Canadian Airgun Forum

5.9" is INCREDIBLE fast, even faster than those fast twist .22's that guys were shooting 90gr. bullets from, back in the 60's. I think they were 6 1/2" to 7" ROT's.
'course, long lead slugs are low speeds require it.
40" for pellets at long range - interesting. seems to work for Mike.

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Best Wishes
Daryl

Well, I'm still collecting bits and pieces for the new guns.... The barrels are on order, I'm getting a couple of Crosman PRod pistol trigger assemblies from Lloyd Sikes along with some tubing, and I gave my wife a big hint for a new 8-32 x 50 Scope for the .183 cal. for Christmas.... I have a Hawke 6-18 x 44 I took off my Hatsan for the .22 cal pellet barrel.... I have some more 6" long Picatinny rails coming, and my son has done up some tank spacer blocks with his 3D printer.... I got a new Ninja/Umarex regulator from Hajimoto, set to 3600 psi for the .183 cal, and I have a 2200 psi Ninja regulator for the .22 cal.... These will mount between the "Inverted Y" block that holds the two tanks and the front of the plenum/main tube.... The benchrest rear stocks will be a simple 2x4 attached to the bottom of piece of PVC pipe, slid over the main tube.... The bottom will be parallel to the barrel so that it will slide straight back on the rear bag during recoil....

Anyways, I haven't made any chips yet, but I'm getting closer....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

If you a looking for a 8-32 scope I'm actually selling one surplus to my needs, just saying.

I was looking at different designs for an adjustable rail to allow setting the scope on a downslope to the barrel, to allow shooting out to at least 500 yards.... I found one called the Eratac (patent pending) that uses an asymmetric octagon to change the height of the back of the scope rail....

https://youtu.be/XAalf49foi4

It only has a total of 70 MOA of adjustment, and I needed about twice that, so I came up with a linkage to do that....



As you turn the adjusting wheel (black) clockwise, each time it engages a new flat on the blue cam, it raises the back end of the red bar by 0.020".... Since the distance between the center of the cam and the pivot is (3600 / 1.047 / 1000) = 3.439", each thou changes the angle by 1 MOA, so each step changes it by 20 MOA.... There are 7 steps (140 MOA), and I intend to machine 20 MOA of angle into the bottom of the base that bolts to the barrel (which sights the gun at about 100 yards), so that gives me a total of 160 MOA available, which should be plenty to allow shooting at a target at over 500 yards away with pretty much any decent slug, starting at a MV of 900 fps or higher....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

160 MOA is 800" at 500yards. Will you need that much elevation?
Interesting design, Bob.
Would you say the slug would have a BC of .150?

OK - did some testing on the Hawke program - 18gr. .150BC, vel. 900fps drop at 100 is 600".
A .172" 20gr. Vmax. bullet has a BC of .181 according to Hornady. My drops/sight settings out to 520yards seemed to bear this out
closely with the program I used for it.
Same with their 17gr. Vmax with BC of .175 - drops/sight settings to 280yards.
I picked a BC of .150 as this seemed more realistic for a grooved cast slug.
My rifles were supersonic, of course, but also had 9" ROT.

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Best Wishes
Daryl

Yeah, I think 140 MOA of adjustment from a 100 yd. zero is generous.... I used a BC (G1) of 0.100 and 900 fps, and got 143 MOA (748").... With a BC (G1) of 0.150, 120 MOA should be enough.... but I wanted to be sure I could reach 500 yd....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

Yes, of course.

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Best Wishes
Daryl

Just to make you jealous, here is a Google Earth view of one of the locations I have permission to shoot ground squirrels and marmots on, just 10 km. away....



The two red lines are 500 and 1000 yards long, so running out of range for testing airguns is not an issue....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

That's pretty cool Bob. Nice to have a private range.
Wind a problem in the valley?
This is ours, not as nice, but do have 1,400metres now.
Picture taken from in front of the benches, at the central stairs down onto the range.

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Best Wishes
Daryl

Nice range, Daryl.... 1400 metres, WOW!....

Well, after months of collecting parts (I still haven't received the barrels, but LW has them on order), I finally got back into my shop to do some work on this project.... The shop needed a thorough cleaning (3 years of dust and debris) but it was sure nice to be working on an airgun again.... I decided my first project would be the adjustable scope mount.... I haven't machined the radius into the bottom to fit the barrel yet, but the rest of it is finished.... The base will sit on a 20 MOA slant, to put the scope centered at 100 yards, and the adjustment gives me a total of 140 MOA up from there in seven 20 MOA steps, for a total of 160 MOA from the boreline.... Here is a photo of the top view of the parts....



and here is the bottom view of them....



On the top is a 6" long Picatinny rail, with the cam follower bolted to it.... The groove on the bottom of it is to locate the upper arm of the spring, which is from a clothespin.... The middle portion (bottom in those photos) has a large groove machined into the top to hold the spring, two threaded holes to mount the Picatinny rail, and on the bottom it is machined to clear the mounting screws and the bump in the baseplate.... The shouldered pivot bolt, and the cam mounting screw, are threaded into the side of it.... The baseplate is an "L" shape, machined from a 3/4" x 1" bar of 6061-T6 aluminum, the same grade material is used for the other parts.... There are two mounting holes on 4" centers, and the vertical part has holes for the shouldered pivot bolt and the cam support, which have very close tolerances to minimize play.... The "bump" has a transverse hole to accept the bottom leg of the spring.... Here is a photo showing the spring and cam in place....



The next photos show the mount assembled.... The first two are the right side, showing the mount at minimum and maximum height adjustments....





The next two show the left side, again at the lowest and highest settings....





To adjust the height, you loosen the two screws on the right side (cam and pivot) a half turn, and turn the knob to the height desired.... It has a nice snap from one position to the next because of the generous flats and the spring tension.... When you reach the height you want, you snug the two screws up again, to draw the middle section against the vertical part of the baseplate, while pinching the cam against it as well.... The cam screw moves up and down with the mount, which is why there is an asymmetric hole through the cam.... When the screws are tight, the mount is completely rigid....Here is a photo of my Vector 8-32 x 50 Sentinel scope adjusted to the maximum tilt....



I will be mounting this setup on my .183 cal, on the bull barrel, just ahead of the loading port.... I have already determined that I can get the required eye relief with the scope, and as you can see, it will clear the barrel at maximum tilt.... First part of many, basically finished....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

Getting THERE, Bob. Good work.
I currently have an old 1" tube Bushnell 8-32X40 on my Palma Match rifle with the .224 (.220 Swift Shorty) gopher barrel mounted.
The duplex reticle makes a poor choice for rat shooting. Better to have mil dots or MOA slashes.

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Best Wishes
Daryl

Glad to see another build, I enjoyed following along all the others. It has been a while since you posted a build on the forum, thanks for taking the time to do so.

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SKANZY

Between Covid, getting into Chesesmaking, and getting a puppy, I've been busy for the last 3 years, believe me....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

I know exactly what you mean, Bob. My summers are all used up, only the Winter to do anything. The spring is used up getting ready for the Summer and fall is used up
getting winterized from the summer.

_________________
Best Wishes
Daryl

I got my lathe repaired, so today I roughed out the two tank blocks.... My milling attachment for the lathe has a vice that is only 1" x 2.5", and opens just 2.3", so I had to mill the middle of the 1.25" thick block to fit into it.... .... I had to turn the block end for end, and make one block on each end.... A lot of it will get cut away to shape it.... Here is the one for the 18 x 1.5mm Regulator (for the .183 cal)....



and here is the one for the 5/8" x 18TPI Regulator (for the .22 cal)....



All four of the threaded holes for the tanks are 18 x 1.5mm.... I have some all-thread studs made from Metric bolts to attach the tanks.... The smaller through holes, which will be on the front of the tank blocks, have yet to be threaded 1/8" NPT, one for a gauge (tank pressure) and one for a male Foster fill fitting.... I also need to drill the air passages to connect the tanks to the regulator, and plug them at the bottom with threaded plugs with O-rings.... Once all that is done, then I can cut and mill away all the extra material....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!