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Old January 4, 2012, 11:19 AM   #1
Dan D
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stiff 870

Hi all, I bought a 870 wingmaster a couple years ago and the action is still stiff. The first half of the stroke is smooth but once it gets halfway it gets really stiff. I had the gun apart last night and had just the forend in, no bolt, trigger group, and its still stiff once you get past the halfway point. I checked the action bars and they were tweaked so I squared them up and it is still stiff. The only thing left that I can think of is that the channels the bars ride are out of spec. Any ideas? Thanks.
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Old January 4, 2012, 01:35 PM   #2
SoilworK777
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With the action all of the way open, does the forearm rub the receiver on either side? That might cause the friction you feel. To fix it, either sand down the forearm a little, or change the alignment of it with a forend wrench.

Tim S.
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Old January 4, 2012, 07:57 PM   #3
Dfariswheel
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The 870 gets stiffer as the bolt comes to the rear because at the same time, the bolt is pressing the ejector spring against the wall of the receiver, cocking the hammer, operating the shell lifter, and operating the shell release.

With most everything out, the ejector spring and shell release adds stiffness.

You can help get smoother operation by applying a little grease to the left side and bottom of the bolt, the bottom of the bolt locking lug where it contacts the ramp on the slide, the slide grooves in the receiver, to the front of the hammer face, and the action bars.

Also, compare your 870 to another 870 to determine if possibly something is wrong with yours.
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Old January 4, 2012, 08:12 PM   #4
Dan D
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Tim- no rubbing. Dfariswheel- at first I thought it was the ejector spring pushing against the bolt but with the bolt removed its still as stiff. I would think with a bare receiver the forarm wouldn't have any resistance. Im going to dig out a micrometer and compare the channels with my buddy's super mag, I have a feeling my gun was milled on a friday just before lunch and the machinist didn't feel like changing a worn cutter.
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Old January 4, 2012, 08:18 PM   #5
nogo
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I too suspect that ejector spring presssure against bolt is a contributor. Flitz polish applied with rag and elbow grease will smooth up things nicely. If you polish parts, remember to rinse well to remove grime and grit. I've found that using Rem-oil from a spray can works. For example, you could hold the action downward over an outside trash can while spraying. I suggest that you remove mag tube contents and clean here before complete reassembly.

My suggestion is to shoot the fire out of it, and, of course, a little judicious gunsmithing won't hurt. Avoid power tools for this.

Let me say it again. If you polish, grind, or sand, rinse thoroughly--or crud you can't see will defeat your purpose.
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Old January 4, 2012, 08:24 PM   #6
nogo
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Dan--check the action bars for the two indentations that activate or move the shell stops. Also, I'm not sure that operating the action with bolt removed is giving you accurate info. The plate that the bolt sits on holds the action bars apart...so the action bars would not fit properly in the receiver.
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Old January 4, 2012, 08:43 PM   #7
Dan D
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I think I got it, the action bars are square and even with each other, they are just angled ever so slightly up. Going to swap forearm with my buddy and see if it helps. By the way, I have shot the s'not out of this gun, I stored keeping track when I hit 15,000 rounds.
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Old January 5, 2012, 08:36 PM   #8
Dan D
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So, swapping forearms didn't help at all. I borrowed a push/pull gauge from work and it takes 8.5 lbs to rack it with only the carrier plate, no bolt or trigger, measures the same with bolt and trigger installed. That, to me rules out the ejector spring and hammer being cocked. I just noticed that there are no wear mars on the mag tube except in the top, right behind the dimples for 4" and then there are wear marks on the bottom right before the receiver. Bend mag tube?
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Old January 5, 2012, 11:49 PM   #9
M4BGRINGO
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Same thing happened to my wifes 870, got harder and harder to open the action. I had it apart several times, she finally saw what was wrong. The action bars were tweaked because the piece of metal they were attached to was ripping-apart internally.

We were able to bend the arms and the action was now smooth, but I knew it wouldn't last long. Bought a new assembly plus a new bolt breech since there have been changes over time. I have another 870 with a different bolt breech and action bar assembly.

You said you swapped them with a friends, did you try your stuff in his gun yet?
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Old January 6, 2012, 12:00 AM   #10
Dan D
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All my parts worked in his gun. We put a straight edge on the top of the receiver and there was a 3/16" difference between the front to back of the mag tube , looks like I need to have it replaced.
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Old January 6, 2012, 02:46 PM   #11
Dave McC
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Kuhnhausen's shop manual for the 870 has a procedure shown for straightening out bent mag tubes. Or, pay a smith a few bucks.

HTH....
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