Classic replica air pistol review: Crosman Model 451


If you asked replica air pistol collectors to name the first CO2 powered, pellet shooting replica airgun styled to look like a semi-auto pistol but using a concealed internal rotary pellet carrier, many might suggest the Umarex CP88 from 1996.  But they’d be wrong.  Some might nominate the Crosman Model 1088 RepeatAir from 1992.  But they’d be wrong too.  To find the very first one, you have to go all the way back to 1969 and the Crosman Model 451 “GI 45” Auto Repeater.  Crosman, riding high on the success of replica air pistols based on the Colt SAA and S&W .38 revolvers, decided to produce a pellet shooting, CO2 powered repeater based on the Colt 1911.  The result was far from elegant and less than reliable and it sold like ice cream in December.  Despite that, the little-known 451 is now one of the most sought-after and collectable of all Crosman’s replica pistols.  But, would you really want to own one of these?


Relatively little seems to be known about the development of the Model 451.  Most of the information in this part of the article comes from the book My Life, Our Lives by Roger Molina, Head of Sales at Crosman in the late 1960s.  If anyone has additional information on the development of the 451, I’d be happy to hear about it.

The idea of a Colt 1911 replica initially came from Ed Denniston, CEO of Crosman in the late 1960s and preliminary design had been completed when Roger Molina and Denniston visited the US Army Infantry Training Center at Fort Benning in Georgia.  The main purpose of the visit was to discuss the possible production by Crosman of a conversion kit for the M16 rifle which would allow it to fire BBs, ideal for training inexperienced troops destined for the conflict in Vietnam.  During the visit discussions also covered an air pistol which could be used for training army personnel who would be using the Colt 1911.  The US Army Training Center had evaluated the multi-shot Crosman 600 as a possible training weapon, but rejected it because it was just too different in use to the 1911.  When the people from Crosman described the 1911 replica they had on the drawing board, the Army trainers seemed interested.  Sensing that they might be able to achieve sales if they could produce a reliable, multi-shot air pistol which resembled the 1911, work on the development of what would become the Model 451 accelerated.

Like the Crosman 38 series of revolvers, the 451 was designed initially as a training tool which would replicate the feel and function of the original firearm as far as possible.  The rear and top of the slide was a moveable part and some of the CO2 from the firing valve was used to push this backwards via a rod actuated by a nylon piston when the pistol was fired.  This replicated the recoil effect of the cartridge firing weapon and cocked the hammer.  As springs moved the slide forward, it also indexed the pellet carrier for the next shot, resulting in a true single-action trigger as on the 1911.  However, early testing showed that the blowback system used more CO2 than was desirable.  Prototype versions produced plenty of power, but gave only ten shots or less per 12g C02 cartridge.  This was thought to be unacceptable both to potential army users and hobbyists.  Power was therefore reduced to improve CO2 consumption, but production versions still only managed between 15 and 20 shots per CO2 with pellets leaving the barrel at around 300fps.

Despite these issues, some people within Crosman were still confident that the 451 would be the best selling air pistol the company had ever produced.  In addition to possible interest from the US Army, it was known that air pistol shooters in the US and elsewhere would be very interested in a reliable multi-shot air pistol which was also a replica of a well-known semi-auto firearm.  Although the Army had not made a decision to use the 451 for training, the decision to commercially launch the 451 was taken in 1967 and work began on producing the tooling required to produce this model in large numbers in the Crosman factory in Fairport, NY.


However, in addition to the relatively poor CO2 consumption, testing of the 451 also revealed recurring problems with pellets jamming in the barrel, particularly after power was further reduced to improve CO2 consumption.  The Crosman Engineering Department claimed that these problems had been addressed, but other people within the company felt that the 451 was not sufficiently developed to be ready for commercial sales.  Sadly, the pessimists proved to be right.  When the 451 was launched, jamming soon proved to be a major headache.  Large numbers of 451s were returned to Crosman Service Stations across the US because of pellets jammed in the barrel.  The problem was so serious, particularly when it involved a double jam of two pellets, that these often had to be returned to the factory for repair or replacement.  In response, Crosman tightened quality control checking on the 451 in late 1969, but this led to a rejection rate of around 50%.

Unsurprisingly, the US Army showed little interest when the 451 proved to be unreliable.  Added to this, poor commercial sales, loss of revenue through returned 451s and the unacceptably high QA rejection rate meant that instead of being a best-seller, the 451 was a commercial disaster in which Crosman failed to re-coup the high costs of design and development.  After just twelve months of production, the 451 was quietly dropped from the Crosman range.  It has been suggested that the large amount of money fruitlessly poured into development and production of the 451 was a factor in the losses which led to the sale of Crosman to British company Bagnor Punta in 1970.


The 451 had a very short production run compared to most Crosman replicas.  The Model 451 “GI 45” Auto Repeater was introduced in 1969 to a fanfare of publicity: “The most asked for pistol by our customers“, “Another Crosman pace-setter“, “Superbly crafted in the tradition of fine gun making“, “As sleek and beautiful as its famous firearm counterpart!“.  However, “sleek” and “beautiful” weren’t the words which most potential buyers used to describe the rather bulbous and ungainly looking 451.  Worse still, although it represented technical innovation, it was unreliable in use.


In addition to jamming, the other main problem was the hammer, which was made from sintered steel and was simply too brittle to withstand the forces acting through it.  Hammers cracked regularly, and if this happened the hammer could not be repaired by welding or brazing because of the material from which it was made.  It has been suggested that if the 451 had been produced with a steel hammer, many failures could have been avoided and it might have proved more popular.  We’ll never know if this might have been true because the 451 retained its fragile sintered steel hammer throughout its production life.  The 451 also suffered from premature wear of the nylon piston which actuated the slide.  If this wore, CO2 leaked and the slide eventually stopped working entirely.  Added to these problems was comparatively high C02 usage (15 -20 shots per CO2 for the 451 compared to 30-35 for the Crosman 600 and anything from 40 – 70 shots per CO2 for the 38 series revolvers).  No wonder that buyers in 1969 were reluctant to buy the 451 – it has been claimed that it would actually have been cheaper to shoot a cartridge firing 1911 in 1970 than to use the CO2 gobbling 451!

By the end of 1970, all sales of the 451 had ended.  Like many aspects of the 451, no-one is completely certain how many were made during its short production life though most estimates agree on somewhere in the region of 10,000.



The Model 451 is a hefty, all-metal replica (only the grips are plastic) which is close in weight to the Colt 1911 which it resembles.  The metal used is mostly cast alloy and sintered steel (though some internal parts such as the rifled barrel are steel) with a painted black finish and brown, wood effect grips.  Pellets are loaded into a six shot rotary carrier which is located horizontally in the top of the slide above the trigger and causes the odd bulge in the profile of the 451.  However, unlike most modern replicas which use a vertically mounted, removable rotary carrier, on the 451 the rotary carrier is fixed in place and has pellet chambers cast into its circumference.  To load the 451, .22″ pellets must be pressed into each of these chambers, skirt first.  To load pellets, the magazine cover button must be pushed forward which moves the slide to the rear and reveals one pellet chamber in a recess on the right side of the pistol.  A pellet is pushed into this chamber and then the pellet carrier is rotated manually using a grooved thumbwheel to expose the next chamber.  You must do this six times to fully load the 451.  Once done, the magazine cover button is moved to the rear which moves the slide forward and the magazine cover button then masks the open pellet chamber.


Magazine cover button forward, slide moved to the rear and pellet chamber exposed for loading

CO2 is retained in the grip and tightened and pierced using the rather unsightly knurled knob in the base of the grip.  Just as on the 38 revolvers, the right hand grip (which must be removed to load CO2) is retained by a spring steel clip, one leg of which attaches to the CO2 cartridge.  So, the right hand grip cannot be attached unless a CO2 cartridge is in place.


The hammer must be manually cocked for the first shot – like the 1911, the 451 does not have a double action trigger.  The 451 fires when the hammer strikes the firing valve.  A charge of gas is then sent up the hollow tube which also forms the spindle on which the rotary pellet carrier rotates.  This gas is directed towards the pellet chamber opposite the barrel, firing the pistol.  The blowback action is snappy, fast and fairly strong and this is (as far as I am aware) the only pellet shooting semi-auto replica which uses blowback action to cock the hammer and index the next pellet for shooting (most current pellet shooting replicas use blowback only to cock the hammer).  This provides a very light, short, single action trigger.


No manual safety is provided.  Instead a hammer safety is used.  To engage this, the hammer is pulled back from rest until the first click is heard (approximately ⅛”), or carefully lowered from the full cock position.  With the hammer in this half-cock position the pistol cannot be fired and is claimed to be drop safe.


Using the 451 is a mix of good and bad.  CO2 loading is simple and works well.  Turning the CO2 loading knob anticlockwise lowers the whole bottom part of the grip.  With a CO2 cartridge in place, turning the knob tightens and pierces without major loss of gas.  Loading pellets however is a pain.  It’s fiddly to accurately seat a pellet in the single, recessed visible chamber if you have large man fingers and you must do this six times to fully load the pistol.


When it’s finally loaded, shooting the 451 is fun.  The blowback action gives a delightfully light (around 6lbs), short and consistent trigger action.  A well maintained 451 will shoot at around 300fps and you can expect groups of 1″ at six yards.  The fully adjustable rear sight (adjusted using slotted screws on the right side and top of the sight) means that the point of aim and point of impact can be set to coincide at your preferred shooting range.  The 451 fires with a loud bang and blowback is strong and snappy.  Despite Crosman claims that it should be used only with their “Super Pells“, the 451 works well with almost any type of .22” pellet.

CO2 consumption isn’t great.  Depending on temperature you can expect anything from 15 – 20 full power shots from a single CO2 (though some users report that 25 – 30 shots are possible).  That means you may not even get three full loads from a single CO2.  High CO2 consumption also contributes to one of the major problems with the 451 – pellet jamming.  As CO2 pressure falls, it’s possible for a pellet to become jammed in the barrel.  With the light trigger on the 451, you can fire six shots very quickly indeed.  If you fail to notice that a pellet is jammed in the barrel and fire again, you may get the dreaded double jam where two pellets are stuck in the barrel.  This can be difficult to clear and, if one of the pellets sticks between the rotary carrier and the barrel, the entire action can be locked, making it even more difficult to remove the jammed pellets.  Crosman correctly identified jamming as a potential problem on the 451 before launch.  A rod intended to remove jammed pellets was included with the 451 and if you read the Crosman manual for the 451 it’s notable that almost one whole page of the four page manual is devoted to how to clear jammed pellets.  If you are shooting a 451 it’s important to take the time to be sure that a pellet leaves the barrel each time you shoot if you are to avoid a double jam.


Early publicity for the 451.  Which makes you wonder if someone in Crosman had a rather sneaky sense of humour – “fool proof, jam proof shooting fun” was one thing the 451 was almost guaranteed not to provide.

Buying a 451

If you’d like a 451 for your collection, the first problem will be finding one.  Only around 10,000 were made almost fifty years ago, and it’s probably safe to assume that many of these were either returned to Crosman due to immovably jammed pellets or quickly destroyed by enthusiastic but inexperienced users unfamiliar with blowback semi-auto replicas.  Inherent weaknesses such as the fragile hammer and wear to the nylon actuating piston have accounted for many more over the years, so there just aren’t many working examples still around.  This means two things: prices tend to be high due to scarcity and spares are almost impossible to find – the limited numbers still in existence mean that it just isn’t worth any service company setting up tooling to produce parts for the 451.


The finish on this well used 451 is far from perfect.  It’s still worth more than just about any modern replica though.

If you can find a working 451 in good condition, you can expect to pay anything from 400 – 600 dollars in the US and Canada (the main markets where the 451 was sold) and 400 -500 pounds in the UK.   That’s a lot of money for an elderly air pistol with known reliability issues.  So, why would you want one?  Well, it’s still the only pellet shooting blowback semi-auto replica with a true single action trigger for one thing.  It’s also accurate and satisfying to shoot and it’s one of the most collectable Crosman replica air pistols, so you are unlikely to lose money if you keep it working.  But that’s the main problem here.  The fragile sintered steel used for the hammer will probably be even more brittle almost fifty years after it was cast.  If the hammer on your 451 cracks or breaks, there’s not a great deal you can do other than try to find someone willing to make you a new hammer out of steel, not an easy or inexpensive job.

The risk of experiencing a difficult to clear double pellet jam is also just as high now as it was in 1969.  Well used 451s also suffer from a cocking problem where the slide fails to fully cock the hammer (though you can still do this manually).  Finally, the rear sight, which moves as the rear part of the slide retracts, can shear off.  So, do you risk shooting your precious and expensive 451, knowing that it may suffer terminal damage?  But, if you can’t shoot it, why would you want to own one?  After all, part of the fun of owning replica pistols is actually shooting them.  While other vintage Crosman air pistols like the 600 and the 38 revolvers go on providing a reliable and satisfying shooting experience year after year, the same can’t be said for the fragile 451.


Find one as good as this and you’ll be doing well. You’re still likely to need that clearing rod though…

The Crosman 451 was an ambitious attempt to produce a functional replica of a semi-auto pistol.  However, in many ways it was ahead of its time, or at least ahead of materials and engineering  technology available in 1969.  Twenty-five years later, Umarex produced the Walther CP88 and proved that the concept of a revolving pellet carrier, dressed up in alloy castings to look like a semi-auto firearm, could produce a reliable, powerful and accurate air pistol.  The 451 was also one of the first (or perhaps the first?) CO2 powered replica pistol to use blowback to mimic the function of a moving slide.  This was a bold experiment, but one that was poorly developed and executed and it proved to be a commercial disaster for Crosman.

I can understand why you’d want one of these in your collection.  It represents a level of innovation that’s rarely seem in any branch of commercial engineering.  But the 451 failed in 1970 because it was expensive, complex and unreliable and suffered from basic design flaws.  All these things are still true today, compounded by the wear and deterioration which affect any older replica air pistol.  If you’re happy to own an air pistol mainly for display and very occasional use or if you just want to complete your Crosman replica pistol collection, you may be prepared to pay the going rate for a 451.  However, if you want a vintage air pistol which you can also enjoy shooting without worrying that it will self-destruct, you may want to spend your money on something other than Crosman’s quirky Model 451.

Related pages

Classic replica air pistol review: Crosman 38 revolvers

Classic replica air pistol review: Crosman Wild West revolvers


Classic replica air pistol reviews


Crosman manual for the Model 451

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