Longtime Guild readers will know that I'm a big fan of the AutoCocker, in no small part because it's endlessly customizable and personalizable. They're fun to build, fun to tinker with, fun to play with.
However, while we've modified, altered and/or tweaked damn near every part of the gun, one thing has stayed surprisingly unchanged- the sear.
Yes, companies have made some out of tool steel using high-precision wire EDM, and others have added little wheels to reduce some of the sliding friction, but none that I know of actually changed the geometry.
The 'Cocker sear is, of course, a direct decendant of the Sniper sear, which was in turn a direct decendant of the Sheridan PGP sear, which itself was basically the exact same sear that Benjamin-Sheridan was using on their pellet pistols sixty years ago.
By accident or design, the old pellet pistols had a very short hammer travel- in other words, when the sear released the hammer from the cocked position, it didn't travel very far before it contacted the valve stem. This short travel and the high chamber pressures (from unregulated CO2) required an extremely stiff mainspring- far stiffer than anything most paintballers are used to today.
That heavy spring got carried over to the P-series brass paintball guns (which used a valvetrain virtually identical to the old pellet guns) and later still, over the the early Snipers.
The first three or four years of Sniper and Sniper-II production essentially used a turned-down PGP valve, what was basically a PGP hammer that had been drilled for a cocking rod, and a PGP mainspring. Cocking actions were fairly stiff, and trigger pulls kinda heavy- neither of which were a problem in games where a "massive firefight" might involve upwards of twenty shots.
The advent of the AutoCocker required a change- the cocking mechanism in those early days was unreliable, which was made even worse by the high pressures needed to cock that heavy mainspring.
The fix was to convert over to springs out of the most common style of marker available at the time, a Nelson based gun. A dozen manufacturers made extensive kits of color-coded springs for Nelson guns, since in many cases you had to swap springs in order to chronograph the marker.
A modded hammer and a new rear plug, and your 'Cocker could use far lighter Nelson springs. That eased the pressures needed on the cocking pneumatics, lightened the trigger pull, and made it less likely to chop a ball. Eventually WGP switched over to using those springs from the factory, and all was well.
Except no one apparently ever thought to alter the hammer travel.
No matter the age of the 'Cocker, the sear catches the hammer at about the same place- which is about the same place as it was back in the PGP days.
Why is that an issue? Easy- give the hammer more time/distance to accelerate, the greater the impact it'll have on the valve for the same spring tension.
All else being equal- same hammer weight, same spring tension, same valve specs, same air pressure, etc.- if a the hammer started from, just as an example, one inch from the valve instead of just half an inch from the valve, you'd get a higher velocity.
Or, in our fixed-max-velocity world, that means you can back off the mainspring, or make a lighter hammer, or reduce your inline pressure, or whatever.
I've been thinking about this for years- I can't count the number of 'Cockers I've built where I had to, in my opinion, "band-aid" the valvetrain because of this. I've done experiments and modded parts... I've got a junkbox full of bits.
But recently, I was dealing with a customer's gun, a scratchbuilt based off an old 2004 Prostock body, and I was getting it set up with an AKA Tornado valve. I have my little tricks for squeezing a max shot count out of a good LP setup, and yet again, I was annoyed with the heavy springs I had to pile in there in order to get a decent velocity- especially with the common inserted barrels we're all but forced to use these days, thanks to the tiny paint. (A Freak insert, for example, is only a little over 5" long- that's a really short barrel.)
As I said, I've done some experiments over the years, so I decided I'd do one up right. In this case, I'd simply make a sear approximately 1/8" longer than factory.
That might not sound like much, but it's over 30% more than stock. I'd have gone a bit further, but too much and it starts making the trigger stiffer, since the leverage from the sear pivot changes.
I looked at that, and wondered if I couldn't move the pivot point as well, to help keep the overall geometry roughly the same. More on that in a minute.
Now, making a new sear is nothing particularly difficult, though unlike the typical aluminum or brass part we often deal with, there's the added steps of hardening and grinding. It also doesn't have to be particularly precise- the sear lug on the hammer is adjustable, so as long as we're close into the ballpark, we're fine.
I started with a chunk of 1/2" O1 steel. O1 is oil-hardening tool steel, and supplied in an annealed state for easy machining.
I didn't have any flatbar so I had to cut it from round, but that was an easy job. And here's a good trick for milling something fairly tough when it's hanging out of the vise by a bit:
That fixture is a heavy-duty work stop I picked up a few years ago at a guy's garage sale. It's almost certainly shop-made, and quite rigid- in this case, rigid enough to back up a part being cut. I tightened the stop rod against the part somewhat firmly- it may have pushed the work out of line slightly, but as the finished piece will be ground to size later, a minor difference in thickness wasn't going to be a problem.
After cutting one side, flip and do the other:
After that, it was a simple matter of coloring the cut face with a Sharpie, scribing part of a standard sear, shifting it over about 1/8", and scribing the rest.
While I could have milled the waste off, it would have been a tricky part to hold, and would likely have vibrated or chattered. Instead, I simply ground the bulk away with a bench grinder. (Of course, keeping it cool lest I accidentally harden a spot or two.)
Hacksaw it off...
And clean up the rest on the grinder again.
Now we go over to the die filer- it's basically a heavy-duty jigsaw that holds a file instead of a teeny saw blade. The table is adjustable for tilt and pitch, so I can adjust it with a simple square, to give me a near-perfectly square cut on the edges.
It's slow going, but eventually we sneak up on the scribe lines.
After a few comparisons with the original, and then more filing, we're left with a copy of the real thing, just slightly longer.
Now, I did come up with a way I could alter the pivot point slightly, without leaving an empty original hole in the grip frame: Mill out the 1/8" original to 3/16", but offset the new hole.
Technically that only moves our pivot point by 1/32", but then again, it doesn't necessarily have to move much. The idea is to keep the contact point on the trigger in the same place, and just move the rear "hook" end of the sear back by about 1/8". I haven't done the math yet, but generally speaking, if the pivot point were in the center of the sear, it would only have to move rearward by 1/16" in order to keep the ratio of the front and rear halves of the sear the same.
Roughly speaking.
Anyway, once I had the grip drilled, I marked the location on the new sear and drilled it to match.
And now, we've got something we can test. It's not hardened yet, but it'll hold up just fine for limited testing.
The WGP swing-trigger frame I'm working with, uses a set-screw to retain the pivot pin, so I don't have to worry about driving it in and out. The screw now bears on the pin off to one side, but that's more than sufficient to lock it into place.
At this point the sear now holds the hammer about 1/8" further back than stock- the scribe line in the Sharpie ink shows the back edge of the stock sear:
Now, the whole gun is still being fitted and tested, but the valvetrain is pretty well set. I was having issues with a used Mini-Rock I got off of MCB (he neglected to tell me it was missing the reg seal, for example ) but i could still pop a little paint through it out the back door.
Switching between sears made a significant difference in velocity- I hadn't tuned it yet, but with no change other than the sear, there was an easy (estimated) 100 fps difference. From "way too low" bloopers to "that's pretty close" velocity.
As soon as I cure the other unpicked nits, I'll do a proper test and record velocities, but as it was, I was dealing with a leaky bottomline and a leaky/inconsistent LPR.
Regardless, I knew it worked, at least to some degree. So it was time to finish it- that way I wouldn't have to worry about damaging it in later testing. (It'd already gotten a slight scar from the sear lug, just in some brief testing.)
I drilled a couple of holes to lighten it a bit...
And chamfered 'em a little.
Then, a couple of propane torches to get it yellow-hot...
... And a dunk in some oil to harden it.
A quick (and kinda rough "by eye") temper to get to down from "glass hard" to somewhere around Rockwell 55C or so...
And a final run through the surface grinder to smooth, square and true it:
Note the old trick there: For small parts that might not have enough "grip" to the magnet on their own, a couple of radius gauges (or other wide, flat steel pieces)along with it helps hold everything in place.
Purty.
Break the sharp edges slightly with a fine stone in a Dremel, and it's done- shown here compared to the original sear.
Lightly oiled and installed:
Now, in direct comparison with an unmodified frame, you can see the sear point is noticibly further rearward. I wasn't going for an exact number (IE, exactly 0.125" or whatever) at least not on this one, but it is roughly an eighth-inch extra.
Here's a composite shot comparing it to the body, hammer and sear:
The top one is the (barely visible) unmodified chrome frame, the lower is the blue frame with the custom sear. It's not quite perfect, but I tried to hold the grip frames in the correct fore/aft alignment to the body.
And finally, here's some precise figures:
Uncocked, the rod sticks out 0.716". In this state, the hammer is resting on, but not compressing, the valve stem.
Using the unmodded chrome frame, when cocked, the rod sticks out 0.977".
And using the blue modded-sear frame, the rod sticks out 1.097".
Subtract the uncocked/at-rest number and we have a stock hammer travel of 0.261", and a modded hammer travel of 0.381", a difference of 0.120", or pretty darn close to a full third more travel than stock.
So, all that just to keep from having to turn the adjuster in a tad more?
Yep. I think it'll be worth it.
Doc.
