1377 Tactical Carbine

[pump-n-dump]

My 1377 Tactical carbine is coming along well. I just zeroed in the scope at 30 yards and put a dozen shots through it. Without a bench, I got constant groups of approximately 3/4". I don't have a chrony so I don't know the power output yet. However, I have a challenge.  I'm retaining air at 16+ pumps and want to be able to fully dump at least 20. I know a Discovery hammer spring will be stronger for a longer valve duration and I think it would solve this issue but I want to know if that will introduce failure risk to the cocking pin, bolt handle, and valve exhaust stem? Any recommendations will be most welcome. 

Here's what I've done to it.

Valve work: I flat topped it and feeding it is a AGS brass piston (very nice piece). Increased volume by removing material from the rear half, tapered the exhaust valve head and stem, removed two threads off the front half, swapped in a lighter spring with smaller gauge wire, angled the exhaust port and matched it to the transfer port opening. Transfer port has been opened up a little and I'm using a cigarette lighter oring on top of it to the barrel.

Hammer assembly: Polished the hammer, power adjuster in the Tippmann 98 stock adapter for the hammer spring (fully engaged before the bind prevents cocking).

Other do-dads. Solid arm pin with clips, steel breech, 24" .177 barrel, 6.5" TKO brake (.22cal), reground and polished the trigger sear, replaced the sear spring setup with lighter one and cleaned up the crown and polished the leade too. Whew!

On another note, I don't plan to keep the brake installed all times - especially when transporting it. So, I found a great deal on a simple cigar tube that is adjustable length. It was $3 with free shipping so I couldn't refuse.   I put some foam padding in both ends and store the hex screwdriver in the brake. Viola! Here's the link if anyone's interested in one.
http://www.ebay.com/itm/151188459952?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[breakfastchef]

Another option is to try a lighter valve spring to dump the air in the valve. A sear spring can be used.

An time you start pushing a system to it's limits (and beyond), you do run a risk of component failure. Hitting the valve stem hard, stresses caused by over pumping, increased friction in the trigger group from heavy hammer springs, etc. are examples of things that may cause premature failures.

[vertguy]

Nice setup!

I like the cigar tube idea for protecting the TKO

[bgmcgee]

Nice shooter you got there.    I also like the cigar tube/ tko holder. You can also try adding some pre-load to your hammer spring that might help without using the heavier disco spring.

[targettgii]

That's a great idea for the tko.Nice looking build also.

[quickster47 †]

Love    those long 24" barrels.  Great build so far. 

Carl

[pump-n-dump]

Another option is to try a lighter valve spring to dump the air in the valve. A sear spring can be used.

An time you start pushing a system to it's limits (and beyond), you do run a risk of component failure. Hitting the valve stem hard, stresses caused by over pumping, increased friction in the trigger group from heavy hammer springs, etc. are examples of things that may cause premature failures.

Thanks Chef. I actually do have a light spring in the valve already. Lighter than the stock sear spring. In fact, pre-cocking is a must even if the power adjuster is backed all the way out. Another thought is to use a spring guide at the hammer end. Not only is it helpful with the coil stack but I think a little more mass might help out and it could add a little more preload, as suggested by Salidashooter, before I put in a stronger spring.

[pump-n-dump]

I'm glad to hear some of you like the build! 

[KevinP]

Nice looking  ... 

[DBOdude]

good lookin gun 
you can try stretching the hammer spring to increase it's pre-load ....

[pump-n-dump]

good lookin gun 
you can try stretching the hammer spring to increase it's pre-load ....

Thanks. That's certainly the fastest and least expensive option. Do you think that a new 'set' would keep? I wouldn't want to weaken the spring's long term integrity for a short term gain.

[pump-n-dump]

For those of you looking for a cheap and effective grip enhancement, I went to a large locally owned sporting goods store to shop for a slip-on grip that would fit the 13xx frame. They were glad to let me try them on as I'd brought my Phase II frame with me for just that possibility (it's actually going on the Phase III carbine shown earlier). After several models, I found one that worked out quite well for my preferences. It's a Pachmayr part no. 05162 that's made for a CZ 75/78 pistol. It not only fits snug all over, it provides good grip and finger choils. Here's a picture of it alone and I'll post one of it on the carbine later this evening.

[BigErn]

Looking real good pump! Thanks for the ideas for the TKO and the grip frame 

[Takis63]

That's a really nice rig you got there 

[DBOdude]

Thanks. That's certainly the fastest and least expensive option. Do you think that a new 'set' would keep? I wouldn't want to weaken the spring's long term integrity for a short term gain.

here's a thread where i asked about springs ....

http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,13368.msg175544.html#msg175544

mixed responses , but springs are so cheap and easy to find locally if i hurt one i can easily replace it so i stretched my hammer spring a week or so ago with no problems so far . when i get bored i'll replace the valve spring in my AC Customs valve with the compressed spring from my old stock valve . i'm not currently retaining air with 20 pumps , but i want to see if it makes pumping easier ...... not that it's difficult now .

i'm not lazy , i'm energy efficient