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Ackley Improved |
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Roy Finn
MODERATOR Steiner Junkie Joined: April/05/2004 Location: United States Status: Offline Points: 4856 |
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You have to keep in mind and I said this before, that you have to use the same components that the manual you are using as a guideline. Don't assume that because one manual states that 58 grs of say IMR-4831 with a 140 Nosler BT is safe to use if you switch to a 140 Barnes TSX that may have a longer bearing surface, harder or softer copper jackets etc. etc....Lots of guys make that mistake. |
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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That's an incorrect assumption. Yes, you would know very soon after loading for that rifle. It's possible the mfg cut the chamber outside SAAMI tolerances (too deep). You could have out of spec sizing dies. More than likely, you will be within spec on both, but it's not a certainty. Mistakes can and do happen. The only way to know for absolute certain is to check headspace beforehand. There are sizing tricks you can use (i.e. creating a "false shoulder" on the base of the neck during sizing) when handloading that will enable you to know by feel that you have tight headspace. |
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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To check for excess headspace can I compare a fire formed case against a nosler 280 ai case and an unused 280 round? Also could I check a resized case in the same way?
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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Unused nosler brass and a factory loaded 280 round. I keep both.
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Roy Finn
MODERATOR Steiner Junkie Joined: April/05/2004 Location: United States Status: Offline Points: 4856 |
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Not sure that you could just measure a fired case due to the fact that there is a certain amount of spring back when a case is fired in a chamber. How much I don't know. Using "virgin" brass wouldn't tell me much of anything. Probably the only way to really determine if you have proper headspace would be to have a gunsmith measure it with the proper gauge. All factory virgin brass
will be undersized for obvious reasons.
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ccoker
Optics Master Joined: February/13/2008 Location: Austin, TX Status: Offline Points: 2041 |
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As someone who has had a gun blow up in his hands (Sako 85 270) I don't push the envelope on speed.
100fps isn't worth it. And to preemptively answer your question, I was unable to pinpoint the cause after much research and ended up throwing it in the trash, that HURT.
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Roy Finn
MODERATOR Steiner Junkie Joined: April/05/2004 Location: United States Status: Offline Points: 4856 |
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Sako's are POS....................
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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On the types metal and differing bearing surface, I have read and seen as much looking through manuals. I'm a numbers geek and do compare and contrast way more than I should. Right now I'm loading a 130 Speer spritzer and am working off of data for a 130 grain Sierra hollow point. My observation is that the Sierra develops pressure per weight and powder quicker than a nos bt. Would. It's similar to what I see Barnes bullets do. The Speer May do the same thing but I have a feeling it won't, although I will assume it will, for safety.
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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Yes, you can, by measuring height from case head to shoulder datum and comparing. However, it's better to size your cases to get the aforementioned "false shoulder" so you feel slight resistance when you close the bolt on a "dummy" round... or check the chamber with go/no go chamber gages. The chance of you having a chamber with excess headspace is pretty unlikely, but it's still possible. I brought it up as a hypothetical example of how you could have catastrophic case failure without seeing pressure warning signs first |
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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As far as the sako, the gunsmith that built my ackly won't build a rifle on anything other than a Remington action or a known custom action. Perhaps that's overkill, but don't even try talking him into another production brand.
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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That's because Rem 700's and other round action clones are mechanically and geometrically simple. It's easer to work on than flat bottom actions and actions with more complex exterior geometry. The round shape makes it much easier to chuck in a lathe for blueprinting, and easier to bed properly. There are a ton of good aftermarket triggers and other parts for the 700 and custom clones. The 700 was designed to be relatively economical to manufacture and easy to make shoot well.
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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again all thing being equal etc. you miss the point of all things being equal, Its physics, the equal forces regardless of the conditions will exert the same force pushing it to the same velocity the rest is bs.
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I love little league baseball-- it keeps the kids out of the house
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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Perhaps the ease is a good reason. Not so in my gunsmiths case I would say. He actually likes a challenge and the money is largely immaterial. He's independently wealthy and I think uses lathes that most independent gunsmiths would only dream of.
He's told me that he likes the strength of the 700 action. Maybe I'm wrong and he is blowing smoke. I will say that he doesn't just spit them out with production in mind. |
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Roy Finn
MODERATOR Steiner Junkie Joined: April/05/2004 Location: United States Status: Offline Points: 4856 |
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Of course, but that's not what he was saying. Just because two different rounds have the same "peak" pressure, does not mean they will yield the same velocities. |
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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he says that in the first part, but changes the supposition in the second. more powder more chemical energy. thus all things being equal yes, including the inverse, less powder which negates the supposition. again all things being equal,yes same pressure same velocity all things being equal means the same amount of energy is applied by definition unless he is a democrat then who knows. |
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I love little league baseball-- it keeps the kids out of the house
Yogi Bera |
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sakomato
Optics Master Joined: February/28/2008 Location: Houston Status: Offline Points: 1166 |
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A lot of tangents here, everybody going in different directions. On flattened primers, it is NOT a good indication of pressure, it is a good indication of headspace. For example, my 280AI is a TRADITIONAL chamber and not a SAAMI spec chamber. It was made before Nosler and Remington came along and F'ED up 40 years of gunsmithing. So if I shoot a new Nosler 280AI case, I would have approx. .014" of headspace and this is what happens this with a known fireforming load and velocity not excessive, no hard bolt lift, no extractor marks and primer pockets good. A sign of one thing - EXCESSIVE HEADSPACE. The firing pin and primer explosion blow the case forward to the shoulder, the primer backs out and reseats flattened when the case head is slammed back to the bolt face. If you are using 280 Remington brass for fireforming then this is not a problem, but there is no relativity of new to fired brass shoulder position, the 2 are in totally different positions and even at a different angle, how could you compare them? The AI chamber is supposed to hold the case in stasis with no headspace between 2 contact points - the case head and the shoulder/neck junction. So how could you measure headspace with a typical tool? Once fire formed you have essentially eliminated headspace (at least to within .002" or so) and can set amount of headspace from SIZING with a typical tool. If your gunsmith will only work on Remingtons BECAUSE he thinks all others are inferior, then you need a new smith badly. If you think Sakos are a POS, then you probably don't like Rancid Coolaid Porsche 911 Turbo either and need to stick to your horse-and-carriage Remingtons!! |
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Guns only have 2 enemies, rust and politicians
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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Dale, if the "he" you're referring to is me, then no, you're still incorrect; I did not "change the supposition."
You said same pressure = same velocity with the same bullet, and that isn't necessarily true. Just because 2 cartridges operate at the same pressure doesn't mean that they will drive the exact same bullets at the same velocity. The rate and duration of the climb to peak pressure is key. Even less peak pressure over a longer duration can yield more velocity, as exemplified by the .30-06 vs. .308 comparison. The .308 operates at 2K psi greater peak pressure than .30-06, yet the -06 is 150 - 200 fps faster with the same bullet because it uses a slower combustion powder that climbs to peak pressure over a longer duration. "All things being equal" only applies when all things are truly equal. "All things" are never equal when we're talking about 2 cases of different capacity, which is what this thread is about to begin with. |
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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ugapaul
Optics GrassHopper Joined: January/27/2011 Status: Offline Points: 47 |
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The headspace for the traditional chamber and the saami chamber are the same. The respective schematics are using different measurements. Don't get mad, research it.
So, sounds like your smith didn't know how to read schematics properly or the sako was pos. |
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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Excellent post, Bob. To answer your question above, you can't easily compare virgin standard brass to fireformed AI brass without using an optical comparator or some kind of chamber gage comparator attached to caliper jaws, for the reasons you state. Hence my recommendation to neck up to next caliber with expander, then neck back down to correct caliber with sizing die incrementally in length until the case will JUST close with slight resistance in YOUR chamber. In so doing, you're forming a false shoulder at the neck/shoulder corner that duplicates the zero headspace of standard SAAMI case in AI chamber. Here's a good tool for comparing virgin vs. fireformed case HS length of the SAME design... http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/rcbs-precision-mic-cartridge-headspace-tool-prod33476.aspx |
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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Bob was using the traditional .280 AI he has and the recently SAAMI standardized .280 AI chamber as an illustration of what happens with excess headspace in the post above, and he is 100% correct. In this case, the headspace for the two chambers are NOT the same; the traditional .280 AI has .014" longer headspace than the newly SAAMI-standardized .280 AI. The origin of the difference is explained here: http://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/ |
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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