Is it possible to be this far off with a different pellet?

Hi I am new to this forum and I am not sure if this the right spot to post this question. But here goes. I have a Umarex Surge XT .177 cal air rifle. I have been using Gamo Rocket 9.6 grain pellets that I bought when I bought the Rifle. The rifle has a cheap scope but after sighting it in the rifle was fairly accurate up to 40-50'. I bought some H&N Barracuda hollow point pellets based on the great reviews and to try something different. The first shot was 4" low and 6" to the right at 35'! I thought I must have flinched so I shot again this time 5 shots. Not a very tight group and all low and way right. I figured I must have bumped my scope and tried sighting it in. I was able to bring the group up and left a little but no matter how much I adjusted (I kept track) it would not move over and up to the target. I reset the scope and for the heck of it ran a Gamo Rocket through it and was 1/2" high and right of the bullseye! I was amazed to say the least. I ran a H&N through it again and bam approx 4" low and 6" to the right and a sloppy pattern. I am new to air rifles and I have read that you have to find the right ammo for a particular rifle, but, is it possible to be that far off?? Do pellets differ that much? Does it have anything to do with the silencer? I am anxious for feedback on this one.
 
Yes it is possible. Sight in at about 25 yards for a springer. But every pellet will be a bit different. Some extremely different. Only use ones that group well even if it is not on your crosshairs. You can adjust your crosshairs but not the accuracy of the pellet. If it does not group well dont use it and try another. Dont get crazy with special pellets either. Just use a good round nose pellet that is accurate and stick with it. I would try crosman premiers and jsb pellets. If they dont work keep trying others one at a time til one is working. The gimmicky pellets dont do much in springers. Trust me I spent a lot of money trying. Good luck and dont give up. Springers are tough to master. Find the right pellet and stick with it.
Its not the silencer. Every pellet is a different weight and shape making it travel differently at pellet gun speeds. 
 
Amazing how different 2 or 3 pellets can be, even from the same manufacturer. Here's my FX WIldcat .177 at 25 yards (bucket and sticks)

On right - JSB 10.34 - on left - Crosman "Premier" Piranha 10.5's. The "Premier" group is OVER 2.5"
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Then I handed my son the gun with some 10.5 Crosman "Premier" in the brown box. These shoot almost as good as the JSB.
A fly landed on the target. Now mind you my son rarely shoots my guns. Last time was Easter. Hit was "dead" center.
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Wow quite a difference! Check this one out. I apologize for the crude target. The oval shaped group on the right was with the H&N's and I was aiming at the middle target! Then I switched back to the Gamos and aiming at the center target again I got the group in the center target. Not great but they were in the target at least. The target on the left was with the Gamos and with the rifle supported and steady. The distance the H&N's were off is amazing. Lesson learned for me.
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Yep....very possible! Here are a few groups shot at only 18 yards from my .177 R9 with a cheap Daisy assortment from the plastic rotary container. Notice that the center of the "pointed pellet group" was about 1 1/2" to the right of the "wadcutter group" (aim point marked with arrows). LOL.....all the groups were very poor when the Daisys were shot from my R9...........
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Now here is another target I shot at 50 yards when checking the accuracy of a few different brands of pellets from my .177 R9 (aim points marked with "+". LOL....notice the CPL group in the upper left corner.......
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While "good pellets" were much more consistent than "cheap Daisy pellets", the poi did shift depending on the brands, or even different variations of the same brand.
 
Perhaps, but it 'pends on the gun since I haven't found another pellet brand that has been MORE accurate than a good fitting die lot marked and dated boxed Crosman pellet from my R9. When I sold my brother a home tuned .177 Beeman R9 he shot 10.5 grain CPHs exclusively and shot these two 3 shot groups at one sitting from his bench...........
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He was new to airguns and shot "3 shot powder burner groups" back then, however I figured that two tight 3 shot groups at one sitting was at least as good as one 5 shot airgun group. ;)
 
Every gun can be different. Most of mine do best with Crosman Premier Lite 7.9 from the box or JSB 8.44. None of them group in the same spot except 1 HW97k that shoots the CPL and Air Arms 8.44/4.52. Today after doing a tune to this rifle I was getting same POI with these 2 pellets but accidentally grabbed some JSB 8.4. They did not even hit the target. Other guns, JSB is supreme. 
I hate to use many different pellets because I forget which one likes what. I tried getting them to like the same one but found that did not work at all.
Also keep in mind that different pellets have different lead/alloy composition. After cleaning the barrel and/or changing pellets it may take several shots to lead the barrel for consistent results. Some folks say the barrel should be cleaned before changing pellets but I got tired of that pretty fast. Some say they never clean the barrel and their guns are dead nuts accurate. That is very possible. Myself, I resorted to just pulling 3-4 dry patches through when accuracy starts to drop off.