.308 Build
Ordered all the pieces from AF today so I can build my .308 Condor. Frame, trigger asembly, power wheel, fore arm grip. I have 28″ barrel and bigbore Blod valve. I will make everything else. Lathe is going to be here around 12:00 tomorrow. Can’t wait to start making things on a real lathe. I will then have .22 .25 and .308. Want to try and break 400 fpe with .308.
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Did some testing yesterday and took a couple shots with 171gr today. Put the .308 setup in the .25 valve body. It was down about 30 fps with no tank dumps. But another problem happens with it. I guess so much air is going through the valve that it sucks the spring along with it and causes tank dump. Spring tries to go past the acetal seal. At first I though it was something I did like rounding the corner where the spring sets. So I made a new stem seal with a nice square edge and it still did it
So I gave up on that spring and made a new stem seal for a little bigger spring. Also took the spring retainer out .030″ to open up the air flow more. Well it shot about 10 shots and valve stuck open. This time the spring is stuck and I have to rip it out. So I make a new stem seal again and put the same kind of spring in again. About 10 shots and same result.
So now a little frustrated I decide to put the .308 valve back together. Only thing different is I’m using my second stainless stem retainer and I made the hole .325″ instead of .312″ where the seal seals. First shot on 3000 psi was 978 with 106gr Before the best I had gotten was 970 fps on 3200 psi. This was with tophat around .102″.
Today some more test slugs showed up. I got 2 kinds of 118gr and 171 gr sized to .308. Of course I wanted to try the 171gr. Well I kind of got tank dump again but left 1000 psi in the tank. So I pop the stem out and put in a .030″ acetal spacer. Now it shots the 171gr at 823 fps with a tophat of around .075″. Not bad for 171 gr. I can’t wait for my 150gr from Jerry. This .308 thing is driving me nuts and taking a lot of time trying to figure out this valve thing.
I’m real good at making stem seals 😀
That valve looks so cool.. and it was pritty crazy how that tank dump threw thar crony around like it was nothing. Was funny but not funny becauseit could have broken it
interesting…. I don’t really know if the 4 slot ports would be all that much better, but having the ports dip directly into the tank as opposed to the air having to travel up through a small portion of the valve body and around a short stem piece has to help.
Looks like you are on the right track anyway
Well today I took my bigbore Blod valve and turned the tophat down for .308. To my surprise it was about 114 fps slower. 824 fps to 938 fps with 118 grain. I’m glad I didn’t make the whole stem. I still might make one and give it a larger hole. It has a .285″ and I coud go .325″ because it has a larger stem.
I’m going to make another stem for my valve and do a 4 port like Dave’s pic and see if it changes any thing.
Looks good, one thing that has worked well for me is having the ports milled along the length of the stem like this
Also, where you have the portion that pushes into the valve seal, then the taper going up to the stem OD, I have done a portion that pushes into the valve seal, then a step that goes straight up to the stem OD, meaning that when the valve opens, the ports are dunked straight into the 3000psi of air available.
like this almost
Might end up working well but I have never really had a proper tank dump so I couldn’t say weather it would help with your problem or not
Dave
Ok learn a few things today I guess and I’m still scratching my head also. Put 11/64″ holes for the ports first thing this morning. Came out with a nice strong stem. Put it in and it shot 860 fps with 150 gr. Cool now I will take it out and open up the the sides of the ports to make them more of a triangle then a circle. Came out with some nice ports larger then the first stem but way stronger.
Well to my disappointment I had tank dump with a 62 ci bottle. Blew my chrono across the garage and ripped the lights off of it. I figured 900 fps was going to be easy with how much more air it was going to flow. Now I’m a little puzzled. So I put a larger spacer to bring the tophat to .090″. Also put back in the heavier hammer spring I changed out this morning. Wanted a spring that I could use the power wheel to adjust power instead of 0 power wheel making the same power as 8. Problem is when I pre load the power wheel it puts more pressure on the tophat after it is fired.
So I settled on 850 to 860 fps and called it quits. I guess porting the stem does something with closing it. I was going to make a Blod style valve that would work on .308. I even had the bar in the chuck when I started looking at my bigbore Blod valve trying to figure out what to do. That’s when I desided to make another stem and not port it. I also made it with a .280″ hole instead of a .312″. Where the step for the ports was I moved the step for the ports .075″ closer to the tophat and put the holes in steeper.
Put it in the tank and first shot was 824 fps. So I put it back in the lathe and took the hole out to .312″ like before. I also left of the spacer on the stem to show my boy what tank dump is. Well is didn’t tank dump and shot 878 fps with 150 gr. So now the tophat is around .130″ with no tank dump. so I will make a spcer to bring the tophat to .100″ to .105″. I’m thinking of making another stem and making the corrections on it and tring 4 ports instead of 3.
Left is last one with 11/64″ ports, middle is 11/64″ then ported, and end is original with 3/16″ ports
I want 900 fps with 150 gr and I will be happy. I have some 170 gr slugs coming also to see what they do.
Thanks. I was really surprised how it shot. Making a new stem right now and will see how it goes. Next my goal is to make it quiet. I think I can. Would be real nice to have a 270 fpe gun that is quiet. Pretty bad when your airgun is loader than the 20 gauge shotgun shooting with you.
Doyat100,
Well, i will at least say that 250 FPE is a good place to start plus or minus some fpe. Especially with 115-170 gr bullets. At or about that power level, those bullets will maintain some DECENT 200 yard accuracy and power. Even further actually. Remember, 308 cast bullets closely resemble 308 winchester PB bullets in profile and BC numbers (lol, they ARE REAL 308 winchester PB bullets) . But this is whats interesting about your post, watching and waiting to see what you end up with. Your FINISHED outcome could be the same as the Corsair or even MORE. I think what your doing is pretty cool.
Dan recently posted on the XP airguns website that they are taking orders for the UPCOMING SCOUT 308/357. So far 330 fpe/177 gr in 308 and about 420 fpe/201 gr in 357. They are gonna be using high PSI #s, heavier bullets and longer barrels to make the power. I personally hate LOOOOOONG barrels on theses guns. They look like brooms and look way outta balance….lol.
Also, and i’m not sure how long your barrel is but, power in these things is also maintained through long ass barrels. A 24-28″ will only get you so much FPS before your seriously dumping air to obtain those FPS/FPE levels. That’s why Dan and Jack Haley are using 32-34-36″ barrels. It’s much easier to obtain POWER. Its CHEATING….lol.
They also use long barrels to get the speed as opposed to using brute force from the hammer striking the valve (less wear on internals). So with the combo of a long barrels, high PSI fills, 5 ounce hammer weight, and the correct valving/porting, they get the speed. But of course with more speed comes the RIGHT barrel twist to make it all work.
Doyat100 you could still make it side cocked without touching frame. The cocking knob would need to be shaped “L” . Only thing is that it would probably could unscrew sometimes from cocking but to prevent that you could either use strong glue on thread (but this would be rather permament solution hard to unscrew if needed) or better would be to add small screw to prevent the cocking bolt from unscrewing (for example in this place marked red you could add extra screw )
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Why not try a 1:8 twist a lá 300 whisper? The powder gun sends 220 grains @1000fps with 5-12 grains of smokeless. Seems like the closest to 308 as condor could be realisitical. And the accuracy of the longer 220s in the 1:8 is supposed to be swell.
Took the stem out to remove my spacer and clean up the ports a little. I noticed it is starting to collasps. Started a new one and will use a 11/64″ instead of 3/16″ that I used. I shot over 100 shots to day and I’m happy. Wish I would have made it a side cocker but didn’t want to weeken it to much more.
Made a .750″ cocking knob to try and make it easier on the thumb. Going to put it back in the lathe and make it hollow then cap it with a piece of delrin to lighten it up.
Put the frame in the mill and notched it the same way my .25 is.
im one of the guys tofaz is talking about i have a haley 308 that will make over 300 fpe with the 1-20 twist i have molds for 190 and 210 grn bullets and be ready cause they WILL KEYHOLE and accuracy SUCKS so i backed my gun down to 260 fpe and it shoots 3/4in groups at 100yds btw thats 310fpe with 170 grn bullets and the accuracy is not there 2in groups at 50yds if u have any questions ill answer them to the best of my ability the 260fpe is with tofaz’s 150grn HP bullets
Ok valve works good now with a stiffer return spring. Shot it a couple of times thru chrono and 858 fps was the best it did. Put it all together and took it to friends house to shoot it. Amazing how far it shoots. I was hitting 1’x1′ steel plate at 150 yards. Still going to see if I can squeeze a little more out and try some heavier slugs, 170 gr and maybe 190 gr. Seems like the 118 gr do pretty good at a little over 920 fps. The 106 gr go around 970 fps.
Got home early from work and finished redoing the hammer. Don’t know where it went but it is only 103 gr now. Sunday I’m going to make a trigger guard for AR grip. Want to get the gun closer to being finished before I start test firing it again.
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Haha crazy, those springs are getting battered.
Is there a way that you could incorporate blod’s spring idea of having the valve return spring behind the tophat, thus increasing flow massively to the valve seat?