I had a quick look at the breaking strength of manila cordage, and 2" circumference manla rope has a breaking strength of about +/- 4000 pounds. Consider that there are two of them onto the gun, so the strength should not really be an issue as that rope is plenty strong enough to lift the gun straight up. Normal rolling resistance on a flat surface is only 10% of total weight, which, depending on the inclline, climbs to 100% on a straight lift.
3" rope is around 10,000 pounds, which means 20,000 for the pair. Certainly no reason to need that kind of strength to pull/lift a 6 pounder.
Bear in mind that a rope should not be used over 75% of it's rating or you can permanently damage the rope.
I grabbed these numbers off the web. If need be, I can pull out some of the old recovery manuals which I am sure will have these numbers.
Kind of surprising actually. I had forgotten that rope could be that strong.
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