[Historian]

Can I use CCI 400 small rifle primers in my.40 S&W loads and if so should I lower my powder weight?

Historian

[jcwit]

I would drop charge by 10 to 15% and work up again. Try a few with just primer and no bullet to make sure you spring is strong enough to set them off, but I doubt you'll have any problem.

[rcmodel]

Sm Rifle Primers are "taller" then Sm Pistol primers by a few thousandths.

Beware you don't leave any seated high, or above the case head, which could cause a slam-fire.

rc

[Remo-99]

should I lower my powder weight?

If your running your loads at the upper end of loading data, it's good practice to back it off around 10% and work back up, when switching any components/brands etc. ie Like just changing from brand A pistol primer to brand B pistol primer.
Same deal if substituting a SPP with a SRP.

Modern unaltered handguns usually have a heavy enough firing pin strike to set off SRP's without issues.
My target 686 only likes Federal SPP, but it's trigger mech. has been worked, including lighter mainspring, to lighten the double action.

[jcwit]

rcmodel no-no large rifle are taller than large pistol
Small rifle/pistol are the same height.

sorry

[rcmodel]

Oops! :o

rc

[Historian]

Well, I loaded 50 rounds last night with 5.5g of 800X under a 180g Barry's. Just got back from the range. They cycled perfectly through my M&P and look to be pretty accurate considering that I'm new at the pistol game. I have a surplus (if that's possible) of CCI 400 smr and they seem to work just fine. Thanks guys.

Historian

[45crittergitter]

You absolutely should NOT do that.