Rem 870- need advice

[SteelChickenShooter]

Can those that have 870 shotgun experience evaluate this scenario and render some advice?
I fired my new 12ga, rifled barrel, rifle sights, to see how 4 ammo brands hit the paper. In the shop, after shooting was done, I found the barrel was a little loose. I could wiggle it- not a large amount, but it did wiggle. I turned the cap nut about 4 clicks and the barrel was then secure. I'm thinking I should re-shoot. Here is how the 4 brands compared:
Hornady SST 1.5" high, 3.5" right
Brenneke 440gr 0" high (even), 6" right
Brenneke 490gr 3" high, 7" right
Federal Tru-Ball 3.5" high, 8" right
Looking at the rear sight, it looks very close to being about centered or maybe a bit left as if a factory person fired it and corrected it.
Perhaps a re-shoot is in order to see if the hits are the same?
My calculations say the rear sight needs to come left by .032".
Looking at the rear sight at the gaps on either side of the top screw, I can see if I move the rear sight, the left gap that is already wider than the right gap, would be even wider yet. However, the index mark does appear to be aligned on center. Perhaps the rear sight is cemented in place a little too far to the right side of the barrel?
Anyway, thanks for your assist, and if possible, let me know what your own rear sights look like with your ammo hitting on center at 40 yards.
I'm not concerned about up or down. That's easily corrected. I'm curious about the first 4 hits being different distances right. And if the barrel wiggle really amounts to a meaningful error on target?

[LSnSC]

Not sure what you are asking??? Are you expecting to different loads to have the same point of impact?

[Lee Lapin]

A slightly loose barrel could have some effect on your POI (point of impact). Were I you, at this point, I'd choose whatever brand/load presented the best group, and use that one to actually zero the sights.

If you didn't actually shoot groups (at least three shots) with each different brand/load, but only fired one round of each, IMO you didn't really determine very much. Single shots on paper don't really do anything to account for shooter variations.

Where the rear sight winds up when the sight-in is done means little, as long as the rear sight is within the normal range of adjustment.

It's not likely different brands/loads are going to shoot to the exact same POI. Pick one, and sight in for that load by shooting groups till you get POA (point of aim) and POI correlated to your satisfaction.

fwiw,

lpl

[Scattergun Bob]

Your barrel nut being loose will affect point of aim / point of impact. If this nut keeps loosening under firing use one or two wraps of white teflon tape (same stuff we use on faucets) this should solve that problem. I normally place a witness mark on the top of the barrel and receiver to realign each time I remove the barrel or it moves.

There is a vast difference between accuracy (the ability to place a certain number of projectiles into a gathering of acceptable size) and precision (the ability to strike the exact point of aim with a given number of impacts). One first must always establish accuracy and then precision.

If I were in your shoes, I would: align and witness my barrel and make shotgun sure that the nut was TIGHT. Buy at least a box of five of whatever I wished to test. go to the range and set up a target at 25yrds and shoot of the bench and bags for groups. KEEP checking your witness mark and barrel nut. PUT UP WITH the recoil, don't flinch or jerk the gun. I would consider 4 shots in a gathering and 1 flyer acceptable. At this point we should have the best accuracy available to us. Select the best and move the sights (make sure you re tighten the sight screw correctly). Now shoot a precision group that will be around 2 to 3" low at 50 yrds. It would not matter to me where the actual sight blade ends up, all that would mater for me is POA = POI.

Shotgun barrels are a black magic art, no two seem ever to shoot the same with the same ammo. The good news in testing several hundred 870 barrels I had very few that failed to pass muster.

Hope that helps

Good Luck & Be Safe

[TheKlawMan]

There are at least two types of barrel not retention systems on an 870. The "old" and the "new" types. The old is used with a spring loaded detainer that is inserted and staked into the muzzle end of the barrel lug. This ratchets in cut outs on the bottom of its style of barrel nut.

The ne type works with the magazine dimples that need to be removed if one wishes to add a magazine extension.

If you don't have the proper barrel nut for the old type or you have a new nut but your dimples have been removed, you can use a wave washer to keep the barrrel nut from backing off. It will do a pretty good job but it doesn't hurt to check it for tightness every box of shells.

http://www.brownells.com/.aspx/pid=2...ND_WAVE_WASHER

As for the barrrel twisting or being askew when tightened, I have the very problem. It isn't much but the barrel has what I estimate to be .005" rotational movement when the barrel nut is loose.

How much of a problem this presents I don't know, but I do know that when tightened down the barrel can be askew by the same amount.

The suggestion to use a witness mark, if I understand the term, is a good one so you at least know that the barrel is in the same place when tightened.

[SteelChickenShooter]

To answer my own question, the second range session was productive. The answer is that the wiggle I had in the barrel results in substantial error.
It invalidates all the first session hits.
I overlooked the Federal TruBall was a rifled slug meant for smooth bores so I throw that one out. I picked up some Rem Buck Hammers for the comparison.
The nut holding the barrel tight is not coming loosed when firing. It was loose from the dealer when I brought the gun home. I neglected to check it before using the gun.
Do I expect the holes to be in the same place? Well, on the re-shoot three brands were. I clover leafed three slug brands one inch tall and inch and a half wide. Setting the rear sight one index mark left brought the rounds over as desired. Six brands all grouped well and were about half the distance off compared to the first round with the barrel wiggle. The rear sight has 5 index marks. As delivered the sight was on number three (centered) counting from left to right. As adjusted, it is on index mark number four, and it is obvious the rear sight hangs a bit off the left side of the base. This suggests to me that perhaps the rear base is a hair off to the right as attached to the barrel. If the base was wider, so you did not see the sight hanging off one side, it would not bug me. Anyway, the story has ended. Barrel is secure and I can shoot any rounds I have on hand. Three are clover leafing dead nuts on, and the others are within inches well within the kill zone. Turns out to be a decent deer gun.

[Lee Lapin]

Glad to hear it steadied down for you... good luck when you go after that rocking chair rack!

lpl