chamber runout issues

C

chuck williams

Guest
i used to be able to keep runout under .0005 easily. my setup has not changed but now i see runout as much as .001 regularly. the rifles still shoot fine but this is driving me crazy! any ideas? could it be that my headstock bearings need to be adjusted?

chuck
 
maybe your tail stock has an issue, or your set up is moving a little? If you will check your run out after ever operation you will see what step is causing you the issue. Lee
 
chuck williams said:
i used to be able to keep runout under .0005 easily. my setup has not changed but now i see runout as much as .001 regularly. the rifles still shoot fine but this is driving me crazy! any ideas? could it be that my headstock bearings need to be adjusted?

chuck
Click to expand...

Tell us how you are measuring to get this reading. For example, is the finished chamber running out in relation to the tenon, the bore at the chamber neck???
 
all work is done through the headstock. either a 4 jaw or spider in front depending on barrel length and a spider in rear. muzzle and breech BORE are indicated to within .0005 before starting and work. I check periodically throughout the process to make sure I am still within .0005 runout with a tenths indicator on a surface that I know is concentric with the bore. my set up is rock solid. I prebore all of my chambers and start with a dead center and finish up with a pusher like many of you use here. similar to what mike Bryant shows on his website. after the chamber is cut and headspace set I always put my indicator in the finished chamber prior to removing from the lathe just to see how much runout is in the chamber. used to be .0005 or less. now its almost always .001. any ideas?

chuck
 
Your headstock bearings may have worn a little and you may need to tighten the jam nut on the end of the spindle. Paul Dorsey told me to chuck up on a 1/2" rod and then chuck the other end in a drill chuck in the tail stock. Then place a dial indicator against the chuck face in the spindle. He said to adjust the spindle to where it had .0002" back and forth movement when you move the tail stock handle back and forth. I tried that and it seemed a little too tight to me as I couldn't turn the chuck easily when the lathe was in neutral. Still not a bad way to adjust the bearings, but I'd shoot for a little more movement than .0002". You can check it though and see if that might be an issue by using the 1/2" rod to check back and forth movement.
 
thanks mike. that's an excellent idea to check the bearings. I will do that and see what I find. do you think worn bearings could cause the runout issue I am seeing?

chuck
 
chuck williams said:
thanks mike. that's an excellent idea to check the bearings. I will do that and see what I find. do you think worn bearings could cause the runout issue I am seeing?

chuck
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I'd think that the spindle bearings needing to be adjusted would give you variations in runout, but I guess it could give you changes in runout depending upon where the bearings came to rest as they move. Sure worth checking though and seeing.
 
I'd be interested to see your results if you push the reamer with a dead center for the entire chamber; don't use the floater, just to see what difference you might see..

I assume your tail stock is aligned with the spindle.. Most are not. I don't think that will account for runout but might cause an oversize chamber when using a dead center ..

good luck!
 
what if there was an issue with the hole headstock not being swept in dead perfect? I don on my little yet i had to adjust the hole head stock assembly to run true with my bedways. Not sure this is an issue on the OP lathe but on these import lathes there are four bolts that adjust the headstock, and i always checked mine on a regular basis. This can be a pain in the old rear end to get set properly, but it has to be done. Now maybe this wouldnt cause run out, i dont know. I can see where this might cause an oversize chamber though. Just a thought. Lee
 
Try our new reamer holder and all your troubles will be gone.It takes care of all the above. Thanks Dave Kiff.
 
chuck williams said:
all work is done through the headstock. either a 4 jaw or spider in front depending on barrel length and a spider in rear. muzzle and breech BORE are indicated to within .0005 before starting and work. I check periodically throughout the process to make sure I am still within .0005 runout with a tenths indicator on a surface that I know is concentric with the bore. my set up is rock solid. I prebore all of my chambers and start with a dead center and finish up with a pusher like many of you use here. similar to what mike Bryant shows on his website. after the chamber is cut and headspace set I always put my indicator in the finished chamber prior to removing from the lathe just to see how much runout is in the chamber. used to be .0005 or less. now its almost always .001. any ideas?

chuck
Click to expand...

I noticed that you emphasized that you indicated the breech BORE for your setup. I have seen some variation in groove depth, especially in button rifled barrels such that if the bore is indicated true, the land diameter (which supports the reamer pilot) may be out of concentricity .001 or more. I set up basically the same way you do, but i make sure to indicate the lands at the breech end. I have a long enough indicator stem to reach slightly past the throat so that my reamer pilot is running nearly at the spot I indicated as the chamber is finished.

If your indicator shows less runout at the mouth of the chamber and increasing runout deeper in, I think this would be a clue.

Scott Roeder
 
Don't always assume that the reamer is perfect. If they don't cut properly they can cause many problems as well. If your problems are with a different reamer then go back to one that worked well for you and see if you can still cut a good chamber. If it works well then you have another source for your problems.
 
SGS said:
I noticed that you emphasized that you indicated the breech BORE for your setup. I have seen some variation in groove depth, especially in button rifled barrels such that if the bore is indicated true, the land diameter (which supports the reamer pilot) may be out of concentricity .001 or more. I set up basically the same way you do, but i make sure to indicate the lands at the breech end. I have a long enough indicator stem to reach slightly past the throat so that my reamer pilot is running nearly at the spot I indicated as the chamber is finished.

If your indicator shows less runout at the mouth of the chamber and increasing runout deeper in, I think this would be a clue.

Scott Roeder
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Scott, not to be disagreeable, but if the top of the lands are not concentric with the bottom of the grooves, you might get better runout with your neck with a tight fitting pilot when indicating on the top of the land, but your neck would probably not be concentric with the grooves in the barrel. I think that the top of the lands is just along for the ride. I want the bullet to start off concentric with the grooves and not the top of the lands. I've seen better results by going to looser fitting pilots than what you would normally consider the correct sized especially when there is a difference in concentricity between the top of the lands and the bottom of the grooves. That's with drilling and boring out most of the chamber and just finishing the chamber with the finish reamer. That's just my opinion and worth about as much. Just something to think about. You can have everything concentric and right on runout wise with your completed chamber and still have barrels that won't shoot competitively. But, as long as we've done the best we can putting the chamber and crown and the work that we've actually done, then we give the barrel the best chance to shoot as well as it's capable.

Mike
 
Another thing to keep in mind. If your test indicator reads .001 run out in your chamber, your actual runout is only .0005 and that isnt to bad. Im no pro by any means, and actually dam far from it, but if my chambers are less than .0005 i feel ive done a good job. I have had a few barrels less than that, but none over 0007 "on the dial" and i have seen no difference in how they perform. I have chambered a couple match winning barrels and not a single one of them read perfect .0000. not one!! I think as long as we do the very best we can every time, the rest is up to the barrel gods. Lee
 
Mike Bryant said:
Scott, not to be disagreeable, but if the top of the lands are not concentric with the bottom of the grooves, you might get better runout with your neck with a tight fitting pilot when indicating on the top of the land, but your neck would probably not be concentric with the grooves in the barrel. I think that the top of the lands is just along for the ride. I want the bullet to start off concentric with the grooves and not the top of the lands. I've seen better results by going to looser fitting pilots than what you would normally consider the correct sized especially when there is a difference in concentricity between the top of the lands and the bottom of the grooves. That's with drilling and boring out most of the chamber and just finishing the chamber with the finish reamer. That's just my opinion and worth about as much. Just something to think about. You can have everything concentric and right on runout wise with your completed chamber and still have barrels that won't shoot competitively. But, as long as we've done the best we can putting the chamber and crown and the work that we've actually done, then we give the barrel the best chance to shoot as well as it's capable.

Mike
Click to expand...

Mike, I have heard of that strategy before and It may well be worth the effort. I have plenty of pilots, but I have never attempted to intentionally use a loose one to overcome a groove depth imbalance. I have cut a chamber where the uneven throat to the lands was easy to see with my borescope. I may want to try the loose pilot and set up on the lands next time I encounter a barrel like that.

If Chuck did indicate the grooves, and he used a tight fitting pilot, and the grooves were out of concentricity to the lands; he most likely would have introduced a small amount of runout into the chamber. Your solution might be the best for that situation.

Scott Roeder
 
SGS said:
Mike, I have heard of that strategy before and It may well be worth the effort. I have plenty of pilots, but I have never attempted to intentionally use a loose one to overcome a groove depth imbalance. I have cut a chamber where the uneven throat to the lands was easy to see with my borescope. I may want to try the loose pilot and set up on the lands next time I encounter a barrel like that.

If Chuck did indicate the grooves, and he used a tight fitting pilot, and the grooves were out of concentricity to the lands; he most likely would have introduced a small amount of runout into the chamber. Your solution might be the best for that situation.

Scott Roeder
Click to expand...

Scott,

I agree with Mike. I chambered 750 barrels last year on my Haas. All where set up the same as I do on my manual machines. Two spiders and I indicate in the throat area or as far as I can reach. I push the reamer allowing it to find it's own way. That's the point I'm trying to make. I use bushings 5 tenths under bore diameter. Common sense says the reamer will self center in bore from the cutting forces. The miniscule differences between groove and bore diameters shouldn't affect anything. The one wild card is the location of the bushing in relationship to the throat. A reamer that has the bushing a considerable way out in front of the throat will, with a close fitting bushing, cut a chamber that will be nonconcentric. How much is dependent on how straight the bore is. A crooked barrel means a throat off center. Runout in my chambers average .0003" TIR or less on the breech and about the same maybe a little less in the neck and throat.

Dave
 
Dave Tooley said:
Runout in my chambers average .0003" TIR or less on the breech and about the same maybe a little less in the neck and throat.

Dave
Click to expand...

Dave, do you really mean average .0003, or "rarely exceed" .0003? I bet "rarely exceed" is more indicative of your chambers -- IIRC, all the ones you did for me were about .0002, with a couple under that. (In the old days, Dave use to let me hang around while he chambered my barrels...)
 
There's a lot of good suggestions here.....and the obvious ones have been covered quite well.

I don't claim to know everything....maybe I'm not even qualified to comment.....but have you checked your bushings????

There's a junk drawer with a LOT of those little critters out in the shop that aren't EVEN close to concentric.
 
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