Greetings Rick the Ranger,
When it comes to trying to duplicate a long arm that would be period correct for the ALAMO period, the door is wide open.
Any rifle, musket, or shotgun of that time period or older would be correct. That could enclude a Hawken. The Mexican Army carried away all weapons after the battle. No detailed inventory list exist today.
The rifle used by David Crockett at the Alamo has never been identified, but he did not take "Old Betsy" or "Pretty New Betsy" with him to Texas. Those two rifles are on display in Tennessee today.
One rifle he brought to Texas was traded to one "Andy Thomas" and is dislayed at the Alamo. Originally a flintlock, it was converted to caplock, and weighs about 14 pounds.
Hope this will help you. For more information about Alamo weaponry, check out the website,
www.thealamofilm.com
Best regards and good shooting,
John L. Hinnant
If you are not an NRA member, I am carrying your load.