Rapid 7 Mk 1 - accuracy gone

[Waingro]

I have a .22 Rapid 7 Mk1 that, when I got it second-hand, could virtually hammer in nails it was that consistent. I fed it domed Crossman Accupells, which it seemed to like, from a genuine Theoben 7-shot mag. Time passed. Now, the accuracy seems to have deserted it in that it fires large groups, and the zero seems inconsistent. At first I thought it might my scope, so I swapped with the scope off my Rapid 7 FAC but the results were the same. I've swapped bottles to make sure it was getting full pressure, but that made no difference. I tried a pull-through to clean the bore, then shot some more to re-lead it, but still the same scatter. I have rebuilt it with new seals, etc and it now has the Delrin valve body as the gun was leaking, but isn't any longer

So. Stupid question. is there an obvious starting point with these guns that would explain a loss of their famed accuracy?

[Ca_Varminter]

Well Leading of the Bore(serious amount)...
It may need a good scrubbing with a cleaning rod and nylon brush.
Pull-throughs are good to minor amounts of fouling!

Also clipping your Mod..
Pull the mod off and see if this helps with the accuracy.

Other than that You may need to talk to the Doc...KevG

Stuart
 

[Waingro]

Thanks Stuart. I hadn't tried it with the moderator off as I never thought it could start clipping for no apparent reason.

I have a phosphor-bronze brush from my .22LR days as well as a plastic bristle, so I'll give the bore a good clean, take off the mod and try again.

I believe it takes a few shots after the bore is cleaned for it to settle and achieve maximum consistency again.

[Squinty]

mod clipping
worn magazine or tension.
loose stock

Checked over a chrono? Any odd velocities?-
Could be pellets, grease on the hammer, the probe and spring can cause otherwise untraceable issues that disappear upon replacement.

Worn bottle valve thread/ bottle mounted bi-pod- the bottle lifts and touches the barrel.

[Waingro]

mod clipping
worn magazine or tension.
loose stock

I'll check the clipping, but I don't understand why it would start out of the blue. The moderator is the Theoben original it came with.
I've tried several magazines
The stock is tight

Checked over a chrono? Any odd velocities?-
Could be pellets

To be honest, no. Just scatter on a target. And I'm feeding it the same pellets as always

, grease on the hammer, the probe and spring can cause otherwise untraceable issues that disappear upon replacement.

Interesting. But I don't see how they could become contaminated without the rifle being stripped

Worn bottle valve thread/ bottle mounted bi-pod- the bottle lifts and touches the barrel.

I've tried three bottles, including the large one off my FAC - no difference. I don't have anything attached to the bottle and the barrel floats free

I'm not trying to be negative and thanks for the list - you've certainly given me some things to think about

[DB.20]

Barrel transfer port aligned with block correctly, barrel not a bit loose in the block??

[angrybear]

I'd blame the pellets, old stock can Oxidize, if they do it's a bin job,
new pellets even the same brand from a different batch can be all over the shop.

Where did the new delrin valve come from ?
if it was ebay that's probably the answer, lot's of sub standard home made garbage sold by idiots, buy one from either Kev or Dr Bob.

[Waingro]

Barrel transfer port aligned with block correctly, barrel not a bit loose in the block??

Barrel's never been off during my ownership. Feels tight as ever

[Waingro]

I'd blame the pellets, old stock can Oxidize, if they do it's a bin job,
new pellets even the same brand from a different batch can be all over the shop.

That's something that never occurred to me - I thought pellets were immortal. I'd bought a batch of tins some years ago and I'm still using them. The FAC obviously uses a different, heavier pellet (Bisley Magnums) and that has kept its accuracy. New pellets for the sub-12ftlb is something to try, thanks

Where did the new delrin valve come from ?
if it was ebay that's probably the answer, lot's of sub standard home made garbage sold by idiots, buy one from either Kev or Dr Bob.

I can't remember but it was part of what I think was an official service kit. When I did the rebuild (to fix a leak) it was accurate and consistent once I put it back together  - it's lost it since then.

[Squinty]

So the only thing you have changed is the valve and a couple of o-rings.
it is possible I suppose that the valve body or stem is longer and it's bottoming out the exhaust spring.
As i recall the metal valve stems and acetyl valve stems weren't interchangeable.
Might be enough to cause some bounce that affects accuracy.

Or back to Premiers/Accupel
I've had issues with them in the past, up to 0.75gr difference in weight which on further inpection related to differneces in headsize.
This is 50yds FAC 980fps. Over half in one rough hole..14 shot mag

[Waingro]

Or back to Premiers/Accupel
I've had issues with them in the past, up to 0.75gr difference in weight which on further inpection related to differneces in headsize.
This is 50yds FAC 980fps. Over half in one rough hole..14 shot mag

Oh, that's interesting. And exactly the sort of scatter I'm seeing at a slightly shorter range, which makes me not want to use the gun for vermin for fear of wounding. The "rough hole" you have is approximately what the gun would previously produce