870P New Barrel Causing Cycling Issue

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ccolluney

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**NewUpdate**
Fixed, sanded down the forearms inner channel where it was making contact. Took off about 1/16 of an inch. Shotgun now cycles smoothly, thank you everyone.

*Update*
The issue is being caused by a forend clearance issue. The forend needs to be reprofiled to accommodate the new barrel. Something I have no experience or knowledge of. Now looking for advice on how to make the forend fit the new barrel.

I recently purchased a new to me 20 inch Remington barrel for my 870P, when I installed the barrel for the first time I realized that it did not have the ball detent that the 14 inch barrel that came with the 870P did. I tightened down on the mag cap as much as I could and tried to cycle the action. Cycling the action was not smooth at all, there was a little resistance halfway through pumping the forend back and when I reached the end the forend became stuck. It required significant force to rack the forend forward. I understand that I need the ball detent system to properly mount the barrel but I am wondering if the lack of a ball detent is causing the cycling issue? If it is causing the cycling issue would I be better off installing a ball detent on the 20 inch barrel or trading the barrel for one with a ball detent? One other difference in the barrels I noticed was the ejector cut on the 20 inch barrel appeared to be shorter and rounder then on the original barrel, could this cause the cycling issue in any way?


The new 20 inch barrel under the 14 inch that came with the 870P when I bought it.


Ball detent on the 14 inch barrel


No detent on the new 20 inch barrel


Ejector cut on the original 14 inch barell


Ejector cut on the 20 inch barell


Scuff on the bottom of the 20 inch barrel after getting stuck

The shotgun cycles perfectly with the 14 inch barrel installed, it also cycles perfectly with a 28 inch barrel with ball detent and same style ejector cut as the 14 inch barrel that I borrowed from a friend. This makes me think the cycling issue must be caused by the lack of a ball detent or the difference in the ejector cuts.

Any insight or advice is appreciated.
 
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My only thought is that the lack of a ball detent is causing the new barrel to not mount in the correct position. Possibly making the barrel sit a few millimeters too high?
 
I don't think that the detent would interfere in that manner. I would wager that your forend is contacting the barrel wall, possibly due to differing outside diameters for the barrels. You can verify this by using a caliper to check the diameters of each barrel where those rubbing marks appear. If that's the issue, the only fix is to reprofile the offending section of the forend.

The extractor cut could affect how the bolt closes in battery, but not further rearward in the cycle.
 
Thanks for the input alpining, it didn't occur to me that the barrels could be different diameters. I don't own a caliper, might need to go out tomorrow and pick one up.
 
Most barrels for the 870 have the same diameter profiles regardless of the manufacturer. About the only barrel that has a significantly different profile is the "Light Contour" found on the 1992 and newer Wingmaster guns. These barrel have a smaller diameter and forearm has a matching barrel channel cut into it. They will have cleareance issues when trying to use other 870 barrels.

You have an 870P so the forearm has the large barrel channel. Your forearm is essentially getting wedged between the barrel and mag tube. When you install the 20" barrel check that the rear of the barrel extension is fully seated into the receiver. If that ejector cut is indeed out of spec (too shallow) it will prevent the barrel from fully seating and cause those clearance issues...I'd almost bet that that is your problem. If I'm wrong you'll need a dremel, rasp or sandpaper to relieve the forearm barrel channel till you have the required clearance.
 
Thanks for the suggestions VLT79, I will look and see if I can find where it is getting wedged. I find it interesting that I have no issues with the 14 or 28 inch barrels I have put on, while this new 20 inch causes a problem.
 
I have noticed that a lot lately, especially with Hogue forearms. I have had to relieve the sides on 3 of them. Dlask aftermarket barrels seem to be the fattest and the forearm almost always needs relieved with them.
 
I'm curious about the distance from the bottom of the barrel to the top of the inside diameter in the attachment ring.
It almost sounds like the ring is closer to the barrel on the 20" than on the 14" or 28"

That difference would definitely cause binding and scraping.
Does the barrel just "drop in" when you put the new barrel on, or does it require a good push to get the barrel to seat?

If you are worried about the extractor groove causing the binding try assembling the gun without the bolt or carrier.
Also the extractor groove and extractor will show signs of interference fitting like your barrel.
 
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If it was the extractor groove, the bolt wouldn't close right, or that last 1/8 inch would be very tight, you might even pop the extractor. It is almost certainly the forearm (the forearm shouldn't leave marks on the barrel). What you could do is remove the forearm off the slide, re install the slide minus the forearm and then cycle the action. If it doesn't bind, you just have to relieve the forearm a bit. Or you could just relieve the forearm a bit and see if that cures it. By the way, I notice you have the hole for the detent, it is a $10 part (detent and spring) and maybe another $10 for the proper punch (the proper punch makes it much easier) from Brownells, and it is a 2 minute job, or any gunsmith can do it for probably $30
 
Thank you Ciphery and Dogzilla.
Ciphery, you were correct the new 20 inch barrel is 1/16 of an inch higher from the top inside diameter of the ring and the bottom of the barrel. Dogzilla, I am going to remove the forend and see how the action cycles.
 
i had a forearm interference problem on a winchester 1200 that i bought . the gun was at least thirty years old and no one had clued in to why it pumped hard . a few minutes with a dremel and a world of difference .
 
So I removed the forend from the slide and reinstalled just the slide like Dogzilla suggested and the action cycles perfectly with the new barrel. So it is definitely a forearm clearance issue. So re-profiling the forend is definitely needed, unfortunately I do not have any experience or knowledge on how to do that. I definitely don't want to ruin my forend. Does anyone know of any tutorials?
 
ccolluney said:
Thank you Ciphery and Dogzilla.
Ciphery, you were correct the new 20 inch barrel is 1/16 of an inch higher from the top inside diameter of the ring and the bottom of the barrel. Dogzilla, I am going to remove the forend and see how the action cycles.
Click to expand...

If you have a 1/16" taller barrel lug on the 20" tube you actually have more clearance than the 14" barrel does. Did you check to make sure the ejector notch isn't preventing the barrel from fully seating into the receiver?
 
I think the way I explained it was just confusing VLT79, the new 20 inch barrel when installed is fully seated into the receiver exactly the same as with the barrels with the older style ejector cut. The 20 inch barrel when seated sits 1/16 of an inch lower then both the 14 and 28 inch barrels, causing it to make contact with the forend. My issue now is that the forend only has about a 1/16 of an inch of plastic where the barrel makes contact. I'm wondering what the best way to trim it is.
 
Use a dremel with a sanding drum or just wrap a piece 180 grit sand paper on a dowel and sand away till it doesn't bind any more. You can also wrap the barrel with electrical or masking tape and use it as your dowel with the sand paper.
 
Went to the hardware store today and got a dowel and some 180 grit sandpaper as suggested. Got home and started sanding. It went really well, ended up sanding very close to 1/16 of an inch down the entire channel of the forend. Installed the forend and mounted the barrel and cycled the action. Perfectly smooth, just like the original 14 inch barrel. So problem fixed. Thank you to everyone who commented with tips and ideas.
 
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