Question for Slavia 600-Series owners about pellet fit & apparent bore diameter



Author Topic: Question for Slavia 600-Series owners about pellet fit & apparent bore diameter  (Read 511 times))

Offline subscriber

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I just got a few cans of RWS Supermags and decided to try them in my new 634.  They shoot fine, but I noticed that they take only a light push to chamber.  Perhaps half or less of the effort to push home compared to the pistol Meisterkugeln I have been shooting.  So, with apparently smaller head diameters.

This got me curious about how tightly the Supermags would fit in the muzzle.  I was expecting to have to push harder than at the chamber end.  To my horror the pellets just drop into the muzzle with the lightest touch. Much easier than at the chamber, where they need a push.

Even JSB pellets that chamber much more deliberately seem to enter the muzzle "too easily".

The Slavia recessed crown is unusual, but the pellet heads are dropping in well below that. 

What I have established is:
That this barrel has no choke. 
That the muzzle end has a larger land diameter than the chamber end. 
As the rifling depth seems constant, that suggests the groove diameter is also larger at the muzzle.
That that pellets heads are not supported by the lands at the muzzle very well, if at all.  (Or not at all, after being sized down at the breech end).

After that long into; would Slavia 634 owners please compare the fit of their favorite pellets at the breech and the muzzle of their air rifle barrels to see if mine has an unusual internal barrel contour?

Looking into the barrel from the muzzle and breech ends reveals nothing unusual or glaringly obvious.  The lands run all the way to the crown.  The only thing I see that looks possibly odd is what I might describe as a reflected ring, half way down the mirror finished barrel.  Nothing odd near the muzzle.

I would appreciate the Slavia fans out there trying this rudimentary muzzle sizing test and reporting the results. Now, if your 634 is accurate, you might not want to know if the muzzle is oversized.  In theory, a loose muzzle should kill accuracy...  :)

I have not pushed pellets all the way through the barrel.  That may reveal some more useful info.  Will try that later.
« Last Edit: November 19, 2018, 11:25:27 PM by subscriber »
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Offline anti-squirrel

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Re: Question for Slavia 634 owners
« Reply #1 on: November 19, 2018, 10:20:12 AM »
I'll check mine out later today.  I've noticed that pellets with a significant difference in head versus skirt size slip in too easily for my preference, but a dead sparrow doesn't seem to know the difference.

Side note: of all the springers out there, I know people talk up the R-7 and HW-30 as the best starting point in quality springers.  IMO, the CZ is every bit as good and the synthetic stock means it can be a bit of a knock-about gun.  The sites especially won me over after I found some good pellets for it.

Despite the fact I had a few thousand pest kills using a .20 R-7 back in '97 (Interspersed with Sheridan Blue Streak kills), I think the CZ is a better choice for a full-sized adult. 
Richmond VA

SPA and Crosman stuff
Turkish & Czech springer

and some slingshots for when the pellets get low

Offline lefteyeshot

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Re: Question for Slavia 634 owners
« Reply #2 on: November 19, 2018, 01:05:31 PM »
I use to say my 631 was a poor mans 124.
  • Savannah, Ga.
SPRINGERS:
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Offline Rick67

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Re: Question for Slavia 634 owners
« Reply #3 on: November 19, 2018, 01:55:30 PM »
Never had a CZ Slavia but it is an accurate gun as I have shot one.

Was about to buy one when I was still in Asia but chose the CZ S200 instead when one of my shooting buds convinced me to go PCP.

He was at the same gunstore when I was about to pay for the wood version of the Slavia so I ended up going to the bank to get more cash, lol!

The plastic versions were actually more expensive in that gunstore.

I remember liking the black and gray. They were over $200, the Slavias.
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Offline lefteyeshot

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Re: Question for Slavia 634 owners
« Reply #4 on: November 19, 2018, 02:35:14 PM »
Just checked. The Super Mags fit ok in the breach of my 634 and 631 but would not fit in the muzzle of either without forcing them which I didn't.
  • Savannah, Ga.
SPRINGERS:
Diana 470th,56th,350PC,250 .22
Terrus
RWS 93,320
Dominator 200S carbine, 135,155
ES92
Arrowhead .22(Jap.)
BSA SS SE
Tommy
Norica Massimo .22, Black Eagle
CZ631,634
Hammerli X2 dual cal.
Mendoza RM 3000 .22 ,600,577,377
RM2800 .22/2000 .22 brk brl repeaters
Remington Express
SilentCat GRT
Swarm GRT
Shadow1000 GRT
Beeman: RS2,Mach12.5,2016W DB .177/.22
AirHawkElite
BlackHawkElite in bamboo
Storm in Ben.TH.stock,GRT
Storm GRT
Win.1100, 1000, 800
2 TF99,2 89,59GRT
B40,21,20,B26-2 MM
2 B3,B4-2,B2
2 QB6,B4-1,2 QB57,2 TS45,2 Fastdeer,
2 B3-1AK,QB89,B6Z
GAS RAM:
Proxima
Rem. 777SB
Striker
CO2:  
AR2078
2260MB .22
EIG .177(Jap.)
Armscor .22(phil.)
Zogunz Hawk 010 .22 (Phil.)

Offline lefteyeshot

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Re: Question for Slavia 634 owners
« Reply #5 on: November 19, 2018, 02:38:50 PM »
Also noticed something I hadn't before. The barrel of the 631 is about three inches longer than the 634.
  • Savannah, Ga.
SPRINGERS:
Diana 470th,56th,350PC,250 .22
Terrus
RWS 93,320
Dominator 200S carbine, 135,155
ES92
Arrowhead .22(Jap.)
BSA SS SE
Tommy
Norica Massimo .22, Black Eagle
CZ631,634
Hammerli X2 dual cal.
Mendoza RM 3000 .22 ,600,577,377
RM2800 .22/2000 .22 brk brl repeaters
Remington Express
SilentCat GRT
Swarm GRT
Shadow1000 GRT
Beeman: RS2,Mach12.5,2016W DB .177/.22
AirHawkElite
BlackHawkElite in bamboo
Storm in Ben.TH.stock,GRT
Storm GRT
Win.1100, 1000, 800
2 TF99,2 89,59GRT
B40,21,20,B26-2 MM
2 B3,B4-2,B2
2 QB6,B4-1,2 QB57,2 TS45,2 Fastdeer,
2 B3-1AK,QB89,B6Z
GAS RAM:
Proxima
Rem. 777SB
Striker
CO2:  
AR2078
2260MB .22
EIG .177(Jap.)
Armscor .22(phil.)
Zogunz Hawk 010 .22 (Phil.)

Offline bhh

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Re: Question for Slavia 634 owners
« Reply #6 on: November 19, 2018, 07:23:59 PM »

I would appreciate the Slavia fans out there trying this rudimentary muzzle sizing test and reporting the results.

I'll check mine later, but for now just wanted to throw out that I have two of these rifles. One of them I chopped 2" off the barrel and it's as accurate as the other one and as accurate as it was before the chop. The chop was a simple hacksaw/file/square/sandpaper job.
  • Southern Ohio

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Re: Question for Slavia 634 owners
« Reply #7 on: November 19, 2018, 08:49:05 PM »
Just pushed some pellets through the Slavia's barrel from the breech; and from the muzzle.  My conclusion is that rather than a flare towards the muzzle, there is a slight restriction at the breech end. 

Specifically, as soon as the pellet is fully into the barrel from the breech, it slides with near constant but very low friction all the way to the muzzle.  I think "chamber" reaming may have left some raised material, although I can't see anything obvious.   

After popping over the crown, pellets pushed in via the muzzle move smoothly, but with more friction than those pushed from the breech; until they hesitate just ahead of the "chamber".

H&N Field Target Trophy pellets have a "much larger" head diameter, with "much longer" land engagement than RWS wadcutters.  So the H&Ns provided the most feel.

The upshot of the above is that at some point in the near future I may want to lap the barrel at and just ahead of the chamber.  Also, as the bore seems "loose" compared to my HWs, the Slavia may shoot better with the H&N pellets...

What is interesting is how the RWS skirts take "more than double" the force to push past the Slavia's leade compared to the H&Ns.  This while seating the H&N heads takes "more than double" the force to seat by thumb for shooting.

Slavia seem fixable; assuming this is a real problem.  If I was 45 years younger and just shot 5000 shots this past week (like I used to do with my 620 during school breaks), the tight breech would probably have fixed itself already :)   This makes me wonder if shooting 25 pellets with JB compound on their bearing surfaces would do the trick...
« Last Edit: November 19, 2018, 08:52:30 PM by subscriber »
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Offline TF89

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You may or may not want to lap the breech.  If as you say the pellets fit loose in the muzzle then there is a possibility that the pellets will also fit loose in the breech if you clean it up.  The current fit at the breech is keeping the pellets in place while cocking the gun.

I have a break barrel where some pellets fit loose and it is easy for the pellet to either fall out or be damage when closing.

Typically on break barrels the bore is tighter for the length of the breech block.  This happens because the barrel is swaged into the breech block, kind of a reverse choke.  If the muzzle is a tight fit for a new pellet then I will sometimes lap the breech area to bring it more in size to the rest of the barrel, especially the muzzle.   

Having a nice consistent fit for the pellet all the way through the bore is what I shoot for.  Still as long as it shoots well, why mess with success?

I have found that pellets with thin soft skirts like the JSB exacts work best in barrels that are tight in the breech.  I believe that the soft skirt will open to fit the larger bore size as it passes past the restricted area.

On one break barrel I gained about 30-40 fps by lapping the breech bore area of the barrel.  I did leave the first 1/4" tighter to insure pellet fit.  This also allowed an expanded list of pellets that would shoot well in the gun.
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Offline subscriber

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Thanks for the insight and info, Dave

Now, on Monday I actually did some fire-lapping, using a technique I have not seen mentioned anywhere:

Instead of rolling pellets between steel plates to load them with abrasive, I applied JB Bore Paste directly to the first 1/4" or so of the leade and bore by means of a Q-tip.  The idea was for contact pressure against the breech cone to impress the abrasive into the pellet.

The Q-tip was first saturated in light oil to reduce the viscosity of the JB pasted; and to enable a thin layer to painted evenly around, just where I wanted it.

I then loaded a loose fitting RWS wadcutter and shot that into the trap; followed immediately, without refreshing the abrasive, by a very tight fitting H&N dome.  Then I reapplied fresh JB paste and loaded a H&N dome. After shooting that, I immediately fired a RWS wadcutter; and so on.  By alternating the pellet types the idea was to "feather" or distribute the wear at the hard contact areas; rather than create a pellet specific "step".

Anyway, after 12 fresh abrasive loading cycles I decided I was going to stop and do an assessment.  The RWS pellets seemed to be loading smoother than before.  Light, but not at any risk of falling out due to gravity.  Still perhaps four times harder than when these RWS pellets are pushed into the muzzle.  That, while the H&N pellets were still loading too hard for comfort.  So, if I managed to remove steel, it was not much.  Certainly, not too much.

I looked through the barrel after every two shots.  There was no buildup of paste. It actually looked surprisingly clean.    Paste build-up would be unlikely, as the actual amount of JB introduced incrementally, was probably no more than half a Q-tip head volume in total.  Most of it was swept out by the pellets.  Some of it must have been dragged against the barrel wall, at higher pressure against the tight areas.  Some of the paste may have been over-ridden; hence the second pellet for each abrasive loading.

After I thought it time to stop, I shot a few balls of oil soaked tissue loaded directly in front of wadcutters. This was followed by a few dry pellets.  I might be imagining it, but the barrel looked very clean.  The mirror finish seemed brighter.

Anyway, I figured I should shoot it as is and see if there was any change in operation.  Could always come back and do it some more later.  It seems that pellets slide into and down the barrel more smoothly; after their skirts have popped over the chamber entrance.  The release force does not seem to be reduced.

I did not want to do any hand lapping in a stationary barrel; as that is an invitation to wear it in an angular fashion and out of round.  If I have a barrel in my lather chuck where I can very slowly rotate it, then my concern about wearing anything but an even cone when hand stroking a lap, would be alleviated.  Obviously the lap must be completely free to follow the barrel, and not ever strip across the lands. 

I figured that by fire lapping, the pellets would concentrate the wear at the tight spots, and do almost nothing to the rest of the barrel.

Many use a cleaning rod to drive felt pads trapped in such a manner that they make tight contact with the bore; or shoot Q-tips loaded with abrasive ahead of pellets.  However; I figured that those methods are good for improving the finish of the bore everywhere.   What I wanted, was to selectively wear down the tight parts of the barrel near the breach, at both the land and groove diameters; without rounding the corners of the lands all the way to the muzzle.  Hence, a "hard lap" in the form of successive pellets.

Anyway, I just measured the RWS Supermag pellets that seem almost loose in the muzzle at 4.48 mm.  This is rather small, so the Slavia's bore may not be "over-sized". 

These RWS wascutter are much smaller than the 4.53 mm H&N domes I used for half this fire-lapping exercise.    The latter still take a hard push to seat in the breech, and would become annoying if one wanted to shoot more than 25 pellets in a session.  This suggests I should find and shoot some 4.5 to 4.51 mm pellets.  A partial can of RWS Meisterkugln pellets I have, measures 4.51 / 4.52.  These have "normal" feel on loading.    These wadcutter pellets are soft lead, and have a very narrow full diameter "land" at the head.  I did not try pushing them into the muzzle.

If the Slavia does not like the "small headed" Powermag pellets at longer ranges, my Daisy 753 really likes them at 10 yards.  Will try those in other airguns that have tighter barrels too...

Of course, I just bought 5 cans of the Powermags for a bargain.  Perhaps they are not all from the same batch/dies.  Hopefully there are some that measure at least 4.5 mm...


« Last Edit: November 22, 2018, 07:18:12 AM by subscriber »
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Offline bhh

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Interesting. How did your group size average change before and after the lapping?
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Offline subscriber

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Interesting. How did your group size average change before and after the lapping?

As I have been shooting offhand at 10 yards, I can't tell if there is a difference; other than I feel better :)

What I tried to address is a theoretical problem, that I would not have know about, if not for the small headed Powermag pellets.  It would not have occurred to me to try them in the muzzle.  I would not have discovered the breech was tighter than the muzzle, as they seem to shoot just fine offhand at 10 yards.

I will do more shooting with more pellet types and batches, before applying any more aggressive "improvement measures".  First do no harm, and all that...
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Offline BrushPopper

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That’s pretty much how I firelap, except I’ll cut the head off the Qtip and just use the ‘stick’ to apply undiluted lapping compound.

Seems less messy than putting paste on the pells. Usually fire 2-3 shots and reapply/repeat. I usually wet-patch the bore abt every 10 shots...

Works well to smooth rough spots and easier than hand lapping
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Rifles:
C-1 .22
XS-25
Diana 25
B3-1 AK
Beeman Falcon 2
El Gamo 68
Benj "F" model
Benj 312
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Offline pault

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If there is a problem with the CZ 634 barrel I would like to know what other guns have the same  " problem" because those are the ones I will buy.
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If there is a problem with the CZ 634 barrel I would like to know what other guns have the same  " problem" because those are the ones I will buy.

The problem may simply be too much measuring and thinking, and not enough shooting.  :)
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