AA410 without power curve

[Remo]

Been shooting my new .177 410 over an F-1 chrony at high power. Filled to 200 bar, shooting down to about 100 bar per the AA gauge. She starts off shooting JSB exacts at around 1100 fps, and decreases steadily thereafter. By the end of the fill, she's shooting somewhere in the 900-950 fps range. I don't have a chrony printer, so I can't post the individual shot strings yet. Has anyone else experienced this lack of a curve?

Eric

[kirby999]

My not shrouded AA S400C carbine, with a 175 bar fill starts about 790fps with a low of 787fps to a high of 804.2fps for 60 shots at 50 degree temps. The shrouded S400C with a 160 bar fill , starts around 800fps , with a low of 793.6 and a high of 822.2fps for 60 shots . One of my AA S400H Classics with a 150 bar fill , starts at 802.9fps , a low of 801.3fps and a high of 825.7fps. for 80 shots. all at 50 -52 degrees outside temps. To answer your question, yes ; I just have to find the "sweet spot" for theses rifles. With higher temps outside I get a bit more shots out of all of them , as the heat raises the pressure in the airtube. I have to be careful with a fresh fill or the temps could cause my beginning shots to become lower in velocity than I want . I have near the end of a field target match , intentionally put my rifle in the sun to gain a few extra shots if needed to finish a match without refilling. 950- 1100fps spread is a heck of a spread , one that I'm sure would affect accuracy at longer ranges . I prefer to keep mine in a less than 30fps ; preferably 20fps spread . I do spend a good bit of time at the bench with a chrony , mapping out my rifles . It does a lot for my confidence . kirby

[Remo]

Kirby,

I will shoot another string tonight and write down the chrony readings and post them here. Unlike most S400/410 unregulated guns that I've read about that have a bell shaped power curve that reveals the "sweet spot", my rifle just seems to start at max velocity and ramp steadily downward as number of shots increases.  This rifle doesn't seem to have a "sweet spot".  Does that make sense?

Eric

[preez]

Hey Eric, I had a similar experience with my low budget discovery. I started on full fill (2000 psi) and expected a valve lock but it did not happen. 1st shot was 796fps and it remained consistant between 790 and 800 fps for the next 12 shots. At that point it was at 1700 psi, which is considered by many as a sweet spot for the disco. I never finished that string, because it was consistant enough for me....


Chris

[kirby999]

Eric; I did have an AirArms rifle that did that . It was a MPR . It was designed to be a 7fpe 10 meter target rifle and the place I bought it said they could bump it up to 12fpe. When i got it , it would start high ; somewhere in the 15-16fpe range about 900+fps then would drop 50-60 fps per shot until it would need a refill. I tried everything I could think of and everything the seller suggested , even swapped out the airtube (that's where the valve was located on this model). It didn't help. I wound up sending it back . Now with yours, Is it an adjustable power model? If so you aren't going to get it to have a sweet spot at full power . At least that's what I've found in my experience with them. I had a 22 cal. S410 and it would shoot best and most consistent just below the mid-range in adjustment . Around 850fps. But that was tearing up my targets . But that's another story . A 22 cal . at 850fps carries some energy . Once you find a setting you can live with, from what I've read, after selling my adjustable model ; there's supposed to be a grub screw under the action that will , when tightened up , prevent an accidental power change. If it's a non-adjustable older model , well we'll tackle that one later. Try turning the power down to half and see what kind of numbers you get. kirby

[Remo]

Thanks kirby.  FYI, I'm shooting the ERB model in .177.  At least I'm not nuts and someone else has experienced it.  I was also encouraged by your observation that there will not be a curve on high power, which is where I was shooting.  I did record a 50 shot chrono string by hand, following are the first and last of 10 shot mags.
1 -  1073 10 - 1068
11 - 1068 20 - 1054
21 - 1049 30 - 1021
31 - 1023 40 - 990
41 - 985  50 - 951

I filled it to 200 bar and shot down to 100 bar.  As you can see, no curve.  I'll crank her down to the 850 fps level and see if there is a power curve at that level.  

On the new model I just purchased the lock down screw is actually located inside the power adjustment knob.


Eric

[Remo]

Hi Kirby,

I wrote down the muzzle velocity for another 40 shots over the chrony at reduced power, starting fill was 200 bar, ending was about 150 bar per the rifle:

802
799
796
792
790
788
794
790
784
786

785
784
782
784
786
784
783
774
781
780

783
782
777
774
773
774
773
772
771
769

766
767
769
764
764
765
763
757
760
761

The rifle shows the same characteristics -- no obvious power curve.  I'm going to call Craig or Kevin at straightshooters and get their input. I'll keep you posted.

Eric

[kirby999]

Something definitely wrong inside that rifle , just like the MPR I had. At 200 bar the fps should start low , the hammer and spring have to over come the higher pressure and the valve spring . Once the pressure drops some the hammer and it's spring will have an easier job opening the valve and the valve will stay open a little longer giving a higher fps in the middle of the power curve until the pressure drops enough to level out the shots. IMO and this is just a guess , the valve spring is too weak allow too much air to pass with each hammer hit or the valve is sticking and needs smoothing up . Either way ,on the lower power adjustment , with the large airtube you have , you should be getting close to 100 shots in the 790-810fps range. I'd definitely send it back. AirArms makes some of the finest airguns for the money there is , but sometimes a lemon will show up with the best . SS should treat you fairly. You may have to send it to Bori at TopGun Airguns , they are the warranty shop for AA in the USA. kirby

[Remo]

Bummer.  I'm going to call SS and talk to Kevin/Craig.  Others on the SS forum and the AA owners club forum have suggested the same issue as you.  I'll keep you posted after I know more.

Eric

[Remo]

In addition to the way the rifle was shooting, a screw in the action on the right side just "popped" out.  Thought it needed to be tightened, but no luck, the screw just slides all the way into the hole just like a nail...looks like the inside of the rifle is stripped where the screw belongs.  Spoke to both Craig at SS and Boris at TopGun today.  Back it goes and the wait for the replacement rifle begins.

Thanks again.

Eric

[kirby999]

Hopefully they will get it straitened out for you. Air Arms make some fine rifles . You just got a lemon. If you got a nice stock, I'd keep it and see if you could just return the action. kirby

[Remo]

It's been a long time since I started this thread, and an update is now in order.  After the usual knuckle biting wait that seems interminable, the replacement 410 arrived.  Naturally, I had run down my tank earlier and not bothered to get it refilled while the 410 was out on warranty, so a little time passed before I was able to refill my tank and then the rifle in order to see how this new shooter performs.

Right away, I will admit to not  checking that all screws were tight.  I'm not going to jinx myself here and start out by assuming the worst.  I load the AA magazine with JSB Exacts, close the lever and begin shooting.  Exactly 10 pellets later, the brand new AA magazine is failing to index.  Fortunately, I already have two excellent OEM magazines by RC Machine to use, both of which have indexed perfectly while two factory magazines have failed.  But that's another thread I think.

I decided to investigate the power curve issue by shooting strings at various fill pressures to test the theories about spring strength that have been proposed by various folks including kirby and several on the Straightshooters and the AA owners forum.  I fired 40 shots, 4 10 shot strings, at fill pressures of 2900, 3000 and 3100 psi over my F-1 chrony.  Results are as follows:

 3100 psi	1	2	3	4
 1	 1052	 1071	 1073	 1061
 2	 1053	 1063	 1074	 1055
 3	 1050	 1070	 1066	 1050
 4	 1057	 1069	 1066	 1051
 5	 1059	 1068	 1067	 1046
 6	 1056	 1068	 1063	 1046
 7	 1061	 1073	 1065	 1041
 8	 1062	 1068	 1061	 1036
 9	 1059	 1065	 1055	 1032
 10	 1065	 1069	 1056	 1030

 

 3000 psi	1	2	3	4
 1	 1075	 1075	 1062	 1035
 2	 1071	 1071	 1058	 1030
 3	 1072	 1068	 1053	 1029
 4	 1072	 1070	 1055	 1025
 5	 1069	 1067	 1049	 1022
 6	 1070	 1063	 1045	 1016
 7	 1077	 1078	 1047	 1014
 8	 1078	 1068	 1039	 1018
 9	 1073	 1064	 1041	 1006
 10	 1075	 1062	 1034	 1005

 

 2900 psi	1	2	3	4
 1	 1074	 1076	 1039	 1015
 2	 1072	 1058	 1032	 1007
 3	 1068	 1055	 1028	 1003
 4	 1067	 1059	 1028	 1005
 5	 1069	 1053	 1023	  999
 6	 1061	 1053	 1032	  994
 7	 1062	 1046	 1021	  990
 8	 1060	 1047	 1017	  993
 9	 1057	 1042	 1020	  993
 10	 1061	 1044	 1016	  985

 

 It appears that the earlier speculation was on target, the power curve appears at the slightly higher fill pressure. 

This rifle also seems to shoot better than the earlier one.  It may be psychological, but the other rifle would have uncalled fliers at very close ranges that didn't make sense.  A behavior that the replacement rifle has yet to exhibit. Also, the new rifle seems to shoot within a tighter velocity spread from the begin of a fill to the last shot.

Eric

 

[gamo2hammerli]

Sorry to hear that 2 of your factory magazines failed on you.  Lucky my one and only .22 magazine haven`t failed....knock on wood.