.40 S&W Bullet Size

[Mauser69]

Anybody here slug their barrel for a .40 S&W to check groove diameter for loading cast bullets? Are the majority of .40 S&W barrels larger than .400"? If so, why are all .40 bullets available in only .400" or .401"?

I have been developing range loads with Missouri Bullet Company 140g cast bullets with a BHN of 18 (hard cast), and I have significant leading in all of my guns. The MBC technical info says that the optimal pressures for a BHN of 18 should be between 20,000 and 25,000 PSI for proper obturation. The test loads I have used are estimated to generate between 20,000 and 30,000 PSI, and have a measured velocity between 875 fps and 1075 fps. These numbers all indicate that these loads should NOT be leading the barrels if they are the correct size.

I have four different .40 S&W pistols, and they ALL measure greater than .401" (measured with a micrometer, not calipers):

Star FireStar = .4015"
Dawoo DH40 = .402"
Ruger SR40c = .402"
Taurus 740 Slim = .4015"

Of these pistols, the Ruger has the worst leading problem, and the FireStar and Taurus have the least leading.

So that seems to be the problem - These bullets (and all other cast .40 I have found) are specified as .401", and the correct size cast bullet is normally .001" - .002" over the groove diameter, which means my guns would all need an unobtainable .403" bullet! What is wrong with this picture?

 

[LiveLife]

Missouri Bullet Company 140g cast bullets

I have four different .40 S&W pistols, and they ALL measure greater than .401" (measured with a micrometer, not calipers):

Star FireStar = .4015"
Dawoo DH40 = .402"
Ruger SR40c = .402"
Taurus 740 Slim = .4015"

Of these pistols, the Ruger has the worst leading problem, and the FireStar and Taurus have the least leading.

What is wrong with this picture?

Your barrels are oversized.

My Glock/M&P/Lone Wolf barrels measure .400"-.401" and do not lead with MBC 40S&W lead bullets sized .401" using mid to high range load data and Red Dot/Promo, Green Dot, W231/HP-38, Herco, BE-86, WSF, AutoComp.

So that seems to be the problem - These bullets (and all other cast .40 I have found) are specified as .401", and the correct size cast bullet is normally .001" - .002" over the groove diameter, which means my guns would all need an unobtainable .403" bullet!

Problem is that larger sized lead bullets may not allow full chambering of finished rounds in your barrels. Try Missouri Hi-Tek bullets instead.

 

[cheygriz]

The BarSto barrels in my Glock 20, 10MM and Glock 22 .40 SW measure .400. I use .401 jacketed and.402 cast bullets. I've never experienced a leading problem, and I load both calibers HOT!

 

[ljnowell]

I helped a friend with a very similar issue. He was having issues with an oversized barrel. The easiest solution was to use softer bullets.

 

[Edarnold]

A BHN of 18 is way too high for such mild paper-punching loads. Drop back to something like BHN 10 and your obduration and leading problems should go away. Hard-cast bullets are a problem waiting to happen for anything but the hottest loads.

 

[Dudedog]

I never had any leading issues with MBC lead bullets in 9 or .45. (Shot 1000s) I used the BHN 18s in 9 and loaded some fairly light loads <1000 fps w/125 with no problems I prefer the BHN 12 200 SWCs for .45.

Having said that, now they they are offering coated bullets I pay the few extra $ and get the coated ones.

 

[Mauser69]

Thanx for the responses guys - pretty much confirms that the issue is oversized barrels. That was the only logical answer for me, but I was really surprised to find all four of my guns with the same problem, especially the brand new Ruger SR40c. With the SAAMI spec for groove diameter at .4005, I cannot understand a decent manufacturer turning out a new gun with an oversized barrel!

 

[cheygriz]

Rugers are as strong as a tank, and utterly reliable. But they are somewhat lower priced, "working class" guns, so you can't really expect the kind of fit and finish or quality control you'd expect from Colt, Beretta or SIG.

 

[LiveLife]

Thanx for the responses guys - pretty much confirms that the issue is oversized barrels. That was the only logical answer for me, but I was really surprised to find all four of my guns with the same problem, especially the brand new Ruger SR40c. With the SAAMI spec for groove diameter at .4005, I cannot understand a decent manufacturer turning out a new gun with an oversized barrel!

Another member grogetr had similar problem with his 9mm SR9 having oversized barrel (.357"+) and leading/accuracy problem with .356" sized Missouri bullets. I sent him an assortment of lead bullets including .357" sized bullets but the problem remained. In the end, I suggested he talk to Ruger again and was sent a different barrel sized .355"-.356" which I believe resolved the problem.

Mauser69, try calling Ruger customer support and reference this thread. Most THR members post positive customer service and perhaps they can send you a .400"-.401" sized barrel.

Some manufacturers like Beretta and Taurus are also known to produce oversized barrels. Perhaps it's done to lower chamber pressures and/or extend the life of rifling rod.

I did contact Taurus for my PT145 oversized barrel (.455"+) and was not able to have them replace the barrel so I ended up using softer 12 BHN MBC 200 gr SWC bullet (Bullseye #1) which resolved the leading and accuracy issues.

You can certainly try calling Taurus for barrel replacement.

 

[popper]

Get the coated ones, unsized and roll your own, size wise. Used them in my XD & Berreta, PX4 was terrible. Coating solved the problem.

 

[steve4102]

I have four different .40 S&W pistols, and they ALL measure greater than .401" (measured with a micrometer, not calipers):

Star FireStar = .4015"
Dawoo DH40 = .402"
Ruger SR40c = .402"
Taurus 740 Slim = .4015"

How did you measure these barrels?

Did you "slug" them with soft lead or some other method?

 

[Hondo 60]

Tell Brad the slug sizes & ask him to cast some over-sized bullets.
I'd betcha he'd do it.

 

[LiveLife]

Only problem is that finished rounds with .403"+ sized bullets may not fully chamber in the barrels.