I did a post the other day about my new m4gery getting fatter and portler with the weight of additions RAS/grips/lights/etc.

The great thing about carbines are that they are supposed to be light handy rifles. But, I've added a Knights RAS and Surfire m900 and have plans for an eotech before year's end.  My beloved politically incorrect "black rifle" is now kind of fat at nine pounds and will be fatter once my eotech is bought.

I think we all would agree that an ideal weight of a carbine would be in the 6-7 pound area. There really isn't anywhere on an ar15 that you can trim weight but for the bolt carrier and the barrel which is why Bushy's new pencil and M4 barrels are so popular.  

My question is why don't the manufacture's offer a barrel made mostly out of titanium?  I know that titanium cannot be rifled but Taurus firearms got around that by simply putting an inner core of steel in their barrels so they could do the required rifling and they encased that inner layer of steel with an outer layer of titanium.

I know it would be an expensive barrel but I would be willing to pay the price for a significant weight reduction. I also own an Armalite AR10T which is a great accurate shooter but total pig as for as weight is concerned. The thing weighs 12 pound by its self and right at 16 pounds when you add the scope,bypod and a loaded 20 round mag.

So in conclusion, Our black rifles where the first truly space-aged guns.  The Ar15 was made with materials that were never used in guns before and we got a great lightweight rifle back in the mid 1950's.  When you really think about it their are only a few basic parts that need to be made out of steel: the bolt,the chamber,and the rifled partion of the barrel.

If anyone has any commets please feel free to add them, as I'm hoping to keep this topic in continued discusion perhaps the right person from on of the manufactures will see this and consider this idea

Such a barrel would not have mainstream appeal due to the cost, but you could surely have one made as a custom job... just a matter of how much cash you want to throw at this kind of thing !

Alternative weight-saving materials that are more likely to become mainstream include ceramics and carbon fiber.

Ti has a lot of flex in it. Would that not affect accuracy? Dont believe it can be rifled either. Some of the new S&W  Ti wheel guns bbls are sleeved I believe... John

Ever see what happens when two dis-similar metals aligned with eachother begin to heat up?    Differences in the way they expand can lead to very strange things.    With tiny little defensive handguns meant for concealment, it's unlikely the accuracy would suffer too greatly nor would many rounds be pumped through the barrel to be much of a problem.


But a long rifle barrel with a steel liner inside of a titanium shroud, can't say as to what type of effects there would be.   The bore would have to be perfectly drilled in the titanium barrel shroud so that the liner could be placed dead center and not have problems.


I'd sooner have a pencil thin barrel.   Problem with them though is how they heat up with sustained firing compared to Hbars and the like.    There is always the option of adding a heat sink to the barrel though, could always put large radiator type fins onto the area under the handguards(JP Enterprises makes such a heat sink for putting under freefloat tubes).

The titanium barrel blank would probably be profiled while lathe centered on the steel liner. It would have to be done by a competent machinist, though, taking into account Ti's prospensity to 'give' against the cutting tool (from what I hear). If machined improperly it would be out of shape, thicker in some areas and thinner in others, because the material slipped under the tool instead of digging in.

As for thermal expansion coefficient, steel expands more than titanium. Get it hot and the liner would simply fit tighter in the Ti barrel. Ti has elasticity and would probably stretch with the liner as it expanded, with no ill effects (emphasis on 'probably'). Of cousre get it hot enough, fast enough, and there might be deformation or even splitting (I think this is extreme, though).

Titanium's thermal conductivity is slightly better than steel.

Ti has a Young's Modulus around half that of steel (and a bit higher than Al), so it's not as stiff.

I am no metallurgist though, nor am I a barrel maker, so take it for what it's worth (about US $0.01).

Do a little research and you'll find that once upon a time Saint Eugene had this super high tech rifle he designed with a titanium barrel, aluminum receiver and plastic furniture.  It was super light but then one of the barrels had a 'catastrophic failure' during testing so they went with a steel barrel.  It was heavier but a lot safer for the shooter.