PSI and accuracy question (FX Indy Chrono results also)

[Anomaly]

Got to borrow a Shooting Chrony and did some testing today on my FX Indy. Took a bit to get it setup right in my basement, but nothin' a floor standing lamp couldn't fix. Being this is my first airgun I'm fairly satisfied with the results. Did have a bit of a scare though when I got into the groove of things and had 2 shots that registered way lower than the others. First time I didn't realize what happened, second time I noticed I put 2 separate holes down range. Turns out in my haste I had double loaded it. Chatted with 454 and he assured me not to worry about it, so that's why 2 of the velocities listed below are off.

I'm gathering a bunch of different boolits designs together to find out what works well with my rifle, as I want more option than just the FX/JSB pellets. From my tests, my rifle prefers 150 bar ~2100psi, when I make my way out to the 50yrd range with the bullet samples, should I shoot at 150 bar or go slightly higher. The range I'm goin' to isn't thrilled about people using chrono's and as much as I tried, I couldn't get a straight yes or no answer from the RO (as such I'm not gonna worry about bringin' the chrony). That being said, since I know the pellets the rifle was designed for function best at 150 bar, is that where I should get the best accuracy from untested boolits as well?

The results from my first chrono test:
JSB Exact .30 44.75gr pellets

250 bar - 660.7 fps   
250 bar - 661.6 fps
250 bar - 668.0 fps
240 bar - 681.8 fps
240 bar - 681.0 fps
240 bar - 681.6 fps
230 bar - 706.4 fps
230 bar - 707.3 fps
230 bar - 712.1 fps
220 bar - 723.9 fps
220 bar - 727.6 fps
220 bar - 724.5 fps
210 bar - 748.6 fps
210 bar - 748.6 fps
*210 bar - 515.5 fps
210 bar - 753.2 fps
200 bar - 775.2 fps
200 bar - 772.5 fps
200 bar - 781.5 fps
190 bar - 801.5 fps
190 bar - 806.2 fps
190 bar -794.7 fps
180 bar - 831.7 fps
180 bar - 836.0 fps
180 bar - 832.0 fps
170 bar - 862.9 fps
170 bar - 866.5 fps
170 bar - 858.6 fps
160 bar - 886.0 fps
160 bar - 886.7 fps
160 bar - 891.2 fps
150 bar - 895.7 fps
150 bar - 896.2 fps
150 bar - 896.2 fps
140 bar - 892.1 fps
140 bar - 893.4 fps
140 bar - 895.5 fps
130 bar - 874.7 fps
*130 bar - 672.2 fps
130 bar -  879.9 fps
130 bar - 876.5 fps




P.S. pardon the formatting, I couldn't figure out how to get the image to go next to the values without the giant gap.

[Rdsail]

I don't know how adjustable your gun in but you need to add more hammer energy. you string is constantly going up. You want your curve to be more like a hump than a line going up or down. you have a 250fps spread which is bad. My guess is you need to adjust the power somewhere aroudn 860-900 and do another curve. You will get a lot less shots but they will be better shots.

A though. Are you suppose to fill that gun to 250 bar? I don't think I would go over 180-200 bar. 

[45Bravo]

I agree with what he said,
Or just fill to 170 bar.

That will put you at the top of your velocity, but less shots.

I would look into cranking a little more hammer spring if you can..

Welcome to the air gun club.

With that rifle, you didn't dip your toe in the shallow end,
you jumped off into the big boy end of the pool.

Keep us posted.

[BrewCityMusic]

You're going to have to experiment with the different rounds, the different weights, etc will likely have each round finding its' own "sweet spot" pressure-wise. That said, the FX SmoothTwist barrels were designed around the JSB pellet, so it may take some trial-and-error to find another round that retains good accuracy in that gun - although it has been done before. If You do some poking around here and on the Yellow, a lot of guys who are shooting the Indy's generally treat them as a "one-shot" or "Two-shot" gun, meaning they find that sweet spot that gives a shot or two at the best power with minimum deviation and just pump them back up after that shot or two.

[45Bravo]

You know Zack, I was still thinking standard pcp. Not selfcontained pumper/pcp.

With the pellet he showed data for, and it gets good accuracy, then
Yep, 160 bar, shoot 3 times, pump back to 160bar.
You are on the top of the velocity string,
And shouldn't take but a few pumps to get it back there.

And since you are not at the high end of the pressure range, it should be easier to pump than at 200 bar.

[BrewCityMusic]

That's why I have always had the Indy in the back of my head as one of my next possible purchases - as a hunting gun, one good shot and possibly another fast follow-up is sufficient, as long as they are consistent ... If a finish shot is needed, well then who cares, LOL, there'll obviously still be enough pressure if You don't feel like pumping (and at a foot or so, accuracy-schmaccuracy, I always say!).

What I like is that the gun can be pumped back up to ready in a jiffy and without carrying any support equipment - if You blow a shot, oh well. If You are having a good hunt, it can keep going as long as You want it to without having to go back to the truck and refill, or carry a pump/bottle, etc - lots of good reasons to keep the Indy in mind! Now, as a paper-puncher at the home range, probably wouldn't matter as the Nitrogen is right there and I'm not sure about pumping every 2-3 shots to stay consistent, but what a GREAT "trunk gun" to be able to pull out and shoot at a moments notice at a buddies place, etc !!! Definitely going to follow this one to see what the eventual results are with different rounds, dangit I HATE getting good info on guns that I'm interested in anyhow, LOL (well, I don't hate it but my wallet does!). 6 shots from 150bar at 895 plus or minus 3 is a great start already though!

[Anomaly]

@Rdsail I'll have to look into what can be done to increase hammer energy, this is bone stock. And officially, the rifle is rated to 220 bar from the manufacture. That being said, all their markings on the rifle say 250. On the yellow, I've seen others take it to 250 and I wanted to see what velocity I would get from it. (but 250 doesn't yield max power so, it's irrelevant to me now). Because I kinda freaked myself out with the double loading, I pretty much stopped, once it started the decline in energy.

@45Bravo and yeah,I have a really bad habit of doin' that, I don't really "test" the waters, I find somethin' that fits my criteria and get it, even if it takes a lil while to save some discretionary cash. And yeah at short range so far accuracy has been fantastic, I've only been able to go to 20yds, but @ 20 I'm shooting a 3/8" hole.

@BrewCityMusic, yeah I kinda figure this to be a 2 or 3 shot gun due to the small tank, but I knew that was a limitation when I bought it. I'm of the mindset, if I was hunting a bobcat or similar, and I can't get it in 2 shots, I'm doin' somethin' wrong. Usually when I'm shootin' it, I fire once or twice and it's 3 or 8 pumps to get it back to pressure. I have an old 68cu in 4500psi fiber tank, and 2 100 cu ft steel scuba tanks (I'm a scuba diver and used to play paintball back in HS), so I was looking at buyin' one of the Jdsairman 4500 psi regulators, and setting it around 2100 after seeing the results of this test. I'm not 100% sure where (since I'm still new to my neighborhood) I can find 4500psi fills, but my scuba tanks are filled to ~2800psi and ~2750psi  right now. I'll likely be buyin' a fill station and whip kit so I can take my bottle to the range.

[45Bravo]

The pressure rating of a gun is like the speedometer of your car.

It might show 180mph, but,

A: will it actually do that? Possibly,
B: was it meant to run at that speed all the time?  No.
C: will it run efficiently at that speed?  No.

When you really get into the guns, you rarely find they work well at max rated pressure.

Yes you can adjust some guns to shoot at that pressure, but you will be wasting a lot of air.
And possibly blowing your accuracy too.

For most pellets, sub 900 FPS is where you want to be.
Much above 900, It starts to enter the transonic range, and accuracy can sometimes suffer.

Did you ever read or study about chuck Yeager breaking the sound barrier? (Or watched the movie)

As he approached Mach 1, his plane experienced a lot of buffeting in the transonic area, as soon as he crossed the barrier, it smoothed out.

Then as he slowed below the speed of sound, the buffeting started again until he slowed enough.
More than one test pilot died in that area.

Our pellets have the same problems, as they get closer to ~1100fps, the buffeting begins, throwing off accuracy.
If a pellet is launched at faster than ~1100 FPS, as it slows, it encounters the buffeting..

Sorry to be so long winded.

[Anomaly]

Yea, I get that, I was hopin' not so much due to fps, but due to shot count to be able to run it at a higher psi. At 220 bar I get like 7 good shots out of it (albeit not the most powerful), but at 150-160 bar, I can get 2-3. For hunting it wouldn't make a difference to me, but for target shootin', it would be nice to get more shots per fill even if they are not runnin' at full power. From what I have seen at 20yds, the accuracy isn't affected much by the PSI with the JSB pellets. Testing the boolits, may show very different results however. I do need to bite the bullet and go ahead and purchase either the jdsairman reg or a ninja reg so I can limit the amount of pumping I do when I go testing at the 50yrd range. Being that my rifle has the ability to pump up, what would be a good base psi to have the regulator set to for testing boolits? (I can always have it changed later)

[starlingassassin]

can the indy accept a reg? 

that would be awesome to have a self contained regged gun that didnt need support equipment.

[45Bravo]

It already has a small reservoir, I couldn't imagine taking up more volume with a regulator.

But I am sure it could be done..
But no first hand knowledge of it..

[Anomaly]

Oh, no I apologize I should have been more specific, I have a 68cu in 4500psi fiber tank. This is what I was lookin' at buyin' a reg for. Just something so I don't have to pump all the way up for each shot when I take it to the range. I have my scuba tanks, and that's fine for at home, but I wanted to utilize this fiber tank that I have now.

Like this (but with my own tank):
Zebra DNA Ninja 4500 psi Carbon Fiber Air Tank & Fill Station for PCP

[45Bravo]

If you are running the gold ring ninja valve shown, it has a regulator built in, it can be adjusted.

That valve won't let you put more than 3000 out.

So setting it somewhere close to where you want, and using a longer tether, would work for bench plinking..

http://www.airtanksplus.com/products/regulators/ninja-pcp-airgun-regulator

[Anomaly]

That's precisely my plan 45Bravo. I see my rifle favors ~2100 psi with JSBs, and I can order the regulator in 100 psi intervals from 1000 to 3000 psi. I can always send it back to have the output changed to another value within' the range, so I'm not locked into whatever I purchase it at. With the Indy, I can also pump up easily, but goin' down in psi requires shootin'. So for testing and finding a good boolit, what do you think would be a good psi to have the regulator initially set to? 2000 psi? Is there a range that generally all boolits and pellets favor with PCPs? (e.g. 1700 - 2600 psi) The boolits I'll be testing range from 50gr to 75gr.

(Interestingly that link you sent only shows 200psi intervals, but Ninja's website shows 100psi intervals, I trust Ninja more)

[45Bravo]

That I can't answer for you, as I have never tried to run 50-75gr. Projectiles from an airgun..
Only your testing on your gun will prove which pressure range gives the best accuracy/power.

Each rifle will be a little different.
Close, but not exactly the same..

Changing the regulated pressure on one of those valves is done with beville washers, (but the paintball guys call them shims.)

And is relatively easy to do.

[Anomaly]

Well, I have a better rough idea now. Got in the first of my test boolits Mr.Hollowpoint's .300 55gr HPs. I didn't wanna waste too many just at home, but was curious to see what fill pressure they prefer. Only tested about 5, but seemed to get the best results around 140 bar with 816.7 fps. More testing to follow in a separate thread once I get all the boolits, and have a chance to make it to the 50yd range. That being said, I figured if I was gonna see what pressure they favored, I might as well see what they do to my ballistics gel at the same time. (rather than my normal pellet trap) Was quite impressed at how well they mushroomed at such a low fps. Penetration floated around about 4.125" but, there is loads more testing to do before I call that an average. At the moment I'm not looking for the best cast HP boolit, as I want the most accurate boolit. I would, however, prefer a HP over a RN of FN provided I can get around 8" of penetration in ballistics gel.


P.S. Ignore that groupin' in the BG that was from a powder burner. Thought it looked better than a pic of the boolit on my kitchen counter.