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Recoil calculator

4697 Views 9 Replies 5 Participants Last post by  joe kuhn
Here's a handy recoil calculator. Since the 'bullet' weight is in grains, you'll also need these numbers:

7/8 ounce (.875) = 383 grains

1 ounce = 438 grains

1-1/8 ounces (1.125) = 492 grains

Joe
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Discussion Starter · #2 ·
Here's the link for the ounces to grains calculator.

On the recoil calculator, for powder charge in grains, you may have to guess. If I'm checking factory shells I use powder charge numbers from my own reloads and call it as 'close enough'. I could take one apart and weigh it, if I really want to be accurate.

With a recoil calculator you can vary one thing to see how it will effect the actual recoil. Your perception of the recoil may be based on other things like junk coming out of the bbl as is the case with paper cards which we've seen with some steel target shells, noise, expectations, desires, etc.
 

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Just yesterday I learned to my surprise that a 1-1/8 oz load at 1200 fps has more recoil than a 1 oz load at 1325 fps. Wow. I was putting too much emphasis on speed and not enough emphasis on shot weight. This is what they make calculators for.
 

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Just remember, this is all speculation unless you know the real weight of the ejecta, and the real muzzle velocity.

Labels on the box are, shall we say, approximations.
 

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Joe:

Now you know why I "stretch" my steel for 16yd... by loading both light (3/4oz) and slower (1150fps) and coupling it with a heavier gun (90T) actual recoil and that perceived is reduced tremendously...

Ran a round the other night with my 3/4oz load...

Jay
 

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We could use some of that advantage for the newer folks who are stuck shooting house shells: 1 oz at 1325 and 1375 fps. Ouch. That's what I've been working on...I shot some 1325s with my 58 auto and I'm sure my teeth rattled. Went right home and put some weight in the stock.
 

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When you check the speed with your own chronograph, you might still be off unless you do averaging with other machines. Yet, you're probably much more accurate than what's printed on the box. Didn't know it could vary by +-90 (see thread titled 'perceptive recoil question' and search on '+/-90'). That seems like a lot.


When we went to Tom Armbrust's shop to have our club recipes checked, he had us subtract 18 from each speed number. Tom purchases SAAMI test shells every year so that his measurements get checked with all the other speed/pressure houses out there. What SAAMI does is take everyone's fps numbers on known recipes, averages them, and gives you a factor to add or subtract to get you to the average. In the absence of anything better, this is what the industry is left with. Tom's number that year was -18.

Sure makes that check weight for my powder scale look easy. There's nothing like that for chronographs. The speed of light is a constant, but OMG. It would be interesting to know how chronograph manufacturers check the accuracy of their machines. Interesting discussion from elsewhere:(http://www.archerytalk.com/vb/showthread.php?t=1085399&page=1)

I'd be curious to know how a pressure machine is calibrated.

Joe
 
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