MRodAir Air Max Varmint in .177

[Ribbonstone]

I like the little rifle...and I particularly like it in .177.  You give up the ultimate power of a .22, but for a .177, my example has been really fast/high energy.

Not all Varmints have had all the posted  problems....what is posted are good solid cures for the ones that do, but don't think that it's universal to the breed.

Trigger adjusted fine, but as you note, it is not a two-stage trigger.  It's a one stage trigger with a lot of take up that kind of acts like a 2 stage, but better to just conisder it a long single stage (basically just a whole load of "creep").

Was perfectly happy with the weight of the trigger and the smoothness, just wanted most of that creep to be gone...basically making it a single stage without that long take up. 

All I did was adjust the little hidden screw (under the front pin in the trigger housing).  NO real take up, just a break (figured 1.1 pounds was as light as I'd ever go on a hunter...in winter, with numb fingers, I'd actually like a little more feel.)






Of course I hosed the usefulness of the safety, which works nearer the start of the long take up than at the end.  Would move in and out and go "click-click", just didn't keep the rifle from firing.

I found a simple way around that...which I'll repost if needed.
DSCN1751[1] by Robert Dean, on Flickr

Haven't found much in the way of burrs or buggers on the tube openings.  A little sharp edged, but nothing more srastic than I'd have expected.  Sounds like that got worse

Did have one of the breech screws feel stripped.  Swapped it for one from the LDC (which got replaced) and it's tight.  Same hole, same thread, so whatever was wrong I just blamed on a sub-standard screw (which on a test, is also loose in the LDC).

Chances are, at least if you are use to other PCP's with LDC's, you'll want to replace the issue LDC.  If you do, steal the set screws and replace the loose barrel breech set screws with the ones from the LDC.

When you take it apart, it was a fight getting the issue o-rings (the "brown" ones) out as they tend to swell and stay swollen. Can't really complain, it was holding air jut fine until I took it apart out of couriosity (was an earlier rifle, and I wanted to see the "guts").  Replacing them with more normal "black" o-rings makes reaseembly/disassembly easier.


Valve is actually fixed in three placed. Do count the big brass transfer port, as it's thickenss is recessed into the valve and corsses the air tube as well, so while it is in place, it adds to fixation.



Evidently, bolt breakage is a problem.   It's not excessive opeing force, this rifle cockes easy.  Might be bolt thrust.  Given that many bolts have a little forward slack when pushed foward and turned down, it could be that the bolt thrust uses that slack as a "running start".  More likely, it's just a really thin threaded shank and mystery-alloy bolts.

Only time will tell if my cure (retapping the bolt hole for a left over Disco bolt..it's not much larger in diameter) will last or not.  Got months/ 1200 to 1600 shots from the issue bolt before it snapped....haven't gotten about 1/2 that number of shots in with the new bolt (one the testing/tuneing is done, don't shoot it nearly as much per week), so no judgement yet.






Power was a bit too much for "normal" wegiht pellets to really group well (too fast for 8ish grain pellets).  Worked well with 10.3gr. JSB's at  975fps or most pellets heavier than that (at lesser speeds), but the shot count was pretty poor (like 12-14 shots inside of 4%).

So I choked the transfer port down.  Know that's not the "in-style tweak of the day", but's simple/reversable/and it worked.  Sleaving that port down to .112-.115 (it's not quite round) brought me to +20 shots inside of 4% (from 18.9 foot pounds to 20.4 foot pounds, depending on pellet weight).


Did add a Rocker1 LDC.  In my case. painted the rear end cap (barrel/fitting) black as the polished Al. refection bothered me when the sun was behind me.


So...with the above  adjustments:



Varmint .177
+20 shots/ +20 foot pounds
(cheap) 3-9X 32mm Hammers scope (different rings)
Medium rings.
Preference for heavy weight  JSB .177 pellets (from 10.3 to 16.2gr.).
As shown, just under 6 pounds.

So...even with a 4 pending adjustments/mods.....

1. Likelyhood of the bolt to eventully break. May not...may...would certainly cock it, turn the bolt sown, and then tug it to the rear to keep that "running start" to the minimum.
2, Likely that the trigger will need to be adjusted...but equal likelyhood of the issue screw providing an acceptable pull (so long as you don't get a rough one).
3.  Likelyhood of the issue o-rings to swell and resist disassembly.  NOT that they leaked, but that you are nearly 100% sure to cause one if you fully disassemble.
4. Likelyhood of the .177 version runing fast/powerful, but for a very shot shot count  until tuned.


...I'll still rate it, by way of accuracy and performance, as the best deal going in a repeater.

[anti-squirrel]

I do not know what it is about them but nothing I have likes the Pirannahs... The making of a proper leade is such a simple thing I am glad that Spa paid attention I hope other makers notice and follow...it is just such a simple thing that makes a big difference... for pellets even a 30* leade would probably work... It would be nice to have a 1* leade for cast but as not many are moving that direction I can understand not going that far...

The fact that many Manufacturers have not bothered to use a chamber cutter that produces a leade at the same time is beyond understanding... It is not like it cost a lot to implement... Thanks Mike..

I appreciate you bring this up.

My other SPA, the PP700 is the least picky airgun I know of.  It has a good leade and likes grouping everything.  And that's from 7 grain wadcutters to 15 grain domes and everything in between.

I'm hoping my Varmint performs as well, but if not, I've made a couple okay barrel into great ones.  And with Mike's and Ribb's information as well as the rest of the stuff in here, I am good to go.

[K.O.]

Yes the barrel does have a proper leade where there is a smooth bore and a proper transition/ angle cut into the start of the lands.  I have tried eight different pellets from @7.4 grains to @10.6 grains with several different shape profiles.  The only pellet it doesn't like is the Crossman Pirannahs.

I did also put a larger chamfer in the "chamber/breach" end then polished this chamfer to alleviate the excessive force and drag while closing the bolt and clambering a pellet.

Just out of curiosity what did you use to cut the forcing cone/chamfer.... when I did my .25 caliber pumper using a XL 725 barrel I did the chamber/leade with a .257 drill bit carved to purpose
(unpiloted reamer)eye and feel to get it right: easy to get  wrong by being off a few degrees but got away with it)... then both got a quick clean up with wet/dry first one direction then the other....


For the forcing cone/chamfer I cut it with a double cut carbide  Christmas tree  bit... then wet/dry cleanup...

[MikeH]

Yes the barrel does have a proper leade where there is a smooth bore and a proper transition/ angle cut into the start of the lands.  I have tried eight different pellets from @7.4 grains to @10.6 grains with several different shape profiles.  The only pellet it doesn't like is the Crossman Pirannahs.

I did also put a larger chamfer in the "chamber/breach" end then polished this chamfer to alleviate the excessive force and drag while closing the bolt and clambering a pellet.

Just out of curiosity what did you use to cut the forcing cone/chamfer.... when I did my .25 caliber pumper using a XL 725 barrel I did the chamber/leade with a .257 drill bit carved to purpose
(unpiloted reamer)eye and feel to get it right: easy to get  wrong by being off a few degrees but got away with it)... then both got a quick clean up with wet/dry first one direction then the other....


For the forcing cone/chamfer I cut it with a double cut carbide  Christmas tree  bit... then wet/dry cleanup...

I used an unpiloted 90* countersink. I could have made a science project out of it, but I was being lazy and it worked out well.  If I had the the time and desire I could properly re- cut the crown and forcing cone/chamfer on some precision tooling, but so far a clean up has proven to be all that was necessary in my sample of one.

When I got my .25 Impact a few months  ago it had major accuracy issues out of the box.  It wouldn't group less than 3/4" at 20 yards, and was scattering pellets between 8-10" at 50 yards.  I was not happy!  The regulator was functioning perfectly as was the rest of the rifle, so I decided to give the barrel,and suppressor a look prior to sending her back for warranty work.  I found that the muzzle "crown" Was definitely cut with dull tooling.  There were significant metal burrs that were "rolled" into the bore.  A quick clean up with a very fine jewelers file to remove the large material, followed by a Cratex cone on a variable speed Dremel and some micro mesh to polish the remaining rough spots cured the problem.  Now it shoots one shot groups at 50 yards.

 I should note that with the SmoothTwist barrel there are no real lands and grooves since the barrel is externally swayed over a mandrel to impart the suedo rifling into the hardened metal liner.  Because of this, there is no easy way to cut a proper crown on those barrels since the muzzle end of the bore is not concentric. The only way I can think to cut a half way proper Crown on a SmoothTwist barrel would be to use a cutter with an extremely long two piece pilot that would be inserted from the breach end, and would center the cutter by using the smooth portion of the bore.  Overall I don't think that is worth the effort, since mine shoots awesome after removing the gigantic knife blade burrs that were causing my troubles.  I do absolutely love my Impact by the way! 

[nervoustrigger]

Mike, do you see any reason the crown of the FX barrel couldn't have been smoothed with the brass screw technique?  With conventional barrels it works great as long as the existing bevel is fairly uniform.

BTW, someone recently posted a close up picture of the crown of a Smooth Twist X barrel.  I was shocked by how awful it looked.  Nobody commented on it so that made me wonder if it's normal.

[MikeH]

Mike, do you see any reason the crown of the FX barrel couldn't have been smoothed with the brass screw technique?  With conventional barrels it works great as long as the existing bevel is fairly uniform.

BTW, someone recently posted a close up picture of the crown of a Smooth Twist X barrel.  I was shocked by how awful it looked.  Nobody commented on it so that made me wonder if it's normal.

The reason why you cannot get a good, even, conventional crown on a FX barrel is the bore is not round at the muzzle. The externally swaged "lands" distort the barrel into a bore with five indentations making their own modified version of polygonal "rifling".

Simply removing the machining burrs did the trick for me on my FX.   Doing the same on the breach end made clambering pellets way easier on my Varmint.

[nervoustrigger]

Okay, yeah I understand it is not round.  I was still thinking the abrasive action would nonetheless be effective at removing material uniformly so as to leave a burr-free muzzle.  That is, the inside diameter of the crown would reveal its non-roundness to the human eye, but it would have no burrs and therefore provide an even release of the pellet.

[tomiboy]

I don't know anything about air rifle repairs and modification, but I'm wondering if I should unscrew the bolt handle and replace it with something else before it does break. This way I don't need to take it apart! Anyone have a replacement they can suggest?

My trigger could be better, so I may look into that, although it hasn't hurt the accuracy as far as I can tell

[avator]

Tom....
What they are talking about here is basically putting a bevel on the end of the barrel that the bolt pushes the pellet into it. This is greatly going to reduce the strain on the bolt knob to set the pellet. Combine that with using your thumb on the back end of the bolt instead of using the knob to close it will lessen the chance of breaking the knob. Also polishing the hammer reduces strain on the knob during the pull back along with letting the hammer "fly" freely during the "strike".
Hope this brings it more into layman terms.

[tomiboy]

Thanks Bill!  I have noticed that JSB lead free Predator GTOs are really hard to push in, but the iead JSB 15.9s slide right in and shoot the best anyway. I will stop shooting the GTOs for sure!

[gendoc]

one of our machinist guys on here need to make a bolt knob/handle of a better/stronger material.
and market it here like triggers, hammers, valves and such are.

[tomiboy]

I'm in for a bolt handle and a better trigger!

[avator]

Ya know? I threaded the grub screw out just a tad to ride on the sear and take up a little creep and I don't dislike the trigger at all.

[Wayne52]

For the bolt handle on my Varmint I drilled the bolt and tapped with an 8-32 tap, then I took the stubby handle I had and used a 8-32 die on it.  A Crosman handle will work in a pinch but in reality it could use more threads that what they have.

[avator]

The bolt knob on my CP-1 is a different shape. I wonder if it's a different material?

[avator]

I mentioned earlier (somewhere) that someone needs to come up with a double tube mod for the varmint. Now I think a power adjuster would be a good mod as well. The poppet pin is very short and the hammer has a two stage diameter (for lack of a better description) to affectively use the BStaley o-ring buffer. Maybe a hunk of thicker neoprene air tube would work.

[Ribbonstone]

Double tube or single tube....it's like doubling up the gas tank on a car...you'll get 2X the miles before a refill, but pay 2X as much to refill it.  In pump-fill terms, 60 pumps in / 30 shots out is pretty much the same as 120 pumps in / 60 shots out.

[avator]

Would need regged for sure.

[avator]

Good news is that these guns are not long in tooth.... I see lots of tricks on the horizon.

[avator]

Well, I been playing with my SPA guns for enough time to decide on some reconfiguring.
Here is what I have to work with...
1) .177 Plinkster w/shorty muzzle break from CP-1 installed.
   This gun sounded so weak with the stock LDC and felt a bit front heavy. The shorty muzzle break from the stock CP-1 gave it a bit more "POP". Betty Lou just loves the gun now. That was my goal.
2) .177 CP-1 with the CP-2 grip and shoulder stock set.
     I also used the LDC from the Plinkster on this gun. Very nice shorty carbine and pistol.
3) Originally this gun is a .177 Varmint. Not for long...
    I am going to use the .22 breech, long barrel and LDC from the CP-2 on this gun.
4) Originally the .22 CP-2.
    This gun will get the .177 breech, long barrel and LDC from the Varmint. It will also wear the shoulder stock it came with. This will work well shooting along side of the Plinkster for competitions with my shooting buddy.
These are some of the "lego" options that these gun offer.