J
Jeffrey
Guest
Butch,
I was working on a Savage and had to make room for the nut to go back farther.
Jeff
I was working on a Savage and had to make room for the nut to go back farther.
Jeff
R
Riflemeister
Guest
I think Jeffrey raises some very interesting issues on barrel setup, particularly one with a lot of bore runout such as I have in the lathe.
With a perfectly straight bore, any of the methods would work well. When the bore has runout, things get interesting.
I think we all agree that a chamber must be concentric with the centerline of the action and the throat centered in the bore within .0001" or .0002" for best accuracy. The question I still have and that Jeffrey raises is how critical is it that the bullet not only gets started centered in the bore, but that it also gets started with no angular difference to the bore? It appears that an angular start will result in the bullet point describing an arc in flight and could possibly degrade accuracy. Any thoughts on this issue?
Range rods make some attempt to correct the angular bore intercept problem, where indicating the throat and the muzzle does not. For the range rod to be effective, it must have the snug fitting pilot where the throat will be.
Back to my initial post on the problems I have with the barrel in my lathe, I have found the following;
1. The pilot bushing on the range rod was over .500" short of the throat position on the 280 AI I was cutting.
2. Not knowing whether I had a straight line excursion of the bore, a parabola or a combination of the two, I should have pre-bored.
3.When I dialed it in and measured .086" TIR runout at the muzzle, I may have had a situation where the pilot on the reamer would pull the throat off even with everything dialed in correctly and then pre-bored. I should have checked with Dan before cutting metal.
I have read posts on this forum before where smiths question the wisdom of even using a pilot on the reamer, especially a tight fitting one. I wonder if these are the ones who dial in the throat and muzzle to chamber? On a bore such as I'm working with, a tight fitting reamer bushing could really pull the throat off if the angle of chamber to bore intercept is very great.
The last point is that it is possible that none of the various setup methods would have given satisfactory results on this obviously crooked barrel. The good news is it has everyone taking a fresh look at how they set up and chamber. I talked to Dave Kiff yesterday and he is making me a new range rod that has a .75" straight section behind the pilot before starting the taper so I can reach the throat area of the longer chamberings.
With a perfectly straight bore, any of the methods would work well. When the bore has runout, things get interesting.
I think we all agree that a chamber must be concentric with the centerline of the action and the throat centered in the bore within .0001" or .0002" for best accuracy. The question I still have and that Jeffrey raises is how critical is it that the bullet not only gets started centered in the bore, but that it also gets started with no angular difference to the bore? It appears that an angular start will result in the bullet point describing an arc in flight and could possibly degrade accuracy. Any thoughts on this issue?
Range rods make some attempt to correct the angular bore intercept problem, where indicating the throat and the muzzle does not. For the range rod to be effective, it must have the snug fitting pilot where the throat will be.
Back to my initial post on the problems I have with the barrel in my lathe, I have found the following;
1. The pilot bushing on the range rod was over .500" short of the throat position on the 280 AI I was cutting.
2. Not knowing whether I had a straight line excursion of the bore, a parabola or a combination of the two, I should have pre-bored.
3.When I dialed it in and measured .086" TIR runout at the muzzle, I may have had a situation where the pilot on the reamer would pull the throat off even with everything dialed in correctly and then pre-bored. I should have checked with Dan before cutting metal.
I have read posts on this forum before where smiths question the wisdom of even using a pilot on the reamer, especially a tight fitting one. I wonder if these are the ones who dial in the throat and muzzle to chamber? On a bore such as I'm working with, a tight fitting reamer bushing could really pull the throat off if the angle of chamber to bore intercept is very great.
The last point is that it is possible that none of the various setup methods would have given satisfactory results on this obviously crooked barrel. The good news is it has everyone taking a fresh look at how they set up and chamber. I talked to Dave Kiff yesterday and he is making me a new range rod that has a .75" straight section behind the pilot before starting the taper so I can reach the throat area of the longer chamberings.
ultramagmed
JKM
Another newby question..........
Since this thread is so hot, I thought I would ask this question here. After chambering is complete, and all runout is checked, is the setup the same to prepare for crowning......meaning are both ends of the barrel indicated in to as close to zero runout as possible using a test indicator on the lands and grooves on the muzzle end? I suppose you could indicate off the newly cut chamber on the chamber end in the outboard spider, is this assumption correct? Also how is a barrel that is already tapered clamped in the chuck on that taper for crowning? Copper wire or something I presume? Sorry if this a little off topic, any replies (or pictures if possible) would be great.
Thanks, JKM
P.S. Thanks Dennis for the pictures, as they say they're worth a thousand words.
Since this thread is so hot, I thought I would ask this question here. After chambering is complete, and all runout is checked, is the setup the same to prepare for crowning......meaning are both ends of the barrel indicated in to as close to zero runout as possible using a test indicator on the lands and grooves on the muzzle end? I suppose you could indicate off the newly cut chamber on the chamber end in the outboard spider, is this assumption correct? Also how is a barrel that is already tapered clamped in the chuck on that taper for crowning? Copper wire or something I presume? Sorry if this a little off topic, any replies (or pictures if possible) would be great.
Thanks, JKM
P.S. Thanks Dennis for the pictures, as they say they're worth a thousand words.
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Jeffrey
Guest
Jerry,
[I]"If the curve is very great, I'd send the barrel back"[/I]. I've not tried sending them back I just write them off or make a "hunter out of them".
"If you have aligned the throat area, predrilled and prebored, and used a snug fitting pilot bushing, and are using a HSS or HSS/CO reamer, the chamber transition will be concentric". I was looking more at "off axis" not concentricity.
"Don't worry about how the barrel OD fits the stock channel. Be concerned where the muzzle exit points in relation to where the stock/action points". Some are barrel mounted in the stock so the action relationship has a different function.
"If you have determined you have a reasonably straight bore, and you have set the barrel up as described above, you will not have that problem!!" I didn't set them up originally I was fixing the work of others.
"How are you going to quantify too much curve? In actuallity, a curved bore can shoot just as well as a reasonably straight one, if it is fitted properly". Do an Index check on the barrel. See Gene Beggs.
"It doesn't matter who the shooter is, if the barrel will not shoot up to winning standards, the shooter looses"!! I guess I just don't get this one. Are you saying that if a barrel can't break the national record then it's no good?
Jeff
[I]"If the curve is very great, I'd send the barrel back"[/I]. I've not tried sending them back I just write them off or make a "hunter out of them".
"If you have aligned the throat area, predrilled and prebored, and used a snug fitting pilot bushing, and are using a HSS or HSS/CO reamer, the chamber transition will be concentric". I was looking more at "off axis" not concentricity.
"Don't worry about how the barrel OD fits the stock channel. Be concerned where the muzzle exit points in relation to where the stock/action points". Some are barrel mounted in the stock so the action relationship has a different function.
"If you have determined you have a reasonably straight bore, and you have set the barrel up as described above, you will not have that problem!!" I didn't set them up originally I was fixing the work of others.
"How are you going to quantify too much curve? In actuallity, a curved bore can shoot just as well as a reasonably straight one, if it is fitted properly". Do an Index check on the barrel. See Gene Beggs.
"It doesn't matter who the shooter is, if the barrel will not shoot up to winning standards, the shooter looses"!! I guess I just don't get this one. Are you saying that if a barrel can't break the national record then it's no good?
Jeff
T
tim in tx
Guest
riflemeister
one thing i might suggest is an indicating rod that dave makes for setting back chambers,it only indicates over an area of 1 inch or so,in a big curve with a range rod by indicating over a 3 inch area you will be in a bind in certain cases but use a range rod first,predrill ,deburr the bottom of the hole with a unithroater and then slide an indicator rod into the area in front of the chamber area,then bore the hole to that centerline in front of the chamber ,your muzzle will have less runout by doing what i am suggesting by do so you are going on down around the curve to get your centerline which should be in front of the chamber and not where you just cut away. i dont know about others but when i use a loose bushing i end up off center by .0005 -.001.so i do use a tight bushing always.but this requirs a no bind in front of the chamber to be effective and to do so you have to be coaxial with the reamer when the bushing stops in travel.good luck sir hope this helps. tim in tx
one thing i might suggest is an indicating rod that dave makes for setting back chambers,it only indicates over an area of 1 inch or so,in a big curve with a range rod by indicating over a 3 inch area you will be in a bind in certain cases but use a range rod first,predrill ,deburr the bottom of the hole with a unithroater and then slide an indicator rod into the area in front of the chamber area,then bore the hole to that centerline in front of the chamber ,your muzzle will have less runout by doing what i am suggesting by do so you are going on down around the curve to get your centerline which should be in front of the chamber and not where you just cut away. i dont know about others but when i use a loose bushing i end up off center by .0005 -.001.so i do use a tight bushing always.but this requirs a no bind in front of the chamber to be effective and to do so you have to be coaxial with the reamer when the bushing stops in travel.good luck sir hope this helps. tim in tx
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JerrySharrett
Senile Member
No good?? Is that what you think I said?? Read it again.
I've been to many 100/200 shoots and several 600 yard shoots. I pulled the target for John lewis (ably assisted by Greg Sigmund, or did I assist Greg) when John shot a new 600 yard HV record of 0.387". I was shooting on the adjacent bench to Larry Isenhour when he broke the LG 600 yard record. I've never seen a bad barrel shoot a record agg, or even a record group for that matter.
Now, that being said, a Tony Boyer can take my gun and beat me, shooting the same gun. But I don't shoot bad enough that Mr. B can take a 0.300" gun and beat me with me shooting a 0.150" gun, shooting in reasonable conditions, and I am not, by any means, an above average wind shooter.
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4Mesh
Guest
I sure am glad I chamber my guns in a CNC with a boring bar, and have a headstock so long that I can't indicate the muzzle. I indicate the throat, and forget about it. Hit the green button...
Ignorance is bliss I guess.
Ignorance is bliss I guess.
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pwolfppc
Guest
Ignorance is bliss I guess.
apparently.
chamber to bore lining up is the same problem. doesn't matter how the metal is removed. if the neck is off with the bore the neck is off with the bore. cnc, n/c, turret lathe, engine lathe, screw machine, off is off.
D
Dave Short
Guest
I sure am glad I chamber my guns in a CNC with a boring bar, and have a headstock so long that I can't indicate the muzzle. I indicate the throat, and forget about it. Hit the green button...
Ignorance is bliss I guess.
Ahem...It sounds like the chamber and bore must be concentric at the interface, but need not be coaxial...Ahem...
Good thing perfectly coaxial isn't necessary; because none of us can get them that way............even by indicating off a rod and letting the bore at the muzzle orbit the centerline.
-Dave-
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Riflemeister
Guest
Crowning
I think the range rod and two .0001" indicators really makes sense when setting up to crown. Setting it up that way insures you have done your best to make the crown concentric and perpendicular to the bore at the muzzle. Deltronic pins might be even better.
I think the range rod and two .0001" indicators really makes sense when setting up to crown. Setting it up that way insures you have done your best to make the crown concentric and perpendicular to the bore at the muzzle. Deltronic pins might be even better.
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4Mesh
Guest
RM,
EDIT ---------
I just removed my previous confusing interpretation from here....
Ok, I think I now understand what you're saying here. Sorry, I think I was asleep before. Ok, you're indicating both ends of the range rod and then the muzzle swings 43 off center and no, I don't think that's all that uncommon. From the people I've heard do that method, it's more common in a smaller diameter barrel, and once I did a chromemoly barrel that easily would have had more error than this. It was definitely the worst barrel I ever did for the breach end being distorted, but, that one was off .010 over 1.5" or so. (.020tir). I only found it cause I always indicate the throat after roughing the chamber out.
Anyway, my short answer would be, it might be uncommon but not unheard of.
/EDIT----------
Somehow, I still wonder how it's possible to have numbers this large without some indicating error cause the barrels I do for myself are no where near this crooked. Not even close.
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JerrySharrett
Senile Member
Ahem... but need not be coaxial...Ahem...
Good thing perfectly coaxial isn't necessary;
-Dave-
Does a crooked bore even have an axel??
Damn, its snowing again....blasted cabin door won't even open!!!
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4Mesh
Guest
apparently.
chamber to bore lining up is the same problem. doesn't matter how the metal is removed. if the neck is off with the bore the neck is off with the bore. cnc, n/c, turret lathe, engine lathe, screw machine, off is off.
pwolf, we're not talking about the neck being off. In either arrangement, the neck is no issue. It's centered (as well as needed I suppose).
Ultimately, the only difference in these methods is that some would consider my method of not worrying about the muzzle means a cartridge in my chamber might not be pointing exactly at the area ahead of the throat, and would be off from doing that perfectly by whatever amount the bore "snakes". However, my cartridge should point pretty close to the muzzle and crown.
In the range rod method, muzzle and crown are not in line with the cartridge (theoretically) but the area ahead of the bullet "is" I guess.
Either way, in a perfect world the result we all look for is the same. First trouble is, the world isn't perfect. Second is, "out" to one person is not the same thing as "out" to another. Obviously, I consider "out" to be different than what the range rod advocates do. I'd challenge anyone to prove either way to be better more accurate than the other. I happen to prefer my way is all. Since I only make guns for me, I guess that's fine.
jackie schmidt
New member
Good Grief
All of us "hot shot Machinist and Gunsmiths" are striving to work within a couple of tenths when chambering, and then go and place rounds in the chamber that have runnout in the "thousanths", not "tenths". Checked any of your loaded rounds lately??
I have checked numerous loaded rounds for shooters at matches, and very few run better than .002.
Is placeing a round that is dead true a chamber that is out .002 the same as placing a round that runs out .002 in a dead straight chamber???.
I have shot 10-shot "ones" in competition with ammo that I know ran no better than .002.......jackie
All of us "hot shot Machinist and Gunsmiths" are striving to work within a couple of tenths when chambering, and then go and place rounds in the chamber that have runnout in the "thousanths", not "tenths". Checked any of your loaded rounds lately??
I have checked numerous loaded rounds for shooters at matches, and very few run better than .002.
Is placeing a round that is dead true a chamber that is out .002 the same as placing a round that runs out .002 in a dead straight chamber???
.I have shot 10-shot "ones" in competition with ammo that I know ran no better than .002.......jackie
Butch Lambert
Active member
From the mouth of Turk Takano, "They ain't no perfect chamber". The reason being is there are no perfect barrels. If you are happy the way you are doing it then don't change!
Butch
Butch
JerrySharrett
Senile Member
Its called tolerance stack up Jackie. A thousandth here, a thousandth there.
A chamber neck with 0.001" or more offset from the groove diameter would worry me.
As to the loaded round, tell me, if you are shooting at the jam (light medium or heavy), with a freebore 0.0001/0002" over bullet diameter, the seated bullet runout of 0.002" will be straightened by the chambering cam action would it not? Something to think about if you are shooting zero freebore.
Moving (straightening) the bullet in the loaded round is easy and requires very little pressure.
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4Mesh
Guest
Sometimes, I almost wish I had a lathe to try this whole range rod thing for myself. Unfortunately, the shortest headstock I have available is way too long to do it, even with a 32" barrel.
I just grabbed two unturned blanks that I have here. Measuring the breach ends, The first barrel is a very old 6 groove of a manufacture I won't mention. The entry hole is easily within .001 of the center of the piece of stock. The blank is 32-3/16" long. The muzzle end hole is as best I can measure, also within .001" of the center of the piece of rough, mill finish material. This is a button rifled barrel and even has a huge smear of metal that came out when the button passed. That material smear is .011" above the surface of the roughed material face.
The second barrel is a more recent manufacture and is a much better known brand name which advertizes on this site. The breach end has a reamed starter hole for the button so I can't actually reach down in to measure the lands and grooves with a caliper. It's close enough for my taste. It also measures to have a hole within .001 of center of the rough stock. Again, neither of these barrels is turned. I specifically get unturned blanks and to my own turning if I decide to taper or whatever. Now, on the muzzle end, this barrel also measures within .001 of center. Neither of these barrels has "centers" cut in them. They're untouched rough stock from the mill. This second barrel blank measures almost exactly 30" in length.
Now, if this is the typical amount of crookedness found in a match barrels from two different manufacturers after gun drilling 30" or more, exactly what are we attempting to fix here?? I mean, if both ends are within .001", how far could the bore possibly snake around? In stainless match barrels anyhow.
I should also say that I"ve seen another manufacturer (well know and reputable) have starter holes in the barrels that were off by 2 or 3 thou. I'd say that's about as bad as I've seen in stainless. In CM, I presume what I saw in that one long ago was a button that was smashed in crooked and that showed up as an off center start. I'll probably never know. I do know I don't see off center issues on the barrels I buy today.
I just grabbed two unturned blanks that I have here. Measuring the breach ends, The first barrel is a very old 6 groove of a manufacture I won't mention. The entry hole is easily within .001 of the center of the piece of stock. The blank is 32-3/16" long. The muzzle end hole is as best I can measure, also within .001" of the center of the piece of rough, mill finish material. This is a button rifled barrel and even has a huge smear of metal that came out when the button passed. That material smear is .011" above the surface of the roughed material face.
The second barrel is a more recent manufacture and is a much better known brand name which advertizes on this site. The breach end has a reamed starter hole for the button so I can't actually reach down in to measure the lands and grooves with a caliper. It's close enough for my taste. It also measures to have a hole within .001 of center of the rough stock. Again, neither of these barrels is turned. I specifically get unturned blanks and to my own turning if I decide to taper or whatever. Now, on the muzzle end, this barrel also measures within .001 of center. Neither of these barrels has "centers" cut in them. They're untouched rough stock from the mill. This second barrel blank measures almost exactly 30" in length.
Now, if this is the typical amount of crookedness found in a match barrels from two different manufacturers after gun drilling 30" or more, exactly what are we attempting to fix here?? I mean, if both ends are within .001", how far could the bore possibly snake around? In stainless match barrels anyhow.
I should also say that I"ve seen another manufacturer (well know and reputable) have starter holes in the barrels that were off by 2 or 3 thou. I'd say that's about as bad as I've seen in stainless. In CM, I presume what I saw in that one long ago was a button that was smashed in crooked and that showed up as an off center start. I'll probably never know. I do know I don't see off center issues on the barrels I buy today.
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JerrySharrett
Senile Member
The ends of the bores are very close to the OD's because of the way the bores are centered and the OD turned in the barrel makers finishing process. Its the bore runout away from the ends that is the problem. A few weeks ago I dialed in a barrel, top of the winners equipment list brand, and the bore looked like a two-girls jump rope when I turned the spindle on. Guess where it went?
If you can run your little CNC with the door open, set one of those barrels up and jog the spindle at about 200 RPM or so, then look at the bore while it is spinning.
333smitty
Tomball Gun Club
Jackie Schmidt and Runout
I had Jackie Schmidt chambered up a Krieger HV 17t 30ppc for the upcoming Tomball Club VFS matches last night. When Jackie was finishing up he asked Guillermo and me to witness the run out on his chamber.
He checked the throat, chamber, treads, etc and all were within .0002. He does this every time he chambers a barrel for me. You actually witness the quality of his work. The "last word" dial indicator does not lie.
This way I know I have a Benchrest Quality chamber....
Vic
FYI, Not only is Jackie a world class machinist, Benchrest competitor,
drag boat racer, and a nitro drag bike pilot. He can sing to. He treated
us to a couple songs during the evening.....
I had Jackie Schmidt chambered up a Krieger HV 17t 30ppc for the upcoming Tomball Club VFS matches last night. When Jackie was finishing up he asked Guillermo and me to witness the run out on his chamber.
He checked the throat, chamber, treads, etc and all were within .0002. He does this every time he chambers a barrel for me. You actually witness the quality of his work. The "last word" dial indicator does not lie.
This way I know I have a Benchrest Quality chamber....
Vic
FYI, Not only is Jackie a world class machinist, Benchrest competitor,
drag boat racer, and a nitro drag bike pilot. He can sing to. He treated
us to a couple songs during the evening.....
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R
Riflemeister
Guest
Offcenter
4mesh,
The problem is not at the ends of the blanks, the problem lies in the middle between the two ends. You really need to find someone with a shorter headstock and a spider on the back side. If you take both those 30" blanks and dial in both ends to run true, I'll bet you will see an alarming wobble in the middle of the blanks. As an aside, the straightest barrel I ever had in my lathe was a M-96 Swedish Mauser takeoff. It had probably been straightened by some little guy with a big mechanical press somewhere in the Black Forest. A lot of old time gunsmithing and armorers books discuss barrel straightening back in the day before we discovered the cure was worse than the disease.
4mesh,
The problem is not at the ends of the blanks, the problem lies in the middle between the two ends. You really need to find someone with a shorter headstock and a spider on the back side. If you take both those 30" blanks and dial in both ends to run true, I'll bet you will see an alarming wobble in the middle of the blanks. As an aside, the straightest barrel I ever had in my lathe was a M-96 Swedish Mauser takeoff. It had probably been straightened by some little guy with a big mechanical press somewhere in the Black Forest. A lot of old time gunsmithing and armorers books discuss barrel straightening back in the day before we discovered the cure was worse than the disease.