Remington 870 3-Gun Build
Rifleshooter.com and Brownells make a Remington 870 competition ready
The following documents our experiences and is presented for informational purposes only. In order to make the steps easier to understand, we separated the choke tube and front sight installations into two different sections, this is why you may notice some photos are asynchronous.
Looking at the old useless 12 gauge 28″ vent rib 870 barrel we t0ok in on a trade, it dawned on us that this might be the perfect start to a 3-gun pump shotgun. With my PD trade-in shotgun in hand, we began to plan. Since we already had an 870 receiver with a Scattergun Technologies rear sight installed, we decided that we would add a front sight to our vent rib barrel. Knowing a 28″barrel is way to long to effectively compete with, we decided to cut and crown the barrel flush with the end of a long 5-shot magazine tube. The stock was an OEM full-length wooden beast from the 60’s, replacing this with a short model would get us on target faster.
This project will require us to:
- cut and crown a barrel
- intall interchangeable choke tubes
- install a ghost ring front sight on a vent rib barrel
- add a shot shell carrier, stock and extended magazine
For the conversion (less the removable choke tube installation) we ordered the required supplies from Brownells:
- 5-Shot extended magazine 100-007-541
- 8-Shot shell carrier 100-003-295
- Speed feed reduced length stock 838-000-009
- 4-Round speed strippers 151-000-030
- Clymer barrel facer 184-352-000
- Bushing for barrel facer 184-252-725
- Scattergun Technologies Trak-Lock Ghost Ring Sights 800-000-008 (see Trak-Lock II installation for the tools required)
- Mesa Tactical Barrel Clamp 100-004-032
- Remington 870 Service Kit 080-870-010
- Win-Choke/Rem-Choke tap 513-044-012
- Rem-Choke reamer 513-046-012
- Bushings for the tap and reamer, these must be sized for your bore
- Starrett electronic calipers 749-008-013
- Manson wall thickness gauge 513-000-066
- Gilchrist choke reamer 170-100-105
- Do-Drill cutting oil 083-007-016
Cut, crown and front sight installation:
Threaded Choke Tube Installation:
Before moving to the threaded choke tube installation, it is critical to verify that the barrel is thick enough. While it is possible to measure the outside diameter of the barrel, subtract the largest diameter of the choke and divide by two; shotgun bores tend to never be truly centered and the walls may actually be thinner then calculated. To avoid this, we used a Manson barrel wall thickness gauge to determine if the walls were thick enough for choke tube installation. More information on choke tube installation criteria can be found on Brownells GunTech page.
Finishing the Conversion:
Since the barrel and sights are in order, we can finish getting the gun ready for the match.
In order to provide additional support for the magazine extension, we used a Mesa Tactical barrel clamp. This model has a handy little weaver rail to attach accessories. Mesa also makes the 8-shot side saddle we chose. While we prefer 4 and 6-shot model for defensive use, the 8-shell carrier will certainly prove advantageous in competition.
Finally, we selected an old favorite, the reduced length Speedfeed solid stock and forearm. The smooth rubber butt plate, shorter length of pull, and aggressive corn cob forearm allow for quick target acquisition and rapid manipulation of the slide. We are ready for whatever the match director has to throw at us!