Which is more accurate, fixed barrel underlever or break barrel ?

[Shed tuner]

Well, you can probably guess that this is a loaded question...

The most accurate springer I have, bar none, is a break barrel (Pro Elite) - admittedly with a lot of tuing, but then I'm only comparing it with other highly tuned springers. The 80 I have is also excellent - on a par with the TXs.

I also noticed something interesting when rebarreling a TX.. the tension in the lock up ball bearing catch does have an affect on POI - around 1-2" at 30 yards.

So where I'm headed is that maybe non-tensioned lock ups (e.g. a sliding catch, not a ball bearing, like on the early 77) might be more accurate on underlevers ? It's hard to say how much variance there may be with the ball bearing, but if it gradually rotates, has gouges in it, isn't perfectly spherical, or the spring behind it moves a bit, maybe it could be pushing the barrel a little out as with my "manual introduced error" ? Might try magnetic retention - it's certainly cheap and easy

I'm also wondering if a full free floating barrel (i.e. with no underlever loosely connected to it) - so either a sidelever, or a concealed underlever, or a break barrel - might be more consistent in terms of harmoics / vibrations ?

Sounds like a project for Jim.....

[bozzer]

... I'm also wondering if a full free floating barrel (i.e. with no underlever loosely connected to it) - so either a sidelever, or a concealed underlever, or a break barrel - might be more consistent in terms of harmoics / vibrations ?

Sounds like a project for Jim.....

Jon

This is something that RobF touched on when talking about the dreaded HW77/97 poi shift.

He had a theory that the tighter the linkage between the underlever and the main action/barrel the greater the possibility that the underlever could interfere with the barrel and pellet release.

[secretagentmole]

Well, you can probably guess that this is a loaded question...

The most accurate springer I have, bar none, is a break barrel (Pro Elite) - admittedly with a lot of tuing, but then I'm only comparing it with other highly tuned springers. The 80 I have is also excellent - on a par with the TXs.

I also noticed something interesting when rebarreling a TX.. the tension in the lock up ball bearing catch does have an affect on POI - around 1-2" at 30 yards.

So where I'm headed is that maybe non-tensioned lock ups (e.g. a sliding catch, not a ball bearing, like on the early 77) might be more accurate on underlevers ? It's hard to say how much variance there may be with the ball bearing, but if it gradually rotates, has gouges in it, isn't perfectly spherical, or the spring behind it moves a bit, maybe it could be pushing the barrel a little out as with my "manual introduced error" ? Might try magnetic retention - it's certainly cheap and easy

I'm also wondering if a full free floating barrel (i.e. with no underlever loosely connected to it) - so either a sidelever, or a concealed underlever, or a break barrel - might be more consistent in terms of harmoics / vibrations ?

Sounds like a project for Jim.....

What you mean like an Air Arms Prosport or BSA Airsporter? They already exist so testing should be easy!

[hmangphilly]

Jon

This is something that RobF touched on when talking about the dreaded HW77/97 poi shift.

He had a theory that the tighter the linkage between the underlever and the main action/barrel the greater the possibility that the underlever could interfere with the barrel and pellet release.

this is about to re-emerge ( is that a real word ? )
springers are back on the agenda .

over centre / eccentric pivot pin is one line of thought .
Can't see any good reason for attaching a cocking lever to an otherwise perfectly good ,floating barrel.

[secretagentmole]

this is about to re-emerge ( is that a real word ? )
springers are back on the agenda .

over centre / eccentric pivot pin is one line of thought .
Can't see any good reason for attaching a cocking lever to an otherwise perfectly good ,floating barrel.

It makes a lever long enough to make cocking relatively easy? The Prosport and Airsporter could be right sods to cock. Especially the box like arm on the Prosport...

[charlie1]

Same, most accurate hw from box 99s.

[Rob Edge]

I have just bought a 97KT Blackline which is my first proper springer in about 10 years. It's super accurate out of the box so I will leave it alone. The best advice I was given was not to over think the shooting side of it. Anything relying on a spring to provide motion to a piston which in turn propels the pellet along the barrel is prone to the odd flyer but that is 99.9% going to be the fault of the person pulling the trigger and nothing to do with the gun.

[PCPShooter]

Never found any difference, the main thing I used to find is that most underlevers were a tad too heavy for me so I shot less well with them, which negated the fixed barrel idea.

That said I just bought an older 77k in 22, because I've missed mine since I sold it, open of the only ones I've ever missed (a 177 k)
That said, jot was never 'quite' as accurate as my Diana side lever !! Which a lot of people don't believe, or don't want to believe .......

[Shed tuner]

What you mean like an Air Arms Prosport or BSA Airsporter? They already exist so testing should be easy!

For a true test, one needs the same gun, and then to make the only change from one of "tensioned" underlever coupling to the barrel, vs non-tensioned (or completely decoupled)...

(although as an aside, I bought an airsporter cocking lever, linkage and cocking slide for £20 off the bay, and am seriously thinking of converting one of my TXs - it will be the gun that the Pro Sport should have been )

[TonyL]

Yet another interesting thread, young JB.

Going back many years, the fixed barrel was seen to be a definite advantage, due to sloppy breech lock up designs. However, in more recent times, many breech lock-ups were solidly engineered so this became a non-issue (take note, BSA). Although many plunger type designs have proven to be solid, reliable and durable, I still like the extra reassurance of manual barrel latches, like those on the HW35, 55, modern LGVs and others. So, a solid breech lock-up and free-floating barrel. The free-floating barrel being championed by many PCP designs, too.

It'll be very interesting to see how any of your experiments progress with the underlever retention not having an effect on "barrel harmonics". One other area that can often be seen as an advantage of under-barrel levers is to aid the weight distribution, so maybe keeping the lever under the barrel, but altering the retainer so that it doesn't influence the barrel, as you suggest, may be very fruitful.

Many examples of all the various designs have proven to be very accurate over many years of testing on the anvil of the hunting, FT, HFT and non-formal target, so there might not be much to be gained by this, and maybe we should all just shoot more (especially me, and improve my shooting), but I find so much of the theory stuff very interesting.

[RobF]

Yeh I can throw a tx or 97 out with inconsistent lockup.

Looking at a non captive lock up device soon.

But as far as groups go my 97 has done sub 3mm ctc 5 shot groups at 25m indoors several times. In terms of keeping that group in the same place then we've found a few issues and sad to say scopes can play a part.

[bmp01]

Well, you can probably guess that this is a loaded question...

The most accurate springer I have, bar none, is a break barrel (Pro Elite) - admittedly with a lot of tuing, but then I'm only comparing it with other highly tuned springers. The 80 I have is also excellent - on a par with the TXs.

I also noticed something interesting when rebarreling a TX.. the tension in the lock up ball bearing catch does have an affect on POI - around 1-2" at 30 yards.

So where I'm headed is that maybe non-tensioned lock ups (e.g. a sliding catch, not a ball bearing, like on the early 77) might be more accurate on underlevers ? It's hard to say how much variance there may be with the ball bearing, but if it gradually rotates, has gouges in it, isn't perfectly spherical, or the spring behind it moves a bit, maybe it could be pushing the barrel a little out as with my "manual introduced error" ? Might try magnetic retention - it's certainly cheap and easy

I'm also wondering if a full free floating barrel (i.e. with no underlever loosely connected to it) - so either a sidelever, or a concealed underlever, or a break barrel - might be more consistent in terms of harmoics / vibrations ?

Sounds like a project for Jim.....

Do you have a 'rough and ready' feel for the amount of change in spring tension to give the 1 - 2" POI change? Are you thinking whole mm's or .....?

BMP01

[Shed tuner]

Do you have a 'rough and ready' feel for the amount of change in spring tension to give the 1 - 2" POI change? Are you thinking whole mm's or .....?

BMP01

So obviously it depends on the stiffness of the spring, but with the std TX ball bearing unit, an increase in compression of about 0.7mm moved poi up by just over 1.25" at 28 yards

[Shed tuner]

Yeh I can throw a tx or 97 out with inconsistent lockup.

Looking at a non captive lock up device soon.

But as far as groups go my 97 has done sub 3mm ctc 5 shot groups at 25m indoors several times. In terms of keeping that group in the same place then we've found a few issues and sad to say scopes can play a part.

Thanks Rob, could to get your confirmation too...

Also, it really must be noted that we are talking very accurate springers here... the PE does around 2.5mm c-c at 20 yards (5 shots), indoors... I think that unless you have a very well tuned, stroke optimised springer, lockup probably isn't your biggest worry - but it's all part of the picture for ulimate accuracy.

[bmp01]

So obviously it depends on the stiffness of the spring, but with the std TX ball bearing unit, an increase in compression of about 0.7mm moved poi up by just over 1.25" at 28 yards

Blimey ! That does deserve some investigation then ! And as stated above the lockup can have a significant load input into the underlever ....now I come to think about it. ....I remember someone experimenting with solid lockup on a TX and remarking that the accuracy went to sh**.
Good luck with experimenting !

BMP01