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07 November, 2010

So does the QB78 HDD fit the Crosman 160?

Given the excitement over the QB78 Hammer Debounce Device (HDD), it's not surprising that many people have asked if it will fit the Crosman 160.

But does it? Here's what I've found through testing on my own Crosman 160 - a "Model 3" with the cast trigger guard (same as the QB78 style).

The short answer is "yes, the QB78 HDD fits the Crosman 160". But, unfortunately it doesn't work like it does with the QB78 - at least not on my Crosman 160.

Now I purchased my Crosman 160 several years ago at the Baldwinsville Airgun Show as a "leaker". I don't know what it's life was before that but I fitted it with an Archer Airguns "2X" Seal Kit and replaced the original valve with one of our replacements. It's a strong gun, giving about 580fps at 65 degrees F and has a very smooth and light trigger pull weight of 1 lb 9 oz.

As this is my only Crosman 160, I can't make comparisons with other examples of the same model. But, what's for sure is that the QB78 HDD sadly doesn't provide any benefit to my Crosman 160.

Why not?

Well we know from our extensive testing that the QB78 HDD works best with shorter hammer springs and my 160 hammer spring is long and feels stouter than the QB78 versions. It may simply be over-powering the HDD. Also, we know that the QB78 HDD doesn't work with guns that have had their hammer pin slots polished, as some people do when tuning these guns. Over the course of maybe 50 years, the hammer pin slots on my 160 have effectively been polished by firing innumerable times. Probably a combination of both factors has rendered the QB78 HDD unable to show it's 40+% improvement in muzzle energy and useable shots that we've seen in multiple test on QB78 family air rifles.

Here's the Crosman 160 / QB78 HDD test target.

As you can see, there were 66 shots - fired one every 30 seconds at 63-64 degrees F - with muzzle velocities above 300fps. That's the same as without the HDD fitted.

I wish I could say something different, but that's what I found...


rknbhg Thursday, 11 November, 2010  

Will the hammer pin slot overtime become polished with the HDD in place and cause it not function as well as when the slot was rough from the factory?

Thanks for all the great and hard work on this!

Stephen Archer Thursday, 11 November, 2010  

Great question! I guess that may become the case after very, very many shots, but it certainly has not been found during our extensive testing with QB78 family air rifles.

All Crosman 160s are now many decades old and the polishing effect on a well-used gun would be significant. Also, I don't know to what extent the original machining on Crosman 160s was different to that on current-production QB78s.

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This blog shares information, ideas and knowledge about air rifles. It compliments the information Stephen publishes on the Archer Airguns website, on YouTube and the Chinese Airgun Forum.

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