Barrel length for spring rifles.

[Rapidnick]

I am interested in members' views on this topic. Also whether or not choking is necessary or desirable and whether the optimum barrel length will vary with calibre.. Please note my question relates only to legal limit springers not pcps or FAC rifles.

[Bruno27]

Hi
I have an on going project based on a .177 Diana 36. I have cut the barrel down to 12" loosing the choke in the process.
Shooting at 10.8 ftlbs, it is now very loud and has lost some accuracy.
Next steps: sleeve the transfer port down to Ø3mm and fit a Konceptus kit.

[Benelli B76]

There is an article somewhere showing John Bowkett cutting small sections off a Weihrauch barrel and recording results. I think it ended up somewhere around 12 inches with the same power after he had added some piston weight. The critical point comes when there is not enough leverage to cock easily.

Baz

[the growler]

Sure my venom hw80 has a 12" barrel. With the silencer on its easy to cock and very quiet. So id say 12" is about the minimum to go to.

[Phil Russell]

Hi
I have an on going project based on a .177 Diana 36. I have cut the barrel down to 12" loosing the choke in the process.
Shooting at 10.8 ftlbs, it is now very loud and has lost some accuracy.
Next steps: sleeve the transfer port down to Ø3mm and fit a Konceptus kit.

Two questions if I may:
What was the power before the cut?
Have you recrowned the muzzle to try and eliminate that as the cause on any inaccuracy?
OK ... 3 questions: How do you define 'lost some accuracy'?

Cheers, Phil

[thevoid]

I'm fortunate enough to have two 25mm HW50s. One had the barrel chopped to 12 inches from breech to muzzle and the other barrel is the unmolested.
The shorter one makes exact same power than the standard but its far, far easier to shoot and not as pellet fussy either in terms of pellet and head size, I think what is as work for me is short barrel, fast lock time and a short stroke make for a superb combination

[Bruno27]

What was the power before the cut?

Unfortunately, I didn't have a Chrono before the chop.

Have you recrowned the muzzle to try and eliminate that as the cause on any inaccuracy?

Yes, but done with a spherical head brass screw and grinding paste.

OK ... 3 questions: How do you define 'lost some accuracy'?

I am no experienced shooter. I have found that once the barrel chopped, the rifle is even more hold sensitive. The firing cycle feels very harsh, more than before the chop, this is why I want to reduce the size of the transfer port. However, I need to work on my shooting technique, to understand better.

This mod was inspired by this

[Phil G]

Didn't one of Theoben's break barrel rifles have a 7 inch barrel? Bet that was a bitch to use

[Happy-Harry]

Didn't G Cardew run tests showing in springers pellets were being slowed down by friction against the barrel after the first couple of inches, and needed circa 8 inches for the rifling to give them enough spin for accuracy?

As others have noted however, for the best results, carbining needs to be done from the breech end to maintain choke and crowning, which isn't possible on all barrel types.

Steel silencers will give the extra leverage to make anything on these sort of lengths possible to cock.

[Rapidnick]

Didn't one of Theoben's break barrel rifles have a 7 inch barrel? Bet that was a bitch to use

Not at all Phil-the Fenman is OK to cock providing you can get a good grip on the moderator. It is also very accurate as the short lock time really added to the joy of shooting the little beauty. No sooner have you pulled the trigger than the pellet has GONE!!
Also bear in mind that the AA barrels fitted to the TX and Pro Sport I believe are only 7.5" Don't be fooled by the shroud!!

[transporter]

Didn't one of Theoben's break barrel rifles have a 7 inch barrel? Bet that was a bitch to use

In .22 they're quite good but .177 they're harsh but keep them at 11 FTP they're very good
Cheers Ray

[Fluffybuck]

I am interested in members' views on this topic. Also whether or not choking is necessary or desirable and whether the optimum barrel length will vary with calibre.. Please note my question relates only to legal limit springers not pcps or FAC rifles.

Choking: useful where mass-production might not have the quality and precision at the price people want to pay. Not necessary if the barrel is carefully manufactured (which would push up the cost).

Barrel length: yes, it matters and it varies according to powerplant (including the likes of long/short stroke variants as seen with the TX mk1/2/3), calibre, required muzzle energy and whether some of that is worth trading off against a shorter lock time or easier handling.
Optimum barrel length for a springer is much less than that required for a PCP.
Cardew's experiments and conclusions regarding barrel length were on 5-8ftlb guns; on 12ftlb guns the barrel needs to be considerably longer to make full use of the air blast.

Put the internals from a .177 TXHC into a .22 TXHC and the muzzle energy will go up. Put the .22 TXHC internals into a .177 TXHC and the muzzle energy will go down. Swap internal between the 13"-barreled TX200 and there isn't much difference in muzzle energy. Similar applies with Theoben rammers - the 10.5" versions can have a calibre change without need ram pressure changes but the 7.5" versions will need ram pressure adjustments if a different calibre barrel is fitted.
I have a 6.25"-barreled .25cal TXHC and it runs at the same energy now with its factory-standard internals as it did in its former life as a 9.25"-barrelled .177cal TXHC (this was estimated in advance). My 9.25"-barrelled .25cal TXHC goes far over the limit with the same internals that are running the 6.25" version at legal power (which are the same factory internals which run the .177cal TXHC).