First range day with my Discovery...some thoughts, and some questions..

[dmoneytt]

Well, the UPS guy dropped off my .177 caliber Discovery today, and I immediately slapped a Bushnell Banner 4-16x40 scope on it that was laying on my scope shelf.  One thing I noticed is that even with the scope rings as far forward as possible, the scope all the way forward in the rings, and a fairly short eye relief for the scope, I could still stand for the scope to be a bit further from my eye.  I foresee some extension rings in this rifle's future. The trigger is absolute trash.. gritty, creepy, vague, and heavy, but I have done probably 100 trigger jobs in my life, so I know I can fix it right up.  I just want to wear it in a little so I can inspect the contact points.  I also wanted to see how the gun shot right out of the box so I could more accurately measure any future improvements.

So, I took it to my rifle club's rimfire range, knowing it would be too loud for my backyard airgun range.  (I just ordered the 6.5" TKO brake minutes before writing this.)  I used the hand pump that came in the combo, and was pleasantly surprised to find it very easy to fill the reservoir.  I proceeded to shoot some groups and the gun was, at first, a little wild.  Groups were around 1" at 20 yards for the initial sight-in.  After 10 shots I had a zeroed group of about 1/2" at 20 yards for 5 shots.  So, I moved the target back to 25 yards and proceeded to shoot some 5-shot groups from a rest.  My groups were not horrible, but nothing special either.  I was getting 3/4" groups pretty consistently.  Granted, I only brought crosman premier hollow points to try since this is just a shake-down run.  Maybe some other pellet will shoot much better, but I have usually had good luck with these pellets in all my airguns.  One thing I noticed is that if I fill to 2000 psi, I am only getting about 23 shots before I hit 1000 psi, and the POI drops consistently for each shot after about the first 5 shots.  I did not use a chronograph, but I did shoot groups at 50 yards. 

I filled to 2000 psi and shot four 5-shot groups at 50 yards.  They ranged from 1.25" to 1.5", and the first 5 shots hit to (roughly) point of aim.  The 2nd group landed about 1/2" low of POA, the 3rd group 1" low, the 4th group about 2" low, and the 5th group 3.5" low.  There was an obvious downward trend in velocity from the first shot to the last.  This, to me, says that the rifle is firing the fastest at 2000 psi, so I am not anywhere near valve-lock at maximum psi.  I know that typically the shot string should be a bell curve regarding velocity, but I was on the downward slope from the beginning of the string.

So, I pumped to 2200 psi for another string of 25 shots.  The exact same thing happened again.  The gun shot highest on the target at 2200 psi, and then each group came down incrementally until it was shooting 3" low by shot 25.  Yet again, 5-shot groups were around 1.25" to 1.5".

So, I guess I have a few questions:
 #1. Do Crosman Premiers typically group this poorly from a Discovery?  I will try other pellets but I really expected better groups.  Suggested pellets to try?
 #2. Is my number of shots per fill typical?  I feel like I have read of higher shot counts on a stock Discovery.
 #3. It appears to me that my hammer spring is a bit strong and that is what is hurting my gun's consistency.  Does that sound correct to you guys?
 #4.  Does the Discovery have a certain amount of "settling down" shooting that needs to take place to see its best accuracy and consistency?

I also recently got a Beeman R9.  That gun, right out of the box, was shooting 1/4" 5-shot groups at 30 yards and 3/4" 10-shot groups at 50 yards, and spring guns usually take many shots to settle the powerplant down.  Am I being unrealistic to expect a $260 PCP to shoot anywhere near as well as a $460 springer?  I have heard a lot of guys say the Discovery will do 1/2" at 50 yards.  I was hoping to see something near that for myself.

[Night_Raider_]

1) Mine (.22) doesn't like premiers, either.  I settled on JSBs, so you might should try those at some point.  You might also want to try CPUM 10.1s.  I had better luck with them than the HPs out of my Prowler and they're all I feed it now.
2) The first Discovery's used thinner springs and got more shots per fill, but Crosman changed them to heavier springs to squeeze more power out of them.  So yes, your shot count sounds about average.
3) It sounds to me like you definitely need a power adjuster to adjust spring pre-load.  Cutting a coil or two off the spring would also help some, depending on how much power you want to sacrifice.  You can order a PA from Discosrus or make your own using a 10-32 machine screw.
Can't help with #4 as I got mine used.
I've had to do quite a bit of testing on my Disco to get it shooting like I want it to.  It has 2 coils cut off the hammer spring, the 2 screw mod done to the trigger, a TKO, a power adjuster, and a second barrel band. 

[Ribbonstone]

Just some thoughts.

Hopefully you did clean the barrel first...if not, go clean it. Are often a little gunky on the inside when new, probably a preservative (after all, they might spend months in transport/storage before they are retailed).

Yeah, the new versions do seem to have traded shot count for a little extra power (your #2 and #3). The need to go to 2200psi and then see the velocity fall off right away pretty well points to too much striker spring tension.  Have been several posts here about lessening spring tension (either cutting the spring or substituting a weaker one) to increase shot count (and decrease energy a bit, but normally the trade off is way in favor of the reduction in energy).

They do smooth out a bit with use.  The moving parts will smooth out a bit with use, which makes for smoother operation and a bit more consistency.

Trigger mods are also well documented with video tutorial, so it's not too difficult to get them adjusted to a pretty nice let off.

Not too many of my airguns will shoot CP's real well.

Didn't get good accuracy from the Discovery and CP's.

[tracker1955]

Did you clean the barrel before starting? Crosman barrels are really dirty out of the box so a good cleaning is in order. I found my first Disco didn't really begin to shoot consistent until I had shot a good 500 pellets down range.

[Martis 1]

I had similar results using Crosman hollow points, although my diso is in .22 caliber.  Crosman premier domes grouped much better, (almost half the group size), as the hp's. 

I too found JSB pellets to group better than the Crosman Domes, but again, mine's a .22 cal and not .177. 

Ron.

[rrdstarr]

I just had a custom stock made for me and it made a lot of difference in how I hold the rifle and my offhand shooting ability. As far as pellets my Discovery likes JSB's.
http://www.airgunforum.ca/forums/topic69473.html

[Case Stuffer]

So, I guess I have a few questions:
 #1. Do Crosman Premiers typically group this poorly from a Discovery?  I will try other pellets but I really expected better groups.  Suggested pellets to try?

Order sampler packs and try many. My Disco .177 like H&N Field target Trophy best , H&H Baracuda Hunter Extreme second best out of over a dozen I have tried.

#2. Is my number of shots per fill typical?  I feel like I have read of higher shot counts on a stock Discovery.

Americans are power hungry o they went to a stroner hammer spring   cut two coils from it an it will help a good bit.  Disco was designed (many years ago)  to be filled to 1,800 PSI and provide a good  bell curve and shot count.

 

#3. It appears to me that my hammer spring is a bit strong and that is what is hurting my gun's consistency.  Does that sound correct to you guys?

Yes , see above

 

#4.  Does the Discovery have a certain amount of "settling down" shooting that needs to take place to see its best accuracy and consistency?

Clean barrel and shot 20 pellets to foul barrel then check accuracy. Do not use powder burner cleaning supplies, bore brushes and such.

I have heard a lot of guys say the Discovery will do 1/2" at 50 yards

.
My guess is not  everyday or even most of the time.

Most weeks i send 300 or so pellets down range.  If I used these to  shot 60 ea. 5 shot groups at 50 yrds.  I could hand pick a few that are 1/2" or smaller at 50 yrds.  however most would be more like  1 to 2"   I have many  20 yrd. prone  5 shot groups that are 3/8" or less  and  even some that are under .200" a few that are 10 to 20 shots that are a ragged hole smaller than a nickle..       


Do the 3 screw trigger mod, replace trigger spring with one from a ball point pen   tweak the shear / safety spring  about 5 degrees and lightly polish bearing / wear trigger surfaces.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                Trigger mod screws functions explained     

http://www.gatewaytoairguns.org/GTA/index.php?topic=64062.msg612614#msg612614               

My cut hammer spring results on another forum

http://castboolits.gunloads.com/showthread.php?281874-Benjiamin-Discovery-Chrono-results-with-H-amp-N-Baracuda-Hunter-Extreme-9-26-gr-pellets&p=3316152&viewfull=1#post3316152                                                                                                                                                                                                                                           
Snip:

Results

Stock Hammer Spring

For first 10 shots

930 FPS Avg / 24 Es / 7 Sd

Cut Hammer Spring
First 10 -Avg 933 FPS


First 15

Avg 928
ES 26
SD 8

AVG FPE 18.3