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Silly Chrono Question


BAWunder

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Just got back to reloading after a 20+ years absence. Back in the day I just bought a few manuals, read them cover to cover (multiple times) and gave it a whirl. Back then there wasn't such a thing as the Internet, well, not like it is now...anyone remember Compuserve? LOL

Never had any "incidents" so I thought I knew what I was doing. Now that I'm getting back into it I've picked up several manuals and have been pouring over the various forums (this one is excellent BTW!). One thing that comes up over and over again is how many folks say you REALLY need to have a chrono.

I get that a chrono will give you velocities of your rounds and will help you identify loads with the lowest SD, which theoretically translate into more accurate loads (or so I understand). Here is the part I don't understand. Folks have said that a chrono will help you from a safety perspective as well. How is that exactly? I didn't think there is a direct relationship between velocity and pressure. Since it is the pressure that will blow up your gun, and perhaps yourself, how does having a chrono make you safer?

Thanks for any and all replies...

Brad

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Most of us are looking at the Power Factor when we use a chrono. If the load is supposed to put out 1,000 fps and we get 950 to 1,050 on the chrono it is pretty close to the published values and we adjust accordingly to get our 125+ or 165+ PF. If we get 800 or say 1,200 fps we look at what is different that is skewing the values so much. Sometimes it is the gun, sometimes it is the load because the published data is a misprint. This is especially important if you are at the top end of safe load values on a very fast powder. A tenth or even a couple of tenths can be the difference between a safe load and one that spikes enough to damage the gun.

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Good question. When you are loading, a manual will give you a max load with a max pressure. So much powder at a particular length with a particular bullet. The other listed variable is the velocity at the max pressure. You can't measure pressure( without specialized equipment) but you can get a simple chronograph and check the velocity. If your velocity is over the book then you're probably over the max pressure as well. It will also tell you if you are loading the round correctly. If you are expecting 1200FPS and you get 900 FPS you need to check why. If you are in competition you need to verify PF before the guy with the chronograph does it for you at the match. Hope this helps.

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Many of the major power factor loads we make can be close to the ragged edge sometimes. High pressure loads need only be loaded as hot as needed to accomplish our specific goals. Running loads at ++p++ velocities can be quite risky without a chrono.

Reloading anything without a chrono is just guessing..

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Reloading without a chrono is to me analogous to cooking something from a recipe in an oven that has no temperature setting. I'd prefer to know it is 375F rather than just "seems hot enough".

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Compuserve... there is still at least one of the original CS forums available on the internet... AVSIG

I'm new to all this, and the Chrony has helped me verify the book values. So far, when I follow the recipes, I hit the book velocities.

My chrony initially was unreliable, until I smacked the rod with a 9mm... it suddenly started working great. I love the computer interface, now have a macro set up to feed excel. I will suggest that my unit survived one .223 hit (note to self, rifle bullets initially drop), but not two hits. :)

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You don't mention what kind of gun you're shooting, or what your doing

with the gun (USPSA?, target shooting, hunting?) :surprise:

For any sport with a PF requirement, I usually fire 5 of each load to get

a rough idea where I am, and once I hone in on a final load I want to

use for action shooting, then I'll fire about 20 rounds thru the chrono

and use the slowest three to measure my PF - e.g. if I fire 20 shots

that range from 900 - 950 fps, I'll take the 900 fps as my velocity,

and compute the PF with that in mind - that way I can't be below

PF. :cheers:

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Hey HPJ. I just started doing some IDPA events. PF comes into play but our local events are pretty low key (100-130 shooters) and I've never even seen them check PFs. I suspect at bigger events, like the regional coming up this fall they will, but I'm sooooo far away from competing in something like that.

So what I'm understanding is that if I stick to the book listings for loads I don't really need to be overly concerned about chronoing my loads. But if I want to either 1) make sure I'm making a specific PF or 2) loading for major PFs I really should be using a chrono. Fair statement?

Thanks again everyone...

Oh, and what am I shooting? For the first two matches I used my old Ruger P85. I just picked up a SA 1911 Loaded in 9MM and that's what I'll be using going forward.

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