Before you decide what to do, go to
US Patent Office and spend some time looking at the various How To's and resource guides (almost all in PDF files) that they have to offer.
It may be worth the effort to hire an IP attorney, but you can do it yourself. The information is there, you just have to be willing to really research your idea. It will take a lot of time and effort.
If after you have spent a few days researching, then you will be armed with the necessary information as to whether or not you need an IP attorney.
There are also other avenues to consider: Such as forming a partnership with an existing manufacturer of the type of device you have envisioned. Remington, Winchester, Hornady, etc. will already have attorneys on call for the process... If they decide that your idea is marketable.
There are NDA's (Non-Disclosure Agreements - That
is something you will need an attorney to draw up) to be made and signed between you and a prospective partner. You will not get 100% of any profits, regardless of which way you decide, but it will cut down on your costs and you will already have a manufacturer ready to put your idea into practice.
So then: You can do it yourself or pay an IP attorney to do it - then search for someone interested in making your idea a reality - for a share of the profits. Or, you can find an existing manufacturer and convince them that your idea is marketable and let them do the legal work - for a share of any profits.
Good luck.