Pellets for .20 Theoben Gas Ram

[maximus]

Hi all, recently fitted a s/h .20 barrel to my Fenman. I have tried FTT and JSB so far. Struggling to get good groups with both, jsb doing the best so far. Barrel has had a recent re-blue and wondered if that could have a detrimental effect. Also both pellets are a really tight fit in barrel (I have checked it's not another .177!!!!!!!). Have ordered some Bisleys but think they could be similar to H&N. Are all barrels as tight as mine?? FTT wont quite seat flush but do not get damaged when barrel is closed. Advice please.

Thanks

Max

[Fluffybuck]

If it's not happy with FTT or Exacts, I'd start getting concerned.

The last worthwhile options would be Bisley Superfield or H&N Silhouette.

Being a Fenman, the short barrels can be troublesome to run above 11ftlb.
What power are you putting out?
I once bought a "non-grouping" Fenman - it was running right up to the 12ftlb limit and was grouping like a shotgun.
I dropped the power to 10.75ftlb and it was much better.

Additionally, the Fenman rather lacks the forend weight that would normally prevent muzzle flip and hold-sensitivity.
Try adding some weight around the silencer and see if groups tighten up.

It's also possible that the gun has - at some point - been run above 12ftlb. The Fenman is especially vulnerable to piston damage and subsequent loss of efficiency when run too high.

[Inspector 71]

I'm surprised the JSBs aren't doing the business. With all due respect, perhaps your technique may have faults? Try to get hold of Terry Doe's book about shooting / managing the Theoben Eliminator. I know the Elim' is a lot more powerful but it does have the gasram in common. Maybe some of the tips for shooting the "nuclear" Eliminator could have benefits for the sub-12 Fenman.

Just a thought.

NB

[maximus]

Thanks for that Fluff. I have owned the gun from new and have recently fitted a new piston seal. I found when I was pumping it up that I could only get just under 11 ft lbs in .177, any more ram pressure caused the piston to bottom ( I think) and velocities went lower. I have not altered ram pressure or chronod it since fitting .20 barrel as chrono is at my mates. It will I assume have gained some power but I would be surprised if it was over 12. The only other thing is that I had not shot it for a while before the week end but now has had I guess 300 or so through it. It is lighter at he front also because I have fitted a Weihrauch silencer in place of the theoben one which is still on .177 barrel. I could make a 1/2 unf adaptor to screw in the back of the Theoben silencer I suppose.

[Fluffybuck]

Ah!

Your gun is probably perilously close to the limit.

....add-in the extra-lightweight front end and I'll bet that's the problem.

I found the muzzle-weight-fitted HW95K was more accurate than the silencer-fitted HW95K - probably due to weight dampening of muzzle flip.

I also no longer have any Fenman or Evo carbine (but still have the longer-barreled guns). The reason being that the 7.5" barrel needs too much oomph, causes too much muzzle blast (which certainly does affect pellet trajectory) and lacks enough front-end weight to stop the gun jumping around when fired.

I agree that the balance of the Fenman is great. But it can't out-shoot the Evo.

[mattrob1502]

I have 3 Theobens

SLR98 in 177
Sirocco in .20
Evolution with standard barrell in .177

I use H&N FTTs in all 3 rifles and achieve good groups with these out to 40 yards

The H&Ns and Bisley Superfields are easy to load and fit nicely in the barrel

The Bisley Superfields get good groups but they open up a bit compared to the H&Ns when you get past 30 yards or so, but i think they hit harder (or they seem to)

Have you checked your rifle over a Chrono for ft lbs and shot to shot consistency? I think that would be worth checking as if it isnt grouping well with H&Ns then i would be a bit concerned as they are one of the pellet brands that Theoben themselves recommend in thier Gasrams

I had a Fenman in 22 and found the barrel tight on cocking, tight to place pellets and it also flipped a fair bit on firing sending my groups all over the place, may have been just my rifle at the time! i like gasrams but couldnt get on with my Fenman so in the end i sold it

As an aside, my Sirocco is the oldest rifle i own 1994 model but it cocks the easiest, isnt that pellet fussy is accurate and fires the nicest, but i think that maybe that the others are in 177 and apparently they are a bit harsher on the firing cycle than larger calibres

Good luck with it

[maximus]

Thanks all. I also have 3 rammers, .177 (now .20) Fenman, .22 Evo 10.5" and .177 SLR. I have found my EVO and Fenman to be pellet fussy. Get the right pellet though and they are superb. For the .177 on Fenman is was AA field, also for th .22 Evo. The SLR likes FTT best. I have just been looking at my last attemps from last night and it does produce excellent groups but there are a lot of fliers too. I mean landing 1 1/2" away from main group @ 30 yards! I will check the power soon and drop to about 11 ftlbs or so if it's above. Can't help feeling the tighnes of the pellets going in the bore could be having some affect though. Was going to have another go tonigh but it's spinttin!!!!