barrel chamber question

alinwa said:
Change your user name???

Just re-register under another name. Can't see the problem. You could be on here under 50 different names if you so chose.

al
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Al, I've had this name on here for over 6 years now, it makes me feel like one of the old timers!
 
I posted this same reply as a new thread called Chambering for Long Range

I hate to mix in some gunsmithing talk in here amidst all this bickering but I have something to throw out here for discussion.
When I first started chambering my own barrels I had a cut blank with a .237 bore made to finish at 32". I chambered it using the Gordy method crowned it at 29" and shot it in competition for the rest of the year.
This barrel was the best shooting barrel I had to date and it was out every bit of .060 at the muzzle. I measured the runout when I indexed the muzzle to shoot up or at 12 O clock.
I could barely get my scope to 0 at 100 yards.
The problem was I never really saw any outstanding groups at 200 yards, I always had some flippers in the group and just assumed I couldn't read the condition well enough at close range to dope the group into one hole.
I have learned a lot these past couple years, and recently pulled that barrel out of my barrel cabinet and sawed it off and dialed it in to run true at the lead and muzzle. I then drilled & bored it true & rechambered it with the exact same reamer & set the headspace right back to where it still worked with the same old brass and die adjustment.
I have never owned a long range barrel that shoots so well at 100 & 200 yards. This thing is so predictable & it rides the bags so well that I can completely free recoil it with my head up watching the flaggs and never flip a shot. I think some of these old timers are onto something here with these short range rifles needing the muzzle directly in line with the rest of the rifle instead of indexed to shoot up or down. I have now shot the smallest groups I have ever shot at my 200 yd range.
The thing that puzzles me is I have yet to shoot a group at 600 yd to make me think it is worth taking to a match.
 
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Jay, you cut a chamber straight by indexing the bbl at 2 points. One at one end of the bbl and one at the other. Did you borescope to bbl to see how the lead/rifling marriage looks? I've seen barrels indicated in the way you did yours have rifling on one side and none on the other because the bore wasn't straight between those 2 points. I wouldn't think .060" would be enough to hurt anything for zeroing a scope unless you had a ridiculous amount of cant in the base or rings. I've seen much worse zero just fine.
 
SM,If he indicates the leade and taper bores to that point and reams it will be concentric to the axis to the bore. Also you might trig out a muzzle that is out .060 and you may be surprised how far the pointof impact is off in 100 yards.
Butch
 
Butch, if he bores it out AT the lead, indicates the bbl in AT the lead, and then chases the chamber to that lead point.

I've seen barrels off by that much, never had a problem getting a 100 yd zero with the quality components I use.

I know .020" of rear scope base shim is 15MOA, but I don't think the same formula will apply to the bbl. Got one that will work?
 
9MOA is respectable, but shouldn't be enough to prohibit a guy from getting a 100 yard zero unless I'm missing something.
 
Superm,
The same formula works. Your scope base is shorter,so the .060 on a 5" base would be a lot larger angle of the leg of the triangle.
Butch
 
Sorry, I left out the fact that I use 20 MOA bases as I am a long range shooter. This barrel I'm talking about will 0 with a standard base.
 
Jay Cutright said:
I hate to mix in some gunsmithing talk in here amidst all this bickering but I have something to throw out here for discussion.
When I first started chambering my own barrels I had a cut blank with a .237 bore made to finish at 32". I chambered it using the Gordy method crowned it at 29" and shot it in competition for the rest of the year.
This barrel was the best shooting barrel I had to date and it was out every bit of .060 at the muzzle. I measured the runout when I indexed the muzzle to shoot up or at 12 O clock.
I could barely get my scope to 0 at 100 yards.
The problem was I never really saw any outstanding groups at 200 yards, I always had some flippers in the group and just assumed I couldn't read the condition well enough at close range to dope the group into one hole.
I have learned a lot these past couple years, and recently pulled that barrel out of my barrel cabinet and sawed it off and dialed it in to run true at the lead and muzzle. I then drilled & bored it true & rechambered it with the exact same reamer & set the headspace right back to where it still worked with the same old brass and die adjustment.
I have never owned a long range barrel that shoots so well at 100 & 200 yards. This thing is so predictable & it rides the bags so well that I can completely free recoil it with my head up watching the flaggs and never flip a shot. I think some of these old timers are onto something here with these short range rifles needing the muzzle directly in line with the rest of the rifle instead of indexed to shoot up or down. I have now shot the smallest groups I have ever shot at my 200 yd range.
The thing that puzzles me is I have yet to shoot a group at 600 yd to make me think it is worth taking to a match.
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Hi Jay,

Yes, but hopefully no-one objects to you getting in the way of a good argument!! Ha ha.... :)

I too have fitted barrels with the GG method in which I knew before i started with it that the bore was visually bowed, that were measured more than 0.045"-0.060" of TIR at the muzzle out when correctly dialled in to run true at the breech end, and then indexed at the muzzle 'high-point-up'. I think that you have overlooked the fact that the barrel maker probably needs a kick in the ass for sending you such a bowed barrel, but from the results one could assume you initially did a pretty good job of fitting it, despite what you had to deal with.

Also, for the short range BR guys if they are shooting with 'frozen scopes', then alot of elevation compensation in the mounting due to the initial fitting method of indexing the barrel muzzle position, could be something to consider. If that is the case, then you may want to go with the 'muzzle centered', but in reality the barrel maker has some questions to answer, in my opinion.

Personally, I prefer the GG method if possible. I think your initial results show that it is sound. Also, the 'flippers' could be due to velocity variations, and to my mind, the effect of this could be more pronounced on the target with an 'indexed muzzle', rather than a 'centered muzzle'.

Hopefully I have not added any more fuel to the fire, or started a whole new argument............

Dean.
 
Good friend of mine (the late Henry Vranian) used the GG method with excellent results but he always complained about the POI from barrel to barrel. We would have good laughs on the phone about the differences. Never did hear him say his scope ran out of clicks.
 
Even the aforementioned 8.9moa can be a problem if'n it's cattywampus @ 45degrees in any direction..............you get into the "corner" of the adjustment. I had a barrel chambered between centers that was bad enough that I had to lap the rings over.

Conversely, the scope CAN'T run out of cliks if you index the barrels and know prior where it points. You want more elevation, index to 12:00 You need to lose el, go for 6:00.

BUT :) barrels are "twisted" too...... don't put the writing on 'til you shoot it!

al
 
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