Slugged my .44 mag Rossi 92 today...

[HDS]

And I got some weird results!

I hammered in a .451" round lead ball from the muzzle and it was tough going but then the resistance stopped after 1-2 inches and I could push the slug through the barrel without almost any resistance, sure it wasn't loose in the barrel but I just had to press on the rod with my thumb or hand to move it along, until I gotnear the chamber, then I had to pick up the hammer again and start tapping it through to the other side.

So it seems my bore is uneven, it's tighter near the muzzle and chamber than in the middle! What the heck!? I got a Rossi 92 .44 mag, it's a few years old but NIB. According to the slugging it's .4295" - .430" at the muzzle and chamber but somewhat wider in the middle. I only measured with a caliper now, need to find a good micrometer to make sure...

Anyway what can I do? Is it possible to achieve any type of accuracy from this gun? It's new, I only shot 30 shots through it with factory ammo and it didn't shoot that well but I cannot say I tried to make a good group I just function tested it and found I dislike buckhorn sights.

I've heard of firelapping it, though I wonder that if the constrictions are .4295" - .430" then what is the bigger part of the bore? How do I find that out? I've heard of rossis and overbore issues before, namely them being as large as .433" but I thought it was the same all through the bore in those cases, not just part of it.

[BABore]

Pound one slug just below flush in the muzzle, then back out. This assumes you can remove the bolt to get a rod in from that end. If not, there are ways to still do it. Then pound another all the way through. I do prefer soft lead, hollow egg sinkers as they have somepllace for the lead to go and suffer the least springback.

With the two slugs, you will be able to determine exactly how much the bbl is constricted at the bbl thread area. This is a very common occurance. You need to use a good micrometer for measuring these. A caliper is not accurate enough and a poor tool for measuring round stuff down to tenths. Any constriction smaller than the muzzle slug dimensions will act like a sizer for your cast boolits. I usually don't fret too much if I only have 0.0004" or less constriction on a newer gun. It doesn't take long for jacketed or high antimony boolits to lap it out. Harder boolits will have enough springback to compensate somewhat.

The tightness at the muzzle is common and preferred. Bbls most always have a taper to them and the blank is typically marked so the smith can work from the correct end.

Assuming you do have a bbl thread constriction, then some form of lapping is in order. Hand lapping takes much more experience and feel than firelapping. I've never done the former and have had great sucess with the later. Your best best is to contact Beartooth Bullets and get a lapping kit complete with manual. One kit has enough compound to do 10+ rifles. You can provide your own boolits for later guns.

[HDS]

I thought that if I just drove it all the way through I would only get the diameter of where the bullet is the smallest (which might be the muzzle or chamber, I see no way to find out what the diameter is in the middle). I am using round lead balls for slugging.

[BABore]

Your likely ok in the middle. Most of the guns I've slugged will start hard til the slug is a couple inches south of the muzzle, then you can hand push them through. In Marlins, you typically get bore constrictions under the dovetails, rollmarked lettering, and at the bbl threads. Once a bbl is properly lapped (fire), you get a slug an inch or two in the muzzle and it will hand push right out the breach.

[izzyjoe]

my marlin44 slugs at .432, but if your's is .430 or close to it that's even better. like babore said calipers are poor for mesuring accuratlly. they are good for coal,and such.

[Ekalb2000]

I shoot the Lee 310 un-sized (433) in my rossi. It will knock pop cans at 100yds all day. Zero leading, Zero.
I say load some rounds up and go for it. Its a starting point for you with boolits.

[blackpowder man]

My rossi .44 mag loves fat boolits. The RD 265 grain i shoot without gas check drops at .432-.433 and my lee TL 240 grain at .431-.432 and .433 roundballs all do great. I really love that gun. Shot it at my first cowboy match saturday and she didn't hiccup once.

[RobS]

The chamber end being tight will give problems if the constriction is too much. Anytime a bullet is smaller in diameter than the bore there is a greater chance for gas blow by. Having a bullet that is soft enough to obturate (bump up) to fit the barrel will help this out and shooting softer bullets (8 BHN or so) while better for obturation will not do as well with the upper end 44 mag loads as the alloy will not have enough strength to withstand the pressures. Firelapping is the easiest route to take care of the chamber end constriction and will also ensure that tapper to the muzzle is still there.

[HDS]

Your best best is to contact Beartooth Bullets and get a lapping kit complete with manual. One kit has enough compound to do 10+ rifles. You can provide your own boolits for later guns.

How long do these guys take to answer anyway? Still nothing and I've sent two mails about the possibility for international shipping.

[BABore]

Marshall can be slow on the emails cause he's always busy. Have you tried calling him on the phone? I've never had a problem that way.

[RobS]

You can also use the Wheeler lapping compounds. If you search you can find how to firelap a bullet by impregnating the compound into the bullet by taking the compound, applying it to the bullet and then by using two pieces of metal roll the bullet between them etc. It is not as easy as this but yet it is.

Here is the Wheeler compound at midway. http://www.midwayusa.com/viewProduct/?productNumber=486249

I don't know where you live internationally, but there may be a Midway located in your country of origin or possibly a midway branch that may be closer to you which could result in cheaper shipping.

[BABore]

The stuff Beartooth uses in his kits is Clover brand 320 grit lapping compound. He specifically recommends that brand because of the silicon carbide grit suspended in a heavy grease will break down to a finer grit size as it works down the bbl. Others don't do this as well. Clover lapping compound can be bought at alot of automotive places. I only recommended Beartooth because of the fine how-to manual. If you want me to walk you through the procedure, shoot me a PM and we can work things out. It's not hard to do, but the first time can be slightly intimidating.