Need advice on 3-gun shotgun modification

[rock jock]

I have a 870 Super Express that I converted to a competition scatter gun a few years back by changing out the barrel to a 18.5" police trade-in and adding a extension tube and Choate stock. However, the gun patterns very poorly because the barrel is not choked. I recently talked with a local 'smith who gave me a couple of choices on this gun:

1. He can ream out the 18.5" barrel and thread it to accept standard 870 chokes. However, he would have to remove the front sight since there are no ribs on the barrel. There is also a chance that the wall thickness will not be sufficient for this work.
2. He can cut the original barrel that came with the gun (28" ribbed) down to any length over 18" and re-ream and thread it to accept chokes. He would also re-install a front sight as part of this work.

I am inclined to have him do the latter since I could add several inches to the gun and thereby get a longer extension tube (thus more shells between reloads). My questions are: (1) which of these two options would you recommend? (2) If the 2nd, what length would you recommend he cut the barrel to?, and (3) What size tube extension should I get to match the new barrel length?

Thanks much,
rock

 

[Andrew Wyatt]

You could always send your current barrel to hans vang and have him vang comp it.

 

[Dave McCracken]

If he hasn't already measured the barrel and found out if there's enough metal there to do the Remchoke machining, he's not a smith I would want working on my guns.

Also, cylinder bore barrels with GOOD crowns on the muzzles oft work well out to 30 yards. My guess is your muzzle crown is either dinged or out of round. Once that is corrected, you may find your patterns acceptable.

Before I'd get a barrel set up for tubes, I'd get the cone done. A forcing cone made about 1 1/2" long mimics 5 POC.

 

[rock jock]

If he hasn't already measured the barrel and found out if there's enough metal there to do the Remchoke machining, he's not a smith I would want working on my guns.

He already told me that he would have to measure this first. He said it would probably be OK based on the age of the barrel, but again, was not sure, so the modifications to the 18.5" barrel were contnigent on the barrel thickness.

Also, cylinder bore barrels with GOOD crowns on the muzzles oft work well out to 30 yards.

Some of the 3-gun shooting has slugs fired out to 50 yards. Even at 30 yds, buckshot patterns have to be pretty tight to knock over some of the heavy plates.

Before I'd get a barrel set up for tubes, I'd get the cone done. A forcing cone made about 1 1/2" long mimics 5 POC.

How do I get a cone done? How is a cone different from a choke? And finally, what is a "POC"?

Thanks.

 

[Dave McCracken]

Not every barrel has choke.Every barrel does have a forcing cone.It's the funnel between the chamber and the bore itself. In days of yore, the cone was made to be about 7/8" long. This helped build pressure with the powders of the time and got the pellets into the bore itself OK.

A longer cone eases the transition between chamber and bore, lowers the pressure spike a bit and deformation of pellets is lessened. This helps keep patterns tight and even lowers kick a trifle, though that may be un-noticable. I used the word "mimic" because since pellets stay in the pattern, it looks tighter on the patterning board.,Actually, it's just denser.

Choke degree is the difference in diameter between the bore and the choke. If the bore is .729" and the chokes mikes out at .719", it has .010 choke. This usually is called Improved Cylinder. Points Of Constriction (POC) are .001 each, so the example here would have 10 POC.

The main users of long cones tend to be heavy gamers, both the clay games and "Practical".

SOME cylinder bores with SOME loads give great results out to 30 yards. Researching the best load and doing the cone will likely do as much as choke tubes. But, there's nothing wrong with doing all of the above if money and time allow.

In your shoes, I'd work over the short barrel and mount a base and bead. Then. you'd still have a long barrel for hunting and clay games.

HTH....

 

[Bix]

Sorry if this is obvious, but it wasn't clear from your post - have you tried a variety of loads through the barrel? With my gun, patterns can be either fist sized or platter sized at the same distance, depending on which shells I'm shooting. In my experience, reduced recoil loads tend to hold comparatively tight patterns.

 

[rock jock]

I'm sorry, Dave, but that doesn't really help me. There is not a plentiful supply of gunsmiths in the area. I'm lucky I found one guy who knows how to ream out a barrel and thread it for a choke. I seriously doubt that re-doing a cone is within his abilities. Plus, from what your saying, I should try to have the cone re-done, which may or may not help me, But, having the barrel choked will definitely help me, so why should I spend $50-75 to have the cone re-done and another $30 buying a variety of shells only to find out that it is not sufficient and that I will have to get the barrel choked anyway for an additional $60. I appreciate your advice, but what I am really looking for is simple solution to this problem. Going through multiple steps only to find that I have the same problem is not worth it to me.

 

[rock jock]

Bix,

Yes, I tried Winchester light loads, Wolf, and Federal. I need something that will tightly group buckshot give good accuracy with slugs w/o having to go to a rifled barrel. Installing a choke seems like the obvious solution. Also, I don't care about chopping down the 28" barrel. I already have a coupld of other hunting guns and the 28" barrel is just taking up space in my safe.

 

[Correia]

For 3 gun you do not want a rifled barrel. Slug shooting is usually less than 10% of your total round count, and rifled barrels often produce really weird shot patterns. I've shot slug targets out to 100 yards in a match with an 18 inch bead sighted gun.

I think you are going to want to try out more than 3 brands of ammo. If you are serious about 3 gun, your practice ammo expenditures are going to make that $30 look really tiny.

You may just want to chop down your long barrel. However 28 isn't that bad of a length. You can install a Choate 10 shot extension on that and be good to go.

 

[rock jock]

You may just want to chop down your long barrel. However 28 isn't that bad of a length. You can install a Choate 10 shot extension on that and be good to go.

28 is too unwieldy for me. What is the maximum length extension I can get if I went to, say, a 22" barrel?

Edited to add: nevermind, I found it on the Choate website.

 

[Dave McCracken]

rock jock, most smiths who can install tubes can do the cone also. You might want to ask him.

Having the cone done WILL help. So will load research. Even with a set of chokes, these are close to essential. Ask the top guns at your next match.

FYI, I ran a few HOAs in LE 3 gun based in part on great shotgun scores with a chokeless 870 back in the day. The cone was done and I spent plenty of ammo finding the best buck and slugs. IIRC, I tried 7 different slugs and about the same in buck.

And check the Archives. Between Corriea, Denny Hansen, Randy Cain and a few other dedicated Practical shooters, you'll find more chokeless barrels than factory cones.

 

[rock jock]

OK, I'll ask about the cone. Thanks.

 

[Carnitas]

You didnt say what class you're compeating in. If its limited you want the barrel length that will give you an 8+1 gun (20 inches). So your short barrel is too short for an optimum Limited gun. If you're shooting open you can go with a much longer tube to maximize capacity. Of course if you're going Open you'll also want a comp and an optic so the 28 inch tube is not a good canidate for mods.

I'd say you're better off just getting a whole new barrel. Whether or not you get a Vang Comp unit is somthing you have to decide for yourself, but personally I think the VC is too much of a good thing.

 

[rock jock]

Does the "Comp" in Vang Comp stand for compensated? If so, I don't think I would want it. AFAIK, most limited 3-gun matches, and all tactical 3-gun matches disallow the use of compensators in shotguns.

 

[mattk]

Unless you are shooting in the Open division of USPSA 3 gun, comps are a no-no. Besides I dont see how porting the barrel would improve his patterns.
As an avid 3 gunner, I will tell what works for me. 24' tube with an Improved cylinder bore choke. I have Fiber Optic sights installed with Green in front and orange in the rear. The front sight is a large HIVIZ tube.
When shooting slugs I line up the front and rear sight like a rifle, when using shot, I just use the front sight like a bead.

 

[Carnitas]

Does the "Comp" in Vang Comp stand for compensated?

Yes and no. VangComp is the name of the company, and their standard package includes porting the barrel as well as the internal mods. However, you can order the just the internal modifications.

People seem to get different results with the VC internal mods; all shoot tighter paterns but some are tighter than other. The tightest of them shoot buck in patterns so tight as to be comparable to the group you might shoot with a rifle while standing under time pressure.

In terms of 3-gun a tightly paterned gun would might benifit you by allowing you to enguage hard to knock poppers at extended ranges, but you'll be much slower hosing a close in set cause you'll have to aim at each one (not enough pattern spread to make up for an off center hold). A tight pattern would also make it very difficult to hit the pop up clays. There is always give and take with SG patterns; too loose and you dont get the shot density you need, too tight and you'll spend too much time aiming. Its no different in 3-g. For myself I dont feel the need to have my 590A1 pattern any tighter than it currently does in stock condition. I'll be spending my SG time and enegry training and equiping to reload the gun faster.

 

[BillL223]

I find that I have a Skeet choke in my gun for most stages. The targets are usually KD steel or clay birds 10-15 yds out. Occasionally steel will be small or heavy and set 20-25 yds. In this case more choke is helpful but this could be overcome to some extent with heavier loads. You might find paper targets in the 25-30 yd range where best 4 hits will be scored and the load is 00 buck (1 shot). Here you will need a mod or tighter choke. The barrel does not have to match the mag tube. You could run an 8 round tube with 18-1/2" barrel with no problem. I have seen tubes that were at least a foot longer then the barrel. I don't notice a difference with slug accuracy through various chokes but I usually don't run anything tighter then Mod. Some tactical matches restrict barrel length to 22" either by rule or stage design.