.44 Magnum issues???

[Mus408]

This is a strange one to me....

I have a new S&W Model 69 with 4.2 barrel and have been testing my handloads with it and of course own a SBH with 7.5 inch barrel that I shoot same loads in.
The mystery is when shooting the Missouri Bullets 240 or 300 gr. coated bullets thru the M69 they leave an ugly trail of coating and lead after 10 rounds.
When shot thru my Ruger SBH the bore is as clean as can be after 12 rounds.

The cylinder throats on the SBH are .432 and the throats on the SW M-69 are .431 with the bullets measuring .4305
The bore of the SW M-69 appears to be smooth and nice and shiny when clean AND shoot my 230 gr. lead SWC with gas check bullets very clean with little if any leading. Plated bullets shoot fine also.

These are mild loads shot with 9 gr. of Unique powder and must mention the 230 gr. SWC/GC bullets are 11-12 BHN sourced from Matt's Bullets. Also the coated Missouri Bullets leaving the lead shoot VERY well.

Of course shooting several jacketed bullets thru the M69 will clean out the bore at the range but just wonder why the these coated bullets don't shoot clean only in my M69.

 

[jsh]

Sounds like thread choke to me.
I am not a fan of shooting out leading, if it works for ya great.

 

[Mus408]

Wouldn't thread choke affect the non coated lead 230 gr. bullets as well?

 

[NikA]

I agree on the thread choke, and suggest the gas checks are preventing this issue with the uncoated bullets. A missized coated bullet might as well be a bullet with little or no lube, in my experience.

 

[Mus408]

OK so you could do a quick check for that using a gage pin at both ends of barrel?

 

[NikA]

A lead ball is more advisible than a gage pin. The steel in gage pins is harder than the barrel steel, and may scratch it.

 

[mikld]

A couple thoughts; perhaps the coating is scraped off during seating from too little flare? I believe thread choke will swage down a nekkid lead bullet and skim off the PC coating of a coated bullet. I have noticed that occasionally my PCed bullets will eave a fouling in the barrel that looks a lot like leading, but is just polymer residue...

 

[Mus408]

I will check for the barrel choke. When shot thru my SBH the barrel is very clean so the coating on the bullet must be working properly.

 

[jsh]

If one were to be heavy handed enough to scratch the bore with a pin gauge, they sure have no place around a firearm with a hammer and a lead round ball.

 

[Mus408]

I machined up a 3/4 inch long aluminum plug that would just slide in the muzzle end of barrel...about .4168 diameter and it slides smooth all the way thru and out.
No sign of thread choke there.

So I have eliminated too small of a chamber throat and any bore restriction.
The rifling looks to be smooth as nice and shiny.

Guess some barrels like coated bullets better than others?

 

[GP100man]

Check throat dia of the 2 revolvers ????

Had GP100 doing the same thing.

 

[Mus408]

Check throat dia of the 2 revolvers ????

Had GP100 doing the same thing.

The bullets push into the throat bore easily and my SBH they fall in.
I shot a few thru my older S&W 629-2E and it doesn't shoot them as clean as my SBH.

 

[Flyover_Country]

This is a strange one to me....

I have a new S&W Model 69 with 4.2 barrel and have been testing my handloads with it and of course own a SBH with 7.5 inch barrel that I shoot same loads in.
The mystery is when shooting the Missouri Bullets 240 or 300 gr. coated bullets thru the M69 they leave an ugly trail of coating and lead after 10 rounds.
When shot thru my Ruger SBH the bore is as clean as can be after 12 rounds.

The cylinder throats on the SBH are .432 and the throats on the SW M-69 are .431 with the bullets measuring .4305
The bore of the SW M-69 appears to be smooth and nice and shiny when clean AND shoot my 230 gr. lead SWC with gas check bullets very clean with little if any leading. Plated bullets shoot fine also.

These are mild loads shot with 9 gr. of Unique powder and must mention the 230 gr. SWC/GC bullets are 11-12 BHN sourced from Matt's Bullets. Also the coated Missouri Bullets leaving the lead shoot VERY well.

Of course shooting several jacketed bullets thru the M69 will clean out the bore at the range but just wonder why the these coated bullets don't shoot clean only in my M69.

Missouri Bullet Company supplies 240 grain .44 bullets in both 12 BHN and 18 BHN but all of their 300 grain .44 bullets are 18 BHN. All of their .44 bullets are sized .430. Plated .44 bullets are .429", MBC bullets are .430 like jacketed bullets.

I suspect the reason your Smith leads is because it is trying to extrude a larger-diameter bullet down to a tighter bore size and stripping lead off of the circumference of the bullet. Copper has a higher Young's modulus (shear strength) than lead and will extrude rather than shear, so you can shoot .430 copper gas-checked or jacketed bullets without leaving fouling but 0.430 lead bullets will lead. Slug your barrel and I betcha your barrel is 0.429" or a touch less, rather than 0.430" plus as Ruger tends to bore them. If you want to try to shoot your current bullets in your Smith, if they are 12 BHN Cowboy bullets, back off to 7.5 grains or less of Unique to build less pressure and you will do better as there is sufficient pressure to obturate but less velocity. If they are 18 BHN, go up in charge weight. A little over 10 grains of Unique is the max charge in a 240 grain SWC bullet and leads to more pressure, and a harder bullet will obturate better/lead less with more pressure.

Call the gentleman at MBC and order some .429" sized .44 bullets, they can do that and I'll betcha they'll shoot a lot better in your Smith than the standard 0.430" bullets. MBC will custom size bullets without any hassle. They are an excellent company to deal with and I've happily bought thousands of bullets from them. They also ship very fast, I had bullets on my porch within 36 hours with my last order from them even with MBC shipping cheaply via USPS flat-rate rather than using a proper non-government carrier.

 

[dg101win]

Didn't S&W use EDM rifling instead of cut rifling on some of the newer revolvers?