Question for you 5.0mm .20 cal HW guys.

[Nate the airgunner]

My R9 I got about 2 months ago has been shooting amazingly, 3/4 inch groups at 35 yards consistently, amazing. It loves to eat JSBs, but with jsbs being almost 20 dollars for a tin now, I really don't want to burn through them. So I purchased a tin of Benjamin .20 cylindrical pellets, locally for a decent price of 12 bucks. They shoot decent groups out of my R9, but every once in a while, at random, it will make a loud crack noise when firing, almost like a dry fire, but the pellet hits where I want it to. This is only with the Benjis, the JSBs shoot perfect and quiet every time. I know it's due to the pellet regardless, and not the gun, is it because the heavy weight for a .20 pellet, or because they are cheaper pellets and probably have bad ones mixed in the bunch?

[Mark 611]

Well let me ask u have u taken the rifle apart to clean out the factory lybe? The rifle maybe detonating? Or it also could be lose pellets? Or a combination of both, if u have not cleaned out the factory lubes? I would start there JMO

[Nate the airgunner]

But it only does it with the benji pellets. Hasn't done it once with a jsb, predator, FTT, or Kodiak. So wouldn't it diesel with every pellet?

[dtdtdtdt]

I have a tin of the same kind of pellets you are having trouble with.  My first impressions were that they might have some oil on them from the manfacturing process.  That could easily cause your dieseling.  If you have no problems with the higher quality pellets, the rifle doesn't have gunk in it, the pellets probably do!!!

As a first step!

Clean a small batch of the suspect pellets to remove any oil or other debris that might have found their way into them. I would get bottle of isopropyl alcohol available at any drug store or grocery pharmacy. 

Put a few dozen of the suspect pellets in a dish or small bottle.  Add the alcohol, shake vigorously for a minute or so. Observe the mixture for any evidence of "stuff." Color in the liquid etc.  Bits of junk in the bottom among the pellets.   Take a white paper towel, Fold in quarters to make a filter.  Pour the alcohol and pellets into the fold and let drain.  Spread the pellets on another paper towel, let dry completely (overnight would be good.)  Unfold the filter and observe any discoloration or gunk.   If you have a coffee pot that uses filters, they can replace the suggested paper towel.

When dry, shoot the pellets to see if you have the same problem.

Second comment:  $15-20 for 500 shots with any arm is a great bargain. You have good groups at a respectable distance.  Don't fight success. I know people who spend $7 per shot with their fancy long range rifles. 

I spent over $200 getting samples of every .177 pellet (over 60 types!)  from 4 gr to 14 gr to test in my two .177's.  This included lead, non-lead, and plastic/lead/copper/steel/aluminum composites  (take your pick) with no improvement over the high quality lead pellets I had found early on.  $12-15 per tin sometimes 250 or up to 500 pellets in a tin.   

[dtdtdtdt]

I just got my 20 caliber around Christmas time and am still shaking it down and getting it broken in.  I bought a tin each of the available pellets to see what I could learn but haven't done anything with them yet.  ONLY 5 pellet types!  The 20 cal is pretty custom so Hector Medina who put it together for me tuned it around the the JSB Exact 13.7gr pellet.  The others will be my curiosity rather than a serious study unless I find something really special!!!

[Motorhead]

As a VERY serious .20 cal shooter having quite a few .20's ... NONE shoot the Benjamin cylindrical 14.3 pellet worth a hoot   

[dtdtdtdt]

Yeah Motorhead:

Just looking at the pellets in the tin make me skeptical.   I haven't shot them yet but am not too thrilled with the design or the roughness that I see.  Dirty looking too. Per the above discussion.

[Tonykarter]

Shoot the Benjamins at night with a strong light aimed down-range.  I did this with a Mrod and a Sheridan, and the Benjamin's spiraling trajectory was so bad I put them up and haven't shot them since.  The spiraling was so bad that they vectored out of the light beam. Good for only 15-20 yards at most.

[north country gal]

Don't know if the Benjamin cylindricals are the same as the old Sheridan cylindricals, but those old Sheridans were definitely a harder pellet with excellent penetration. Used them a lot, backing the day, for squirrel hunting. Accuracy-wise, though, not the best. Definitely not something I would buy, now, since we no longer hunt. On the other hand, our Sheridan Blue Streaks now get fed a steady diet of the JSBs, which they absolutely love. Now and then, I'll shoot some of the cylindricals for memory's sake, since we still have some.

I agree with the comments on the relative costs of pellets. My Sheridan's do so well with the JSBs that I have no hesitation spending the little extra to get them. Even shooting premium pellets, our air gun shooting is still, by far, our least expensive shooting.

Thanks for the post, by the way. I'm still trying to talk the hubby into letting me get an R9 in 20 cal. Good to know yours likes the JSBs, since we have a good supply.