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 (http://www.ebay.com/itm/151188459952?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)
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.
Nice setup!
I like the cigar tube idea for protecting the TKO :-*
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.
That's a great idea for the tko.Nice looking build also. :-* :-* :-*
Love :-\ those long 24" barrels. Great build so far. :-* :-* :-*
Carl
Quote from: breakfastchef on February 04, 2014, 02:50:32 AM
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.
I'm glad to hear some of you like the build! :)
Nice looking ... :-*
good lookin gun :-*
you can try stretching the hammer spring to increase it's pre-load ....
Quote from: DBOdude on February 04, 2014, 06:06:26 AM
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.
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.
Looking real good pump! Thanks for the ideas for the TKO and the grip frame :-*
That's a really nice rig you got there :-*
Quote from: pump-n-dump on February 04, 2014, 04:13:18 PM
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 (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 ;)
Nice job on your build and nice shooting. I like the stock you used.
Mike
DBO,
Just use the Search function - "Ace" springs I posted a couple of posts on 'em, I think.
Thanks guys for the spring links!
Here's a couple views of that Pachmayr slip-on grip.
Nice looking shooter. The pump arm really makes the tactical look. Grip is cool too.
Lead into the back of the striker for preload an dwell time...?
Quote from: T191032 on February 04, 2014, 11:30:22 PM
DBO,
Just use the Search function - "Ace" springs I posted a couple of posts on 'em, I think.
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,2643.msg25166/topicseen.html#msg25166 (http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,2643.msg25166/topicseen.html#msg25166)
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,12376.msg160819/topicseen.html#msg160819 (http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,12376.msg160819/topicseen.html#msg160819)
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,1590.msg13256/topicseen.html#msg13256 (http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,1590.msg13256/topicseen.html#msg13256)
thanks :)
pump-n-dump that looks very nice and comfy :-*
I am using a 2100/2200 spring in my 1325 project and with a ~.125 valve I am able to dump 22 2100 pump tube pumps. About 1/3 more swept
volume, but still not flat topped... but it is moving a 20g pellet around 630fps... It is stronger than the 13xx spring but not as strong as the Disco
spring.
Quote from: pump-n-dump on February 05, 2014, 12:02:30 AM
Thanks guys for the spring links!
Here's a couple views of that Pachmayr slip-on grip.
I really like that, I'm gonna get one for my tac build too thanks :-*
Thanks everyone for the spring advice. I'm going to stretch the OEM one to start and see how that goes, I have a spare one just in case. I'll get a disco spring on the way just to have if needed.
On another note, I've been looking to add a bipod but with the pump arm mobility and the skinny barrel, there aren't any good off the shelf solutions. So this is what I'm going to try. I found a decent bipod that clamps on/off for simplicity and had a spacer made by Robert at Gravity Machine Works to fill the gap between the barrel and bipod mount. I had him make it a bit longer than needed, as I haven't received the bipod yet, and will trim it to fit. All said and done, it's only a $36 setup which I think is very reasonable. Once I get the pieces and install them, I'll post some pics. Robert can be reached at userrb8501@aol.com if anyone is looking for some machine work. I don't know what his limits are but he made my stock adapter and I've been happy with his work thus far. Pus he's very quick. I sent him a sketch with dimensions one afternoon and the next day he had it made. I know it's a simple part but I still appreciate that kind of turn around.
i tried using folded and stacked towels to support the front of the barrel on my DBO 2289 on my "shooting table" (i have a 24 inch barrel) and at 15ish yards the POI jumped up about 2 - 2 1/2 inches . even slight/modest pressure would change POI . i hope you don't have the same issue mounting a bipod to your barrel .
Quote from: DBOdude on February 06, 2014, 05:54:05 PM
i tried using folded and stacked towels to support the front of the barrel on my DBO 2289 on my "shooting table" (i have a 24 inch barrel) and at 15ish yards the POI jumped up about 2 - 2 1/2 inches . even slight/modest pressure would change POI . i hope you don't have the same issue mounting a bipod to your barrel .
Good to know DBO. I'll be mounting right in front of the barrel mount/band that's at the end of the compression tube so flex should be minimized. It's very secure but I may need to get a metal one to make it really tight.
sounds like a plan :-* . i hope the swing of the pump arm allows you to place it close enough to not flex . do you have the stock plastic barrel band or a aftermarket aluminum one ?
Quote from: DBOdude on February 06, 2014, 08:11:04 PM
sounds like a plan :-* . i hope the swing of the pump arm allows you to place it close enough to not flex . do you have the stock plastic barrel band or a aftermarket aluminum one ?
Stock. I think aluminum is going to be a good investment. Any suggestions?
Get one from Michael Chavka or Greg at Bluefork. Greg is a member you can find Mr Chavka on the yellow forum http://www.network54.com/Forum/79537/ (http://www.network54.com/Forum/79537/)
Quote from: pump-n-dump on February 05, 2014, 12:02:30 AM
Thanks guys for the spring links!
Here's a couple views of that Pachmayr slip-on grip.
Nice :-*
An there is the Mr. BigErn Hol(e)y Trigger :-*
Here are some pics of the bipod installed. It has a quick release clamp that fits over the barrel spacer. While the pump arm clears though both legs when they're extended, it's easier to pump when the pump arm side leg is folded - but that's easy enough to do so it's not much of an inconvenience. Being mounted close to the front barrel band and with the length of the barrel spacer, there is no noticeable flex in the barrel based on my test shots. I'm very pleased with the stability and ease of install / removal this now has. :-* The only change I would have made would've been to have the spacer be a little longer. It's currently 2" but 3" would have given some more options.
In my experience, placing anything on the barrel changes the POI, making small targets hard to hit. :)
Quote from: 7624452 on February 19, 2014, 06:45:50 PM
In my experience, placing anything on the barrel changes the POI, making small targets hard to hit. :)
I'm not good enough a shot to hit targets that small - well not intentionally that is! ???
I do agree that any pressure on the barrel can affect accuracy but I've tried to minimize that with mounting the bipod as close to the barrel band as I could.
Looking good :-*
Hi there great build and nice looking to,
atb kev02 :-*
Have you done any before/after comparisons yet? Like shooting 10 shots from a rest (duffle bag) and 10 more shots using the bipod? That way you could see (and of course report back) if there was any major or minor or zero changes in the POI. I do like what you've started, some good ideas. :-*
Quote from: sshewins on February 20, 2014, 04:12:55 AM
Have you done any before/after comparisons yet? Like shooting 10 shots from a rest (duffle bag) and 10 more shots using the bipod? That way you could see (and of course report back) if there was any major or minor or zero changes in the POI. I do like what you've started, some good ideas. :-*
I haven't yet. We're pretty socked in with snow in NH lately so any spare time has been spent dealing with that. >:(
However, when I can I will certainly do some comparison and post the results here. :-*
Fair enough! Yeah, we got some of that white stuff too. Makes pretty much everything outside a big pain in the butt...