.22 MAC1 Discovery Shot Strings

[bwgstock]

Received a MAC1 ( http://www.mac1airgun.com ) prepared .22 Discovery a few days ago and have been testing it over a chronograph to learn about its power curve using Crosman/Benjamin .22 14.3 grain hollowpoints. Thought some of you may be interested in what I found.

My first five strings gave widely variable FPS reports between shots and this had me frustrated at the lack of consistency. I realized the problem was placement of my chronograph, which was too close to the gun muzzle. Moved the chronograph about 13 inches from the muzzle and repeated five strings of 50 shots.

For each string I pumped the gun to between 2100 and 2200 PSI (I estimate using the gun's gauge); stated differently, the gun's gauge reported pressure just above line between yellow and red. For two of the shot strings the pressure may have been slightly less (I did not check this closely initially).

Below the first graph shows results of the five 50 shot strings. The second graph shows the mean FPS for each shot across the five shot strings. This mean is provided to help give a general display of what I can expect for this gun.





As the two graphs illustrate, I average almost 30 shots between ~840 FPS and ~880 FPS for each string. Using the mean graph, the mean (average) for the 30 shots between 840 (actually 837) to 880 FPS is 862.28 with a standard deviation of 12.52. This works out to an average FPE of 23.6. This is my first .22 air rifle and I can say I am thoroughly impressed by this power when compared with my 15 FPE .177 air rifle.

The sweet spot on the curve for my gun seems to be between 2050 and 1100 PSI; that provides FPS between 840 and 880. Lowering my cut-off to 820 FPS gives me about 7 more shots for a total of about 37 shots. I just order a HDD from Big Ed, but now that I have seen the consistency of this gun as prepared by the folks at MAC1, I am not sure I will install the HDD when it arrives since I am very happy with the current performance. I may attempt to fiddle with the power adjuster to determine whether I can get more shots that average about 840 FPS (range between 820 and 860), but the power adjuster seems to be set firm (perhaps with loctite) so I may not touch it at this point.

I have not fully tested this gun for accuracy since I have spent most of my time trying to learn the sweet spot with a chrony, however, the few times I've shot it at targets the pellets landed almost exactly where I aimed at about 20 yards. That's more accuracy that I am accustomed with my .177 springers. I think this gun is a keeper.

I paid MAC1 $400 for the Discovery and pump (plus $20 shipping), and can state that I am very pleased with the performance of this gun. I can highly recommend buying a Discovery from MAC1 given the fine tuning they do to each Discovery.

For those interested, the shot count FPS are reported below. The areas noted by +++ are errors from my chronograph. The first column of numbers is the shot count (1 to 50), the next five columns are strings 1 to 5.

01 811 +++ 798 794 803
02 809 +++ 798 792 800
03 816 815 803 794 801
04 815 820 808 798 805
05 821 823 813 785 802
06 825 820 811 798 805
07 +++ 822 817 801 813
08 847 830 821 800 808
09 840 832 823 817 813
10 847 837 831 814 816
11 843 842 829 824 817
12 842 838 836 818 825
13 852 877 837 828 821
14 861 847 841 825 828
15 874 851 844 833 833
16 861 850 847 836 837
17 865 858 852 835 848
18 866 863 858 842 851
19 870 862 864 845 848
20 874 865 853 856 857
21 874 868 863 859 851
22 870 872 862 841 857
23 875 871 871 862 859
24 880 871 869 867 865
25 875 879 871 870 874
26 879 886 876 867 868
27 876 879 867 868 868
28 877 881 878 869 878
29 879 885 877 865 873
30 867 882 882 868 881
31 870 880 883 875 879
32 870 877 878 877 877
33 887 863 877 870 876
34 884 865 881 869 872
35 875 858 877 874 871
36 868 856 873 874 873
37 869 851 869 872 865
38 856 842 866 866 868
39 854 836 862 863 863
40 851 831 859 862 857
41 826 826 853 858 855
42 815 816 850 858 847
43 805 807 841 853 836
44 800 798 840 846 834
45 784 794 829 839 828
46 774 781 821 832 820
47 766 775 811 826 814
48 +++ 764 802 819 806
49 756 752 794 814 799
50 742 741 788 804 791

[melloroadman]

Bryan did Tim give you a test sheet with a recommended fill rate when you purchased the rifle . Marvin

[bwgstock]

No, did not see one included. Is that standard with purchases of Discovery from MAC1?

[melloroadman]

I am not certain about it but I thought he did when he set the rifles up . But I could be wrong . What distances are you sighting in for and are you hunting or target shooting . Marvin

[bwgstock]

I usually shot between 20 and 50 yards, so will probably go for 25 to 30 scope set. I don't hunt, just like to shoot.

[melloroadman]

That's what I do with my .177 Discovery . It looks like you have a good .22 . Let us know how it goes .Marvin

[PBJ]

You might look on the back of your manual. That is where I have read that he puts the info from the tune.

[mackeralboy]

I bought my .22cal Disco from Mac1  back August. Tim the owner of Mac1 tunes all of the Discos he sells as part of the base price. Tim is a master Airgun smith, all around great guy, and I can't recomend buying an air rifle from him enough. My experiences with my Mac1 Disco are pretty much right on par with Bryans findings. As far as accuracy goes mine will consistantly shot 1/2" groups at 50yards while between 1100 and 2000psi. If you are going to hunt with your Disco and you want to get the most from its power then get it in .22cal.

[bwgstock]

Thanks for the tip but nothing about suggested pump fill was included in the material I received. It's unimportant now since through testing I've identified the sweet fill spot for my gun. Been shooting today 30 good shots per fill and this gun hits very hard. Accuracy seems very good too. As I wrote above, this is certainly a keeper.

PBJ - 1/4/2009  5:54 PM

You might look on the back of your manual. That is where I have read that he puts the info from the tune.

[SAVAGESAM]

mackeralboy - 1/4/2009  6:10 PM

I bought my .22cal Disco from Mac1  back August. Tim the owner of Mac1 tunes all of the Discos he sells as part of the base price. Tim is a master Airgun smith, all around great guy, and I can't recomend buying an air rifle from him enough. My experiences with my Mac1 Disco are pretty much right on par with Bryans findings. As far as accuracy goes mine will consistantly shot 1/2" groups at 50yards while between 1100 and 2000psi. If you are going to hunt with your Disco and you want to get the most from its power then get it in .22cal.

What is the difference is Fpe in .177  Vs. .22 Cal. ???

[waunderin]

my .22 had a high  of 25.8 fpe with the beeman kodiaks at 742 fps mv.
my .177 had a high of 20.5 fpe with the crosman heavy's at 938 fps mv.
 both guns done by mac1.   john

[SAVAGESAM]

waunderin - 2/28/2009  8:38 PM

my .22 had a high  of 25.8 fpe with the beeman kodiaks at 742 fps mv.
my .177 had a high of 20.5 fpe with the crosman heavy's at 938 fps mv.
 both guns done by mac1.   john

Thank you very much. That's EXACTLY the kind of info I needed.

[waunderin]

you are very welcome! now i have a question, what do you use to make your graphs with. i did some on graph paper, and it is a lot of work. i didn't know what increments to use so it would spread out. mine looked like a hay stack

[SAVAGESAM]

I don't make graphs. I assume you are referring to the other gent.

[waunderin]

ok, i must be.  john