Please see comments for more detail

I finally ran the new PCC build this week and it performed much better than I expected. I thought I would have to adjust my buffer set up but that did not happen.

I’ll try to run the D50 next week to see if I encounter any issues.

Aero EPC Upper

NBS Suppressor series rail 9.25”

Novox Research X-SD barrel kit 4.3”

Aero EPC lower (shelf cut)

GMR SS

KVP 10oz Buffer

Kynshot Spacer x2

JRC 8” buffer tube

Tubbs lightweight buffer spring

IDL Industries Gen 3 bolt

Davidson Defense titanium 9mm firing pin

Rex Silentium MG7K 358

9 pictures. Original 1st gen Colt Unramped bolt provided for measurement/documentation by a fellow Redditor and will be returned shortly. It arrived with what apperars to be a 3rd gen model ramped Colt bolt as well for comparison purposes.

This is, to the best of my knowledge, a very early production 1st generation Colt original 9mm AR 635 bolt. If so, it's a bit of a unicorn, so I wanted to share pictures before I had to send it back. I'm planning on making a video about it, covering some of the information below.

The fact that it does not have a lateral groove in the "reverse ramp" just below the firing pin should mean it was produced before the Henry Tatro/Colt patent for a “Safety Device Preventing Conversion To Full Automatic Firing” that used a notched bobbed hammer to stop the gun from firing if the disconnector was tampered with. The patent was applied for on September 25, 1985. and the patent approved (U. S. Patent No. 4,658,702) on April 21, 1987.

Colt started producing the 9mm 635 SMG around 1982, about 3 years before they applied for the patent.

The "2nd gen" grooved bolts were used in both military and civilian models, but the bobbed, notched "9mm hammer" for conversion prevention was only installed in civilian models. The military models used a standard M16 trigger set. This "1st gen" bolt would have only been used in early military models.

Note the "reversed ramp" under the firing pin. This was a feature of the 1st and 2nd gen bolts and known to be very abusive on the hammer pin, often causing them to snap. This is how 9mm AR's got the reputation for breaking hammer pins. Instead of ramping the bolt to fix the problem, and getting rid of the "Safety Device..." baloney, Colt started using stronger stainless steel pins that egged out the holes in the receiver and still snapped. Later, Colt did start ramping the bolts (3rd gen) and abandoned the "Safety Device..." idea.

This reverse ramp may (my hypothesis) have been used as an attempt to create a leverage disadvantage for the bolt when cocking the hammer, much like the firing pin stop on an old Colt 1911. If the 1911's firing pin stop has a very shallow curve at the base, which most older Colt 1911's did, it requires more recoil pressure to push the hammer out of the way when the slide reciprocates back. Applied to a blowback 9mm, this may help reduce the bolt velocity by adding a leverage disadvantage over the hammer spring when cocking the hammer compared to a ramped bolt.

It makes sense that Colt would try to apply this technique from their 1911's to other platforms.

I tested 3 bolts in an AR with a force gauge, standard carbine spring, standard milspec hammer spring:

- Gen 1 Unramped Colt bolt: 12.2lbs. of force to cock the hammer

- Gen 3 Ramped Colt bolt: 11.8lbs. of force.

- Modern Outerwild bolt: 11.2lbs. of force.

Almost all modern bolts are ramped, allowing the bolt to more easily reset the hammer.

I took a number of measurements and will be adding the data to my bolt database. An updated chart will be uploaded soon.

CAR15 SD.

A glorious shoot today. I think I may be settling in on a Spikes variable pitch buffer spring with a Kynshot 5000A5 in an A5 buffer tube.

That seems to run around 620. When I plugged in a Tubb lightweight the ROF dropped to 585 - a bit too slow for my liking.

I may try a few clips off a Tubb 556 and see how that does. The full 556 Tubb is a bit strong to consistently FRT with this HSL 115.

The 5000A5 really does push most of the SD gas down bore and out the muzzle - quite awesome!

FM9 7” with Integrated Folding Lower, plus obsidian 9, zentinal holo, and applesauce charging rod and handle… atrius SS

ISU at home?

For a PCC.