13xx accuracy issues

[K.O.]

Ok now here is the part that saves my gut instinct...

Op said 13xx not 1377,

so lets look at a 1322

which is .0379 * length

@  18"  that is .7822 for volume so,  1200/7.82=153  and 1000/7.82= 127
@  20"            .858                                        = 139                       = 116.5   (getting down to those efficiencies )
@  24"           1.09                                         =  110                      = 91.7 

90% efficient looses  100 psi at 1000 psi so...

just how efficient are the 1377 & 1322 systems?

[Bill in SC]

OK, I removed the LDC and saw little to no improvement. My next move will be to drop $50 or so on a new scope when the eagle flies Friday.

Bill in SC

[BDS]

Bill, before buying a new $cope use some open sights, even if they are make-shift taped in place, as long as they don't move on you they will work. Playing card stock with mag-marker can work for the rear and a cut-down finishing nail with a dab of Elmers glue for the front.

[K.O.]

Hello folks. My new to me 13xx is giving me some accuracy issues. When I first got it the breech was kinda loose, resulting in scope movement. I tightened it all down and it still won't group too good. I was just wondering from you folks who have dealt with these airguns, what are some of the things to look for that could create accuracy problems. It has a 24 inch barrel with LDC, flat top piston and flat top valve, and extended probe. Everything is tight and working smoothly but it won't group. Seems to hold air fine. Perplexing. Was thinking of maybe installing a 10 1/2 inch or 14 1/2 inch barrel. A friend shot it a day or two ago and he said he could see the pellet in flight and one shot went out a ways and took a hard right. Wondering if the LDC has anything to do with it. Thansk in advance for any tips. BTW: I did look at a youtube video of a 13xx dis-assembly and it will be real easy to work on. Just need to know WHAT to work on. One more thing. I "think" I read somewhere that there is supposed to be some sort of buffer between the barrel and the breech/air tube. Seems like I read that the barrel flexes a tad during discharge and the buffer prevents barrel movement. My gun is open in that area.

Bill in SC

The barrel does move when firing it is called barrel harmonics and the longer barrel will move more but it usually does so in a consistent manner.  the barrel spacers well they are not needed for shorter barrels in fact with a short barrel and steel breech I feel with good care a free floated barrel is more accuate.

with the 24" barrel well that brings us to the pump end plug/barrel band. you did not mention what type. If it is simply a drilled out 1377/22 band  and the barrel is loose within it well it could be part of the problem...

also what pellets, group size at what range,  is it shotgunning or are they strung vertically or horizontally.

also shine a light from the breech (I made a bore light from a $store l.e.d. reading light)  Take a look down the barrel.  my 2100b had a slight bow to it. the rifling really will help you see it if it is even slightly bowed. 

Believe it or not even a dirty barrel can cause accuracy probs...

you are not curling your fingers around the barrel when pumping are you?  The stock 1377/22 pump grips encourage this as a way of avoiding pinching.

just throwing out all the things I can think of...

[Bill in SC]

  Yes, it's shotgunning, about 2 1/2 to 3 inch groups at 10 meters. Occasionally it will put a couple in the same place. The barrel appears straight.  There is a set screw securing the barrel band to the barrel and there seems to be NO play there. Enclosed is a pic of it.

  I think I may have found the problem. When I took the LDC off today, my tired eyes glanced at the barrel crown and I could see that it was beveled. Tonight I put my glasses on and actually inspected it. Though the crown has a nice symmetrical bevel, it appears somewhat ragged. I rubbed a cotton ball over it and it did NOT snag, but to the eye, it looks ragged. I will try to get a macro shot of it tomorrow when the light is right and see what you folks think of it. I sure hope that's the problem because I didn't want to HAVE to buy a scope tomorrow. I do want to upgrade my scope, but when I can afford it better. Whatever it takes to get it right will be done asap though! I like the accuracy in all my guns to be nothing less than stellar, and it's hard to lie down at night knowing one isn't right! Thanks everyone for ALL the replies. You guys ROCK! And yes, it might pay me to run the bore rope down the barrel a few passes. BTW: CPHP pellets from Wal-Mart. Not curling fingers around the barrel when pumping but rather opening up my hand and pushing in with my palm, keeping fingers out of the pinch zone.



Bill in SC

[K.O.]

rested or unrested?  also I have never shot 10 meters with a scope but I can hit a quarter 4 times out of five at 20 yards with my 2100 and a $7 4x15.

at ten meters the crown IMO would not have that large of an affect...

It is beginning to sound like you are trying to shoot offhand with a very light, heavy triggered long barreled pistol( shoulder stock?) with a knackered scope...

The roll pins on these seem to like to move and that can cause the barrel band to move while pumping, it did on mine and was causing the same problem they are the first thing on my list to replace and if building a flat top they should not be reused. Yours look reused...

I would follow BDS's advice first  and shoot rested groups with some home made sights... 

[mudduck48]

Ragged, you want a ragged crown? Look at the crown on my 1300. Talk about shotgun groups, this one had them. Took a angle grinding stone  and some 800gt sanding paper and I think I fixed it. The target is at 17ft, 3 shots from my bench rest. 2 shots in the same hole. Your problem might just be the crown, mine was.

[K.O.]

I no zero about flat top pistons and valves but it seem that if they are adjusted to tight it would cause the barrel band to move a bit along with other problems.

you might want to research adjusting flat top pistons...

still just brain storming.

[Bill in SC]

rested or unrested?  also I have never shot 10 meters with a scope but I can hit a quarter 4 times out of five at 20 yards with my 2100 and a $7 4x15.

at ten meters the crown IMO would not have that large of an affect...

It is beginning to sound like you are trying to shoot offhand with a very light, heavy triggered long barreled pistol( shoulder stock?) with a knackered scope...

The roll pins on these seem to like to move and that can cause the barrel band to move while pumping, it did on mine and was causing the same problem they are the first thing on my list to replace and if building a flat top they should not be reused. Yours look reused...

I would follow BDS's advice first  and shoot rested groups with some home made sights...

LOL. I am shooting from a padded bench on my home range. The trigger is not great, but fair. I have shot much worse with better results. I DO think a ragged crown would show inaccuracy at 10 meters. The roll pin observation is interesting, and I will address that after the crown issue.

Ragged, you want a ragged crown? Look at the crown on my 1300. Talk about shotgun groups, this one had them. Took a angle grinding stone  and some 800gt sanding paper and I think I fixed it. The target is at 17ft, 3 shots from my bench rest. 2 shots in the same hole. Your problem might just be the crown, mine was.

OK, my crown looks a LOT like the crown pic just posted. It's daylight here, but cloudy and not enough light for a good macro pic of it. I will attend to getting a pic put up of the crown, around lunch today. I think we are getting close to figuring this out. Again, I appreciate ALL the replies!

Bill in SC

[K.O.]

At 2.5"-3" group size at 30'  well I thought it would take an easily visible bad crown to the point of deforming the pellet skirt not just a mildly  ragged  crown.

I honestly did not think it was the shooter but I have had to eliminate myself from the eq a couple times just to be sure when shooting off hand with an air rifle that had a trigger like the crosmans tend to (long and a bit heavy).

I have not worked on my triggers yet despite a bit heavy pull and being long...

On mine they  are so dang predictable they are eeeeasy to adjust to the 2100s trigger behaves great loooong travel but I know just how much travel to take up and can hold there.

It would be very cool if it was just the crown.

[Bill in SC]

My trgger is somewhat heavy, but breaks rather crisp, without much travel. Yes, I do also hope it's just the crown. I'll keep eliminating each idea one at the time until I have it right. 'Ppreciate it again! BTW: Was gone all day and it's raining now so no crown pic today.

Bill in SC

[Bill in SC]

Changed my mind. Fixin' to cut the barrel length down to a more compact size. Since I have to rework the crown anyway...  Pics up later.

BB in SC

[Tater]

Good luck with the cut. This is a very informative thread.

[Bill in SC]

I cut 10 inches off the barrel and did a quick crown job with the dremel. Accuracy seems about the same. But, it LOOKS way cooler, and handles a WHOLE LOT better. I guess my next inspection area will be the barrel band and roll pin.



Bill in SC

[K.O.]

Hey does look cool 

I just ordered a steel breech,14.5 barrel and the bugout pump grip  for my 1322 on Monday.

Seeing yours in about the same config ( no ldc for mine may make  or use drilled daisy 853 barrel weight) Has my anticipation level back up!

I have my PC77 apart right now so I went and shot my first 10 meter group yesterday with my 1322.

the only thing that is not stock is the roll pin (it is one of Davios here because I think they look the best) and the 1399 stock.

before it got it I used drill bit shank.

so anyways prone, no rest, 10 meters stock sights (peep end), premier hollow points, quarter size target, 5 shot group was basically a wide two in one, two more touching the 2 in one, and one about a cm away.

All where high, very top of quarter,  because I am sighted for 25 yards. 

Honestly it was a lazy group point and shoot not worried about form more like hunting (a relaxed shoot before it moves away type form)

Point is these things do have the accuracy in them.

when I get my next order it will be for the PC 77  I think I will go with a 16.5 cut on the barrel mainly for ease of handeling but also for a long barrel there is the 2100

which looks right and protects the barrel

to me the 13xx looks great as a carbine <16" or so  and silly as a long rifle.

I have been resisting scoping mine but dang it  seems my limit is about 25 yards.

The quarter size back dots I make,  well at 30 yards well they let me know if it was a quail and harder to see I would have a bit of trouble.

Thank for sharing the pic It is very close to what I want with mine...