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Rifles, Reloading, Optics, Equipment
Gunsmithing
Timing a Barrel, how much impact in Long Range?
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<blockquote data-quote="Rustystud" data-source="post: 181361" data-attributes="member: 9964"><p><strong>Arc and Indexing</strong></p><p></p><p>AJ:</p><p> </p><p>There have been two different scenarios brought up here that I am reading. One is the natural arc of a barrel due to gravity. This is a natural phenomenon and can be compensated for or just accepted. The other is the alignment of the bore in relationship where the bore points at the muzzle.</p><p> </p><p>From a gunsmiths point of view there are several schools of thought. We all will agree that barrels are not drilled perfectly.</p><p> </p><p>One school is to start off straight and end up straight. This means dialing in the barrels on both ends. Most smiths do this within .0002 or better.</p><p> </p><p>The other school is to align the axis of the case and bullet with the bore. This is done by drilling the bore out about 3/4 the lenght of the case, then boring it out with a boring bar within about .0015 of finish diameter. Then the barrel is redialed in using two points of indication in the throat area. The tendon end is dialed in crudely. Then the indicating rod is indicated near the throat and with another indicator back on the rod near the tendon face. The rod is dialed in by adjusting the spider end of the barrel.</p><p>The muzzle end is left out of center. The high spot is marked on the chuck so the barrel can be indexed to have the high side point up with the finished barrel.</p><p> </p><p>There is a third philosphy and that is to use a floating reamer holder that floats both co-axially and concentrically. This may leave a little more runout in the web area but aligns off the reamer pilot at the throat area of the chamber. Most chambers cut this way will be within .002 or better in the web area. PT&G reamers are generally tight (small) in the web area and chambers cut with them require a little polishing to open then up. </p><p> </p><p>The with either method the end results are so much better than factory barrels and chambers that there is no comparison.</p><p> </p><p>AJ this is a real bone of contention with the BR shooting community. You will have the most heated debates on which methodology is the best.</p><p> </p><p>The idea of a tight chamber is not always the one that shoots the best. I can tell you this from experience. I chamber a fair number of precision barrels. In my opinion stress and alignment in fitting barrels to actions and bolts to actions, and actions in stocks have more to do with good or bad performance. Todays top flight barrels are all capable of shooting sub .25 moa.</p><p> </p><p>Hope I have not confused you more. I am sure some others will chime in.</p><p> </p><p>Rustystud</p></blockquote><p></p>
[QUOTE="Rustystud, post: 181361, member: 9964"] [b]Arc and Indexing[/b] AJ: There have been two different scenarios brought up here that I am reading. One is the natural arc of a barrel due to gravity. This is a natural phenomenon and can be compensated for or just accepted. The other is the alignment of the bore in relationship where the bore points at the muzzle. From a gunsmiths point of view there are several schools of thought. We all will agree that barrels are not drilled perfectly. One school is to start off straight and end up straight. This means dialing in the barrels on both ends. Most smiths do this within .0002 or better. The other school is to align the axis of the case and bullet with the bore. This is done by drilling the bore out about 3/4 the lenght of the case, then boring it out with a boring bar within about .0015 of finish diameter. Then the barrel is redialed in using two points of indication in the throat area. The tendon end is dialed in crudely. Then the indicating rod is indicated near the throat and with another indicator back on the rod near the tendon face. The rod is dialed in by adjusting the spider end of the barrel. The muzzle end is left out of center. The high spot is marked on the chuck so the barrel can be indexed to have the high side point up with the finished barrel. There is a third philosphy and that is to use a floating reamer holder that floats both co-axially and concentrically. This may leave a little more runout in the web area but aligns off the reamer pilot at the throat area of the chamber. Most chambers cut this way will be within .002 or better in the web area. PT&G reamers are generally tight (small) in the web area and chambers cut with them require a little polishing to open then up. The with either method the end results are so much better than factory barrels and chambers that there is no comparison. AJ this is a real bone of contention with the BR shooting community. You will have the most heated debates on which methodology is the best. The idea of a tight chamber is not always the one that shoots the best. I can tell you this from experience. I chamber a fair number of precision barrels. In my opinion stress and alignment in fitting barrels to actions and bolts to actions, and actions in stocks have more to do with good or bad performance. Todays top flight barrels are all capable of shooting sub .25 moa. Hope I have not confused you more. I am sure some others will chime in. Rustystud [/QUOTE]
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