50% higher shot count at same FPE
Hi Ya guys,
I joined the forum the other day because I am getting interested in these airforce guns ( not enough to buy one yet though ). I am looking for the go-to guy that loves to mess around with their gun.
After as much reading as I can about these guns it appears as if “efficiency” is not all the great for a large bottle that you guys run and you count on hammer weight for power or shot count.
I think I may have a little something different that may help out or design that little something. Of course I am new to these guns and have not read everything about what you all have been doing but, I sure would like to see what I can do.
I come for the Mrod of air gunning. I pulled off a 22 synrod to .357 conversion and back again to a 22 with over 93 shots on regulations at 25 fpe with the stock airtube of 190cc and recently a 25 mrod pushed to 90 fpe on “stock modified-valve” then back to a 40/40 tune (40fpe-40 shots) or 24 shots at 50 fpe on a stock air tube with regulator at 190cc. No after market valve nor SSG/FFH and stock barrel length.
I have a strong feeling that I may be able to help with you all’s shot count and power level. I would really like to work with someone on this platform that is willing to mess around.
Please keep in mind, I am a nobody. Not a tuner nor vendor. I just love the messing around with these airguns and I think I am as far as I can take the Mrod platform and it’s time to move on.
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Viewing 9 replies - 1 through 9 (of 9 total)
My guns are far from stock.
Hammer stroke is 1.25″ and it is 3″ from PW to the hammer.
Right now this gun is shooting 165 gr at 990 fps on 3200 psi regulated.
Yes I will go out in garage here soon
Dayotat100,
Thank for the information. I started reading a bunch of your posts and it seems like you have done a lot with the these platforms.Boy these guns put out some power at low pressures.
Any chance you have some measurements on some stuff to share:
Cocking stroke length.
Distance between power wheel adjuster set at 0 and when hammer is at home against valve.
Distance between power wheel adjuster set at 10 and when hammer is at home against valve.
I am trying to run some spring formulas to get a better understanding of cocking force vs the needed max load of the spring to crack the valve at 2800psi/3000psi using a short stiff spring with no preload on the valve.
I don’t have any stock guns. I do know that when I went from a 4″ to 3.5″ spring it made the valves I make make more power. The main problem is that the stock spring is to long and hammer is to heavy. On a talon 0 PW still to much and people can’t get a curve. There is to much preload just putting the gun together. I found the benifit by accident. I was building a 308 valve and was having tank dump issues. So I went to century spring and got a few shorter springs.
I don’t have any 3″ springs that are just a little stiffer then stock. I only have 13 lb ones.
That’s a newbe for you. I guess there is some more reading to do about these airforce guns.
Kidcurry,
I am going to have to retract the offer for the springs. Sorry man, I couldn’t find any posts about people running short stiff springs. Dayotat100 is right about getting these springs off the shelf too. I just didn’t do enough research before opening my mouth.
Looks like to be around .075″/.085″ wire diameter with about 10/13 turns at 3.5″ long.
Here’s a link to these kind of springs:
https://www.thespringstore.com/pc081-850-13-40-mw-3-500-cg-n-in.html
Hey Dayotat100,
Did the 3.5″ springs make a difference with the efficiency and power.I am curious to know if it works as good as it does in my Mrod. Do you have any data supporting running a 3.5″ spring over the stock length or maybe a post you can steer me towards?
Thanks in advance
You can buy shorter stiffer springs. I run 3.5″ springs in all my guns. I even have 3″ springs for my 257, 308 and 338 but haven’t played with them yet. Stock is 4.7 lbs. I’m running 13 lb with 150 gr hammer but my valves are massive compared to stock.
I have never seen a AF gun hammer bounce though. Not sure if it’s just the design or what but they are not the most efficient. But when it come to power it’s hard to beat.
Way to go Kidcurry.
I am thinking of a slightly different hammer spring that uses a negative preload. I started gathering some info on the hammer springs and they appear to be around 6Lbs/inch to 8/lbs per inch at 4″ long and a max diameter of 1″. All that being said and when installed in the gun at 0 or 1 on the power wheel has around .25″ of preload.
It seems like from what I have been reading is that these guns run better (have better efficiency) around 2200/2500 psi with the power wheel near 0 but, As soon as you start adding preload by increasing the power wheel, efficiency goes way down.
To me, it seems like the problem to get a short stiff spring in these guns are due to the actual diameter of the spring and size constraints. Hence, most or all of you start getting longer springs for more preload to increase power.
I may have a different solution but I have no idea if it would work in one of these platforms. I call it the dual wire hammer spring. It’s 2 wire’s wound in parallel to keep the profile the same dimension while doubling it’s power. By, using the negative preload the hammer somewhat free-floats in the negative preload area. What this does, is reduces the extended dwell caused by the preload when the hammer comes home and helps with preventing hammer bounce (Well it does in both my Mrods).
I am more than happy to make a spring for you to try out. It will look very different than any other spring you have seen. If it messes up your gun, I don’t want to be responsible. This may be a stupid question, have you ever pulled your hammer spring out ?
You still in ?
Tim
Ok, I’ll bite. What would you like me to do with mine? :fishing:
Viewing 9 replies - 1 through 9 (of 9 total)
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Yup,
Your gun sure ain’t stock. Looks like I am in the right place though. I have the same sickness :biggrinn:
I did run some numbers though and thought you may be interested.
From what you have described,
It appears as if you run one setting on this gun (0 power wheel) at around 350FPE. I am not gonna kid with ya, that’s about 200 fpe more than what I have ever touched. My .357 conversion of the Mrod hit around 120 FPE with the stock barrel length of 20″.
Although with your current set up I have a feeling it can be improved with just a spring swap.
Your gun right now has about a 6lb load on the valve and when cocked is just at 21 Lbs of max force using that 3.5″ spring.
To have the same power level (pretty sure about this) with a spring at or just under 3″, you need a 17/18 lbs per inch spring. This will also keep the cocking effort the same.
I found 1 springs that would work for this:
This one is a 17lbs/in at a length of 2.78″. PW at 0 will have a negative preload and be the most efficient at a slightly lower power but, at 4 or 5 on the PW will make it the same as what your running now. It will also go spring bind at PW setting of 4 or 5 with a cocking distance of 1.24″.
If you where to put this spring in there, it should give you more versatility from 350fpe down to around 250 fpe with better efficiency (more shots).
I think :smilen:
https://www.thespringstore.com/pc095-921-13-00-sst-2-780-cg-n-in.html
I just didn’t have the dimensions for the inside diameter of the coil. This spring has .73″ ID.
If I had wire at .095″ I would have made one for you and send it to you but, I only have .048″ in the garage now. Looks like you can get this spring for under 10 bucks.
If you did buy this spring and put it in your gun, please don’t forget about me. I would really like to know if it worked as planned.
Kidcurry,
I didn’t want to sound like I was ditching you :sadn: Sorry man. It’s now starting to sound like nobody is running a short stiff spring in their gun with 0 or negative preload.
If I do get some stock numbers on a gun:
Cocking stroke length.
Distance between power wheel adjuster set at 0 and when hammer is at home against valve.
Distance between power wheel adjuster set at 10 and when hammer is at home against valve.
We might be in business again. And, you better believe you would be the first one to get a spring to try out since you hooked first. I owe it to you.