mini14 spliting case's

M

Matt308

CGN Regular
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COKL Bantario
Hey guys, recently picked up a mini14 fitted with a model 700 .223 barrel. She shoots like a dream but has a habit of riping cases apart. There is no pattern to it, some times it pull's apart in the middle, some times just up from the base and one pulled apart just below the neck. Im using NEW A.E .223 "tatical" I went through 5 box's on the weekend and it riped 4 casings apart. I scrubed the shat outta the chamber, checked fired brass for any signs of a bur in the chanber, nothing, looks fine.
any idea's wtf is going on?
 
Matt308 said:
well thats the therory I have been working on too. How can I adjust the timing?
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perhaps an adjustable gas block? this is taken from the accuracy systems website :

"Tired of hitting the fellow 3 shooting benches down in the head and him throwing the brass back at you?
Tired of having to change gas bushings only to find you didn't get the right diameter installed and had to start the process all over again?
Our new gas system will allow you to save all the lost brass that is ejected normally 20 to 30 feet by your factory gas system.
Our new gas system will save your scope as well as your receiver during the violent impact that happens every time you fire a round off and the operating rod whacks the receiver.
Our new gas system will actually help your rifle shoot better by reducing the harmonics that are produced when the operating rod comes in contact with your receiver during high speed cycling of the operating rod.
Our new gas system can be tuned from no cycling at all for you single shot bench shooters to wide open for you high capacity magazine junkies who don't care where there brass ends up.
*Our new gas block offers a factory look but with an enhanced feature of a user friendly Quick release sling swivel hole. Instead of the unfriendly non-removable factory sling loop. Ours is even the correct width so you can use the swivel of your choice.

Installation is as easy as removing the four factory screws that hold your gas block top and bottom together. Then installing our new gas block, new gas pipe, your gas bushing and putting your four factory screws back in. We then suggest that you load up a magazine and fire a round, notice where the brass lands then adjust the tuning screw a half turn and repeat the process till the outcome you desire is met."

I read once that you can tell how well a semi rifle is functioning/timed based upon the brass ejection patterns. following that line of thinking :
adjustable gas block = changes brass throwing
brass throwing = timing
therefore timing = adjustable gas block ?
 
I am thinking this is a headspace issue too... Is there "strech rings" on the cases that didn't separate? Maybe section a case and look at the case walls and see if there are signs of separation.

A less than scientific way of checking for excessive headspace is to take an unfired round and place a layer of tape on the base of the cartridge (trimmed to the same diameter with a razor knife). Keep placing an additional layer of tape on the base until the action will no longer close. Remove the last layer of tape and measure the thickness of the "tape stack" with a micrometer or vernier caliper.
 
I wouldn`t shoot it again until I got the headspace checked, if i were you. Not a betting man, but that`s where I`d put my money based on what you describe.
 
so its a toss up between timing and headspace eh?
when I drop a live round into the chamber its lose and can wiggle slightly so I dont think its to tight. The past owner said he never had any problems with it riping cases apart, but he also ran it as a bolt action. I thought a headspace issue would damage the case near the base? These are coming apart about 1/3 to 2/3 of the way up from the base.
 
hm,ok. So, live round, bolt closed, I can fit a .003" feeler gauge between the bolt lug and the reciever...I assume this is bad. Im sifting through my fired brass right now, not seing any pattern's yet. Any idea's why this was not showing up to the past owners? Of did I just have a pile of junk un loaded on me.
 
what kinda issue's would I have if it was trying to pull the brass from the chamber too "soon". It rips out the back half and the remaining bit gets jamed on the end of the fresh round.
 
How you are "measuring" is not a reliable way to determine headspace. Spend a bit of cash and order a .223 no-go or preferably a "field reject" .223 headspace gauge from brownells. It should only cost 30 bucks or so but will give you a definitive answer as well as a mechanism to demonstrate to the guy who built it or sold it to you that it is a lemon if they did in fact screw up the headspacing of the gun.

If the gun will chamber (with a closed bolt) the field reject gauge then you have your answer.

As the gun is gas operated, provided the gas port is drilled to the correct size I can't imagine that you're having anything relating to so-called "timing" issues. The new factory guns are set up such that they already have what I would consider to be a massive amount of extra gas that certainly effects "positive ejection". I wind up making a custom bushing that has literally half the inside diameter as compared to the factory one, and the amount of gas they let through is likely less than 1/4 of what the factory bushing will get you.

Cheers, and good luck!

Brobee
 
Matt308 said:
what kinda issue's would I have if it was trying to pull the brass from the chamber too "soon". It rips out the back half and the remaining bit gets jamed on the end of the fresh round.
Click to expand...

If it does not give the brass a chance too cool and contract so it can release from the chamber, it can leave the brass behind in the chamber or rip the rim off the case.

If you have a piece off brass that is not ripped you can measure the head space that way. I'm in Bolton Ontario I have the mic that can measure that for you, if you want to contact me.
 
thanks for the help guys. I will order the proper gear from brownells. Its always nice to have an excuse to get more stuff. I went through the bag'o stuff that came with the rifle and found a smaller gas port and installed it last night. I might go out tonight and test it if I have time after work. I bought it from a fellow cgn'er who got it from another cgn'er a while back. Neither of them said they ever had an issue like this.

2katz I will pm you for your adress and send ya a few if you dont mind?
 
brobee- I realy cant tell you weather or not the gas port in the barrel is the right size. the bushing I removed was bigger then the the port in the barrel, the one I installed looks to be the same size or a bit smaller.
 
just an update, sent out the brass to get checked, installed a smaller port and will test fire today if I get some time. How tight should a live round fit into the chamber? they fit tight in a 308, but the .223 drops right in and can move around left and right a bit.
 
Matt308 said:
so its a toss up between timing and headspace eh?
when I drop a live round into the chamber its lose and can wiggle slightly so I dont think its to tight. The past owner said he never had any problems with it riping cases apart, but he also ran it as a bolt action. I thought a headspace issue would damage the case near the base? These are coming apart about 1/3 to 2/3 of the way up from the base.
Click to expand...


Ran it like a bolt action......
And it has a custom barrel fitted to it....

How many other people do you know run a semi like a bolt action.
If the previous owner has some unique ideas for this rifle - wouldn't it stand to reason that the barrel might be fitted/chambered to the action to best optimise the use of this gun as a bolt action.

I'd have a gunsmith check everything.....

L
 
as far as I know it was not built to function like a bolt action. He just pluged the gasport and ran it like one for better accuracy. Least thats the story I got. Idunno, Im starting to get frusterated. Maybe i need to stick to my rule of not buying used guns on the EE. Maybe the previous owners will weigh as I dont see a need to mention names and drag anyone into it.
 
Matt308 said:
just an update, sent out the brass to get checked, installed a smaller port and will test fire today if I get some time. How tight should a live round fit into the chamber? they fit tight in a 308, but the .223 drops right in and can move around left and right a bit.
Click to expand...


Received the brass today and I do have bad news.

According to ANSI spec's the .223 REM. chamber headspace should measure from 1.4636" - 1.4736" a maximum of .0100" ten thousand of an inch difference. This is from the tables of my RCBS precision mic.

Yours measure .0180", .0180", .0200", .0200" and an oddball at .0060". If we throw out the oddball you have an average of .0190" or nineteen thousands of an inch after they cooled and shrunk. So if we add .0030" to that for shrinkage you are looking at .0220" twenty two thousands of an inch. more than double the maximum allowable.

As a reference I measured 10 pieces out of my Remington 700P and the average was -.0020" after cooling and shrinkage, so my actual headspace is .0010" where yours is .0220". My opinion would be that the rifle is dangerous to use as is whether as a bolt action or semi action. You have a very dangerous situation in you hands, a more powerful .223 round than you are using can have disastrous results.

Further visual observations show that all 5 pieces are at the edge of failure; severe thinning near the base, poorly fire formed and the only case that was .0060" had the primer popped out of it and severely bulged.

Best case the barrel might be salvageable, it needs the shoulder to be re-cut/set-back and the chamber cut to the correct headspace to match your bolt. The problem with that is it needs to be set-back by one thread pitch so the gas port is indexed correctly but that brings the gas port closer to the receiver and that may cause a problem with the op rod and closing of the bolt. Worse case you will need a new barrel.

Given that the mini's barrel is not a standard profile or configuration and not too many gunsmiths work with them you may have a problem finding one that will work on it. If you do, I don't imagine it will be cheap with either option.

I can't tell you what to do but if I were in your situation I would be sending it back to the seller. He sold you a problem that he created whether he knew it or not.

Keep in mind that this is my opinion and not of a gunsmith.

I have been around firearms for a very long time, reload and do all my repairs. I am a machinist so I do understand what it takes but that still does not make me a gunsmith.
 
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