Gunsmithing Acceptable amount of muzzle runout?

[Disasterpath]

Hey guys, getting ready to chamber another barrel and when dialing in the barrel in the lathe I decided to see how much runout I was getting at the muzzle. I indicated only the breach end using two 1/10000 indicators and got it dialed in perfect. I then put the range rod in the muzzle and measured .034" of runout. The barrel blank is 31.5" long. I have chambered a few barrels this way and all have shot 1/2 moa or better but I never bothered to see how much the muzzle was out of line with the breach end. I can see the muzzle moving with just my eye but i have seen this before so I didnt think anything of it. I plan on finishing the barrel at 26" so i would assume the runout would be less once cut back but I wanted to get an idea of what you guys are getting before i proceed with chambering.

 

[chpprguy]

Re: Acceptable amount of muzzle runout?


Perhaps a little more explanation on how you "chuck" your barrels up?

I would assume you do through the spindle?

Many build a "spider" on the back side of the spindle to get as good a runout on the back side as they do on the work side.

My spindle is too long to allow this, I typically make a slip fit
bushing for the barrel that centers it in my spindle.
This gets me about .001-.002" at the muzzle.

Many would find this unacceptable (too much) but since I am not a gunsmith, and only build my own, it works for me...

YMMV
Andy

 

[300sniper]

Re: Acceptable amount of muzzle runout?

after dialing in the chamber in, i put a dial indicator on the od of the muzzle to find the high spot. once i thread the tenon, i set the shoulder of the barrel back so the high spot of the muzzle indexes with the top of the receiver. the one i did yesterday had exactly .030" of runout near the muzzle when the chamber end was dialed in to less than .0001" on a range rod with two indicators. your measurement doesn't sound that far out of line to me.

 

[Rhys]

Re: Acceptable amount of muzzle runout?

Your runout is not uncommon. There is a fair chance you will actually see just as much or more when you trim it back. I set up similarly. I indicate straight to the first couple inces of the bore, chamber, thread, the flip the barrel cut to length, indicate the last couple inches of the bore, and crown.

 

[Hateca]

Re: Acceptable amount of muzzle runout?

You just found out why some loose windage in there scope and think it’s the scope base holes. You want to put that run-out TDC or BDC in relationship to the action or you to will loose windage just as 300sniper said.

This is also why you never cut a chamber after indicating a barrel at both ends at the same time. You indicate the barrel just as you are, only the end you are working on.

It's also advisable to cut the barrel close to what the finish length will be before doing any dialing in. The run-out at 31" may not be the same or exit the blank at the same spot as say 24".

You’re run-out is normal for lots of barrels.

Amazing what you discover when you check isn't it?