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Using a Chronograph for accuracy


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I've been reloading for a little over a year now, but I'm still having a problem getting accuracy from my reloads. I seem to be more accurate shooting factory Hornady SP’s than any bullet I’ve reloaded. (I can easily get sub MOA from them) So far, I’ve only shot 55 grain bullets from my 1/9 twist bull barreled AR, about 4 different kinds… some Noslers, a few different Hornadys, and one other brand I cant remember. The most accurate were the Hornady V-Max, (almost 2 MOA) but they were still not as accurate as store bought Hornady SP’s. My question is, what exactly is the process for making accurate ammo? I know you can weigh each bullet, group them by like weights, and reload the closest weights, also do that for cases. Make sure the cases are the same length, clean the primer pockets, and then shoot through a chronograph, but there’s where I get lost. Am I looking for a certain FPS to get accurate ammo, or do I just need to get above a minimum FPS, then keep trying different recipes until I find an accurate one? So how do I use a Chronograph to make more accurate ammo?

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If you are that far off from factory accuracy, you've got more of an issue than a chronograph can fully fix. The chrono can spot if you have variations in velocity, which can pinpoint problems caused by inconsistant powder weights,col, or poor crimping technique. You should be able to,at least, match factory stuff. As far as FPS, you're looking to get confirmation of what you expected from the recipe. I would reevaluate your reloads and see if you can improve on the quality control.

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Have you tried the same bullets as in the factory loads ??? You should be able to duplicate the accuracy you get from the factorys with the same bullet if - as stated above - you are using good loading practices.

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Doing some sort of crimp on the rounds?

If so, pull one of your crafted bullets from a round and see if your process is deforming the bullet any. A wee bit overcrimp will do that and destroy the projectile accuracy.

OAL of the cartridge variations might help but since this is a auto-loader can't dork , er adjust, with that a whole lot but it could be worth tweaking to best ability. Meaning try to

get that ogive a bit closer to the barrel lands once chambered.

One half grain or less plus or minus from a given point can alter groupings, I've seen it happen with bolt actions. I suppose same can happen with auto loaders. Of course

again, one has less wee way due to the functioning of the weapon.

You do not mention if you are using a powder drop or anything. Maybe be a bit more specific in what you are actually doing to produce the rounds, what gear, methods.

If you are using a powder drop are you taking a lot of test measures to verify the thing is dropping in the range of values expected?

Try producing a batch of rounds produced purely by hand weighing each powder load.

Assuming one has a scale that is providing repeatable readings..... I've seen some that are pure garbage. Verify by being paranoid.

Oh, a Edit. On a chrono graph being of use.

THey can be but they have limits and can introduce confusion as well.

I've seen my competition electronics chrono provide varying results depending on SUN ANGLE on bright days. I have concluded my chrno is best

only used on over cast days with diffuse light OR at a high sun angle. Low sun angles, are problematic as hell. Complicating factor. Also, the ambient

TEMP of the day of testing will alter overall readings. So when taking notes I always notate the ambient temp of that session. I might start noting overcast or not, now

that I think of it.

A chrono won't be your magic bullet it is just another tool in the chain. I suspect your issue lies elsewhere that a Chrono won't really help.

Edited by Buzi
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Have you tried multiple factory loads? Measure each factory load for OAL, bullet weight, and velocity. Since the Hornady load seems to be your most accurate, try to duplicate those variables. Guns have harmonics to their barrels. It is a matter of matching a specific weight to a specific velocity.

If your hand loads are +/- 10 fps the accuracy will be much greater than loads that are +/- 100 fps. If you measure the Hornady's at 3,000 fps and your load is at 2,800 or 3,200 fps the increase or decrease in velocity is more than enough to open the groups up even if your average velocity is +/- 10 fps.

Bullet weights that are +/- 0.0 grains will have better accuracy than +/- 0.1 grains, which will be better than +/- 0.2 grains. This is figuring that your charge weights are very accurate from load to load.

So it all comes down to consistency within a specific velocity range that your rifle likes for that bullet weight.

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