If you look at the screws in Contender/G2 barrels, you should find at least 4 1/2 threads or 4 1/2 turns of thread contact, which with just 4 screws is not much to hold a base on a high recoil caliber like the .375 JDJ or .444 Marlin.

For full holding strength of a screw, its depth should be at least equal to its diameter, preferrably greater. In the Contender/G2 barrels, this parameter is met if the threads go pretty well to the bottom of the holes and the screws are fitted to reach the bottoms of the holes without bottoming out before the base is pulled down tight.

If you have less thread contact length than the screw's diameter, you run a stronger risk of the barrel threads stripping out.

If they strip out, the best solution is Brownell's .146x48 "oversize" 6x48 screws, which do require using their special size .146x48 tap to chase the original barrel threads.

But the best solution is prevention. Strap the scope on the way it should be in the first place, and the more of those tiny 48 pitch screws the better.

As a side note, in another thread, I believe it was Bobby Tomek who cautioned about using the TC Duo Mounts due to inadequate thread contact, which is very true of this overpriced, but poorly conceived mount. I'll ditto his comments about avoiding it. It is too much to pay for duck decoy anchors.

For about the same price as the TC Duo Mount, you can get my modified Weaver 92A bases converted to the same 6-screw hole pattern as used by SSK, Virgin Valley, and others AND three of the Bushnell rings. The whole set up is about 1/2 the cost of the SSK TSOB mount, does the same job, and at arms length looks the same. The only difference is the recess down the top of the Weaver base where the TSOB is flat, and this has no functional effect.

Please excuse me, but $90 plus for a set of extruded aluminum rings and an extruded aluminum base is a bit absurd. The best machined steel mounts don't cost this much! Think about it.

If your barrel is already drilled and tapped 6 hole with the extra two holes using the same spacings as the original 4 holes and you have your own rings or have another choice in rings such as the excellent Burris Signature Zee rings, all you need is a $20 bill for my modified Weaver base with the screws already ground to length to give the 4 1/2 turns of thread contact.

http://www.bellmtcs.com/store/index.php?cid=23

If the barrel is not drilled and tapped for 6 screws, and you or your local RELIABLE gunsmith are up to doing the drilling and tapping, you can screw the base on using the 4 original screws, then use a spotting punch for a #6 screw through the two open screw holes in the base to locate the holes to be drilled .135" deep in the barrel. Since the holes are ahead of the chamber, then can be drilled a bit deeper, but no more than about .150" for safety's sake. The screws are ground for .135" deep holes, so unless you substitute longer screws, the deeper hole depth will not gain anything.

All the holes should be finish tapped with a "dead bottom" tap which will usually pick up about 1/2 thread at the bottom of most factory screw holes.

Any "gunsmith" worthy of his salt should be able to do the basic drilling and tapping operations. If he isn't, give him a wide berth with any project and suggest another occupation for him.

There is always the chance of breaking a tap off, and there are a number of ways to remove them without damage to the barrel's threads. One of the safest and best ways, though not cheap, is an EDM machine. In the event you get your tailfeathers in a kink with a broken tap and don't have access to EDM, there is one just down the road from me. They usually charge about $35 to EDM a broken tap from a hole.

Charges for drilling and tapping vary from one source to another, but expect to pay about $10 to $15 per hole.

Doing the numbers:
$20 for a modified Weaver base,
about $30 for two pairs of Bushnell rings, and
about $30 for drilling and tapping.

That is still less than the TSOB even IF you have to pay for the drilling and tapping.

I'm not against the TSOB mount. It is an excellent mount, but not everyone is in a position to pay $90 for a scope mount that will keep a scope on a high recoil barrel. While the TC guns are not cheap, they do not have to be a rich man's game either. Point being, there are other options, and you DO NOT have to be boxed into a corner paying $90 for a mount setup. Nor do you need to risk degrading an expensive barrel with inadequate barrel screw holes that are more prone to stripping out under severe recoil or rough use in the field.

If you want a more refined scope base, then by all means take a look at the beautifully MACHINED bases made by Virgin Valley. However, I would caution against using their machined steel base on high recoil Contender/G2 barrels. Stick with the lighter aluminum bases for less inertia against the screws. Also, if their bases come with fillister head screws like they used to, and especially if the barrel has a muzzle brake, substitute Weaver "cone head" screws which will prevent the fore and aft shifting of the base on the barrel caused by the brake.

Also, when mounting Weaver type rings on braked barrels, to keep the rings from shifting on the base, slide two rings to the forward side of the cross notches, then slide the 3rd or 3rd and fourth rings to the REAR of their cross notches. Brakes, especially those with the ports angled to the rear as on the factory Muzzle Tamer brakes, will cause the scope to slide to the rear when they do their job of limiting the rearward movement of the barrel.

Remember, when the bullet is being accelerated, the barrel is coming back, and the scope wants to remain at rest, sliding it forward..... rather, the barrel is sliding back under the scope, to be more correct. But once the scope is in motion it wants to stay in motion. When the brake jerks the barrel forward as it does when the ports are angled to the rear, the scope wants to keep going to the rear.

Thus you get a fore and aft movement of the scope which has to be halted by the cross screws in the bottoms of the rings. If the rings are not positioned so the cross screws butt up against the cross notches on BOTH sides of the notches, the only thing holding the rings in position is just tension between the base and the clamping surfaces of the rings, and they WILL slide under recoil and the jerking effect of a good brake doing its job.

Hopefully the above will dispel some myths, clear up some uncertainties, and result in more satisfaction from shooting these excellent guns!

All the best,

Mike Bellm

Mike-
Great info...as always...

Bobby,
I second that motion!

Mike,
Great to hear from you again. I've been out of touch for a few weeks as we've been moving to a new house. As if that wasn't enough, I then had no internet access at home as it took the cable company (have both 'net and tv access w/ them) ELEVEN DAYS to swap over our service to the new house!! Anyway, now that I've vented, I'll ask my semi-related question: on a factory Contender barrel, is the scope mounting screw a 6X48? If so, is this a commonly available tap? You've probably guessed it by now, but after 25 years of messing w/ guns, I've finally managed to foul up the threads on one of the scope mounting barrel holes on a factory 223 Rem barrel. Was trying (in vain) to find a Weaver screw that was not toooo long for the hole.... Gary T.

Thats good info mike, but its not that much price difference if you have to pay for the tapping. At SSK barrel drilling and tap are included in the price of the mount with 3 rings. For $88 I dont think thats bad. They also have a lifetime warranty. I would have considered purchasing yours had I known sooner, because I think either way your getting a good solid setup. Ultimately though its not that big of price difference. I honestly think with what the smiths here in Alaska charge it would have been more. You saved me $70 with that G2 trigger job and I know you'll do it right. The best price I got for it here was $125 and I dont even know if he would have done it right. Thanks mike and keep up the good work on the TC's! I cant wait to take a caribou and moose with my 375 JDJ this year.

Thanks, Bobby!

Gary, the holes are 6x48, and, no, this is not a common SAE tap size.

Whip out your Brownell's catalog. The carbon steel taps are ok, but if you want to do it right, get their ground thread high speed steel tap. They really cut nicely.

If you messed up your threads, it probably means you damaged them to the point you may have to go oversize like I mentioned above... the .146x48 size. Unfortunately, Brownell's sells only one length of this screw, about a half inch long. Which means you will learn how to grind screws to length as opposed to hoping to find one the right length.

They are expensive, but Brownell's sells a special pliers for holding screws while you grind them. Saves burnt fingers and lost screws!

What I use for odd jobs is just an old hacksaw blade. I break if off about 5 or 6 inches long, then fold the piece of blade in half. I slip the screw through the hole in the blade then holding the doubled over blade like a tweezers, apply pressure to the head of the screw while grinding the exposed end to length.

Brownell's has a "screw gizzy" I think the call it. Does essentially the same thing.

Another way I cut screws to length is with a bar of aluminum I drilled and tapped. I screw the screws into the bar and hand file them to length with the bar held in the bench vise if it is just a screw or two. The same bar has about a dozen such holes in it, and it is sometimes used in the mill where I mill the screws to length.

But the handiest thing yet is a Harbor Freight mini-chop saw Stan Toombs gave me. I made a block that is drilled and tapped for the no. 6 screws. It is positioned in the vise on the chop saw so that when a screw is turned in all the way, the chop saw grinds it to the correct length.

If you need help, whistle.

Mike

Alaskan,
You are right if the price of the TSOB includes drilling and tapping. But recall also that the figures I posted were for TWO pairs of Bushnell rings. SSK gets more than $88 for the 4 ring set up. Plus, if you send a barrel in, the shipping and handling is more and is doubled going and coming back. The price for a 4 ring set up with shipping and handling probably approaches $120 or more.

I just like to see you folks have options instead of feeling like you are boxed into a certain price point.

Will be doing triggers at Bradbury's in the morning and probably not making a shipment until Monday. Be watching for it!

Thanks!

Mike

Your right its nice to have options. I want to say my total price was $110 with shipping, installation and 3 rings. I just didnt know about your services when I did mine. Like I said both systems seem like they would be sturdy. Thanks Mike I will watch for it.

Oooops, Alaskan, I spoke too soon. Your frame has not arrived yet, but it still might get here Monday and get turned around same day.

All the best,
Mike

UPS said it should make it monday. I sent it 2nd day air thursday. So we'll see. If not oh well. Thanks mike.

Mike,

Good to see you posting here... Thanks for the info...

$bob$

If it shows up Monday, it still may make it back out same day.

Mike