SVI Infinity 2011 5in vs 5.4 help needed

[EVANB]

I have a 1911 Springfield 5" 9mm  that I recently milled the slide for Holosun 507K and the slide in not looking back to the rear with Federal premium 115 ammo, I've tried 3 different springs weights 13, 12, 10lbs and three different mags and replaced the slide lock with Wilson bullet proof one  and still it's not locking back on the last round, but locks back when I rack it by hand. I guess the only thing left to try another ammo. I'm new to 1911 platform so I'm not used to have the slide not locking back on the last round! 

[donnyglock]

4 hours ago, EVANB said:

I have a 1911 Springfield 5" 9mm  that I recently milled the slide for Holosun 507K and the slide in not looking back to the rear with Federal premium 115 ammo, I've tried 3 different springs weights 13, 12, 10lbs and three different mags and replaced the slide lock with Wilson bullet proof one  and still it's not locking back on the last round, but locks back when I rack it by hand. I guess the only thing left to try another ammo. I'm new to 1911 platform so I'm not used to have the slide not locking back on the last round! 

Try a 9lb or even an 8lb recoil spring. You can also go with an extended firing pin and drop the mainspring to a 17 lb. 

[EVANB]

3 hours ago, donnyglock said:

Try a 9lb or even an 8lb recoil spring. You can also go with an extended firing pin and drop the mainspring to a 17 lb. 

Thank you, but what is the relation between the firing pin and the slide not locking back ? 

[donnyglock]

6 hours ago, EVANB said:

Thank you, but what is the relation between the firing pin and the slide not locking back ? 

The lower the power mainspring the less force it takes to reset the hammer. The slide has to move to the rear to get that hammer moving. The lower the spring pressure the less force that takes. Usually makes more of a difference than the recoil spring. The reason you put an extended firing pin in the gun as it takes less force from the mainspring to ignite the primer. 

Edited February 22, 2023 by donnyglock

[EVANB]

Thanks, I've ordered a different recoil springs and mainsprings to test out, in the mean time I had much better success after removing the shock buffer, I hope that won't cause lots of stress on the slide without it. 

[donnyglock]

5 hours ago, EVANB said:

Thanks, I've ordered a different recoil springs and mainsprings to test out, in the mean time I had much better success after removing the shock buffer, I hope that won't cause lots of stress on the slide without it. 

Definitely remove the buff. It won’t hurt a thing not using one. 

[EVANB]

On 2/23/2023 at 3:53 AM, donnyglock said:

Definitely remove the buff. It won’t hurt a thing not using one. 

Thanks, I did remove mine and for sure the guns feels and function much better without it.