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CTI 75mm grain spacer O-rings

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timbucktoo

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Assembling my first 75mm CTI reload, an M1101. It's a 4 grain. Question - each grain comes with an O-ring so do I only place the O-ring in between each grain and end up with an extra O-ring or does the 4th O-ring go on top of last grain in between grain & forward insulator disk?

I do not see the last O-ring in the supplied drawing so I just want to make sure it's done correct!

cti 75mm 4 grain.jpg
 

timbucktoo

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Thanks! There is room for it so I will use it!
 

watermelonman

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I think I am on my seventh Pro75 motor and the last O ring has fit every single time. I am curious how much variation there is in grain and liner length, what the production tolerances are.
 

timbucktoo

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I had room for it so I used it. Without it, the grains floated. With it, everything is snug. Production date Jan 27, 2016.
 

watermelonman

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Good luck with that certification flight. Here was my M1101 flight -
 
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