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BBGun Bob · Veteran Member

Question ??
I want to put a .20 cal barrel on a Crosman Quest .177 Cal.what would be considered the best length this barrel should be.So many pro's and cons on this issue I am at a total loss.
I plan to both hunt and target shoot with this rifle.
It has been tuned with a JM spring.debured, lubed and nice trigger work to the stock trigger.
I have read that after 9"-12" of length you lose velocity because of friction on the pellet and amount of air pressure applied to pellet,accuracy does not change.But I have never figured out what is the best all around length a barrel should be for a certain power plant and caliber.In this case a Crosman Quest 1000X with a Walther .20 Caliber barrel.

By the way the stock .177 barrel is 15" from front of receiver to end of muzzle.It is 18 1/2" from back of receiver to muzzle. Where do you measure from??
Thanks Guys for any input on this subject.

BBGun Bob
In Michigan

AirGunEric · Site Admin

It's all about air displacement and movement- then throw in a bit on expansion rate, specific weight and coefficient of friction on a pellet and I'm sure there's some way to calculate this to an exact size/length. What this formula is or isn't- I have absolutely no f'n idea!

The actual length of the barrel needs to be measured on it's internals- i.e. from in front of the loading/transfer port to the end of the muzzle- not a muzzle cover or front sight- but the actual barrel's muzzle.

All that being said- Maccari (who's spring you have installed) may have the best idea on what barrel length would work best. If this was a .177 gun and his spring was "optimum" for a stock length barrel and an 8gr or so pellet- plug in the numbers- i.e. a .20 caliber pellet is approximately 13% larger, diameter-wise, than a .177, and a typical .20 cal. pellet is around 13gr, or 63% heavier than an 8gr .177. Put those together for an average of 38% more "loss" in velocity due to the mass and size differences (I'm assuming all else is equal here)- and you need a barrel to be about 38% shorter than what you've got to be in the ballpark of the same velocity at the end of the muzzle. What's the Quests stock barrel length? I don't know offhand- somewhere around 14" I would think, so if you want an 9" barrel- you'd probably be in the right ballpark. It's be one funny looking rifle I would think- almost a pistol at that point.

Alstone · Moderator & Site Supporter

I read someware recently that a barrel only needs to be 11 1/2" for a 12 ft lb rifle, but where I haven't got a clue.
One intresting fact is that the TX200HC has a 8 3/4" barrel and the TX200 has a 13" barrel and both perform the same and are considered to be amongest the most accurate springers.

So size isn't everything. Wink

Al