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Rifles, Reloading, Optics, Equipment
Gunsmithing
? about bad barrel blank
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<blockquote data-quote="70oldsracer" data-source="post: 1772953" data-attributes="member: 95943"><p>Okay, there are a lot of questions that I'll try to address. The rifle was shot with factory ammo, 139 grain Hornady sst. I can not and do not reload due to the fact that I live in NYC, need I say more. The rifle was shot off of a lead sled and I posted the 25 yard target to show that I shot once and moved the scope and it seemed to track fine. Yes, I could have taken a few more shots, but I've never had any issues like this sighting in. The stock is not bedded and it's the Hogue stock with the full length bedding block. I only dialed in the chamber end and used both spiders to do that. Unfortunately I can not get any closer to the headstock while chambering due to the small spindle bore of only .750". If I remember correctly, the twist rate was 1-8. My tailstock alignment was adjusted to the best of my ability with a coaxial indicator. I remember it wasn't perfect, that's why I used a floating reamer holder. I know there are a lot of variables here, but I'm 52 years old and I know when I rifle isn't shooting correctly. I really don't feel I don't have enough lathe for what I'm trying to do. I read an article once written by retired gunsmith Les Brooks, retired gunsmith. It's titled Rifle barrel fitting 7x12 mini lathe. Unfortunately, I can't locate the article. I have it as an email and will try to post it. The only reason I blamed the barrel is because I sent it out to someone that knows a lot more than me about machining and gunsmith work. This was his response to me:</p><p></p><p>Here is what I think. Chamber to bore run out is less than .0015. About .0012-.0013 best I can tell. Pretty good I think. OD run out to bore at the muzzle is .0055-.006. Not so great. My Green Mountain AR barrels are less than .002 in the full length. Out of a 100 barrels, most are better than that. OD run out to chamber is .001-.0012. OD run out in the middle of the barrel is .0125. Bad. So either you really poured on the Cerakote at the muzzle and the middle of the barrel, exactly in line with each other, or the barrel is flawed. My guess is that maybe the barrel was not stress relieved properly and when the OD was profiled, whether you did it or someone else, it went banana. That would account for what you are experiencing. I am not a barrel expert but everything I have read is that you do not want more than .003 wall thickness variation, even if the bore is straight. If it is too much, when the barrel heats up, it will slowly start to curve. I do not have a full length gauge rod to check a curved bore. Very few do. Did you profile the OD or was it already done? Did you cut the threads? great job if you did.</p><p></p><p>this too:</p><p>Run out at the muzzle could be fixed. That much run out in the middle of the barrel is a problem. If you put the range rod in the muzzle, and the reamer in the chamber, between centers it is way out in the middle. Hard to believe that with their CNC lathes, they would have been that far off. .003-.005 maybe but not that much.</p></blockquote><p></p>
[QUOTE="70oldsracer, post: 1772953, member: 95943"] Okay, there are a lot of questions that I'll try to address. The rifle was shot with factory ammo, 139 grain Hornady sst. I can not and do not reload due to the fact that I live in NYC, need I say more. The rifle was shot off of a lead sled and I posted the 25 yard target to show that I shot once and moved the scope and it seemed to track fine. Yes, I could have taken a few more shots, but I've never had any issues like this sighting in. The stock is not bedded and it's the Hogue stock with the full length bedding block. I only dialed in the chamber end and used both spiders to do that. Unfortunately I can not get any closer to the headstock while chambering due to the small spindle bore of only .750". If I remember correctly, the twist rate was 1-8. My tailstock alignment was adjusted to the best of my ability with a coaxial indicator. I remember it wasn't perfect, that's why I used a floating reamer holder. I know there are a lot of variables here, but I'm 52 years old and I know when I rifle isn't shooting correctly. I really don't feel I don't have enough lathe for what I'm trying to do. I read an article once written by retired gunsmith Les Brooks, retired gunsmith. It's titled Rifle barrel fitting 7x12 mini lathe. Unfortunately, I can't locate the article. I have it as an email and will try to post it. The only reason I blamed the barrel is because I sent it out to someone that knows a lot more than me about machining and gunsmith work. This was his response to me: Here is what I think. Chamber to bore run out is less than .0015. About .0012-.0013 best I can tell. Pretty good I think. OD run out to bore at the muzzle is .0055-.006. Not so great. My Green Mountain AR barrels are less than .002 in the full length. Out of a 100 barrels, most are better than that. OD run out to chamber is .001-.0012. OD run out in the middle of the barrel is .0125. Bad. So either you really poured on the Cerakote at the muzzle and the middle of the barrel, exactly in line with each other, or the barrel is flawed. My guess is that maybe the barrel was not stress relieved properly and when the OD was profiled, whether you did it or someone else, it went banana. That would account for what you are experiencing. I am not a barrel expert but everything I have read is that you do not want more than .003 wall thickness variation, even if the bore is straight. If it is too much, when the barrel heats up, it will slowly start to curve. I do not have a full length gauge rod to check a curved bore. Very few do. Did you profile the OD or was it already done? Did you cut the threads? great job if you did. this too: Run out at the muzzle could be fixed. That much run out in the middle of the barrel is a problem. If you put the range rod in the muzzle, and the reamer in the chamber, between centers it is way out in the middle. Hard to believe that with their CNC lathes, they would have been that far off. .003-.005 maybe but not that much. [/QUOTE]
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? about bad barrel blank
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