Domains
Run your store on your own domain
Using your own domain on your is easily doable; although a little technical of nature. If you don't exactly what you are doing here then rather don't do it: ask your registrar or ISP to assist you with this instead.
Please note at this stage we do not check if your domain resolves to us which means if you enter an invalid Live Domain your store will simply be unavailable.
The Development Domain
The Development Domain is the sub-domain that your store kicks off on. It will always be a sub-domain of the domain 'someammo.com'.
The Live Domain
The Live Domain can be any domain you manage, or have access to. In the case of certain stores there will already be an existing domain (yourdomain.com) and an existing site (www.yourdomain.com). In such a case it is suggested to map a relevant sub-domain (store.yourdomain.com) to your store to ensure your site remains operational and intact.
Mapping your domain to your store
Using yourdomain.com & www.yourdomain.com
To use "yourdomain.com" on your store, add or edit an A record for '@' and point it to 107.20.228.0.
To use "www.yourdomain.com" on your store, add a CNAME record for 'www' and point it to @.
Using store.yourdomain.com
To use "store.yourdomain.com" on your store, add or edit a CNAME record for 'store' and point it to get.someammo.com.
General tips
Forwarding and redirecting
Make sure domain/url forwarding or redirecting are NOT turned on.
Registrar-specific tips: Namecheap
To add or edit CNAME records for a domain managed with Namecheap
log in and go to:
My Account / Manage Domains / yourdomain.com / Modify
Domain / All Host Records

Also see the Namecheap support entry on How do I setup host records for a domain.
Registrar-specific tips: GoDaddy
To add or edit CNAME records for a domain managed with GoDaddy
log in and go to:
My Account / Domain Manager / yourdomain.com / DNS Manager
/ Zone File Editor / Add Record
Mapping yourdomain.com on GoDaddy

Point the A-record of the domain to '107.20.228.0'.
Mapping store.yourdomain.com on GoDaddy

Please make sure you hit the Save the Zone button after you add the record, and check that you have removed any conflicting A-records too.
Also see the GoDaddy support entry on Managing DNS for Your Domain Names.
Registrar-specific tips: Network Solutions
Please see the Network Solutions support entries on A records and CNAMEs.