Ok, you're lucky it's that coarse. You may just need a simple, manually flushable sediment bowl. My last house had that issue due to the well producing over 56 gpm.
First thing I would do is to pull the pump and make sure the torque arrestor is PROPERLY installed, if it has one at all. The torque arrestor keeps the pump from banging around in the shaft when it cycles. You can buy it from Lowe's. It is a simple expandable rubber contraption that clamps on the pipe about 4' or so above the pump. It needs to be expanded about 1 or 2" bigger than the diameter of the casing. It will be a bit tougher to get the whole works back into the hole, but it will help a ton.
Second, if you have "wet pipe" well above the pump (like 30' or so), I'd raise the pump about 4' to
maybe get the pump above the water vein that is bringing in the silt. Only do that if you have the water volume above the pump to do so. Knowing what GPM the well is capable of will be a determining factor as well as the total depth and static water level. I'd still like to see those numbers.
Third, I'd install a sediment pre-filter. It will catch a bunch of the bigger stuff before the drop in filter. The cartridges will last much longer.
Now, if you're still reading, I'd wait on the pre-filter to see if the torque arrestor and pump raising works. I'm willing to bet a dollar or a six pack that the torque arrestor isn't there or isn't spread out enough to do it's job.
Torque arrestor:
http://www.lowes.com/pd_130540-1564...t=torque+arrestor&N=0&langId=-1&storeId=10151
Pre-filter:
http://www.cleanwaterstore.com/MS005270-p-filter-strainers.html
While you have the pump out, it's not a bad idea to install the wire standoffs to prevent chafing. Chafed wires has haunted me in the past. Well pump wire is EXPENSIVE to replace. Wire standoffs are cheap. I'd put up a pic of the standoffs, but I can never find one on the net. They're just white plastic spacer that keep the wire from rubbing the casing or rock. they're found at Lowe's in the same place as the other well stuff.