muzzle runout Gordy's method

It's a long way to the front of a 338 Edge chamber and in my case most easily reached with a Grizzly rod and bushing.

I don't think it matters if you taper bore or step bore... the reamer will follow either...
 
And oversize if the bore curves since the reamer will work to cut across the chord of the curve.
Click to expand...

That's why I said use a rougher first. The chamber cut by the rougher may be oversize (to the rougher); how about the one cut by the finish? Or if that really worries you, touch up the roughed chamber with the bar, then run the finish reamer. Don't think I'm that fussy, though.
 
Butch Lambert said:
You know if you indicate to just in front of the throat and taper bore to that indication, you don't need no damn bushing.
Butch
Click to expand...

Sometimes!! Use the bushing. It will not wear out. The blend of the leade and the barrel bore will be perfect if a snug bushing is used. Ferris Pindel showed me that.
 
Butch Lambert said:
Charles E,
If the rougher goes wacko, so will the finisher.
Butch
Click to expand...
Help me out here Butch, What I'm saying is IF the only problem with the rougher is that it winds up cutting an oversized chamber, then when the finish reamer is run in, the chamber will no longer be oversized. If the roughed chamber is out of square, then of course, the finish won't fix that.
 
Charles,
It appears to me whatever made the rougher cut the base over size will cause the same with the finisher. The problem that affected the rougher is still there.
Butch
 
Charles E said:
Help me out here Butch, What I'm saying is IF the only problem with the rougher is that it winds up cutting an oversized chamber, then when the finish reamer is run in, the chamber will no longer be oversized. If the roughed chamber is out of square, then of course, the finish won't fix that.
Click to expand...

I think you are exactly right as long as the rougher oversize doesn't exceed the margin between the rougher and the finisher. The roughed chamber may be oversize relative to the rougher because of bore wander, but it won't be curved, so as long as it's smaller than the finish reamer, the finish reamed chamber shouldn't be oversize.

Fitch
 
Last edited by a moderator:
OK, on the assumption that rougher/finisher cuts a very good chamber, here's part B.

Let's assume you are willing to cut the chamber before cutting the tenon and threading it and cutting the shoulder. Let's assume too that the shank of the reamer -- the opposite end of the bushing -- is ground, or if not, you could specify that it be ground.

When you indicate the barrel in at first, as exactly as you want, you haven't (likely) picked the exact spot where he pilot bushing will fall after the chamber is cut. So, as you make the last pass with the finish reamer, leave it in, and check things by running the dial indicator on the reamer shank. If it shows runout, re-indicate the barrel using the reamer shank. Then cut and thread the tenon and shoulder. Now the chamber end of the barrel will be square to the case head.

Actually, using his slightly different approach, I think this is essentially what Gordy is doing. The only difference is he's "pre-indicating" based on two points at the chamber end of the barrel, points selected about where the bullet will be. He's essentially splitting any error between the chamber and the shoulder. As Phil (& others) have pointed out, we're not talking large numbers here.
 
Charles E said:
Let's assume you are willing to cut the chamber before cutting the tenon and threading it and cutting the shoulder. Let's assume too that the shank of the reamer -- the opposite end of the bushing -- is ground, or if not, you could specify that it be ground.

When you indicate the barrel in at first, as exactly as you want, you haven't (likely) picked the exact spot where he pilot bushing will fall after the chamber is cut. So, as you make the last pass with the finish reamer, leave it in, and check things by running the dial indicator on the reamer shank. If it shows runout, re-indicate the barrel using the reamer shank. Then cut and thread the tenon and shoulder. Now the chamber end of the barrel will be square to the case head.
Click to expand...

On the subject of using the chamber reamer to align the barrel in the headstock. When I recently chambered a barrel for an -03 Springfield I had occasion to have to put it back in the headstock and realign it due to headspace issues. I used the chamber reamer shank to do that. It only gave me a 1" seperation between measuring points so I was a not sure it was going to work. However, when I was done, and I checked using the tenon and shoulder, the previously turned tenon and shoulder both ran dead true. So did the Griz rod stuck into the throat. I was sure glad that approach worked because I wasn't sure what I was going to do if it didn't. Might have been luck but I'd try it again if I had to.

That said, I don't know that I'd want to insert that alignment approach into my normal chambering process, but it worked for me once, and might work again.

Fitch
 
Update to my opinions...

They have not changed much.

I had the opportunity to see a barrel recently that exhibits this 'wandering bore' situation. It was machined using methods that I already said probably are the cause of such issues. I also then had time to get another of my barrels out, an unturned blank, and looked at it. Low and behold, it did not exhibit this phenomenon. I'm fairly confident it won't when I get done working on the OD of it either. (if I ever do).

How much error did I see? Well, I saw enough error in the OD work to convince me I'm not changing brands of barrel any time soon. Nor am I changing to purchasing pre-turned ones. it wasn't mine, and I didn't have time to mess with it to measure, nor was I really interested. I made a guess, I trust my guess, and won't post it here but it was well within (less than) what some folks have said they have seen. More along the lines of what Gordy said he's found typical, even probably less than that. It was still enough that I'll never be buying one of them. Not that I wasn't convinced long ago on them, but, this was another ancillary nail in that coffin.

Ultimately, the barrel was chambered with the "Old" setup method (more or less), and the indicating job done in the throat was perfect. The resulting throat was THE most perfect throat I have ever seen. For that matter the transition To the throat was amazing as well. How it will shoot is another story.

Be that as it may, I still maintain my opinion that these issues are caused some time after the drilling process. What method you use to setup in order to "correct" this is your business. And as even Gordy says, proving either method to be "better" than the other is not his interest. I think it comes down to whatever method makes you "feel" you are getting better results. If you're convinced, that's even better. Proving it would be difficult at best. Proving it to ME might be even tougher!
 
Right On !

Charles E said:
OK, on the assumption that rougher/finisher cuts a very good chamber, here's part B.

Let's assume you are willing to cut the chamber before cutting the tenon and threading it and cutting the shoulder. Let's assume too that the shank of the reamer -- the opposite end of the bushing -- is ground, or if not, you could specify that it be ground.

When you indicate the barrel in at first, as exactly as you want, you haven't (likely) picked the exact spot where he pilot bushing will fall after the chamber is cut. So, as you make the last pass with the finish reamer, leave it in, and check things by running the dial indicator on the reamer shank. If it shows runout, re-indicate the barrel using the reamer shank. Then cut and thread the tenon and shoulder. Now the chamber end of the barrel will be square to the case head.

Actually, using his slightly different approach, I think this is essentially what Gordy is doing. The only difference is he's "pre-indicating" based on two points at the chamber end of the barrel, points selected about where the bullet will be. He's essentially splitting any error between the chamber and the shoulder. As Phil (& others) have pointed out, we're not talking large numbers here.
Click to expand...




Yes sir Charles! This is perhaps the best post on the subject yet. :cool: Good for you man! :)


Gene Beggs
 
Ok lets say you are working with a cylinder 1.250 how much runout from one end to the other if you indicate each end of the bore tohte outside of the material you are working with lets forget the chamber throat relation here for a minute .
stan
 
Stan,

I for one do not understand your question. Could you be more specific please?

Are you asking how how far from the center of the material the bore is at the muzzle end? If so, most barrel makers cut the OD of the barrel after putting a center in it. So, that number should be very little if nothing. I get unturned ones, and it is still nothing.
 
I am reading this post an getting the impression that these guys are saying that there is a total runout of as much as 40 thousands indicating a serious curvature in these rifle barrels and if that is true it sounds like these barrels need turned between centers before work is started because if there is that much of curvature inside of a finished product coming from a barrel manufactor they would be getting it back not saying that a slightly crooked barrel wont shoot but why make more work for yourself.
thanks stan
 
ALL BARRELS ARE CROOKED...... they always have been, they always will be. It's just a matter of degree. This whole thing about "sending barrels back" and "never using that maker again" is just disturbing to me. The barrel makers do a wonderful job. I think I'm going to just shut up on the subject because the barrel makers don't deserve this. And most halfway decent machinists have known this, some have found ways to make their chambering reamers intersect with the bore in the throat area. Others just wing it and "let the pilot follow the hole."


BTW, pulling readings off the reamer shank makes no sense to me. Except that I guess it could give a sort of a weak guess as to how much the bore runs out from centerline. It's like using your reamer for a range rod....my problem with this method is that it's hard to utilize without taking the pusher off the shank. And that if you try use it for indexing the barrel it's inaccurate. Gordy calls the curve a "banana" while I think it more closely approximates a section from a large helix.

al
 
wvredneck said:
I am reading this post an getting the impression that these guys are saying that there is a total runout of as much as 40 thousands indicating a serious curvature in these rifle barrels and if that is true it sounds like these barrels need turned between centers before work is started because if there is that much of curvature inside of a finished product coming from a barrel manufactor they would be getting it back not saying that a slightly crooked barrel wont shoot but why make more work for yourself.
thanks stan
Click to expand...

Stan,

If the barrel is turned between centers all you are accomplishing is the bore is centered in the barrel diameter at each end. It still is 'crooked' in between...
 
alinwa said:
ALL BARRELS ARE CROOKED...... Gordy calls the curve a "banana" while I think it more closely approximates a section from a large helix.al
Click to expand...
Al, I agree. Well sort of -- things are probably even more ramdom. And maybe I'm dense, but so what? Let the outside of the barrel do its thing. All we can do for the bullet is to give it as good a start on a "useful" life as we can. Sounds like child-rearing. Now if/when these are big numbers, there would be a problem, but usually they aren't. If it still drive you nuts, get an unturned blank & contour it yourself, after you've figured out where the bore (more or less) is.
 
alinwa said:
ALL BARRELS ARE CROOKED...... they always have been, they always will be. It's just a matter of degree. This whole thing about "sending barrels back" and "never using that maker again" is just disturbing to me. The barrel makers do a wonderful job. I think I'm going to just shut up on the subject because the barrel makers don't deserve this. And most halfway decent machinists have known this, some have found ways to make their chambering reamers intersect with the bore in the throat area. Others just wing it and "let the pilot follow the hole."


BTW, pulling readings off the reamer shank makes no sense to me. Except that I guess it could give a sort of a weak guess as to how much the bore runs out from centerline. It's like using your reamer for a range rod....my problem with this method is that it's hard to utilize without taking the pusher off the shank. And that if you try use it for indexing the barrel it's inaccurate. Gordy calls the curve a "banana" while I think it more closely approximates a section from a large helix.

al
Click to expand...



I'm trying a new form of editing :p

I realize that Charles is saying that using the reamer is a way to find centerline of the chamber. Two items...... #1, no matter how tight the chamber there must be SOME runout clearance, but that aside, even if we're happy with using this "centerline" the set your threads and shoulder to "square," IMO it's a complete pita to thread last.

Setting headspace on an existing chamber is SLOW and since there are two or three surfaces to adjust there's more chance of screwup. Of course we've all done it but it's much more sensible IMO to finish the chamber last and set headspace with the reamer. I just recently had to do this because my speculation convinced me to re-time a barrel by several degrees. I had the rifle all boxed up to send off for paint when I realized I'd forgotten to strip the bolt and re-measure clearance at the bolt nose.

My bolt nose clearance was three thou.

I'd screwed up.

I took 'er ALL back apart and reset and shaved off a couple more thou.

Stupid.

and all because I broke concentration.

I like to headspace with the reamer.

al
 
I know a gunsmith that faces the tenon, runs the reamer in without any predrill, prebore, or roughing reamer. He runs the reamer in until it is flush with the end of the barrel. He cuts the tenon and measures from the end of the tenon to the shoulder. He threads and cuts the tenon to the correct length and does the bolt nose clearance cut as the last operation.
I personally can't bring myself to do it this way.
Butch
 
You must log in or register to reply here.
Back
Top