don't see any reason not to use the bushing.

 

[V35]

I have seen a few barrels cut different than I think they should, and after checking my setup. It still was concentric to the spindle. Not all blanks have lands that are perfect, some seem to appear that they are.

This is a Shilen barrel I chambered in 300 PRC. The lands looked funny, each one looks identical, but my setup was double checked as good, and when looking in the chamber with a loop the lead and throat looked great. I suppose the button pushed the material unevenly. Its not the prettiest chamber I have cut, but the rifle shoots great, so Im pleased. It was chambered by pre boring and using the same reamer holder the OP mentioned he used. I had a lot of questions I asked myself on this one, and before I removed it from the lathe, I ran my long stem indicator in there and by slowly turning it, I could see that the lands were not flat so to speak. I always indicated in the groove, but from this day forward, I indicate in the grooves and then check the lands and make notes of any irregularities I see. I have gained nothing by doing so, but there may be a lesson in it someday.

 

[Henryrifle]

That is a great picture,@V35 (Bonanza? if yes, so many pilots here). How did you take that? It looks like some form of digiscoping...

I've been shooting the barrel with the lands pictured in the first post and it is doing fine. Easy to forget what you don't like seeing though the borescope when you do like what you're seeing on the target!

Hank

 

[V35]

That is a great picture,@V35 (Bonanza? if yes, so many pilots here). How did you take that? It looks like some form of digiscoping...

I've been shooting the barrel with the lands pictured in the first post and it is doing fine. Easy to forget what you don't like seeing though the borescope when you do like what you're seeing on the target!

Hank

Yessir, just a Teslong scope and yes, let the target do the talking.

And yep, Im a Pilot and had a V35 Bo, In a G36 now.