Shootout: New S&W 66 Snub vs Old 66 Snub

[DPris]

Yesterday finally got around to doing the head-to-head with both guns.
The new 66 snub was new, the old 66 snub was a minty late 80s gun.

With five commercial .357 jacketed loads, the new outshot the old at 25 yards off a rest at an indoor range.

The new 66 with very shallow cone has been reported to shave & spit backwards.
This one did, and the older one also did, to a lesser degree.
The new hit my right cheek once, the old hit my left cheek once. No blood.

A distinct problem in both guns with one load, CorBon's 140-grain JHP.
In the older 66, it shaved copper jacket material sufficiently to lodge small fragments between the cone & topstrap TDC and bind up the cylinder rotation once.

Same thing happened with four rounds in the new 66.

I had to pry fragments out with a small screwdriver in the new, had to chisel them out with screwdriver & hammer in the old.

If considering the new 66, be aware.
If considering that specific load (which has never given me any problems in the past), try it before you use it in a carry gun & make sure it doesn't react that way in yours.
Denis

 

[ArchAngelCD]

Thanks for the report.

 

[Zaydok Allen]

Interesting. Any idea why that particular load was a problem?

 

[DPris]

Peter Pi at CorBon says in his experience it's quite common with 140-grainers.
And I did notice that blowback was greatest in both 140-grain loads, just worse with the CorBon.
May have happened more with the new 66 because of its almost-not-there forcing cone.
Denis

 

[bannockburn]

Denis

Thanks for the heads up!

 

[DPris]

Checking further with my gunsmith, also says this degree of shaving is quite common with 140-grainers.
I may be the only one who's never encountered it before.

Trying to get both guns to him for a range rod drop later today to check for chamber alignment.
Denis

 

[Zaydok Allen]

Can you expound on that Denis? What about a 140 grain slug would make it shave more material than a 158, 125, or other bullet weight I'm neglecting?

I have some 140 gr Barnes all copper rounds in my ammo box. Never have had a reason to shoot them, and I prefer a heavier bullet anyway.

 

[DPris]

Combination of bullet ogive & forcing cone angle.
Gunsmith says he ran into it during his metallic silhouette days (back in the 1800s).
Liked the bullet weight, but his Ruger BH would shave & spit like hell.
Switched to heavier lead semi-wad & the problem went away.

Cone can be cut specifically for a 140 JHP on a gun with thick enough cone walls to allow the angle, but that's not much of an option on the new 66, and once you do that you can create problems with other bullet weights.
Denis

 

[HB]

I have an "old" S.D. Sheriff marked 4" m66. I've shot it primarily with hand loaded 38s (both plated and lead) with some medium tilt 158 357s mixed in. I have not noticed any "shaving".

The concussion/cylinder blast is significant with 357 but are these known to shave bullets?? That seems like defect, not a design quirk.

 

[351 WINCHESTER]

I had two older 66's one was p & r while the other was not. I had to send the older one back to S & W as the forcing cone was cracked & they rebuilt the gun with new barrel/cylinder & other parts. I never had any problems with either spitting lead or jacket material to my face or other body parts. I did have a problem with a model 29 that would shave small pieces of copper jacket rearward.

 

[gotboostvr]

The 140gr spitting lead is interesting to me. I've never experienced that before in that bullet weight.

I worked up and shot alot of 140gr XTP's over a max book H110 load from my 6" 686 for a deer hunting load and liked it so much it became my general purpose hot 357mag load even after I switched to 44mag for deer. H*ll of a muzzle flash, no spitting though.

 

[DPris]

We're not talking about .38s & we're not talking about lead.
Velocity is a component.

Both guns were examined thoroughly this afternoon by my gunsmith.
Range rods showed all chambers in both guns are in perfect alignment with the bore.

A GO/NO GO gauge showed the older 66's cone is perfectly cut, passed the gauge.
Same gauge showed the new cone failed the gauge, it's cut way too shallow. It's also cut unevenly inside; cut deeper on one side than the other.
This would tend to allow some yaw on bullet entry, which could further aggravate the shaving problem.
He suggested not shooting it any further, the barrel needs to be replaced.

This would also help explain why the new 66 shaved bad enough with the CorBons to jam the cylinder four times on the new gun, as opposed to only once on the older gun.

Still trying to determine with S&W if that shallow cone will be standard production going forward, or if the sample here is a glitch.
Very definitely the uneven cut is a glitch.

Understand that I am NOT saying EVERY 140-grain JHP will produce this shaving in every gun.
I AM saying that two people in the industry in positions to know (including the owner of an ammo company)have told me the 140 JHP shaving issue has long been known, I've suggested you check any potential 140-grain JHP candidate for carry to verify function before you do carry them, and I'm relating what I've personally experienced with two 66 snubs.
Denis

 

[DPris]

Update from S&W- they apologize for a defective sample being sent & say the cones should not be this shallow on the new model.
Denis

 

[.308 Norma]

Thanks for the report.

Yeah, thanks!

 

[DPris]

Happy to help.
Denis

 

[Sergei Mosin]

Are they going to send you a replacement sample to re-test?

 

[DPris]

They offered, I declined.
I rarely have the time or the ammo to re-shoot on these articles if a sample isn't quite what it should be.
If it's too far gone to write up at all, I just cancel the piece & move on.
If it's got a couple problems, I run with it as is.

This sample just had a poorly machined forcing cone.
Otherwise it's OK, and I'll again point out that it still outshot the older gun overall.
A best 5-shot group of 1 7/8 inches at 25 yards is perfectly acceptable to me.

The primary issue was the shaving, and a properly cut cone would clear up most of that. The remainder would be attributable to those two 140-grain jacketed loads.

I consider the test valid, despite the flawed barrel.
Denis

 

[shafter]

I wonder how many people have bought one, fired a bunch of 38's through it, and then loaded it with defense loads they never tested. Probably quite a few. Revolvers are great but they have their issues just like anything else. A bound up cylinder would be fatal in a gunfight.

 

[DPris]

That's why I include the warning & suggestion about 140s here.
We always recommend testing up front with an auto, but it applies to revolvers, too.
Denis