Why such a sudden change in POI?

[RickH]

Evening everyone,

I ran into a problem with my Beeman AR2078A a few months ago. I use this rifle exclusively for shooting CMP matches, bought just for that reason. It’s been a good accurate rifle especially if I’m shooting well. I went to a match in October if I recall and had crappy day. I had shot a few 1” groups in practice but at the match it opened up to about 4”. I wrote it off to a bad day. The next month I didn’t practice much but it was worse. In addition to large groups I only barely got 50 shots instead of the usual 65 or so. Being CO2 powered I made sure the rifle stayed in a warm controlled environment. I didn’t shoot it again until today. I ran some cleaning patches through the barrel to make sure it was clean, loaded up 2 12mg CO2 cartridges and started shooting. Temperature was about 70. The group sizes got much better but everything was about an inch left and 2 high. It stayed consistent and delivered 70 rounds. Could cleaning the barrel have made this change? I can rule out temperature variations as weather was shirtsleeve warm which is normal when I shoot this rifle. Same pellets as always. Could something else be going on? The learning curve is still pretty steep for me but I’m getting it figured out. Thanks.

Rick H.

 

[Berserkeley Mike]

Does the rifle have a moderator or anything else non-stock that pellets may clip or that may move around?
Are your optics locked down tight? Maybe something was loose during the 4" group that snugged up again today a bit in a slightly different spot?

 

[marflow 777]

the simple answer for the accuracy is yes
a lot of people ask the question when should i clean the barrel and the normal answer is when the poi changes
the hammer hitting the valve meters the CO2 so that outcome is an unknown
people that use Crosman pellets will clean their barrels more often on the norm
might be a preparation change, clean the barrel reseason it and then compete

 

[Long_Gun_Dallas]

If fouling is an issue, consider doing a bore polish and treating it with something like gunzilla after cleaning. Gunzilla alone can easily triple the shot count of my powder or air guns before cleaning is needed. Bore polishing can increase the useable shot count between cleanings further. Carnauba wax is another good treatment, but I would pick one or the other. I have also seen a number of members get some extremely positive results applying lemon pledge to their pellets as well. Though I have never tried that myself. Cleaning a barrel absolutely can and often will change POI, and often it will return to normal after a number of shots thru it.

 

[Treefrog]

Long Gun Dallas offers an excellent idea about the bore polishing. That usually improves the accuracy of these guns. The bores are somewhat rough from the factory. A good polish with Brasso is one of the first things I do with a new QB bore.

Something you might also look at is the barrel band. I've had the kind of shifts that you're experiencing and it was from the gun being bumped into by one of the dogs. Loosening the band, re-centering the barrel and then re-tightening the band cured it. I eventually removed the barrel band and placed a shim between it and the tube. That cured the problem and also improved accuracy a small amount. 0.21" groups at ten yards with .22 CPHPs are now the norm.

The barrels on these guns are only secured by the barrel band, the allen-head grub-screw on the receiver and the o-rings around it in the receiver. Drilling and tapping holes for a couple more in the sides of the receiver would reinforce things some. I plan to do that on mine soon.

Cheers,

J~

 

[RickH]

When I bought this gun it was new but the barrel had been polished and the trigger smoothed. Otherwise absolutely stock. Sights were locked in place, I checked all the accessible screws after the first time and found no issues. it has about 400 shots through it so maybe it was just due for a cleaning. I will try some of the suggested products though, I appreciate the advice. Thanks.

Rick H.