Drop bolt hold open actuator for use with AR-15/M16 type firearms and incorporating a modified and displaceable follower for engaging a bolt catch mechanism such as in conjunction with rimfire ammunition

1. A bolt catch assembly incorporated into a firearm, the firearm including a receiver with an exposed receiving chamber to which is attached a multiple cartridge supporting magazine, said assembly further comprising:

a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with the attachable magazine;

a catch actuator supported in elevated fashion relative to an end of said actuator housing; and

a follower upwardly and biasingly disposed within the magazine which, upon contacting said catch actuator, displacing an associated bolt catch of the firearm to an upper and bolt restraining position, said follower further having a main body exhibiting a three dimensional shape and overall profile matching a cross sectional interior of the magazine and being influenced in a generally upwardly biasing direction, an upper follower body extending at least a length of said main body and being supported in lengthwise displacing fashion relative to said main body.

2. The assembly as described in claim 1 , said main body further comprising an upper configured and lengthwise extending channel, a partial superstructure supported within said channel, and a pair of side defined and upper end proximate slots.

3. The assembly as described in claim 2 , said upper follower body further comprising an upper displaceable member which exhibits a generally elongated rectangular configuration seating within said lengthwise extending channel.

4. The assembly as described in claim 3 , said upper follower body further comprising a lower ledge support and an upper angled/projecting catch actuator engaging portion.

5. The assembly as described in claim 3 , further comprising a pair of seating pins which extend through communicating locations with said slots as well as like dimensional width apertures extending through the upper displaceable member.

6. The assembly as described in claim 3 , further comprising a spring supported in an extending and seating fashion within a hidden location of said superstructure so that an opposite end is biased an abutting end surface of the upper follower body in a rearward induced direction.

7. The assembly as described in claim 1 , further comprising an adjustable screw incorporated into a bottom end location of said housing and, upon rotating, vertically displacing said catch actuator in either of opposite linear directions to modify a contact location established with said upper follower body.

8. A bolt catch assembly incorporated into a firearm, the firearm including a receiver with an exposed receiving chamber to which is attached a multiple cartridge supporting magazine, said assembly further comprising:

a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with the attachable magazine;

a catch actuator supported in elevated fashion relative to an end of said actuator housing;

a follower including a main body exhibiting a three dimensional shape and overall profile matching a cross sectional interior of the magazine, said main body further having an upper configured and lengthwise extending channel, a partial superstructure supported within said channel and a pair of side defined and upper end proximate slots extending along sides of said main body such that said main body is influenced in a generally upwardly biasing direction; and

an upper follower body extending a length at least equal to said main body and being supported in displacing fashion relative to said main body, said follower being upwardly and biasingly disposed within the magazine and, upon said upper follower body contacting said catch actuator, displacing an associated bolt catch of the firearm to an upper and bolt restraining position.

9. The assembly as described in claim 8 , said upper follower body further comprising an upper displaceable member which exhibits a generally elongated rectangular configuration seating within said lengthwise extending channel.

10. The assembly as described in claim 9 , said upper follower body further comprising a lower ledge support and an upper angled/projecting catch actuator engaging portion.

11. The assembly as described in claim 9 , further comprising a pair of seating pins which extend through communicating locations with said slots as well as like dimensional width apertures extending through the upper displaceable member.

12. The assembly as described in claim 9 , further comprising a spring supported in an extending and seating fashion within a hidden location of said superstructure so that an opposite end is biased an abutting end surface of the upper follower body in a rearward induced direction.

13. The assembly as described in claim 8 , further comprising an adjustable screw incorporated into a bottom end location of said housing and, upon rotating, vertically displacing said catch actuator in either of opposite linear directions to modify a contact location established with said upper follower body.

14. A bolt catch assembly incorporated into a firearm, the firearm including a receiver with an exposed receiving chamber to which is attached a multiple cartridge supporting magazine, said assembly further comprising:

a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with the attachable magazine;

a catch actuator supported in elevated fashion relative to an end of said actuator housing, a locating pin installed horizontally through a slot in said catch actuator in alignment with an aperture in said bolt catch actuator housing in order to define a range of vertical motion of said catch actuator as defined by a vertical component of said slot in said catch actuator; and

a follower including a main body exhibiting a three dimensional shape and overall profile matching a cross sectional interior of the magazine and being influenced in a generally upwardly biasing direction, an upper follower body extending a length at least equal to said main body and being supported in a lengthwise displacing fashion relative to said main body;

said follower being upwardly and biasingly disposed within the magazine and, upon said upper follower body contacting said catch actuator, displacing an associated bolt catch of the firearm to an upper and bolt restraining position.

15. The assembly as described in claim 14 , said main body further comprising an upper configured and lengthwise extending channel, a partial superstructure supported within said channel, and a pair of side defined and upper end proximate slots.

16. The assembly as described in claim 15 , said upper follower body further comprising an upper displaceable member which exhibits a generally elongated rectangular configuration seating within said lengthwise extending channel, said upper follower body further comprising a lower ledge support and an upper angled/projecting catch actuator engaging portion, a spring supported in an extending and seating fashion within a hidden location of said superstructure so that an opposite end is biased an abutting end surface of the upper follower body in a rearward induced direction.

17. The assembly as described in claim 15 , further comprising a pair of seating pins which extend through communicating locations with said slots as well as like dimensional width apertures extending through the upper displaceable member.

18. The assembly as described in claim 14 , further comprising an adjustable screw incorporated into a bottom end location of said housing and, upon rotating, vertically displacing said catch actuator in either of opposite linear directions to modify a contact location established with said upper follower body.

19. A bolt catch assembly incorporated into a firearm, the firearm including a receiver with an exposed receiving chamber to which is attached a multiple cartridge supporting magazine, said assembly further comprising:

a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with an attachable magazine;

a catch actuator supported in elevated fashion relative to an end of said actuator housing;

a follower including a main body exhibiting a three dimensional shape and overall profile matching a cross sectional interior of the magazine and being influenced in a generally upwardly biasing direction, an upper follower body extending a length at least equal to said main body and being supported in displacing fashion relative to said main body, said follower being upwardly and biasingly disposed within the magazine and, upon said upper follower body contacting said catch actuator, displacing an associated bolt catch of the firearm to an upper and bolt restraining position; and

an adjustable screw incorporated into a bottom end location of said housing and, upon rotating, vertically displacing said catch actuator in either of opposite linear directions to modify a contact location established with said upper follower body.