How tight is too tight ?

[joneb]

The cylinder chamber mouths in my S&W 696 measure .4288-.4289 is this to tight ?

[cntryboy1289]

Does the gun function or not? If it does, it isn;t too tight.

[UniversalFrost]

Oh wait we were talking about guns not women.

Yeah as long as the rounds feed and extract without binding or jamming then it should be ok. Also check your spent brass for uneven wear or excess marking. If you do have any problems have your gunsmith open up the chamber or polish it a bit.

[joneb]

The gun shoots fine, with my other revolvers a jacketed bullet will just sneak through the chambers, but not in the 696. I was wondering if a chamber under size by .0002 would cause added stress to the cylinder ?

[HSMITH]

If you are shooting jacketed there will be NO problems, shoot some lead and it will likely lead near the cone using loads that a gun with a .4295-.431" cone would not. Shooting lead I would lap the throats, shooting jacketed I would smile and keep on keeping on.

[joneb]

thanks HSMITH, If I want to load lead should I get the .429 variety ? I notice some cast bullet manufactures offer .44 cal in .429 or .430 Or should I avoid cast bullets do to leading issues ?

[cntryboy1289]

If it was myself shooting the gun, I wouldn't avoid shooting good lead bullets if you can load your own. If I had to buy loaded rounds, I might only buy a decent jacketed load though. Either way you are going to need to remove the fouling to keep it shooting accurately.

I have a Ruger SBH and it loves a couple of loads that I feed it using a good lead bullet.

[joneb]

cb1289, I've only shot my reloads through this gun , I live near Nosler and at the shooter's pro shop they sell there factory 2nds. I prefer the 200 JHP with 6.7 grn of W231 or 10.8 of AA#7

[cntryboy1289]

You should be fine with those loads. Must be nice being to able to ride up and go in to buy from Nosler.

[HSMITH]

Jibjab, as long as the bullets chamber easily I wouldn't care if they were .429" or .430" in your case. If the gun had .430" throats I would definately recommend the biggest bullet you could find.

[Harry Bonar]

Dear Sir:
In a revolver slug your bbl for groove dia. Your bullets should be that dm.'

Cast bullets can be .001 larger than groove dia!

Harry B.

[Unclenick]

Harry's got it. You need to slug the bore. If the groove diameter is bigger than the cylinder throat, then you will likely have terrible leading and accuracy problems with cast bullets and it is likely accuracy even with jacketed bullets will improve from "fine" to "great" by getting the cylinders reamed. Reaming all cylinders to a uniform maximum standard dimension is usually the first step in a revolver accuracy job. Ruger did this free of charge on a Redhawk that belonged to a friend of mine that wasn't accurate. He just returned it to the factory with an accuracy complaint. S&W might do the same if accuracy is a demonstrable issue?

The issue is not pressure; the steel is more than capable of squeezing jacketed bullets down several thousandths. The issue is bullets entering the rifling undersized. This can allow them to tilt off axis or, worse, become more deeply engraved by the rifling on one side than the other. This makes the bullet center of mass off-axis from the center of rotation. Key-holing at distance is usually the result if the problem is serious. With lead bullets, gas cutting around the base is worsened by this size problem. Ideally, lead bullets will almost kiss the cylinder throat for alignment, then be sized down slightly by the barrel. For example: .4300" bullet, .4305" to .4310" throat; .4290" groove diameter. This assumes perfect cylinder alignment with the bore, another thing corrected in revolver accuracy jobs.

A question though: How did you measure the cylinder throats? If you did it with the inside jaws of a caliper, they are typically only accurate +/- 0.002", and can't be trusted on small hole diameters because of the small flats on their edges subtending a portion of the radial arc of the hole, giving a false low reading. You need to slug the cylinder throats just like the bore, then compare the results you get for the two slugs. A micrometer is prefered to a caliper for this so you can see ten thousandths. A gross difference will, nonetheless, show up using a caliper on the slugs. Bottom line, measure both the same way.

Nick

[joneb]

Thank's Nick, I used a lead bullet that miced .4295 and tapped it into the cylinder mouth. It then miced at .4289", I measured the slug with a Starret Micrometer.
I ran a slug through the barrel, but how do I get a accurate measurement with five grooves ?

[joneb]

Well to answer my own question (?) I locked the micrometer at .4295" and the slug I ran through the barrel did turn, just catching on the high points made by the grooves of the riflings, when I locked out at .429" the bullet would still turn but this may be do to the softness of the lead. I'm assumeing the rifling grooves are cut at a .2145" radius ?
The slug I ran though the barrel did not easily pass through the cylinder chamber mouth I think they maybe under sized ? The chamber throats are not smooth, I hope a polishing will do and open them up .0005"

[Unclenick]

Jibjab,

Yeah, the odd-numbered grooves are a nuisance to measure. I usually use a slightly tapered steel mandrel to plug and gauge the bore to find its diameter. I then measure across the slug from each land to each groove, take the average and use its difference from the plug gauge result as the groove depth. Two groove depths plus the tapered plug at its stopping point is the total diameter.

Without the tapered plug it gets a little more difficult. I have used a slug chucked in a lathe at one end and turned it under a dial indicator to get an average groove depth.

Your discovery that the the barrel slug has a tight fit in the cylinders is revealing and your best indicator that the cylinders should be reamed. You can firelap them out, but be careful trying to use polish because it is easy to flare the front of the chamber. If you've done honing before and know how to randomize the motion, you may be OK. The plus side to reaming is all chambers done on the same reamer means the best size match.

Nick

[joneb]

We have a good smith out here in Central Oregon but he has been to busy with rifles but now that fishing season is apon us ?? I will seek his help, thanks

[918v]

Unclenick is right. But have a competent revolver expert polish out those throats. Don't give this gun to a local yahoo. Alphaprecision is my choice.

[joneb]

Thanks 918v, I will look into your recomendation

[Unclenick]

Some fellows on another forum like Cylindersmith. $37, including S&H, and less than a week for turnaround if you call ahead and let them know it's coming. I haven't tried the service, but the price seems fair and the specialized service a lot faster than a general gunsmith who is usually backlogged.

Note: This service depends upon you sending the cylinder alone. That avoids all the transfer and FFL paperwork. The site says specifically NOT to send the whole gun. You are not paying them enough to do disassembly and reassembly for you. I am sure some people send whole guns anyway, but that will either invoke the paperwork nightmare and slow the service way down and add charges, or else they will just refuse delivery.

Nick

[joneb]

Thanks again Nick,
But that sounds way to easy, there must be a harder way

[Unclenick]

There is, but I've misplaced my directions for homemade precision diamond laps. I seem to recall something about an extemely high pressure and temperature vessel and some coal?

Nick