1322 ACP Carbine Saga Continues

I’ve finally gotten in the parts I was needing to continue working on my 1322 ACP (air conserving pumper). One of those parts was a flat top valve and piston set from Airgunsmith. I highly recommend this setup, as the parts are well machined and thought out. The primary reason I chose this setup was for the felt oiler. Multistroke pneumatic airguns need to maintain a film of oil for consistent powerful results.

I also added a Crosman steel breech. I had to rethread the bolt handle, but aside from that, they make a killer breech for the money. It adds a nice heft to the carbine and gives a rock solid scope mount as well. There was a good deal of bolt flip with each shot, so for now, I’ve added a disc magnet below the bolt handle to correct that. This helped to tighten the extreme spread.

1377 ACP Carbine

Once all the new pieces were installed, performance went up a good deal. With 11 pumps for the initial fill and 8 pumps between shots, it was averaging 505 fps with CPHPs. Accuracy is great when the LDC is properly adjusted and the right pellet for the barrel is selected:

Looks like I need to stock up on RWS Superpoints

H&N Sniper Lights and RWS Superpoints are nearly neck and neck in performance, easily capable of shooting dime sized groups at 20 yards. Since I am building this for hunting at sub 25 yard ranges, I just placed an order for 1750 of the Superpoints to keep the carbine well fed.

I wasn’t satisfied with the performance, as I’d like to be able to hunt squirrels with this rig. To improve performance, I turned my attention to tuning my free flight hammer. The spring guide and everything attached to it is accelerated with the hammer. The more massive this setup is, the more energy it robs from the hammer. I installed a nylock wingnut for the external stop, cut off the wings, and ground it as close to the nylon as I dared. All excess parts of the spring guide were ground down. Here’s the end result:

Lean, mean spring guide

Performance has gone up dramatically. It is now tuned for an initial fill of 15 pumps, with 9 recharge pumps between shots. Average muzzle velocity with H&N Sniper Lights is now 553 fps and muzzle energy is 9.5 FPE. This is good enough for my intended purposes. Combining a quick sip of high pressure air with the LDC makes this carbine super quiet.

An even lighter spring guide combined with a 18″ barrel will probably get me over the 600 fps mark. I’m hoping to achieve that with no more than 10 recharge pumps. I’ll continue to document my progress as time allows.

Daisy Powerline 880 Receiver Strengthening

If you never disassemble your Daisy 880, you’ll probably never need to do this modification. People like me who can’t make it a week without opening their rifle will quickly discover that the screws that hold the upper portion of the receiver halves together will strip out their holes leading to poor accuracy and problematic scope mounting.

Upper receiver halves to staying together
Upper receiver halves not staying together

More drastic measures may need to be taken later, but I’ve got a simple solution that so far has worked quite well. I carefully drilled out the existing holes with a 1/8″ drill bit, chasing the bottom hole a little deeper to give more thread engagement. The next thing I did was to thread them carefully using a 6-32 machine screw.

Location of holes that need to be drilled and threaded
Location of holes that need to be drilled and threaded marked by the long screws

Now that the holes are threaded, I cut a couple #6 screws and dressed the ends so they would fit my receiver perfectly. I reassembled my 880, tightening these top screws first, then working my way down. The heads protrude just slightly and could use some paint, but the important thing is that my scope can now hold zero because the halves no longer flex along the top.

The 880 receiver halves are locked in place now
The 880 receiver halves are locked in place now

Should this arrangement wear out, I’ll simply drill all the way through and hold the two halves together with a machine screw and nut. In the meantime, I’ve got my accuracy and spent next to nothing on the modification! A similar process can be used for the two small stock screws, as these tend to wear out as well.

Bear River Sportsman 900 Project

I picked up a refurbished Bear River Sportsman 900 back in July. Right out of the box, it had a intake check leak. I bought it primarily to develop a LDC for it, but went ahead and attempted to contact Bear River regarding the leak. They finally emailed me back a couple days ago. This got me to tear down the rifle and see if I couldn’t fix it myself since I’ve gotten pretty much nowhere with them.

Ready to slay some Special ops squirrels!
Ready to slay some Special ops squirrels!

Luckily, the leak was caused by a bit of fuzz sticking to the intake check seal. I reassembled the rifle and chronographed it. It averaged a measly 583 fps with 7.4 grain pellets at 10 pumps. Time to tear it down again and fix everything they did to keep kids from overpumping the rifle to valve lock.

The ugly face of headspace
The ugly face of headspace

The piston features 2 dimples, the valve inlet is a whopping 7/64″ hole 1/4″ deep, and the inlet check has a deep phillips screw pattern leading to terrible pump efficiency. The first thing I did was remove the check seal, chuck the check guide into my drill and grind down the face until it was smooth. I also removed some of the excess material, increasing valve volume and decreasing spring tension.

Making the inlet check better
Making the inlet check better

I then polished the face smooth. The next thing I addressed was that massive inlet hole in the valve. To do so, I drilled a 7/64″ hole into the inlet check and superglued a piece of hex wrench in it. This still allows air into the valve, but takes up almost all the dead space, leading to much higher pressures.

The finished inlet check optimized for maximum pressure
The finished inlet check optimized for maximum pressure

At this point in my project, I haven’t addressed the dimples in the piston head. Instead, I noticed that the metal head of the piston was able to move forward and backward. To eliminate this, I wrapped copper wire around the rubber bumper, forcing it deeper, locking the metal piston head in the foremost position.

Overview of the rifle's guts
Overview of the rifle’s guts

I did some tweaks to the trigger and striker that I’ll address in a future post. All the pump and valve o-rings were changed before reassembly. So where are we now that we’ve made these mods? The same 7.4 grain pellets now hit an average of 645 fps, a gain of 62 fps and 1.25 fpe. Basically, stock Daisy 880 territory. I’m going to continue modding this rifle, the rifle fits me perfectly, looks great, and shoots very accurately. There is still potential waiting to be unlocked. If you’d like to get a LDC like the one in the top picture, use the contact page to let me know, and I’ll help you get a hold of one.