I have a few dozen duke 330's that i want to fully modify. I want to add kill bars, replace the jaw rivets with bolt&nut and anything else you guys would advise. My question is what size lock nut and bolt should i use and what size round bar for the kill bars?

If anyone has pics of how they go about fastening the kill bars to the trap would be awsome!

Any pics of modified conibears would be appreciated!

NC, I just bought some of these a couple weeks ago. I'm sure they will work fine, but the first thing I noticed was those rivets.

Last time I checked, the duke 330s did not swivels. I’m not sure if they’ve changed that, but if not I would add some.

I don't think adding kill bars to a trap not designed for them is a good idea.It may increase the clamping force,depending on the springs design and strength,but it will likely slow the trap down and decrease the striking force.This could lead to a more inefficient trap than the one you started with.
If you want a full closure trap,best to buy one designed that way and tested for performance.
Some mods that can improve a bodygrips performance is putting on a belisle trigger and dog and tuning,adding a swivel and waxing the trap.

Leave them as they are. I have lost track of how many beaver and otter I have caught In Duke 330s .

If your trapping cigarette papers you would probably have to have a trap with full jaw closing. But since most beaver are about 5" thick I see no need.

But If you feel the need just do one and see how It works out for you.

I haven’t used very many duke 330s but when I take dead beaver out of them I’ve never thought to myself that I should have modified it or used a different trap. Just a few days ago I had a 60 pounder get in one right after I set it. I’m pretty sure the short struggle was just nerve reaction. That beaver was out cold instantly.

I have Bridger and Dukes and just add cable to extend them to tie off and got beaver and otter and rats in them.I did not do anything to the traps otherwise. I cold dip my in a dip I got years ago from the one I use to sell to and buy traps from.This season I got a otter in the Duke ,it did not have much of mark on the flesh side.That trap have strong springs.

I've did exactly what your wanting to do .SURE it makes the trap look awesome. But I cant say that it was totally needed other then now it can a will hold a rat by the tail. Which is why I decided to do it in the first place! Got tired of finding snapped empty traps! Not being abel to read sign under water I wanted to get to the bottom of this problem. I soon found out rats are the biggest part of this problem. FYI as stated it can and does slow them down. so if your going to do this id recommend adding new springs as well. as far as material I used 5/16 cold roll that I shaped to fit then welded it all on. I've yet to catch a otter in that trap to see how it performs.Otters will prove to you how fast or slow a trap really is! Honestly the time and money it takes makes belizes a cheap investment. Another thing if you order new springs be sure and get duke springs!Like a dipstick, I just ordered 330 springs got those ridiculous tiny spring hole bridger springs! man I hate those things

The most important thing you can do to your BGs Is to make some trigger adjustments. The less trigger movement before the trap Is sprung Is very Important In making good clean catches. To much trigger movement will result In to many hip catches.

I held a 50 pound beaver by the rear foot in a straight out of the box Duke 330 a couple weeks ago. It was held fast and not going anywhere. Everything else I caught in that trap was a normal catch so I don't believe it was a trigger issue, I just think that beaver somehow hit the trap sideways. Only mods I make to them is add a teardrop ring, a swivel, a few links of straight link chain and a spilt ring as I anchor all my bidygrips with extension cables. The dog and trigger usually needs a little work to make the trap fire quicker, important on otter, beaver normally get wacked behind the ears or suitcased regardless.

First thing I do is cut factory chain off, I use a small chunk of chain and go threw spring 0 end than a swivel to 1/8" cable 30" long and tie of end. And twist the trigger wires together a couple time. And treat them.

Have you done what Paul has in the Basic Sets Forum?...with the dog?
I also reduce the swing of the trigger by widening the yoke by putting yoke bottom in vise and tapping down with a nail/hammer (photo from another t-man guy, Joel?)
Then I cut off the chain because I want to attach it so the trigger is out or in depending on the situation and may need to anchor better on 1 side than the other.
My 2 ft chains with swivel added in 1st 3" are attached with a 1/4" quick snap (carabiner) after my cable extension gets anchored.

...in addition to my above post, I have found NO reason to do all you are thinking.
I trapped beavers full time for 6 yrs doing ADC work, using Duke 330's, and when a beaver hit that trigger, it was waiting for me

Getting rid of all that trigger slop assures a quick closure behind the head.

If ya want kill bars, bring your traps to our convention and I'll do it for ya, then ship them to ya before season...using same diameter as jaws.

Duke 330s work fine for me with no mods.

I agree the only reason I did was it was a junker a guy was going to toss! The jaws had rusted bad enough they were weak and bent so I straighten them then to insure they wouldn't bend again kill bars were added. but I see no reason to do it again to a perfect trap. but as I stated it will hold a rat by the tail now.. performance of a belize with half the cost. If I was to do any mods now it would be a spot of weld to hold the trigger assembly in the middle like the 660s or add better safeties! duke safeties are sloppier then bbq ribs!But you get what you pay for

Whats the best aftermarket safties? I have a belisles but i have a few old dukes that i wanted to mod

Wrap 14 or 16 ga wire around the factory safety catches so they act like Belisle and stay in place.

John can you please post a pic of that? Or are you referring to making belise type safeties and adding them to dukes?

On the topic of coni modifications... where would one recommend adding a swivel? I can think of ways in which they'd bind up on either end. Not sure if I can really justify adding 2 swivels to every one of my 330s/220s. Would center of the chain be best? Hope my asking on this thread is ok!

one at the trap and one at the anchor point has served me well using 10-8' of 1/8" cable