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5R runout demonstrated

LVLAaron

LVLAaron

Gold $$ Contributor
Here's a barrel a someone wanted set back a thread. Ultimately declined to do it and will at some point chop an inch or two off and start clean.

I didn't bother dialing it in any further. I wish I had for the sake of the video but am sharing anyway - Lots of talk about this but I've never seen anyone share any media. So yes, the barrel is not indicated but the "5R death wobble" is pretty clear on the indicator. Feels like about .5-.6 thou (tenths indicator with a long reach tip)

Indicator is at the top of the body just below the shoulder. It was worse on the neck.



 
I’m not a rifle smith nor a machinist… what is the “5R Death Wobble”? Is it an undesirable feature of 5R rifling?
 
rwj said:
I’m not a rifle smith nor a machinist… what is the “5R Death Wobble”? Is it an undesirable feature of 5R rifling?
Click to expand...

The description is something I just made up.

That chamber is shaped like an pentagon. It happens because the 5R barrels have 5 flutes that are "ramped" so they're shaped like this: /-\

It causes reamers (which have 6 flutes) to get pushed around by each flute in the opposite direction of the flute as it's being cut causing the odd shaped chamber.

In the video, every time the dial takes a little jump, it's showing you that the chamber isn't round.
 
Clancy said:
I’m still waiting on the “good” news about 5R rifling.

I’m 4 groove for life, except I may try another Lilja 3 groove because the one I have right now is on fire.
Click to expand...

I like 5R barrels - They're easy to clean. No sharp edges to try and get carbon out of. That's the upside to me. It's possible to avoid this runout by pre-boring the right spots the right amount.

Moral of the story is, if you bring your smith a 5R barrel, also bring his favorite 6 pack.
 
LVLAaron said:
I like 5R barrels - They're easy to clean. No sharp edges to try and get carbon out of. That's the upside to me. It's possible to avoid this runout by pre-boring the right spots the right amount.

Moral of the story is, if you bring your smith a 5R barrel, also bring his favorite 6 pack.
Click to expand...

Or just don't prebore at all on 5Rs so the the pilot is helping the whole way. If I ream slow I get a little "U" at the beginning of the rifling. If I increase the speed to 250+ I can usually get rid of the little U. That said, the little U doesn't hurt anything, but it is a sign of a six flute reamer in a five groove bore.

There has been a lot of hype about 5R, yet almost every LR BR competition barrel out there is 4 groove......
 
All of my LR bbls. are 5r and when chambering I drill n pre-bore. Never have any issues with chambers or necks indicating anything worse than 5 tenths IRO. These bbls. are used in NRA MR and LR prone.
all-of the bbls. we shoot are salt bath hardened. 6 mm BR, 243, 6 XC , 6.5x284, and 308. We are waiting for one 308 with 6500 rds to stop shooting cleans at 600 yds. It’s still going strong.
 
I may be lucky but I haven't had any trouble with 5R at all.my set up and chambering technique are the same for every barrel that goes into the lathe.the interapid, borescope and targets prove it works.
 
I’ve chambered a bunch of them. I just did one on Thursday. It had maybe .0001” of runout to the set up and was very round. I always pre bore and never had a problem. 4 groove or 5 I don’t care as long they shoot..
 
I always pre bore on a taper matched to the cartridge I am chambering for. Never have more than a .0001 run out at base or neck of the finished chamber. If I did I would start over. Guessing not a ridgid enough setup on that chamber.
 
Good Post , interesting read. Having Had and still do have a couple 5R Obermeyer Barrels on Match Rifles .

I wish Boots Obermeyer or a Gun Smith from Wisconsin would jump in?
 
I have not seen any defletion of the chambering reamer, with pre-boring, but have found it impossible to do a good job with a conventional six-flute throater. Spiral fluted throaters work OK . WH
 
A few years ago I had 5r barrel chambered in 6.5 Creedmoor. The Gunsmith that chambered it surprised me with a throat gauge, at no charge, made from the stub he cut off the barrel.

Some time later I got curious about how the diameter of a particular bullet would change as it passed thru the barrel. I pushed one of those bullets thru the barrel stub. When I attempted to measure the bullet diameter, I discovered the measuring tools I have won't give a reliable measurement.

That was when I decided I didn't want any more 5r barrels.
 
Edd said:
A few years ago I had 5r barrel chambered in 6.5 Creedmoor. The Gunsmith that chambered it surprised me with a throat gauge, at no charge, made from the stub he cut off the barrel.

Some time later I got curious about how the diameter of a particular bullet would change as it passed thru the barrel. I pushed one of those bullets thru the barrel stub. When I attempted to measure the bullet diameter, I discovered the measuring tools I have won't give a reliable measurement.

That was when I decided I didn't want any more 5r barrels.
Click to expand...

5R requires a different approach to chamber it. It's possible to have a perfectly concentric chamber... But it takes more time and effort to get right.
 
Tiny boring bar - take out the lands as far in as you can so they don't influence the reamer until you're cutting what will actually be the lands...

And check for runout throughout the job. If it's getting 5 sided... make corrections. Wax paper or patch over the reamer, take a cut, check again. If you ain't measurin' you're guessin'
 
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