Guess the inaccuracy issue BSA Mercury

[Hsing-ee]

Got a nearly new BSA Mercury Mk IV .177 and it groups like 1" at 10 yards with RWS Superdomes. The breech bolt is tensioned correctly.
The trigger isn't great, but really this is springer pistol-level accuracy.

Before I do stuff to it, do you think it is

a. A dirty barrel.
b. A dislike of RWS Superdomes.
c. A scope issue.
d. A barrel crown issue.
e. Poor technique by me.

[maximus]

Is it still on the original spring? The 177 i had was great with falcon accuracy plus. I have been shooting my 22 merc s a lot recently and found it better when I swapped the spring from a cut down titan no.1. You have to be spot on with your technique with these rifles, mainly due to the trigger.

[Zomboid]

Is the barrel drooping? If so the barrel pivot bolt/pin is worn out. This will cause issues with the breach seal.

[evert]

How could I guess?
I dont know if you are a lousy shot or not

[HW777]

How could I guess?
I dont know if you are a lousy shot or not

I would have said, it's all those frilly knicker off cuts made into head bonnets clouding the vision, but what do I know ?

[trajectory]

'nearly new'& assuming the buffer washer hasn't swollen to give zilch or varriable velocity it could be any of the reasons you have offered. It might even be something else........loose sights, mish mash of pellets in the same tin, loose action in the stock, who knows but it will be nice to hear the cause. Mercs arent that bad! Actually I think they are pretty good.

Ps did you get around to the '65 or did I miss your post?

Best of luck.

[Phil Russell]

Suspects:

Dirty barrel? Doubt it. It would have to be extreme to cause this and I have never known it to be that bad.
Superdomes? Maybe but doubted. Try another pellet.
Scope? Possible but doubt it as it would have to be utter failure.
Barrel crown? Maybe but again an extreme case. Try another pellet brand.
Technique? quite possible ... let someone else shoot it to make sure.

I doubt it is fluctuating velocity but worth a check with a chrono.

My guess and to check: stock bolts / screws to ensure they are tight and nothing has broken that can cause the action to move randomly in the stock.

Daft guess 2: Is it really a .22 and you are using .177 pellets (or even .20/)

Cheers, Phil

[zephyr]

Let's think.

The target is moving in the wind
You're pushing the pellets into the lead by varying amounts
The coriolis is strong
Mirage effect
Moles are moving the bench
Sun on one side of the barrel is warping it - hmmm, Scotland, more likely snow than sun
Firing at different points in the heartbeat
Still hungover
Shooting left-handed (if you're right-handed)
Using your blind eye
Shooting through a swarm of midges
Ground shaking due to Ukraine war
Bad haircut day
Engaged in repetitive reciprocating movements while shooting
Somebody else was also shooting the card
Shivering in the cold
Hadn't taken drugs that day
Had participated in drugs night before
Scope on back to front
Your ranging is sh*te, you are really shooting a 100yds
You don't have a problem, your just getting your post count up
Flies landing on your barrel
Shakes due to low glucose levels
You're putting some pellets in backwards

Am I right?

[bill57]

Capture and examine some fired pellets. I had a Webley Airwolf (Original Model 24) which spat pellets all over the place. Turned out it was the front sight dovetail, which is pressed in, not machined, and it had damaged the bore when done. Dirty great marks all over the pellets. I know the Mercury front sight is not done in this way, but it's worth a look.

[look no hands]

Is it because its a BSA and not a HW.

Pete

[Clanchief]

Have you tried it with open sights ? If still crap then the inside needs a look, it may be new but never opened and it’s all rotten inside.

My Airsporter I’ve had for 44 years never liked a scope much and the accuracy went down when the insides needed a lube or new spring.

Since your in Glasgow you likely have an Ox inside it 😁

[TonyL]

Is it because its a BSA and not a HW.

Pete

You're getting the idea, Pete.

[TonyL]

Alistair, it could be any of the reasons (or combinations thereof) as cited by the collective above. As well you will be aware.

Nearly new? I guess you mean hardly used? A service may well help and I'd be taking a look at the buffer. Guessing you'll have fitted a new breech seal?

[RobF]

.20 pellets?

[Captain Bongo]

It's a trick question. There is no inaccuracy issue. 1 inch at 10 yards is pretty good for a Mercury.