Tale of THREE BRods - .25, .30 and .357 Completed, Page 19 !

[KnifeMaker]

WOW!!!

[rsterne]

My later valves use a drilled hole, parallel to the stem and very close to it.... There isn't a lot of room between the stem and the bottom of the O-ring groove on the large end of the poppet.... Using a 1.2 mm CS Metric O-ring helped.... I have used both Delrin and PEEK for the poppet.... The loads are much lower than a conventional valve of the same throat diameter and pressure, so Delrin should in theory be the right choice.... However, the PEEK was easier to machine because it is stronger/stiffer and it is a pretty small part.... and seemed to seal up just fine....

Bob

[rsterne]

Today was consumed with all the little finishing touches on the three BRods…. I had a slow leak in the new .357 cal, which I found was a leaking plug on the bottom of the WAR tank block.... I had glued in that plug with JB Weld, and there was a slow leak spiralling up the threads.... Since I had glued the plug in, I had to heat it with a torch to break loose the epoxy, and once I got it out and cleaned it up, I shortened the plug 1/16" so that it would miss the ASA threads.... I had previously retapped the plug hole, and I went too deep, and the plug was interfering with the ASA threads.... I also removed the male Foster on the tank block and replaced it with a plug, since you fill the bottle through the regulator.... I sealed the plugs with Teflon tape, and that seems to have done the trick.... Once I had that done, I installed the 500 cc 3000 psi bottle, filled it to 3000 psi, and set it aside....

The .30 cal was leak free, so all I had to do was remove the male Foster on the tank block and replace it with a plug.... After a leak and velocity check, I also installed the bottle on that gun, and also filled it to 3000 psi.... Then it was the .25's turn, and I knew it had a serious leak....

It turned out there were actually three leaks, and it took me half a day to repair them.... The first two were easy, a loose plug and a loose gauge.... It was still leaking, so I stripped the gun down completely and replaced the valve O-ring.... but it wasn't that either.... Eventually I tracked it down to a leaking gauge, and once I replaced that it seems to hold air OK now.... I checked the velocity, and it was still what I wanted, so I installed the bottle on that one too, and filled to 3000 psi....

Here is what they look like, now that they are finished.... All three BRods use a modified .25 cal MRod receiver, bored out forward of the front 4-40 screws to accept a 5/8" OD barrel.... They all use a 500 cc, aluminum, 3000 psi bottle for the reservoir, and an SSG to control the hammer.... and have two gauges, one for the bottle pressure and one for the plenum pressure.... The main tubes are from WAR, I believe they were for the FLEX, and yield an 85 cc plenum, including the valve volume.... The tank blocks are also from WAR.... All of them use .25 cal MRod magazines and bolts, modded as necessary....



The top one is the .357 cal.... It uses a Synrod stock, and a Gen 2 trigger.... The barrel is a 1/2" OD, .357 cal, 26" twist TJs, 27" long, glued inside a high-modulas Carbon Fibre sleeve for added rigidity.... It has a steel hammer and a homemade SS valve, and the porting is 9/32" (0.281") or equivalent throughout…. The bolt nose is sleeved up to .357 cal, and the lockup lug is inceased to 10-32 for additional strength.... The mag is a 6-shot one-of that I modified myself....The regulator is mounted on the bottle, and set at 2200 psi.... This results in 2 mags (12 shots) at 146 FPE, using the 81 gr. JSBs at 900 fps....

The one in the middle is the .30 cal.... It uses a modified Bullpup stock that was a gift from Travis, and a Gen1 trigger.... The barrel is a 1/2" OD, .300 cal, 26" twist TJs, 25" long, also glued inside a high-modulas CF tube.... It has an MDS hammer and an ART-SS valve, one of the first production ones with the smaller poppet front end, and the porting is just over 1/4" (0.257") or equivalent throughout.... The bolt nose is sleeved up to .30 cal, and the lockup lug increased to 10-32 for additional strength.... The mag is a 7-shot from AirGunLab…. The regulator is also mounted on the bottle, and set at 2000 psi.... This results in 4 mags (28 shots) at 98 FPE, using the 50 gr. JSBs at 940 fps.... It will shoot the 44.8 gr. JSBs at about 980, and the 59 gr. NOE Hunter Magnums at 880 fps (101 FPE)….

The bottom BRod is the .25 cal.... It uses an airsoft AR stock, on an adapter that I made myself, and a PRod trigger and grips.... The barrel is a 5/8" OD, .250 cal, 17.7" twist LW, 23.8" long, with polygonal rifling.... It has an MDS hammer, and one buffer O-ring between that and the Cothran Powerhouse valve, with 0.257" or equivalent porting throughout, including an oblong barrel port.... The regulator is adjustable, and mounted in the COBRA tank block.... It was a sample from WAR, as I helped them design it, and is set at 1800 psi.... Having an externally adjustable regulator is nice with the Cothran valve, as you have to change the pressure to change the velocity.... This gun delivers 6 mags (48 shots) at 65 FPE, using the 34 gr. JSBs at 930 fps.... It is easy to increase that, or to reduce the pressure to about 1400 psi to use the 25 gr. JSB Kings if desired.... The way it sits, it will launch the Kings at about 1030 fps, which is way too hot....

This has been an interesting project, and I'm happy to say met all the goals I had.... I did some testing with bullets, running unregulated at 3000 psi, and while the performance was remarkable, I think they are much better guns regulated, and shooting pellets.... I hope to be able to do some testing next Spring, after the snow melts.... I must thank Travis for the big box of "spare parts" he sent me when he moved shop a couple of years ago.... Without that, these three BRods would have never materialized.... 

Bob

[Sfttailrdr46]

How much of an effect do the air strippers have on the accuracy

[rsterne]

My previous experience is that when tuned for optimum gap, they help a bit.... and when wrong, make things worse.... I guess you could say that makes them worthwhile.... On these BRods, that determination will have to wait until at least the snow is gone (best case), and maybe until 2021 after we close the Motel (worst case)…. 

I couldn't put one on the .357 because the Hatsan ones (which I use) have 1/2"-20 threads, and the barrel wall is too thin with that bore size....

Bob

[Machinist]

All 3 guns are very, very nice!!!

Someone used the word crafty.  You certainly solved a bunch of problems in ways that make sense and work well.  Easier said than done.

All Hail Bob Sterne!!!    https://thumbs.gfycat.com/GrayOptimisticChanticleer-max-1mb.gif

Steve

[rsterne]

*LOL* @ the .gif....

Bob

[rsterne]

I haven't done any work on these BRods for about 5 years, just taking them out to shoot once in a while, and using them for testing pellets and slugs over my LabRadar.... However, my son showed up for a Grouse hunt, so I set up the .25 cal to shoot 34 gr. JSB King Heavies at 950 fps, regulated at 2000 psi, and he is a happy camper!.... Since this year .35 cal and over airguns are now legal for hunting deer in BC, he asked if the .35 cal BRod could be used for that.... I told him it was set up for pellets, and the magazine was too short for heavy enough slugs for deer, but while sleeping I thought "Why not 3D print a 3 shot shuttle magazine", and convert the gun to unregulated, to shoot .357 slugs....

So, a few prototypes later (to get all the proper fits between the parts, gun and slugs), I had one that worked properly.... I shortened the bolt probe 0.100" because slugs have a flat base instead of a hollow in the skirt (so the pellet probe was loading slugs too far forward), and removed the regulator.... After decreasing the gap in the SSG to work with the higher pressure, and playing with the adjustment, I got a perfect 3-shot string, followed by a gradually dropping velocity.... This is with 127 gr. FN slugs from Accurate, sized to 0.356"....



The first 3 shots are just over 200 FPE, and the 10th shot is 180 FPE, so a great tune for deer.... The 3-shot magazine turned out equally well, here are some photos.... First the 3D printed parts (made from PETG)....



The shuttle has internal O-rings in the holes to keep the slugs from falling out.... I printed the groove elliptical so that the #012 O-ring were flush on the side, and only touched the slugs top and bottom.... They stay in place but the O-ring does not interfere with loading or chambering....



The holder for the shuttle just snaps in place.... It sits over the barrel stub (that normally locates the magazine in an MRod), and there is a 1/4" O-ring in the top of it protruding about 0.010" to act as a detent for the shuttle in the center position....No detent is needed in the end two positions, the shuttle has stops to make sure the chambers line up with the bolt.... One end stop is removable for assembly/disassembly....



When the mag is centered, both outer chambers are available for loading, simply insert the slug from the rear....



When you push the shuttle to one end, you can load the center chamber....



and the other end is flush with the receiver....



We are both delighted with the results, and my son gets to enjoy a couple of my custom projects.... A win-win-win situation for everyone.... 

Bob

[JuryRigger]

Pretty danged cool! 
Do let us know if he gets a deer with it.... 
Jesse

[bear air]

+1 very interested to hear about his adventure as well. Nice guns Bob.

[mackeral5]

Of all threads, I have probably borrowed more tips from this one than any other.  I really didn't think there was more for it to give, but you somehow opened another chapter.  Great job, I look forward to seeing more.