5R runout demonstrated

[LVLAaron]

Is the issue created by having 5 lands/grooves or the land profile?

5 lands. The Ramps make it worse.

 

[INTJ]

Those of you have no issues with 5R. What does the end of the rifling look like after cutting the chamber? If the end is not straight across, then you are indeed getting reamer deflection.

Increasing RPM can help, but again, the U shaped rifling ends doesn't seem to affect accuracy--at least for the type of shooing these barreled are used for. I wouldn't take a chance on a 5R where accuracy is critical, like in any kind of BR discipline.

 

[LVLAaron]

To further confuse the situation- the barrel in the video easily shot a clean score at a hard range.

 

[GenePoole]

For what it's worth, I've never noticed any difference between chambering 4, 5R or 6 grove barrels.

 

[WSnyder]

Those of you have no issues with 5R. What does the end of the rifling look like after cutting the chamber?

Square to the rifling where the throat ends although 5R’s throats do differ in appearance from std rifling. There is a more abrupt taper on one side of the lands from the 5R profile which is to be expected.

 

[ridgeway]

I've never encountered any issues whatsoever chambering 3, 4, 5 or 6 grooved barrels. I just did a 5r a few weeks ago for a top prone shooter and it came out absolutely flawless. Not really following the issue with them....

 

[FireMedic]

I haven’t noticed any difference between, 5r, 4 groove, 6 groove etc. I’d look at your setup if you are having issues.

Certain floating reamer holders can cause all sorts of problems, out of round, oversize chambers, etc.

 

[LVLAaron]

I haven’t noticed any difference between, 5r, 4 groove, 6 groove etc. I’d look at your setup if you are having issues.

Certain floating reamer holders can cause all sorts of problems, out of round, oversize chambers, etc.

Have you put an indicator on the necks when you're done?

 

[FireMedic]

I check every step in my process. Every time.

When I finish, the throat and inch in front have no runout. The neck, shoulder and rear of the chamber will runout less then a tenth and be correct size.

 

[AckleymanII]

If you have reamer chatter in a chamber, good chances it will be a 5 R barrel

 

[AckleymanII]

I have posted this previously, determine bore dia at the muzzle.



Now, cut off enough to locate the new throat at the same dia as the muzzle: GOOD LUCK!



Couple of issues with Set Backs. One is the steel maybe work hardened and chip/dull the flutes in the leade angle, throat, neck that already takes a beating. Flame and cleaning rod makes for a somewhat difficult job dialing in the barrel if you do not find the spot where the bore dia matches the muzzle dia. Otherwise, you can have great results.

You take the risk of a ruined reamer that leaves rings where carbon or hardness chips the reamer. If there is any hard carbon in the throat, just don't set it back.

 

[LVLAaron]

I don't care if the breech end is larger than the muzzle end. Other way around is a problem.

I understand the setback is hard on the reamer. For my FTR barrels, I got two reamers. One for new barrels, one for setbacks. If the setback reamer gets banged up, cost of doing business and getting another couple hundred rounds on the barrel.

 

[INTJ]

Too add to the discussion. Yesterday at work I chambered another barrel with the trendy 5R rifling. For the first time in a long time I was too tight on the headspace when I torqued the action to the barrel (dang remmy sandwiched lug).

So I put the barrel back in the lathe to cut another .001" of headspace. It dialed in very nicely and quickly. I indicated the throat and the breech end. Since there was no rifling, I got the Interapid down to zero movement in both places.

Now on this barrel I didn't get a perfectly even and square cut on the rifling, but it was close. Still, I didn't have any weird runout at all.

So I guess I am wondering about the chamber @LVLAaron showed. Was it just a poor intitial chamber job? Maybe a rushed or imprecise dial in?

 

[AckleymanII]

Many consider .006 dial in ok.

 

[LVLAaron]

I'm frustrated if I can't get things within a tenth or two.

 

[Ksracer]

I've seen a barrel where tool deflection from 5r rifling got so out of hand that it carried all the way down the body. It's not chatter that causes the problem, that's a different issue.
Fired brass from that chamber had 5 high spots on it and wouldn't re-chamber unless it was indexed right.
If you're having problems, stop reaming before the reamer reaches the lands and use a drill that's just over bore size to remove them for the length of the freebore + the neck. If you can get the neck of the reamer fully engaged before the throat starts cutting you generally won't have any more issues.
5 flute tooling also fixes the problem.

 

[jackieschmidt]

From a machinist standpoint, I don’t understand the problem.
I have chambered several 5R barrels, and the only real aggravation is indicating the lands because they are not directly opposite of the four adjustment screws on my Set-True chuck.

what am I missing here?

 

[Ksracer]

From a machinist standpoint, I don’t understand the problem.
I have chambered several 5R barrels, and the only real aggravation is indicating the lands because they are not directly opposite of the four adjustment screws on my Set-True chuck.

what am I missing here?

An odd number of lands and an equal number of reamer flutes causes unbalanced cutting forces. As 1 flute is cutting a land, the opposite flute is in a groove. Assuming your pilot is a tenth or two loose in the bore and there is another couple tenths clearance on the reamer nose, the force from cutting the land can cause the reamer to deflect and cut in the groove. If it's bad enough, you end up with a Pentagon shaped hole with lands that aren't completely removed and grooves that are deeper than they started. The ID of that hole across the 5 points will actually be smaller than the reamer freebore diameter.

If it's left completely unchecked, the deflection can build on itself and make it's way into the body portion of the chamber. That's worse case scenario.

 

[LVLAaron]

Same kind of situation when you're drilling a hole in some steel with a drill press or a hand drill, and end up with a 3 sided hole because the drill bit gets pushed around.

Even with a tight pilot it can happen. Steel moves a lot more than we think it does. Doesn't take much to push the end of a steel reamer in the opposite direction.

 

[AckleymanII]

Tiny land tops to support reamer bushing, can be an issue, 7mm and 30 Caliber, barrel set backs especially. Slop between reamer bushing dia. and lands dia is an issue, control this for great results. A set back on an existing chamber where the original chamber is .005 out, will leade to chatter if you do not cut off enough shank so you can clean up the old chamber with a boring bar prior to reaming.

A taper bore with no reamer pilot will cure all ills in this matter.