Arched vs flat backstrap on S&W pistols.

[BF-109]

Can someone tell me why S&W 5906 backstrap is arched but the S&W 4006 backstrap is flat? Does it have anything to do with recoil? For appearance only?

[mnshooter]

Gravity.

[tombogan03884]

Probably to adjust for the different cartridge size

[MikeBjerum]

My highly uninformed opinion is nothing more than model change.

Glock makes it easy to follow by keeping the model numbers the same and telling you which generation it is.  Look at how they change from generation to generation looking for what customers will find comfortable and usable, and then spend their money on.

General Motors for years claimed that the biggest mistake they ever made was in the Square Body C/K pickups.  Fifteen model years, 1973 - 1987, of very little change.  I worked at a Chevrolet dealership for a few years during that era, parts manager and service writer, and I had customers that would need to replace a hood, emblem, tailgate, grill, etc., and they would request the newest part.  They could make their old truck look new for no extra cost when fixing minor body damage.  Many customers purchase new for the new style.  For fifteen years C/K owners didn't have that reason to buy.

Is it possible that Smith & Wesson was just making a small ergonomic change in the new model?

[Big Frank]

This is a 13 year old post and that member hasn't been on here in 10 years, but if anyone knows the answer I'd like to hear it. The way I understand it, the 5906 was the third generation of the Model 59 and the 459 was the second generation. But the 59 and 459 had straight grips. The 5906 has a curved grip like the single-stack Model 39, 439, and 3906, instead of straight like the other double-stacks. Why the big change all of a sudden?

[Sponsor]

[MikeBjerum]

Look to the 1911, its changing backstraps.  Today there is a good sized market in aftermarket backstraps, if you wish to change from flat to curved, or curved to flat.

[tombogan03884]

I've got a 39, a 469 and they both have arched mainsprings .
The 4601 I just traded had a flat one .

[Big Frank]

I've got a 39, a 469 and they both have arched mainsprings .
The 4601 I just traded had a flat one .

Is the 4601 a double-stack or single? If it's a single it doesn't fit with the old pattern they started with the 39.

@ Mike. I've even seen semi-arched mainspring housings that were halfway between 1911 and 1911A1 style. Maybe for people who couldn't decide one way or the other what they wanted. 

[tombogan03884]

Single stack same as the 39.

[Big Frank]

Single stack same as the 39.

That's what I thought. But they had that pattern they went by for years AFAIK, and I admit I don't know much about it, but for a long time I could see a picture of one and know just from the shape of the backstrap if it was a single or double column. Even if I don't know the model number, and I usually don't. They have so many. Then they switched to flat mainspring housings on the single stacks too, or some of them.  Now if I see one with a flat mainspring housing I don't know what it is and have to read the description, or look up the model number online if I can even find it.