In this post I’ll be modifying a Remington 870 barrel that came on a Police trade-in shotgun. This smooth-bore 20″ barrel is equipped with rifle sights from the factory. It will be cut and crowned to 18.5 inches (without a lathe), it’s rifle sights removed, a bead sight installed, and the exterior surfaces polished.
For this project, I ordered the following from Brownells:
- Clymer barrel facing tool
- Bushing for barrel facing tool
- Heat control paste
- 220 grit abrasive cloth
- Do-Drill cutting oil 083-007-016
- Screw shortening fixture
- #32 drill
- 6-48 tap
- #26 bead
- Cerakote stainless ovencure ceramic coating
- TCE spray degreaser
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Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.
Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.
The barrel is removed from a safe and empty shotgun. Over the years I’ve tried a few different ways to remove irons sights from an 870; I’ve cut , ground, and heated them off. I’ve decided I like heating them off the best. To do this, I use a MAP torch.
I do all my torch work outside, next to a bucket of water, no sense burning down the house. The factory solder Remington uses flows at a very high temperature, so removing the sight requires a lot of heat. As guy who loves restoring 870s, I do this a lot, so I am aware of how much heat the barrel and ramp can take. If I was trying this for the first time, I’d surround the area on the barrel with heat control paste, especially by the chamber end of the barrel.
Once the factory solder starts to flow, I grab the ramp with aKnipex 10-Inch Pliers Wrench and remove it from the barrel. When it is hot enough, the sight ramp will pop right off. I don’t quench the barrel while it is hot because I don’t want to harden it. Note the blind indexing hole located under the sight ramp, this corresponds to an indexing pin on the bottom of the sight ramp. The factory uses this method to ensure the sights are installed at the proper position.
The front sight comes off the same way. Note the front sight and rear sights ramps at the top of photograph above. On the bottom of the rear sight ramp (top), you can see the small indexing pin.
Once the barrel is cool (I wait a long time, don’t want to get burned), I mark the barrel to the finished length. I always cut it long, since 18″ is the NFA minimum, I typically go 18.5″.
The barrel is mounted in the mill’s vice. I align the index hole for the front sight with the center drill, this allows me to align the barrel at top dead center. I am using a mill here, however, this step could easily be done with a hand drill. I find using the factory indexing hole saves time, this is why I wait to cut the end off the barrel.
I move the mill’s vise over and spot a hole for a new bead. I use a #32 drill to drill a tap hole.
A 6-48 tap is used to thread the hole. I like to use a tap guide in the mill to keep the tap straight.
With the new hole for the bead drilled and tapped, the barrel is secured in a Multi-Vise and cut to length with a hacksaw.
There are a few different ways to face (or crown) a shotgun barrel. The simplest is to use a file to make the muzzle square and polish it with abrasive cloth. Using a specialized tool is another method.
This is a Clymer shotgun facing tool (above). It uses a bronze pilot that is sized to the barrel’s bore diameter. The tool is powered by a hand drill. For this operation, the barrel is held vertically in a Multi-Vise with padded jaws.
I like the #26 Brownells bead. It uses 6-48 threads so you don’t need to worry about tapping a small hole. Only downside, is for a direct barrel installation like this (a vent rib has more material), it is a little long. I screw it into a screw shortening fixture and grind off the bottom.
The #26 screw as provided (above, left) and cut to length (above, right).
Last step is to remove the excess brazing material from the barrel. I’ve found abrasive cloth is the best way to do this. 120 is a little aggressive, 220 grit is perfect if you’ll be blasting the surfaces prior to finishing.
The surfaces polish up to a clean finish. One downside of removing the rear sight is the small indexing hole remain at top center, once the gun is coated I don’t think it looks bad. Had I elected to grind off the sight, rather than heat it off, the hole would still be filled with the indexing pin. Something to consider when deciding on sight removal methods.
The barrel requires refinishing from all of the work I did on it. Cerakote is my preferred finish. This one was done in graphite black.
The rear sight ramp indexing hole looks clean after the barrel has been refinished.
The #26 stainless steel bead looks great. Can’t wait to shoot this one.
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