another suppressed lightweight takedown rifle

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quietoldfart
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another suppressed lightweight takedown rifle

Post by quietoldfart » Mon Apr 10, 2017 6:53 pm

As some may remember, I have dabbled a bit in making takedown .22lr rifles. Well this is my fourth attempt, and while the machining is still somewhat on the 'raw' side owing to my modest capabilities and tooling the result is quite satisfying. Having only tested it indoors at 10 metres the accuracy remains a question, but I'll be going out to a forest for a bit of shooting tomorrow and will try at a greater distance then. Suffice to say for now that it is reasonably accurate, suffering more from my inability to hold it steady than from inherent inaccuracy - the thing being only 32 ounces in weight makes for something of a challenge in holding steady. I can hold it by the suppressor body which helps considerably, but point of impact tends to elevate slightly as the 2mm thick, 12mm OD CF tube epoxied to the 8mm thick barrel liner isn't quite as stiff as had been hoped. At any rate, here is the thing:

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The overall length assembled is 35" and the longest part when dismantled (the barrel/action assembly) measures 13.75". The 32 ounce weight is including 12 rounds stored inside the tubular steel stock, which are suspended between two lightweight springs to prevent rattling and contained with a threaded section of aluminum on the T handle which goes into a matching piece of black acetal plastic. Materials used include a .22lr barrel liner, which has 12mm woven CF tubing with an 8mm ID glued onto it using steel-filled JB Weld. There is a mild steel plug turned to fit the ID of the main tube (thin-walled plumbing pipe with the seam worked smooth) which is soldered to the first inch of the barrel liner, then bonded to 1" of the main tube with JB Weld. Two steel wedges are bonded to the top of the tube upon which the scope mounts, the foremost wedge being bonded with JB Weld and two 10-32 bolts, countersunk, while the rearmost is soldered in place. A steel collar is fitted to the rear of the tube and brazed there, with a slot carved into it through which the bolt lug passes. The bolt itself is more mild steel with the high carbon steel lug brazed into a machined rectangular flat slot with dovetailed tapered ends - a decent mechanical bond established prior to brazing and final carving.

The inner workings consist in a 1mm x 8mm spring which drives a steel striker, which itself is slotted for a plunger/pin type sear. The firing pin is a carved bit of drill shaft brazed into a shorter steel rod, which when struck is able to move about 1mm forward (insufficient to cause damage to the entry point of the barrel if accidentally fired without brass in place), and in over 200 test shots I've yet to have a failure to fire. The tip of the firing pin is round, about 2mm in diameter. The firing pin assembly would be able to slide out and probably rotate, forcing disassembly, should the cocked rifle be tilted upward or shaken, so this is stabilised using two 1/8" neodymium magnets which are embedded beside it in the bolt. Even violent shaking with the muzzle pointed straight up cannot force the pin to fall backward. The barrel liner protrudes slightly into the chamber to allow the extractor (some bit of hard bolt steel carved to fit into the bolt with a rocker block recessed and pinned and a spring at the back end) some small distance ahead of the cases for gripping.

The bolt face itself is stepped, twice. The inmost hollow is milled flat and exactly the size of my largest .22lr casing. The outer step is about 8.3mm diameter to just clear the barrel liner and overlap it by about 1mm. This containment ensures that even an over-powered round will not blow powder into my fingers, with my left hand wrapped around the action for firing. Extraction is clean and easy, and as with firing reliability, I have yet to see a case getting stuck. I chambered the liner prior to assembly using a ground and polished twist bit just big enough that a case could be forced into place, then polished with abrasives.

I've fired only Fiocchi, Remington, and CCI so far, all subsonic rated. Likely this will use CCI Quiet primarily. But even with the messy Remington Subsonic it is the quietest .22lr I've accomplished to date, measuring between 96dB and 101dB using a budget SPL meter. For direct comparison (the only use for such meters) my Unique D4 pistol with 5" of K baffles (6 baffles total) meters between 104dB and 106dB with the same meter. A suppressed 20fpe PCP rifle meters about 102dB. So definitely a success. I did try one outside shot last evening into a distant soil bank and the noise was very pleasant indeed, hardly anything to take note of even for someone quite nearby.

The scope is I believe 1950's vintage, a Weaver B4 model with 4x magnification. I dismantled the front and rear lens elements for cleaning as they were somewhat clouded, but the reticle is perfect and adjusts nicely. The mounts I fashioned using cast aluminum tripod leg clamps from an old compact Manfrotto which was never very steady. The 3/4" inside diameter of a couple of these was perfect for the Weaver scope tube. Some carving and a bit of aluminum welded to the bolt side of each then further carving made for a fairly simple mounting and alignment fitting to the steel mounting wedges on the body of the rifle. The scope needs a slight thump with the heel of the hand to set it in place, but after first firing the modest recoil sets it more securely. It takes a substantial thump with a block of wood or similar against the rear of the bolt to disengage the scope after a session of shooting. I've made a soft padded roll for it, weighing another 4.5 ounces.

I'm quite pleased with functionality in this fourth attempt at recreating, more or less, the rifle from the film 'The Jackal' made in 1973. I've abandoned elements I did not like and gone to more modern materials to keep assembly simple and weight low. The 9" K baffle suppressor mounts to a glued on adapter made of 7075 alloy, with the front and rear plugs in the suppressor and the baffles themselves also turned from 7075. Threading was all manual using taps and dies. The tube itself is 6061 with a 1" OD and 0.866" ID. 9 baffles plus a 3/4" long tubular spacer near the middle to break up the impulse.

If I should decide ever to make yet one more, it will be with a much more time consuming approach and perhaps even a written/drawn plan, contrasting with the improvised nature of this project. In this case I merely started with the barrel liner (oh, yes, forgot to mention that the barrel measures 8" in total and has a 1:16" twist rate) and the hardware store steel tube and rod and just started cutting bits away and adding bits until it became a rifle, with no clear idea how I was even going to attach a scope until it was almost complete. I like the carved steel block which provides anchor points and guide for the trigger/sear assembly (long stainless steel spring used to press the pin sear into place, bent and shaped pawl on the trigger rocks to lift the sear pin free) as well as a mounting hole for the stock tube, so that would be repeated but made slightly thicker to allow for a larger diameter sear guide - as it is the hollowed bolt which doubles as a bolt slot guide is rather more delicate than I'd like, but works.

quietoldfart
Senior Silent Operator
Posts: 104
Joined: Mon Jan 27, 2014 4:28 pm
Location: France

Re: another suppressed lightweight takedown rifle

Post by quietoldfart » Mon May 01, 2017 10:41 pm

In case a brief video of the rifle being fired is of any interest... my apologies for the poor quality. It was something of a struggle finding a format which Photobucket would accept this time around and I processed the original through several different programs before a version would successfully upload. The round being fired is CCI SV, and the secondary noise resulted from the bullet striking a rotted stump about 50 feet away. The impacts were generally slightly louder than the actual firing.
http://vid1319.photobucket.com/albums/t ... 9wwfa3.mp4

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doubloon
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Re: another suppressed lightweight takedown rifle

Post by doubloon » Mon May 01, 2017 11:35 pm

Interest. Video quality is fine.

Love the whole write up, excellent post.
http://www.youtube.com/watch?v=BDtd2jNIwAU MUSAFAR!
http://www.youtube.com/watch?v=8CrOL-ydFMI This is Water DavidW
Complete Form 1s http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895

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Sigproshooter
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Re: another suppressed lightweight takedown rifle

Post by Sigproshooter » Tue May 02, 2017 8:54 pm

Very cool build. Nice job sir
Regard your soldiers as your children, and they will follow you into the deepest valleys; look on them as your own beloved sons, and they will stand by you even unto death.
Sun Tzu

PBinWA
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Re: another suppressed lightweight takedown rifle

Post by PBinWA » Fri May 05, 2017 9:46 am

Tres bien! Nice job.

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