I just purchased a Diana 75 from Neal Johnson (see the ad from which I purchased at http://www.nealjguns.com/ss_store/UsedAirRifle.html). I need advice to decide if I should:

a. send it back for a refund.
b. send it back and ask for a replacement gun - they show 4 more left.
c. keep the one I've got, hoping it will improve with use or with some other pellets
d. keep the one I've got, but try to improve the gun with my own "work."

Here are the facts, as I see them.

The gun I received does not shoot as well as I need it to. Average 5 shot groups, using sand bags on a bench at 10M and a scope sight, range from 0.100" to 3/4" for 25 different pellets. I was expecting groups to be less than 0.050" C-T-C at that range (1/2 minute of angle) for many pellets.

There is noticable "recoil" when shooting, much more than my Daisy 953 pneumatic or my Alpha CO2, and I believe it is as much or more than a FWB 300 that I used at one time. If I shoot without touching the gun on the bags, it bounces off the target center by a few inches during the shot (and doesn't shoot as tight groups).

Pellet velocities seem OK and are quite consistent. Here are some 10 shot stats: R10 7.0 gr - 650fps, s.d. 1.0!, H&N Final Match 8.1gr - 586fps , s.d. 4.6 (but this was my most accurate pellet), Gamo Match 7.8gr, 601fps, s.d. 3.7. (The R10 and Gamo both gave 5 shot groups of 0.20".)

I was TOLD when I ordered the gun that it was NOT a spring piston gun, but a pneumatic (see the ad). And I was told that the gun had just been reconditioned by one of their repairmen. The gun looks as good as I expected, but it didn't appear to me that it had been "reconditioned." It squeeked a bit while cocking (seemed to be very free of any lubricant) and wasn't clean around the loading port at all, nor did the seal against the barrel look like it might be new. The only thing that does appear to be new work is crowning of the bore. It appears to be newly cut, and it doesn't look that well centered to me. (I could be wrong.)

I've read that good quality air rifles are supposed to be very accurate. I have an old Daisy 953 that shoots almost any pellet into 2 minutes of angle, and a number of good pellets into 1 minute of angle. This Diana doesn't do any better than my old Daisy, and much worse on most pellets. Am I wrong to expect an old Diana 75 to give consecutive 5 shot groups under 0.050?

I realize that this is a spring piston gun, but I've read that it is supposed to be recoil free. Is mine normal, or is there some imbalance in the twin pistons?

Do the velocities that I have recorded above appear to be on-the-mark for a Diana 75 that is working properly?

Should I try to take the gun apart and carefully lubricate everything? (I did oil the moving parts on the exterior, and the squeeking did go away.) And, if so, is there a web site that gives instructions for disassembly/assembly - and is it possible to do without special tools?

If the problem with accuracy is the crown job, would it be wise for my to try to smooth out the crown job with a small ball and lapping compound, or should I put it into my lathe and recut it before lapping it?

If you can answer any of these 5 questions, please do so.

Thanks so much.

I would contact Neal Johnson's first.

It seemed to me that I should get all the info I could before contacting Neal Johnson's shop. Today I called, and they seem to be very genuine about making customers happy. They indicated that they will be putting a number of used air guns on sale during the next couple of weeks. They will call me to see if any of these would better meet my wishes, and I can exchange this gun with one of them. That is what I hope to do.

Thanks for your excellent "obvious" suggestion.

Hi Ibexman, Something's strange here; your mod 75's velocity seems right on the
mark. Sorry but your standard deviation info is useless for me, I only can
understand FPS difference. Your accuracy may be fine also. Don't expect to
achieve the rifle's accuracy potential with a scope off sand bags. you will
be more accurate at ten meters with the rear diopter sight(I think). Also,Diana
gets(I mean got) those accuracy numbers shooting from a mechanical vise.
I got an RWS Mod 75 t01 from Ted Malone's NJROTC sale awhile back and it is
completely recoiless. It makes a springy twangy sound when it shoots, but the rifle
is motionless at trigger release.

Your Mod 75 seems capable of accuracy for scoring tens. But as Anonymous has
suggested; give Nealjguns a call, they should be able to respond to all of
your questions. meanwhile just shoot and enjoy your Mod 75; and don't spend
so much effort trying to measure theoretical performance.
Have lotsa fun popping asprins at 15-20 yds;
Tony G

An acquaintance in town heard about my order and bought a Diana 75 also. I got a chance to shoot his yesterday. His is almost free from recoil; it doesn't move from the spot during firing. It appears that mine does have some type of imbalance, since it always jumps to the left.

A standard deviation of 1.0 means that the total range of velocity, over a large number of shots should not vary by more than about 6 fps (+-3). The total difference from minimum to maximum on the actual 10 shot string I fired was only about 4 fps. I've never recorded such consistent velocities before. That does indicate that the seals must be very good.

There is no way that I could hold as consistantly on target using the "iron diopter" sights as I can with a good scope sight. I've been using the BSA 4-16x40 Mil Dot, which adjusts for parallax down to 10 meters. At 16 power you can see every speck on the target, and you sure don't need any other spotting scope.

Thanks for your input. (Look at the response I gave to Anonymous also.)