Scope mounting on a magnum springer, and problems with flyers

[ron4231]

Hey All, 

While I'm an experienced firearm instructor, competitive shooter and armorer ofr I 'm pretty new to the forum and to air gun shooting. I recently acquired a Walther Parrus in .177. It isn't my dream gun, but it was what I could get my hands on that seemed like an economical place to start. The gun shot as well as i could shoot it with the factory sights, but my mature eyes require optics to get better accuracy. I mounted a Tasco Air scope on it with the supplied rings, and quickly learned what the term "barrel droop" means. I then installed an RWS Lockdown compensating mount in my favored "more forward" position that didn't allow me to use the stop pin. Tightening the mount as much as I dared did not stop it from moving rearward as I shot the magnum springer, so I re-located it where I could use the stop pin. The scope stays put now , but I don't care for the short eye-relief.

Any solution for mounting the scope that meets all 4 of the following criteria: 1) Low mount 2) further forward (more eye relief) 3) being able to use the required stop pin 4) droop compensation built in?

My second issue is that I'm getting a flyer or two out of every 10 shot string. I will literally shoot 3 or 4 shoots in the same hole, then get an unexplained flyer, always at 6 o'clock and about an inch low at 10-15 yards. the gun will go back to zero again, for a few shots and then I get another flyer. I knw this is an inexpensive scope, is it possible that the erector tube is moving out of zero every 4th or 5th shot and then returning to zero?

I bought the scope because I have one on my RWS 24, and it serves my purposes well on that gun, but the recoil of the Parrus may be just too much for it.

 

[bandg]

No experience with that Walther myself but my first thought would be possibly a little change in lockup position since the POI is noted as consistently low and near the same position but I guess scope shifting is not out of the question. Cleaning the breech area really well is free and easy enough to do before changing something else.

 

[nervoustrig]

x2 on the barrel lockup. That was also my thinking regarding the occasional low shots. 

It’s unlikely you would see such a dramatic shift in POI at such short range due to a velocity spread unless the breech seal or piston seal were damaged. So it wouldn’t be a bad idea to shoot over a chronograph to confirm the low shots have a similar velocity as the rest.

You are also right to consider the possibility of the erector tube shifting. If either turret has to be backed off quite a lot to zero it, the erector spring may not be holding much tension on it, increasing the odds of it shifting. As a practical matter, I will usually install a different scope temporarily to see if the problem stays or goes away.

 

[nervoustrig]

Regarding the mount, I think your best bet is a droop-compensating dovetail adapter
https://www.pyramydair.com/s/a/UTG_Drooper_Scope_Rail_11mm_to_Weaver_Adapter_Compensates_for_Droop_Stops_Scope_Shift/4191

and an offset scope mount on top. One that looks like this but which has a Weaver/Picatinny base
https://www.pyramydair.com/s/a/Leapers_Accushot_1_Pc_Bi_directional_Offset_Mount_w_1_Rings_High_11mm_Dovetail/2409

I didn’t spend much time searching but that may be the issue. All the ones on P.A. seemed to be for 11mm or 3/8” rails. 

 

[Odoyle]

The 177 Parrus will throw fliers unless you shoot at least 13.4gr JSB Monsters or heavier in 177.

The 22 not so much issues shooting light to mid weight pellets being heavier anyway in 22 and it's the 177 you have to shoot real heavy pellets.

 

[c_m_shooter]

I alsp think it is those light pellets. Shoot 10.5's out of it.

 

[ron4231]

Thanks all,

I have tried some 10 grain pellets but got better groups with the 7.4 gr ones with the exception of the fliers. I'll have to order some of the13.4 grain and try them. I do have another identical scope I can try on it and i will check the barrel lock up to see if there is anything going on there that could alter the POI.

 

[ron4231]

I think I figured out the problem with the low flyers on the Parrus. You guys who were talking about barrel lockup were correct, but not because of a dirty breech. Turns out that the two screws that secure the forearm of the stock to the action were impinging on the cocking linkage when it was nearly at full extension, and not allowing the barrel to close in a consistent fashion. If you look carefully at the picture you can see that the tabs that these two screws thread into were actually starting to bend forward a bit from the impact and pressure generated when closing the breech. I replaced to two M5 screws that were about 12mm long with a shorter ones that clear the clevis on the cocking linkage and shot the rifle, and while the vertical flyers were gone, and groups tightened up considerably the gun was now shooting about 10 MOA high. Apparently what I had written of as barrel droop was actually caused by the barrel not being fully closed. before the linkage collided with the stock screws. The "group" on the chicken represents what I was getting before the fix. After adjusting the scope for elevation I shot the group that you see on the pig. I shot both of these targets with Crossman Premier 7.4 gr pointed tip pellets.

Parrus owners may want to check these screw to see if they have a similar problem

 

[Odoyle]

Shocked you get good groups doing supersonic!

 

[egd]

At 10-15 yards I'd guess he is still supersonic when the pellet hits. Isn't it when the speed drops from super to sub and enters that "trans-sonic " area that you get all the wonkiness in accuracy?

 

[ron4231]

I'm kind of surprised that its groups better with the 7.4 pellets too. the 10 gain Crossmans shoot loose in this particular gun. Need to get some quality pellets that are heavier and give it a go 

 

[BeeGee11]

I'm kind of surprised that its groups better with the 7.4 pellets too. the 10 gain Crossmans shoot loose in this particular gun. Need to get some quality pellets that are heavier and give it a go

Mine don't touch, but they are very close. There is no reason that those screws need to be that long, I'll replace them to be on the safe side of future frustration.

 

[mcoulter]

Wow, great catch finding this!

 

[BeeGee11]

Wow, great catch finding this!

VERY good catch!

 

[bandg]

Yes, very nice work in locating the problem. Hope it shoots well now.