Can a break barrel ever be as efficient as a sliding breech springer

[Barryg]

sure it can


HW80


I edited your post to focus the question.

The HW80 TP is a mystery to me I can understand why the short sliding breech TP is so efficient but the 80 is just a straight offset tube, but you are right it is efficient
Are you sure it is as efficient as your 52?

[TonyL]

I started a similar thread a few days ago.
My main question was would a cheaper, more flimsily built break barrel result in a shorter transfer port, inadvertently making it more efficient, whereas some of the more chunkily and solidly engineered rifles have a longer TP, owing to their robust build philosophy?

How short (in other words how thin could the cylinder end wall be) could we have the TP and still retain strength and reliability? Some of the answers that were coming back did indicate that quite a few break barrels do indeed have quite short TPs.

I suppose that, as long as the internals are properly set up and balanced and we're not getting piston slam, this shouldn't be an issue?

[Lol Moore]

I started a similar thread a few days ago.
My main question was would a cheaper, more flimsily built break barrel result in a shorter transfer port, inadvertently making it more efficient, whereas some of the more chunkily and solidly engineered rifles have a longer TP, owing to their robust build philosophy?

How short (in other words how thin could the cylinder end wall be) could we have the TP and still retain strength and reliability? Some of the answers that were coming back did indicate that quite a few break barrels do indeed have quite short TPs.

I suppose that, as long as the internals are properly set up and balanced and we're not getting piston slam, this shouldn't be an issue?

I am new to this "problem" so bear with me, I deal with fluid dynamics but not in guns!

The relationship between any hole and the passage of fluid through it is complicated and the length Vs diameter relationship is critical, the longer a hole is the more resistance there is due to frictional forces at the edges, in effect a hole with a very small length will give much less resistance to the flow through it than a hole which is of the same diameter but longer

Also the condition (turbulence) of the fluid at the inlet and outlet will be very different for different length holes

I know none of this helps answering what is the best port but helps to understand

As i think you intimated Tony what about a gun with no transfer port, i.e. the barrel face is pushed back into the cylinder (with an outer seal) with the pellet already in the barrel, to stop piston slam what about some smaller diameter "probe" on the piston end that enters the barrel as the piston nears the end of its travel thus blocking the barrel and creating a buffer of trapped air?

[brian747]

As an aside i took my sfs tuned hw95 ex -Helaquin/Paul .22 and my recently new LGV Challenger .22
for an side by side plink yesterday morning, and i have come to the conclusion the sfs tuned hw95
is smoother , has a better trigger and out of the two is a better gun, i shall put more pellets though the
LGV before its future is considered!!!!!
atb brian

[bigtoe01]

The HW80 TP is a mystery to me I can understand why the short sliding breech TP is so efficient but the 80 is just a straight offset tube, but you are right it is efficient
Are you sure it is as efficient as your 52?

consider..I tuned the AGT80 .22 and the 25mm 0.22 D52 to produce the same power output...the weird thing is both needed the same swept volume to attain the same shot cycle feel. Then I measured the transfer port length on the D52, coupled with the breech seal its around 8mm, not really that different to that of the HW80.

[Barryg]

consider..I tuned the AGT80 .22 and the 25mm 0.22 D52 to produce the same power output...the weird thing is both needed the same swept volume to attain the same shot cycle feel. Then I measured the transfer port length on the D52, coupled with the breech seal its around 8mm, not really that different to that of the HW80.

What do you make the size of the seal? I make it 3mm in this pic
http://i1213.photobucket.com/albums/...psbffbdf26.jpg
What is the length of the 52 TP and the 80 TP? also there is a 8 thou gap between the breech face and the cylinder on the 80 not much I know but all interesting stuff, its also interesting about the swept volume you mention

[bigtoe01]

The one i have here is 3mm depth....the port is 5mm so 8mm total, closer to the 7mm of the 77 than the 80 really as the 80 is 11mm or so.

Its pretty obvious that a TP around 10mm or less is what we need, the 80's is still pretty damn efficient, i feel its starting to be pushed on the 95/98 at 15mm.

Barry...you really need to shoot a 25mm sleeved down 52 in .22 with 70mm stroke...way way different to a normal 52. Im doing a 75mm stroke .177 next
Also you need the full fac spring in the sleeved down guns to get the power, consider if I removed the sleeve, reinstalled the 28mm piston I would be pushing 24fpe thru this D52.

105mm stroke 28mm piston is around 65CC
70mm stroke 25mm piston is 34CC

The D52 has near double the amount of swept volume needed to make 11fpe in .22 in standard trim, this should tell you how lazy the spring needs to be with the 28mm piston....not good

[Amac]

I always thought that the sliding breech design was conceived to remove the likelihood of poor barrel lock up and therefore miss alignment issues. For my own average skills however, I have never noticed any difference in accuracy between say a well fettled 77 or an 80. Both are equally as capable, and with the solid engineering skills and design of the originators ( and further modifications of various tuning houses) in my own hands its all about the internal dimensions of the piston/stroke rather than how the barrel/cocking happens to occur. The new Walthers guts appears to resemble the internal dimensions of my own 80 Lazahunter that was made in 2004. Very coincidental?

Andy

[bigtoe01]

The walther has an FAC stroke length and an inefficient transfer port. If you could alter the transfer port length on the walther to 6 to 8mm with the same spring/stroke/preload the gun would be doing 16fpe I bet.

One way of improving the Walther may be to alter the barrel so the barrel tube stocks thru into the breech face. Bore down into the breech face leaving around 6mm or so of breech face for the transfer port.