Off center 870 chokes

[Red Label]

I'm pretty sure this has been discussed before but I couldn't find much on the search. I was getting my trusty 20ga 870 out for a little slug practice and remembered that last year the gun was shooting low and to the left with a modified choke at 50 yds. The gun seems to pattern fine with shot. Is there a way visually to tell if you have one of the barrels with the choke bored off center or do you need to measure it in some way? Was this just a problem with the 12ga or were all guages affected? I obviously can't get my finger down the barrel in my 20 so I can't feel for anything. Looking down the barrel with a light doesn't show anything abnormal and from the muzzle the tube appears to be straight so why would my gun be so inaccurate and how do I measure for a crooked tube or installation?

 

[HSMITH]

I don't mean to be insulting so please don't take it that way, but that you asked the question is a pretty good indicator that you don't have the tools to do it.

If you reload or have a buddy that does a simple set of calipers will find gross errors, just measure the wall thicknesses and roundness of the barrel and choke tube. If the choke bore is crooked in the barrel you may or may not be able to see it with calipers. Anything further you will need to take it to a machine shop or a gunsmith.

If I were in your position I would buy another choke, prefferably aftermarket, and try it before I worried about anything else.

 

[Rupestris]

How does the gun group (regardless of POI)?
what type of sights are you using?

A set of adjustable sights might be all you need to make the SG accurate at 50yds.

Also, try an Improved Cyl. choke too.

 

[Red Label]

Group was not good but all shots were low and left. About a 6" group at 50 yds and that could have been just me. I'm just using the front bead and my eyeball. I will try an I/C tube. As far as measuring wall thickness with a caliper I will try that. I have a caliper. That would indeed tend to show if the hole was off center. I was just wondering if the tubes were off center or actually tipped sideways also.

Hopefully the different choke will make the difference and I wont need to fool with it any further. Thanks guys!

 

[Lone Star]

Would not a more open choke be better for slugs, anyway?

Anyone know what the rules are for firing slugs from guns with interchangeable choke tubes?

Lone Star

 

[kudu]

Anyone know what the rules are for firing slugs from guns with interchangeable choke tubes?

Make sure the choke is tight in the barrel and well lubed with a good choke lube.

Full choke has the potential to cause problems, and most choke tube manufacturers recommend not using them for slugs.

Modified and less choke should be fine as long as they are kept tight.

If shooting lots of slugs at a setting, check to be sure the tube is staying tight. The rifling on the slug may spin the tube out depending on the direction of spin.

 

[sm]

Agree with -

HSMITH - go aftermarket.

kudu on explainations and suggestions.

IME the 30 POC ( depending on individual bores , forcing cones...etc.) which is Modified , throws a better Buckshot pattern, "across" the board in the many guns I've tested.

Folks that want to carry / shoot / both buck and slugs for defence often find this "Modified" gives them good performance with two different loadings.

Hence the reason we advise the Pattern board is your friend.

HTH

 

[Red Label]

I was able to locate an improved cylinder choke tube today although it was a Remington. Could not locate an aftermarket one in the time I had at lunch. I did a quick range test when I got home from work and at 50 yds the group is now within 2" and is still low but not shooting left anymore. I would say this is acceptable. The "low" problem is more than likely my hold and can obviously be adjusted. Either the modified tube was machined incorrectly or it just didn't work well with the brand of slugs I am using. I am quite happy with a 2" group shooting off hand. I thank you again guys for your suggestions and I am still going to check my chokes and barrell with my caliper. I just need to remember to bring it home from work!