...to my twin-tube SamYang 909, after this advice: [www.airgunrendezvous.com]]
Today was fine with shifty winds. I set up at 50 yards and proceeded to shoot 3 shots at 2600 psi, 3 at 2800 psi, and 3 at 3000 psi. I had the chrony set up too, but a difficult sun angle gave me only 6 out of the 9 readings. Here are the results:




Allowing for my shaky shooting, the 2600 psi shots were pretty much on target, and from there on the shots dropped low as the psi increased. Just to add to the picture, the chrony recorded the first 3 shots (2600 psi) at 670, 670 and 677; then one at 649 (plus 2 errors) in the 2800 psi series and 607 and 611 (plus 1 error) in the 3000 psi series. I measured the drop from zero (assuming the 2600 psi shots were at zero) was 1.68" average for the 2600 psi shots and 2.11" for the 3000 psi shots.
So, your thoughts Gary?
Cheers
Neil
PS I got the 909s out for a quick shoot too, and shot this .75" group at 50 yards, not spectacular, but at least they're all touching!

Mmmmmm, partial valve lock above 2600 then?
Looks like 2600 psi is the sweet fill unless you mod the gun to get that valve open at higher pressures....

Yep, 2600 look like it....
Cheers
Neil

Hello Neil,

Good job. Nice test. Results are very usable.

First ... click your scope a few to the left. You have a right bias in all the targets, which does not change throughout the various pressures. That's good.

I don't see any wildness - so the tubes seem stable over the 2,600 - 3,000 psi range.

For shooting groups with this rifle, Start at 3,000 psi ... aim 1/2" above the top of the diamond for your first shot. For the second shot ... aim at the top of the diamond. For the third shot ... aim dead on. You should have a good group.

The only "flier" I see is the center shot in the 2,800 test. But, it's close enough to just call it an error in aim.

I don't think you have any trouble. Just take the data you've gained, and apply it. If you are going hunting ... fill to 2,600 and aim on. If you want to shoot groups ... use the above technique.

You may wish to try a slightly different diameter on your slug. Half of a thousandth can tighten up results.

Good job.

Gary

Your last posted group is very good. I think you are saying that's a different gun then? It's a more "natural shooter" than the first.



Edited 1 time(s). Last edit at 05/16/2009 02:06PM by barnespneumatic.

Thanks Gary, that helps to get it in perspective for me, much obliged for your help. I may try some slightly bigger slugs too, but at least it's clear for now where the sweet spot is....
The last group was from the SamYang "909s", which is the single tube model. I had it tethered to my scuba tank at around 2800 psi, which helps with the consistency. Within the next 2 weeks I have a regulator coming for the 4500 psi CF tank I purchased recently, so I can do more shooting at controlled psi. I'm looking for some decent 100 yard groups
Regards
Neil

Hi Neil,

With that 50 yard group you posted, you'll definitely get good 100 yard groups. And those Raptors are well capable of reaching out.

Don't forget the camera!



Gary