Longer barrels
 

Hello all, let me get some practical knowledge from you guys. If some of you are engineers, and I know some are, then please be gentle and explain to a non-engineer type of guy :(">


So, I know that a longer barrel will increase velocity, the powder can burn longer and has more "thrust". Okay and a heavier bullet (normal is usually 115 grains and so I bought 124 grains), the bullet being heavier should cause drag (?) and therefore increase pressure? And kick?


So, why do you have the possibility of the toggle not kicking enough when you put on a longer barrel.


Why?


I have a 4 inch and a 8 inch Luger and they are fine, but in my discussions with some of the guys, they said that by putting on a 6 inch barrel (being done right now )that some Lugers don't have a strong enough spring to cycle correctly?


Why?


thanks,


Ed

Re: Longer barrels
 

Hi There,

I have an opinion, Just a gut feeling that it has to do with whe added mass of the additional barrel length.

ie; longer barrel more mass and therefor less velocity of the cannon assembly for any given combination of projectile, powder, and recoil spring serength.

I hope this helps explain. If you still need more detailed explanation E-Mail me, stating what you question and I'll try to help.

ViggoG

Re: Longer barrels
 

The recoil of the breechblock not only has to compress the spring, it has to accelarate the mass of the cannon (receiver/barrel/toggle/breech) assembly. With the input impulse being equal a gun with more mass has to have a lesser spring to work with underpower ammo. Luger barrels tend to give the most velocitys 90-124 gr with 6-8" barrels and medium speed powder. Hugh Clark has confirmed this with some loads maxing out in a 6" barrel being a little faster than the 8" The amount of powder in the small case is the limiting factor for velocity gains per barrel length.

After the powder is completely burned, increasing the barrel length after that point just slows the bullet down at the muzzle end of the barrel! Thor

Re: Longer barrels
 

I can just agree to what the earlyer posts have said about mass.

I have rebarreld a number of lugers with 4-10,5" heavy oktagon barrels and in all cases will a weaker mainspring be needed.

The mass of the action is as important as the weight of the recoilspring.

Regards HÃ?Â¥kan



http://www.vapensmedjan.com

Re: Longer barrels
 

A weaker mainspring?

For some reason that surprises me, I thought it would have to be stronger, rather than weaker!


Ed

Weaker Ed, because the spring resistance i
 

only part of the inertial mass that must be overcome to make the action move upon firing.


A stronger spring when combined with the additional mass of the longer barrel would most likely prevent the breechblock from reaching the maximum rearmost position necessary to grab the next round from the mag.


The compressed recoil spring must be a balance between providing enough inertial energy to load the next round from the magazine and enough spring resistance to catch the inertial mass being propelled backwards to prevent damage to the pistol...


These small design details are why engineers are so much better at designing and building semi-auto pistols than convicts with files and scrap metal (LOL)


-John (an armchair weapons engineer)

Re: Longer barrels
 

The velocity of a bullet will continue to increase as long as the pressure multiplied by the area of its base exceeds the friction (or drag) between the bullet and the barrel.


The mainspring absorbs the kinetic energy (not the momentum) of the recoiling parts. Since a more massive recoiling assembly has less velocity and energy, a weaker spring is sufficient. Note that mainspring strengths measured by HJones for different Lugers showed no significant differences, except for the carbine which was much weaker (and, of course, the 02 carbine also has an assisting spring in the forearm).

Re: Longer barrels
 

I didn't think of the barrel recoiling back would have a lot to do with the spring, but of course that makes sense.


So, the barrel (which I knew recoiled back) uses the cartridge power and the extra weight of the barrel (making more inertia to initially move the barrel) makes the cartridge appear not as powerful as it should be and the spring takes the actual recoil and the recoil of the barrel into account. Correct?


Since the spring is obviously important, there must be a fine line between a too weak of spring and one too strong.


Too weak of a spring results in excessive banging of the toggle and other parts, while too strong results in the weapon not wanting to operate correctly.


Amazing world we live in. How the heck did people like Borchardt / Luger or Browning come up with these ideas? I can picture many things, but I have trouble doing the opposite on a stupid 45 degree cut, such as in carpentry.


I appreciate the insight.


Ed