Does anyone know of a supplier for a .40 or .45 caliber, 7.5" upper for the AR?  Thanx...

Try Olympic Arms or SOCOM MFG, I think that they have both made PCC's in .40 and .45 cal.

socom makes it ive seen it does anybody make an upper in .357 sig or can i change the ballel of an upper .40 s&w into 9mill.. would this work

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socom makes it ive seen it does anybody make an upper in .357 sig or can i change the ballel of an upper .40 s&w into 9mill.. would this work
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40S&W and a Sig 357 would use the same boltface, 9 mm boltface would be different. Changing out the boltface would be required, the carriers are the same.(Olympic Arms, not Colts).

There were some whom had 9mm ammo shooting in Glocks designed for 40S&W, apparently the 40S&W extractor was able to get enough purchase on the rim of the 9 MM case to extract. But I have never heard of it tried on a AR. They would basically make a Glock barrel with 40S&W specs on the outside but with a 9mm bore and chamber, I remember making a few runs of these when I was at Oly Arms. One of these modified barrels and a 9mm magazine was all that was needed to shoot 9MM ammo out of a Glock originally chambered in 40S&W.

Swapping out a barrel would require specialized tools (def not a terribly diffcult procedure mind you), its actually something I wouldn't recommend on a regular basis. It would lead to uncommon wear on the associated parts.

Seperate uppers would be a better solution.

357 Sig was tried but found not to work very well, esp because the cases tended to blow out their bottle neck shape, thus making reload of the cases difficult if not immpossible. Couple that with the cost of 357 Sig ammo lead to the 357's less than popular status.

Fritze Out