I bought a pre-ban Colt 6450 years ago.  I haven't shot it much, but it always been 100%.  Is this gun supposed to have a buffer spacer of some sort in it?  Currently it just has a 9mm buffer and standard spring, no spacer.  Is the spacer something that was dded later on?  Also, I have a couple spare VLTOR A5H2 buffers (5.33oz)  Could I drop one of those in with the existing carbine spring and buffer tube?  Thanks

My understanding is the Factory Colt 9mm have the heavy 9mm buffer with no spacer.

As to the Vltor A5 Buffers, yes the work and eliminate the need for any spacer with a standard carbine length reciever extension. I used an A5H4, for the extra weight and length, works 100% in my build.

Awesome, thanks.  Do you think the A5H2 would work, or should I jump up to the A5H3 or H4?  Or should I just add a spacer?  I have an H2, anything else I would need to buy.

I'm leaning toward the H4 A5 buffer.  Will I be ok to use it with the stock carbine spring, or do I need something else?  I'm using standard pressure ammo, not suppressed, 16" barrel.  Thanks

You should be ok with an A5H2. Weight on those is about 5.3 vs your 9mm buffer at about 5.5.

I went with the H4 to gain weight. I am using a 8.5 barrel unsuppressed. The extra weight just helps it stay closed a little longer before it ejects. I use a rifle spring with mine, but I have seen regular carbine, as well as extra power of both used. Again, the longer spring helps it stay closed a bit longer.

Mine has been 100% with no tuning, just the A5H4 and the rifle spring. I just took the middle of the road of what I had read.about people using. Some use buffers as high as 12oz, but generally suppressed. Other use heavier 308 springs, again, mostly suppressed. But overall the general concensus seemed to be heavier was better.

I just realized that I have a Wolff XP spring laying around as well.  I might just run that along with the A5 H2. Thanks again