I think I have "thread choke"

[whisler]

I am fairly inexperienced with shooting cast boolits. That said, I slugged the barrels of my 2 Ruger .357 Mag. revolvers, a Blackhawk and a New Vaquero.

Slugs pushed most of the way through the barrel but not through the barrel/frame junction measured 0.357 with micrometer on both guns. Slugs pushed all the way through measured 0.3565 on the Blackhawk and 0.3562 on the New Vaquero.

I'm not particularly surprised by the restriction since I have been reading of it here for some time, but what does surprise me is the difference between the location and length of the restriction in the two revolvers. The New Vaquero restriction is right at the threads and seems very short; a light tap causes the slug to fall through. In the Blackhawk the restricted area begins slightly before the thread area and goes from there to the forcing cone.

All chambers in the New Vaquero seem to be 0.357+ as the slug falls through, but the Blackhawk has one chamber that requires a slight push with a pencil eraser to pass the 0.357 slug.

Is firelapping the best cure for the restriction and what effect will it have on chamber size? Comments, observations, suggestions all welcome.

[williamwaco]

I have only had that once. It was a .44 Special. "Bull Dog" it would not hit a paper plate at ten yards. I sent it back and they replaced it. The new one shot clover leafs at ten yards.

[DLCTEX]

I'd fire lap it and then if the one chamber still seems tight, polish it with fine emery cloth.

[canyon-ghost]

If you're fairly new to cast boolits, I would approach fire-lapping cautiously. In fact, I would anyway.

The Blackhawk doesn't sound too bad, the Vaquero is a little worse. My Blackhawk is tighter at the muzzle than anywhere else. I'm not sure how I'd react to .005", it isn't very much.

Read up, you're going to need it,
Ron

PS: Just gotta say this, it fits the situation. One night in chat, we were discussing fire-lapping. I asked one of the guys why he didn't fire-lap something. He told me, "Yeah, I could, then again, I could just shoot it for another 20 years!"

[Wolfer]

If you go to Beartooth bullets and get in tech notes Marshall has a very detailed story called
Ruger America's best do it yourself kit. Good read.
My new vaquero had a pretty bad restriction. I tried fire lapping but didn't help much so I just lapped it out and polished the bore. It now the best shooting handgun I've ever owned.

[whisler]

Been reading here for several years, almost every night. Don't post much because I don't consider myself very knowledgeable. Don't cast as much as I would like except round balls for muzzleloaders. Life just seems to get in the way. Just found the varying locations of the restrictions to be odd, and thought I would ask for opinions and suggestions. Thanks for both!

[whisler]

If you go to Beartooth bullets and get in tech notes Marshall has a very detailed story called
Ruger America's best do it yourself kit. Good read.
My new vaquero had a pretty bad restriction. I tried fire lapping but didn't help much so I just lapped it out and polished the bore. It now the best shooting handgun I've ever owned.

Can you describe your lapping process, please

[geargnasher]

How about you just go shoot them first and see what gives? As is said, "It only matters if id does", right? At most you might polish that one tight throat to match the others, but also do a daylight check with a round slug to see how out-of-round the throats are before you obsess over it.

I'm big on firelapping myself, it's a good fix for lots of problems, and is particularly easy with revolvers to remove thread choke. If you feel you need to, just swab the forcing cone and first half inch of the barrel with 320 Clover compound and fire some LIGHT, like gallery light, loads using an alloy of about 11-13 bhn. Re-swab between shots. If you have a stainless steel barrel it might take 30-40 to make a significant difference, but if blued considerably fewer. This technique will also get rid of front sight and roll-lettering restrictions which are common with Ruger revolvers, and won't mess with your cylinder throats or get grit in your brass and reloading dies.

Gear

[whisler]

The New Vaquero is stainless and the Blackhawk is blued steel. I'll have to read up on lapping and fire-lapping, but i will shoot them some and check for excessive leading first. Don't want to go to a lot of trouble if no real problem exists.
By the way the previous owner of the New Vaquero had a trigger job done by a pro and it is really slick.
Thanks for the comments.

[geargnasher]

A Brownells wire spring kit for the cylinder bolt and trigger and an adjustment to the factory hammer spring has done wonders for all of my Ruger revolvers. I haven't had to touch one with a stone yet.

Gear

[MBTcustom]

I would just fire-lap it. I would do it exactly like geargnasher said except maybe with 600 grit clover leaf. Rugers are famous for this, you are not the first one to have this problem. If it were me, I would shoot it with known loads that are not prone to leading and see what you get. I highly suspect you will get some leading out of those guns but you might get lucky. If they give you problems, go ahead and fire-lap them. If it doesn't work, sell them to somebody that shoots J-words. (they'll never know the difference!:twisted:)

[stubshaft]

I've done quite a bit pf firelapping but prefer to pour a lap and do it by hand. Less mess and I can feel when the restriction is gone.

[Wolfer]

Can you describe your lapping process, please

I'm with stubshaft, I like to feel my tight spots and only work on them
I cut most of the bristles off an old bore brush leaving all the bristles at the very end. I put a patch or two on the end of the brush ( whatever it takes to seal the bore ) and push it in the muzzle until only the threads are sticking out. Some people heat their barrel but I have plastic inserts on most of my guns and don't bother. Besides the wrinkles hold more compound. With the lap centered in the bore I pour in the lead nearly to the top. Screw a rod on it and slide about halfway out. Wipe on your grit of choice and push it through til you hit a tight spot. When the lap wears out just stick it in the melt for a moment to clear the brush and start over.
I have the Wheeler bore lapping kit from Brownells. It came with 220,320 and 600 grit and I'll work through all of them.

The thing about lapping is your sanding tool exactly mirrors your bore so it's hard to do any damage. Plus it takes quite a bit of lapping to remove a couple thousand' s.

Some people say you should never let the lap come all the way out but I have lots of times and could never see a problem

[MBTcustom]

A word of warning about hand lapping a barrel: every time you reverse direction, you remove a lot more material and the finish changes. That is exactly why Lilja makes their rifle barrels 34"in length and they cut off both ends where the reversing took place. Look it up. I will only fire-lap a barrel unless I plan on re-crowning the barrel after pulling and pushing the lap all the way through the barrel on both ends.

[Iron Mike Golf]

Your Blackhawk may be fine, depending on the load and boolit. You might get minor leading that you can brush out with solvent.

I'd shoot both and find out if whatever leading you get is bad enough to worry about fixing.

Having said that, if you do decide to firelap, you'll find that Ruger stainless is one hard steel.

I firelapped my stainless Redhawk and it took just over 100 rounds to remove the thread choke. That was using the Beartooth compound, which I think is 320 grit. I followed that with a dozen or so rounds using Wheeler 600 grit compound.

I worked about 6 months at trying to find a combination of boolit, alloy, powder, and load to cure the leading, without success. My groups would open up from leading after 3 cylinders. I am very glad I did it.

[MtGun44]

Start off shooting a few hundred rounds of jbullets at high velocities and then recheck
your barrels. It is likely that the one may clear up all by itself, and the other one may
be much better.

THEN, try shooting good designs of boolits, Lyman 358477, 358429 or Lee 358-158-RF
size to throat diam or throat +.001, no harder than air cooled wwts, using a known
good lube like LBT soft blue or NRA 50-50 and see how they perform. Only then will
you know if you really need to do anything.

Bill

[HangFireW8]

I'm with MtGun44. Only try fixing it, if it turns out to really be a problem, such as uncontrollable leading.

Lapping of any kind is basically rapid barrel wear. For custom rifle barrels, they make them a tad undersized (like .0001"-.0002) in the first place, knowing that they are going to lap. For factory barrels, they don't even try to hold tolerances like that.

I like to wear out my barrels the old fashioned way. I only lap as a last ditch resort before rebarreling. But, that's me.

HF