Tubb Bore Finishing For Pistol

[Ronnie j]

The description pretty much sums it up. I've got a used SV limited will an unknown number of rounds through it's schumann barrell ( non AET ). My concern is my load runs about 10 PF more tru my friends schumann barrell . Is my barrell shot out? It's still very acurate. Also It apears that this barrell was hardchromed in and out. So back to my question will the Tubb bore finishing bullets speed my barrell up? Oh the load was 4.6 grn TG and plated 180 grn. Shot 156 pf in my gun and 166 in my friends.

[Chriss Grube]

Sounds like time for a new barrel. The Tubbs system won't help and would proably slow things down even more.

[L9X25]

I disagree with the barrel shot out theory based solely on a 10fps variance. My buddy and I have 3 practically identical guns between us and no 2 barrels have the same velocity and they vary by more than 10 or 15 feet. 10 fps is just not significant. Continue to shoot that barrel until you experience accuracy or bullet stability problems, then it will be time for a new barrel. If you do have significant wear on your barrel the tubb treatment is not going to help you and may just hurt the accuracy/velocity.

Leo

[Larry White]

L9x25, he said it kind of funny but its 156 pf to 166 pf. With a 180 thats 56 fps, that seems a bit much. I dont shoot tg but 4.6 sounds lite, would 4.8 or 9 get him there and is that too heavy? Larry

[kevin c]

I had a new Schuemann Ultimatch put into my P16 backup match gun, and a Limcat tungsten sleeved bbl fitted into my primary match gun. My match ammo, depending on the brand of FMJ or JHP used, is up to 50 fps (9 fp points) slower in the Limcat compared to the Ultimatch. That is to say, with the same bullet, the velocity varies with the bbl.

The load is 5.1 to 5.2 gr VV320 over a Zero FMJ 180 or MG JHP 180 at 1.200".

[EricW]

It's still very acurate.

It's not broke. So, I wouldn't "fix" it.

The only thing I'd be running down that plated bore is bullets. Once chrome starts to peel, things get ugly in a hurry - and that's the ONLY thing an abrasive is going to do for you. If you're getting less velocity, that's a pretty good indicator that your gun is generating less pressure. I'd just up the charge until I hit my PF and watch for pressure signs. I'll bet you don't see any.

What *could* be going on is that the plating is actually making your bore slicker which is why you're getting less velocity. The same phenomena happens with rifle guys and moly bullets: the reduced friction lowers the pressure and the rounds leave the muzzle *slower*.

FWIW - which certainly can't be much...

[Ronnie j]

Thanks for the advice guys. I like erics theory , as I also thought the plating had something to do with it. The bore is mirror bright and appears very smooth. The lands and grooves also appear very sharp and well defined. The load was a liittle light but I'm still trying to develop a load , so I've bumped up the charge to 4.7 and some at 4.9 . I'll head back to the chrono and see what happens

[Patrick Sweeney]

Yea, what they said. I built two absolutely identical guns with brand new Bar-sto barrels, and they differed by 50 fps using ammo from the same lot.

In my discussions with the Tubb people, they have not seen the abrasive harm the chrome in the bore. However, they were looking at .223/5.56 rifles, and the chrome may be thicker, tougher or otherwise different than what may (or may not) be in your bore.

Up your load to make the fps you need. Don't worry that it takes a few tenths more powder, unless you find yourself loading a grain more than the next guy at your club. If you find yourself there, it is time to check your chrono, your scale and your bullets.

[weakeyes]

Can some one give me the web address for Tubbs? Is it like fire lapping?

Thanks Weakeyes

[Bill Schwab]

Can some one give me the web address for Tubbs? Is it like fire lapping?

Thanks Weakeyes

http://www.zediker.com/tubb/finalfinish.html

[Chriss Grube]

You might want to slug the barrel. One of the guys I shoot with had a barrel that was out of spec. His ammo was 10-15 PF off when the ammo was fired through 3 other AET barrels. Wil replaced the barrel. Not sure how he would deal with the chrome plating. 4.6 of titegroup and a 180 should get you pretty close a 170 PF. I've used this load through 4 different guns.

[EricW]

As usual, I may have spoken out of turn. My experience with chrome is mainly on injection molds. We were really careful not to do anything that would abrade the chrome - b/c if it peeled we threw $XX thousand worth of tooling in the scrap bin and started over. Not good.

I like to "lap" in all my barrels with JB Bore Paste, but wouldn't think twice about firelapping a rough bore with Tubb's kit if I thought it needed it. That said, *personally*, I wouldn't use an abrasive in a chromed bore unless David Tubb promised to buy me a new barrel after the chrome started to peel.

[/utterly Unqualified Personal Opinion Mode]