.257 shot strings

[dyotat100]

I decided to empty my tank today to see why my fill nipple would leak here and there. While it was empty I decided to try peek for a seal.

It seems like it opened a tad easier now so I swapped out the 13 lb hammer spring for 11 lb one.

Before I did it would shoot 74 gr at 1094 with 0 PW. Before it would take around 2 to get there and 0 was in the 1070's.

Ok, here is what I get with 0 PW now. If I dial up the PW to 3-8 I got 1087 fps

62 ci tank

3202 psi -1061 fps
3140 psi -1057 fps
3090 psi -1057 fps
3040 psi -1052 fps
2990 psi -1050 fps
2948 psi -1048 fps

Ending 2900 psi

3250 psi -1059 fps
3185 psi -1059 fps
3128 psi -1055 fps
3078 psi -1053 fps
3030 psi -1051 fps

Ending 2980 psi

3304 psi -1054 fps
3250 psi -1057 fps
3200 psi -1057 fps
3151 psi -1054 fps
3105 psi -1058 fps
3060 psi -1051 fps
3024 psi -1049 fps

Ending  2977 psi.

I shot one more shot and it was 1049 fps but don't have the ending pressure.

[SniperM]

Very Very nice Doug, looks as tho its regulated almost, not bad at all. Awesome speed and air friendly thats WIN WIN to me.

[dyotat100]

Thanks.

Waiting for Bob to see it so he can analyze it.

[YEMX]

So it's safe to fill to 3200-3250 psi with that tank you just finished for me?  This is caboose from the TAG... FYI

[rsterne]

Peak velocity is at ~3200 psi.... so you're right at the top of the pressure curve.... Should be OK for efficiency, considering the velocity.... Looks like just under 1 FPE/CI ?....

Bob

[dyotat100]

Yeah thats with no preload on the hammer spring. If I want to get any better with this setup I will need to raise the pressure or lighten the hammer.

I'm in the process of building a 4500 psi setup. Will have 17 ci chamber and a drop down with a 45 ci 4500 psi tank. Also will be able to screw on a 68 ci.

The 7mm will be setup to run 3600-4000 psi. Also I will have one for .257 and .308


I found out from John Bowman that the best accuracy with the Lyman 257420 is right around 1080 fps.

[KnifeMaker]

OH-My!!! Sweet!!!

Looks like i'm going to have to send you the hammer after all. Don't have a collet large enough. Grrrrr!!!

Knife

[ToRmEnToR]

Do those .257 fly true at that vel?

[dyotat100]

Yes they do.

I have shot dime size 100 yd groups and a prairie dog at 292 yds.

[QVTom]

^^ I've experienced it for myself   Amazing how well they shoot and the time to target is amazing.

Tom

[KnifeMaker]

Yes! Yes they do!

Remember, these are bullets, not pellets. In fact, if you can push them even faster, to be able to keep them from crossing back down thru trans sonic,  they will shoot just fine at as high a velocity as you can send them thru an air gun. Same as a PB.  But quite possible, more accurately than a PB. Unrepented proved that!

So far, we have found that the faster you push them, the better they shoot. My limit is just under the speed of sound, both for noise reduction, and the fact that I can't get them far enough beyond the s.o.s. to keep them there  at anything like medium long range for an AG.

Knife 

Knife

[ToRmEnToR]

If I wanted to get into a .257 for My condor.. Would I just need the R&L barrel and extreme valve? Just to get started?

Also, is the valve easy to install? Like TTQC top hat?

[rsterne]

Nor will you push them fast enough to keep them supersonic with an airgun out to 200 yards unless you use Helium.... Remember that even a .22LR high velocity bullet falls subsonic at about 75 yards, even though it starts at 1250 fps.... Transonic drag is just too high to fight when you are starting out with a platform that has its own internal limits also dictated by the speed of sound of air under pressure, and the velocity of the air molecules themselves.... both of which in air are too low to provide any kind of efficiency to push bullets supersonic without using ridiculous amounts of air.... Stay subsonic, it's quieter, and you will get less wind drift than if you try and push too close to (or over) the speed of sound....

Bob

[Scott Endler]

I have shot dime size 100 yd groups and a prairie dog at 292 yds.

Do you size your slugs? I see that mold is sold out at Midway.

[SniperM]

Not speaking for Doug but I size all my bullets to get a proper fit plus it rounds them out as well. They say they make molds that fits properly and does not need to be sized but yet to see one. I hae had some they were suppose to be but definitely was not up to my specs anyway. I produce and make bullets for air rifle and its a must in my opinion. Powder burners have a little more ley way in the fit department but not air rifles.