Canadian Airgun Forum

It a simple enough query, but i haven't been able to find the origin, the reason why, this particular calibre was developed. I can understand .25 cal, even .20 cal, but where the heck does .177 come from?
I would think .175 might be logical, or .15 in a stretch... but why this odd specific number calibre?
I suppose even .22 calibre is a bit odd, since it's 5.56mm which is also weird since .177" is 4.5 mm and .177 pellets generally have bigger head size, like 4.52mm, but .22 pellets have relatively small head size like 5.52mm (.217 calibre).
All I have been able to find is that back in 1905 there was a BSA air rifle that was .177 cal and that became preferable to other calibres, like .22 or .25 (faster, flatter, cheaper)...so what I'm curious about is where, how, why the .177 dimension came from.

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Iacio, ergo sum

4.5 mm

Did they pick it out of a hat? I mean what was the basis of selecting this number? I imagine something like a 20d (penny) nail was used for the original projectile, cut to 1/4" length to make a slug. Then it evolved from there into a diabolo pellet. I can't imagine someone just saying lets make a projectile 4.5mm diameter...I could accept, 4 mm or 5mm but why 4.5mm... is it half of a 9mm calibre (also a common one)? That would make sense as well. You see, a conundrum... maybe no one knows..

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Iacio, ergo sum

I would think they when with lightest pellet back in the early days of week pellet guns
That would shoot small game that was .177 that is my story I am sticking to it
LOL have no idea

Where did competitive airgunning begin? Makes me wonder if it started in Britain with their 12ft lb law, the .177 would give the flattest trajectory. Just imagine a .25 limited to 12ftlb.

Good question, it would be interesting to know the exact answer.

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Steoger XP4 .177
Hatsan AT44MW-10 .177
Daisy 953S .177
Artemis CR600W .177
Diana Stormrider .177
Seneca Dragonfly MK2 .177

https://www.hallowellco.com/shot_size_chart.htm

I read somewhere that BB shot was originally used as projectiles for early air guns. (Hence the moniker "BB guns"). Not surprising since BB shot was an easily obtainable and cheap ammunition.
The chart above shows diameter of shot sizes made the traditional method by pouring molten lead through a sieve.
BB shows .177" or 4.5mm

Occam's razor* cuts again!

* https://simple.m.wikipedia.org/wiki/Occ ... xplanation.

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Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

^^^^ Indeed, it does seem like the most plausible explanation so that's what I'm going with too.
I got some interesting and relevant links form R-Gun Pete (he's quite a historian on air guns). There was a progression from air powered wooden smoothbore guns shooting lead BB birdshot (0.18") introduced mid 1800 and persisting to around 1900, to air powered steel barrels to shoot BB. These then evolved to become rifled steel barrels shooting waisted diabolo lead pellets (BSA, c 1905) and standardization at 4.5 mm (0.177") by around the start of the last century. Later, kids playing around with rejected ball bearings shooting them out of early air rifles lead to the standardization (Daisy) of what we consider as BB guns (with a nominal round steel ball size of 4.4mm). OK, I can sleep now. Thanks!

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Iacio, ergo sum

OK - why are air guns .177 while rim fire and centre fire .17's are .172"?
Why are BB sized shot .180" here and in Europe & not .177"?
The powder burners have been this .172" size since about 1925 or so.
Is this simply an "American" thing?

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Best Wishes
Daryl

It has been lost to time. I can only get sleep now thinking that airguns started off shooting BB then because of manufacturing process and tolerances and involvement of Germans using metric it evolved to 4.5mm and that has stuck for airguns and diabolo pellets. That's my version of history which I will die believing as God's truth or Christopher Columbus didn't discover Hispanola!

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Iacio, ergo sum

When we say .22cal or .30cal, it is generally the bore (land) diameter; 0.219" and 0.300" respectively. It is convention dated back to smooth bore firearms. A 0.300" lead ball is supposed to go into a 0.300" bore.

When riflings came along, grooves were simply cut in the existing smooth bores, so we have groove diameter slightly larger than bore diameter, and rifle bullets should fit the groove diameter. 0.224" bullets for .22cal, 0.308" bullets for .30cal etc.

0.177" is 4.5mm, a nice metric round number. First it was for smooth bore BB. Riflings are cut in the 0.177" bore when pellets came about. What is the pellet diameter? Not 100% sure, but I think it is still 0.177". The head rides on the land like a BB. The thin skirt obturates under pressure to engage riflings. Note that pellet is fin stabilized and it doesn't really need to spin. It does so for the brief moment when it exits the muzzle.

.17cal rimfire is different, although they are collectively called .17cal. Bore diameter 0.168" (4.3mm) and groove diameter 0.172". It is stinkin' powder burner, is it not?

-TL

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That makes sense.

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Best Wishes
Daryl