So, I have been playing with a few falling blocks and wonder how you determine your seating depth off the lands. I know what I do but hope with discussion I can learn something new. Your tricks or tips will be enjoyed by many.
SCG
SCG
Falling block bullet seating depth
- Thread starter Southcountryguy
- Start date
- Location
- Western Manitoba
I can describe a couple ways to find the lands without buying extra stuff, but so far as I know, can only find out best distance to be off the lands by loading and trying. If wanting really exact, need some way to measure to identical diameter on the ogive of the bullet - some literature suggests that half way between bore diameter to groove diameter is the preferred diameter - but measuring Over All Length of a loaded round relies on the bullet ogive / bullet tip to be the exact same for every bullet, and that is not always correct, compared to the base to ogive diameter measurement.
Then, to be very exact, have to repeat the whole process almost every batch that you load - is called "chasing the lands" - you won't know, until you repeatedly measure, how fast the land face is eroding in your barrel, if you want to maintain a precise "jump"... You might start out with a .023" jump, but after 100 or 250 or 500 rounds, will not know that any more without re-measuring, because the land face might or might not be eroding as you fire rounds through that barrel.
Then, to be very exact, have to repeat the whole process almost every batch that you load - is called "chasing the lands" - you won't know, until you repeatedly measure, how fast the land face is eroding in your barrel, if you want to maintain a precise "jump"... You might start out with a .023" jump, but after 100 or 250 or 500 rounds, will not know that any more without re-measuring, because the land face might or might not be eroding as you fire rounds through that barrel.
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I run a stainless steel rod (a cleaning rod, basically) into the bore to the breech face, and mark it. Then insert a bullet into the rifling and hold it there with a small dowel. Slide the rod into the bore again to the bullet, then mark it again. The measurement between the two marks is your max col. Adjust accordingly. - dan
- Location
- Western Manitoba
Nosler 9 Manual - pages 69/70 describes an alternate way to "find the lands" and to come up with a Cartridge Over All Length that is touching those lands - similar end result to Post #3 above. Is actually what I do. However, I am okay with rounds that will "do the deed" out to 300 yards or so. I have read that much more demanding shooters, with much more precise rifles and expectations, will use different techniques, and that they tend to focus on Ogive to Base (OTB) dimension, not Cartridge Over All Length (COAL). It might be all for nothing in many hunting rifles - whatever you load has to fit into and feed from the magazine, first - that is COAL - many rifles that I have here will not give me a lot of choice for how close I can get to the lands, if I want to feed out of the magazine. So in that sense, OP can just "jump over" the COAL thing, since no magazine to worry about.
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Thanks for all the info. I always glean something from you all. My granddaddy always said you often learn the most asking questions you think you have the answers for.
Nice thing about falling blocks is you don’t have to worry about bullets functioning in magazines.
Elk season and I am out!
SCG.
Nice thing about falling blocks is you don’t have to worry about bullets functioning in magazines.
Elk season and I am out!
SCG.
