Disappointed in my Discovery

[Erich99]

Received my Discovery a week ago and have put maybe 300 pellets through it, and find its accuracy not what I expected.

Shooting in my 9-yard garage range from a makeshift rest with a 3-9x scope, my 5-shot groups are in the .75 inch c-t-c range.  THis is no better than my Chinese Springer (TF-97) with open sights.  I'm a newcomer at this and am having a hard time diagnosing the problem, but every group seems to have a flyer.  I've used only Crosman Premium Wadcutters and Tech FOrce Match Wadcutters so far.   Do any of you have any better results with other pellets?
 ( I think I'll try the sampler recommended by another post on the forum.)  

BTW I'm a little disappointed in the Discovery's appearance because it has a long, rather ugly knot just under the stock comb... is this common?

Otherwise the rifle seems good to my inexperienced eyes, trigger a lot smoother than my TF, and nice to have recoil-free shooting, albeit with a pretty loud crack to wake up the neighbors.   Pumping it up is a bit of a workout for an old guy like me, but not a major problem.  I do find that it takes nearly 100 pumps to  restore pressure  to 2000 PSI from the 1000 PSI level after you've taken your 30-some shots, despite the fact than an earlier reviewer claimed it only took 35 pumps to restore it to 2000 PSI.

Do you experts know if there tends to be  large variations in the accuracy of individual rifles of  the same make?  

Thanks.

[DanoInTx]

Check the muzzle crown.  Someone else reported on the Crosman forum that they also had a very inaccurate Disco.  Upon further inspection they found out that the barrel had not been crowned at all.  At that distance you should be able to put them in the same hole all day long, never really had a Crosman barrel that was pellet picky.  One question though, does that scope have an AO adjustment?  Non-AO scopes can throw things off a bunch also, especially at close range.

Wads are not the best choice. Try some JSBs or Diana Domes. Even Crosman hollow points are better than wads. AS the previous poster said, make sure your scope has AOor that can throw you off quite a bit. There are ways around it if you don't.

[Erich99]

Thanks, DanoInTx.
But as a newbie I have NO idea what Muzzle Crown IS even. Never heard of it.   How do I tell if I have it, and what can I do if I don't?  What am I looking for?

 I don't know what AO  adjustment is either.  My scope is a cheap  TF that came with my TF97.... supposedly an airgun scope that can take the double recoil of a springer, but the manual makes no mention of AO adjustment.  Is it like paralax adjustment because I'm using it at such close distance?  I have to admit that it seemed to shoot better with just the open sights, but I put the scope on it because my honey liked it better.

THanks for any advice you can give me.
Eric

Yes - AO is a parallax compensating mechanism. Shooting that close will bring on parallax if the scope isn't adjusted for it. I have a Bushnell Sportsman 3-9x32 on mine with AO and target turrest. Nice scope for that rifle. Comes with rings from Optics Planet for $65 shipped. It is the air rifle model and focuses down to 7 yards or so.

[Big_Bill]

Hello Eric,

First, the crown is on the end of the barrel where the pellet comes out. The center of the barrel should have a relief cut or ground into the center of the barrel, where the pellet exits the barrel. This process cleans rough and peened metal and protects the barrel from small bumps on the barrel end. You should see the center of the barrel go into from this process, and no sharp edges sticking out to touch or interfere with the pellet when shooting.

Second, AO scopes have adjustment on the front of the scope, it will turn, and have numbers from say 10- 1000 on it, some have these numbers in yds. As you turn the front ring as your are looking through it you will see the image become clearer as you approach the correct distance, say 10 or 10yds. P.S. Where did you buy this scope ?

Bill

[Erich99]

Thanks, BigBill...
Yes, my Discovery does have a small bevel on the end of the barrel where the pellet exits ... looks like maybe 10 degrees or so.  It's a bit hard to tell exactly the angle of the muzzle crown because there is also a fat muzzle brake that extends out beyond the end of the barrel  a half inch or so.  But it looks clean, no stray metal shavings, etc. so I 'm doubtful if this could be a potential cause of flyer pellets.

My Tech Force scope does have an adjustable objective lens to focus for different distances down to about 7.5 yards, and of course I have it set at approx. 9 yards... the length of my "range".  I see people using the term parallax adjustment for FOCUSING the lens, but that's a different use of the term than I'm familiar with from photography, where parallax error refers to the different angle of view between a lens and a viewfinder which might be located above the lens.  It seems to me that an analogous situation in shooting would  be the difference in angle between a scope and the BARREL,  and this type of error is adjusted out by the elevation control on the scope  (and is a hefty adjustment indeed at only 9 yards).  But again I don't see it as a cause of wandering pellets.  

But I understand you can get a different point of aim with minor differences of where your eye is vis a vis the scope, so I'll try paying more attention to  keeping my head in exactly the same spot each shot.

THanks for your help.
Eric

[London177]

Hello Erich,
I am sorry to hear about your woes. Forgive me if you have already done this or thought of it. If you are getting nice groupings but the odd pellet does a flyer it may well be just the pellets you are using. Try another test with the scope and carefully note what you shoot. Then do the same without the scope using the iron sights. See if you are still getting the flyers, remember to use the same pellet type from the same tin, repeat with another tin of a different make. See what you get. You should be able to narrow it down. I had the same problem that was the fault of the mounts I was using. The scope was fine but the mounts were not stable even on a CO2 rifle with little recoil. It took me an age to figure it out....
If all of the above does not make a difference and the crowning looks good it may be an issue with the pressure in the air chamber. On my BSA Ultra too much air can upset accurancy. I use a diving tank with a gauge which gives me a good idea of how much I have put it.
After all this and you are not happy take it back and ask for a replacement. Ok, enough from me.
Good luck and best wishes,
Alan :)
PS. Let us know how you get on.

[Erich99]

Thanks  London 177 (Alan),
I'll give your advice a try.  It could be right, because I DID do better with the iron sights right out of the box.  And I'm doing better with the iron sights on my TF97 springer , now that I've removed the scope and installed it on the DIscovery.  THe mount SEEMS tight enough, but maybe it's tough to diagnose.
I'll respond if I figure it out.
Eric

3 tips

1. Clean steel barrel with airgun friendly cleaner and brass brush when new.
2. set fixed fx - remove objective lens ring cover and adjust parallax lense ring to set/focus on the distance you want.
3. Try variety of pellets.  Gamo hunter, match, mag points, BM kodiak xtra heavy are nice.

[scottinharwood]

If you were to dut off a piece of tubing square and flat accross the end, then use a  pointed grinding stone that just fits inside the tube and grind it a little, this create a chamfer on the inside diameter of the tube.  A crown is that same thing.  The crown, where it meet the inside diameter of the barrel should be of uniform relief (i.e., the little angled chamfer should be the same width all around and there should not be any nicks or scratches where the chamfer (crown) meets the inside diameter opening.

I attached a photo of what that inside bevel looks like - that bevel width should be uniform all around an have no rough edges or scratches into the bore.

Scott

[scottinharwood]

Another possibility is what your initial charging pressure is.  Mine had a sweet-spot of no more than 1700#; go over that and the pellet velocities could vary up to 75fps - thats enough to open any group up.  Also, to better inspect the crown, that metal piece on the end comes off easily.  Just remove the from sight and then only one grub screw holds it on - it slides right off.

Scott