Yes. There are multiple companies.

If you have the materials and it's practical to use 4-gauge for your ground wiring, go ahead and do it. You'll never hurt anything by using a larger wire gauge than necessary, nor will you harm anything by using different sizes for power and ground (as long as both wires are large enough for the amplifier's current demand).

Some gun manufactures do recommend you avoid using full choke with slugs, to avoid possible damage to weapon.
Why take a chance of damaging your weapon if you can avoid it.

Plus stop to consider you don’t wont to constricts a slug ( hollow or not ) that could well affect accuracy and range.
I would always try to avoid using full choke, I have one shot gun that it’s full choke is tighter them most extra full Turkey chokes and it‘s about 30 years old.
Every gun is different, but I would play it safe if I had the option.
I would test the weapon with modified and with cylinder to see what it likes.

D58

Hunting with Rifle, Pistol, Muzzle loader and Bow for over 3 decades.
Reloading Rifle, Pistol and shotgun for over 3 decades.

You will want a 16 ga. straight finish nailer. This will shoot nails from 3/4" to 2-1/2", which should handle most of your needs. Do you already have a compressor? Porter-Cable makes several different kits which include a compressor, nailer(s), hose, and all fittings you need. You will find that you will need more than one nailer. When installing casing around windows and doors, I use a brad nailer to attach the casing to the jamb, then I use the 16 ga. nailer to attach the casing to the wall. I have a 15 ga. angle nailer, but I seldom use it. If you already have the compressor, and just need the nailer, go with Porter-Cable or Senco. They are the best out there. Hope this helps.

http://www.amazon.com/Porter-CFFN251N-Nailer-Finish-Compressor/dp/B002JASUQA/ref=sr_1_10?ie=UTF8&s=hi&qid=1249043423&sr=1-10

Its the oil pressure gage. As long as its in the range its fine. At idle it might be lower then on the highway. Some fords regulate it though which is good. Its usually better if its closer to high in the range, but as long as its in the range... dont worry.