mini-14--18.5" vs 16.5" barrel length

[benEzra]

I've been kicking around the idea of having the barrel of my 14-year-old mini-14 shortened to 16.5" from the factory 18.5". Anyone have any idea how much velocity I'd lose, and how much the muzzle blast/flash might be increased?

 

[Amish_Bill]

I'm not certain about velocity and flash, but taking an inch or so ff a Mini-14 barrel is often regarded as an excellent accuracy improver. (just make sure it's re-crowned properly)

 

[WonderNine]

I'm not certain about velocity and flash, but taking an inch or so ff a Mini-14 barrel is often regarded as an excellent accuracy improver. (just make sure it's re-crowned properly)

Can anybody tell me why?

Are you saying Mini-14 barrrels aren't crowned properly from the factory?

I wish there was a Mini with a 20.5" barrel.

 

[Amish_Bill]

I'm not saying they are crowned wrong at the factory.
It just seems like most of them are not made right.

If you visit a dedicated mini 14 forum you will hear lots of testimonials about how much improvement a shortening and re-crowning gives to the rifle's accuracy. One guess is that when it is made, the last inch or so of the barrel is not as "good" as the rest. Another guess is that the skinny barrel doesn't flex as much when it's shorter. For whatever reason, it generally helps.

The common list of accuracy improvers:
cut & crown barrel
add flash hider/muzzle brake
install new (smaller, I think) gas bushings
bed action into reciever

 

[benEzra]

Accuracy was one reason I had in mind, and I also thought a slightly shorter barrel would make it just a tad handier.

WonderNine, I think the reason it tends to improve accuracy has to do with reducing the amplitude of the barrel oscillations at the muzzle as the action begins to cycle. The mini's barrel is notoriously thin and "whippy," and being cantilevered off the gas block, it is bent upward fractionally when the gas piston blasts the heavy op rod backward (thanks to the gas system geometry), setting up all kinds of vibrations in the system. I think if you had a 20.5" barrel on a mini, it'd have to be a bit thicker or your accuracy would suffer.

I figure I wouldn't lose all that much velocity, but I was wondering if anyone had any numbers. Muzzle flash will be more subjective, but a friend's 16" AR seemed to have considerably more flash than my 18.5" mini, and I was wondering if it was just the ammo or if the effect is actually that significant.

 

[Kestryll]

The accuracy increase comes from a shorter barrel being stiffer and less prone to flex than a longer one. The longer any item is the more chance to flex and move under pressure. The Mini-14 also seems to be a bit more susecptable to barrel harmonics than some other rifles. Often putting a simple muzzle break or flash hider will reduce the size of group a Mini-14 will fire.
I'm not sure if it is accurate or not but what I hear most is that for each inch off the barrel you lose 100fps.
If you are looking for accuracy get a bedding kit from Brownell's and bed the stock, it is supposed to add quite a bit of consistancy to the grouping of a Mini-14.
As far as cutting the barrel, I wouldn't worry too much about velocity loss I doubt 2 inches is going to make that much real world difference. You will get more flash as a shorter barrel leaves more unburnt powder to flare as it exits the muzzle.
Go for the full accuracy mod, cut and recrown the barrel, Pick up and Eagle flash hider with HK style front sight bore it out to fit the barrels new diameter and lock it down tight.
And post a picture when you're done.

 

[benEzra]

My first choice would be the Eagle flash suppressor (I REALLY like the front sight on that) but I'm already using a Choate pistol grip stock for ergonomic reasons and so I can't add a flash suppressor yet. IF the AWB sunsets, then an Eagle front sight/flash suppressor and a Butler Creek folding stock are #1 on my wish list.

How much length is added by the double brake that some people talk about?

 

[dave3006]

I had mine shortened to 14.5" and a muzzlebrake added to bring the length to 16" overall. It drastically improved accuracy. It is a 2 MOA gun. MOST IMPORTANTLY, the POI does not shift when the barrel gets warm.

At night, with Wolf ammo, the flash is almost beach ball size.

 

[WonderNine]

I'm not sure if it is accurate or not but what I hear most is that for each inch off the barrel you lose 100fps.

It did manage to chrono some .223/5.56 loads a few months ago.

The South African 55gr. 5.56X45mm surplus averaged about 3,100 fps out of the 18.5" Mini-14 w/ flash hider.

Out of the Winchester model 70 w/ 20 or 22" barrel (I can't remember, I'll check tomorrow) it averaged 3,400 fps.

Chrono was about 5 feet in front of the muzzle.