The challenges of AR 15 reloading.

[joesasnit]

I am new to the forum, so if this has been covered, I apologize. I have been reloading for a few years and have a procedure that works well and has been safe. Never had any problems with pistol loads or bolt action rifles, but the AR type of rifle, totally different animal. First problem encountered, lack of sufficient pressure to eject the spent cartridge, 300 AAC. Solved that problem with much experimenting different powder and charge size. Next problem, failure to chamber. After much studying on the subject found out "each chamber is different". Again had to go through the process of finding the correct neck size for my chamber. The standard casing sizer was of no value. Even though all would check ok, some would not chamber. Solved that problem with much trial and error. Now I have great 300 AAC reloads. Now on to the 223. No problem with ejection, but some, even with the same neck size will not chamber. All have same OAL, but again some will not chamber. The loads were 55 gr. JHP OAL 2 23. Now here is where the problem may be...various brass types. Any ideas.

 

[gmcttr]

Welcome to INGO.

You refer to neck sizing. This can work in bolt action rifles but the AR platform requires full length resizing. If you are only neck sizing..."there's your problem".

I suggest you get a Sheridan Engineering Ammunition Gauge to confirm your loaded ammo is within spec. Their slot gauge is even better and allows you to see exactly what's going on.

 

[55fairlane]

Welcome, ..... an ammunition gauge will help, but from what I'm reading, you need to change how your doing things.....

full leanth resize......full leanth resize......full leanth resize......in AR guns you must full leanth resize

What is your brass trim leanth ? What powder ? What powder charge? What AR rifle?

Aaron

 

[patience0830]

Yeah. What he said. Neck sizing is ok in a bolt gun. Full length sizing is a must for reliability in most ARs.

 

[bocefus78]

Full length resize, trim all cases, and most problems will disappear if the dies are set right. Even with mixed brass. I've used mixed brass for my blasting loads, and never had a problem.

Some report having to use a small base die for AR reloading, but I have no experience there. What dies are you using?

 

[BiscuitsandGravy]

+1 for 'full length sizing'.

 

[joesasnit]

Should have been more specific. I am full ,case sizing, but I have been reading, not just any die set but a small base RCBS die set. That will be my next adjustment. Thanks.

 

[gmcttr]

...I suggest you get a Sheridan Engineering Ammunition Gauge to confirm your loaded ammo is within spec. Their slot gauge is even better and allows you to see exactly what's going on.

Shoulder setback, case trim length, over crimping causing a bulge, etc. can all cause problems. Get the Slot gauge and you can better determine what the problem is.

Their standard gauge certainly helped me get my 300 BLK reloads sorted out but I wish I had spent the extra dollars to get the slot gauge.

FWIW, I haven't needed small base dies for .223's in five different AR's including one with a Compass Lake Engineering competition chamber.

 

[55fairlane]

For my NM I use a Lee full leanth die, and no crimp.....I agree over crimp can cause a problem

 

[x10]

I have a couple ar's and some are factory high speed production and a couple are custom chambering. I have to go with Full length small base dies or I have trouble in my match guns. but as above full length no matter what.

 

[kennedy759]

I have had no problems loading 223 for my armilite, using lake city brass, lee dies and a lee turret press. I, of course, full length size with a light crimp.

 

[joesasnit]

Just got back from the range, not real successful. Again had problems with chambering some of the rounds, but I knew I would. I took both the rounds that fired and the ones that would not chamber and put a micrometer to them in various spots. To my amazement could find little, if any difference. In fact the round that would not chamber was, in some areas, the smaller measurement. Don't know what it has to do with the problem, but I have a Sheridan Engineering slot gauge on order. From what I can see this will identify whatever problem there may be.

 

[mac45]

Sounds like a headspace issue, as in you're not moving the shoulder back far enough when you size 'em.
But the intermittent thing is bothersome.

Just to be clear.....
Factory runs OK in the gun?
This is an actual failure to chamber and not a failure to feed?
(The round makes it into the chamber but the bolt fails to go into battery?)

Also wondering, is this new brass? Once fired from your rifle?, Range pick up? Once fired military?

 

[dukeboy_318]

Just got back from the range, not real successful. Again had problems with chambering some of the rounds, but I knew I would. I took both the rounds that fired and the ones that would not chamber and put a micrometer to them in various spots. To my amazement could find little, if any difference. In fact the round that would not chamber was, in some areas, the smaller measurement. Don't know what it has to do with the problem, but I have a Sheridan Engineering slot gauge on order. From what I can see this will identify whatever problem there may be.

Are you full length sizing? What die brand? Are you putting any crimp on the cases? What AR are you using? Ive had some ARs that seem to like a little more crimp to chamber smoothly than others. Also, what case length are you loading to? How deep are you setting the bullet? What Bullet are you using.

 

[Robert Richardson]

Is your sizing die adjusted all the way down to touch the shell holder?

 

[Sniper 79]

As others have said full length resize needs to be done.

Go to 300blk forum. They have a good and bad brass list. Not all brass will work for the 300. Case is too thick and wont chamber.

Ar15 forum is another wealth of knowledge. We live in a good time. Others have paved the way and it's all available with time and research.

 

[joesasnit]

Thanks to all for your input. The rifle is a 300 AAC Blackout, made by CMMG, MK-4 16" barrel carbine. I have not had any problems with factory rounds. The brass I use varies, but mostly Lake City. I did some reloading tonight to experiment. I had some JAG, Federal mixed in with the LC. I did notice that the JAG were less uniform and would seem to need more pressure to resize, but all the brands seem to vary when resizing. All are size at 1.365 case length. I just started using an RCBS small base die for sizing and setting. The intermittent problem is failure to fully chamber. Once the round attempts to chamber and fails, it requires a tool to help open the bolt. The extremely frustrating thing is when I mic the bad against the good, sometimes I find no difference in measurements. With that said, I realize not all measurements can be taken. I am now measuring each case after sizing, as I have found the magic number for my chamber to be a neck size of .3280, or less, after sizing and not more than .3310 after loading. Now since this is not totally fool proof, as stated before I have a Sheridan Slot gauge on the way. It appears will identify problems that can not be found by other means. What I am doing now is dry loading each finished round via magazine and rifle chamber. Even with my "magic sizing numbers" I will have a non chambering issue on a small % of the rounds. The COL is what is specified for whatever round I am loading. All size of the case is done the total length, until the case holder and die touch.

 

[Sniper 79]

Shouldn't be having problems like this dude. Should be load and shoot. May want to ream chamber or send it back to CMMG for inspection.

 

[bigedp51]

A small base die reduces the case diameter .002 to .003 more and also bumps the shoulder back further than a standard die. Meaning it sizes the case to minimum SAAMI dimensions in diameter and shoulder location.

Questions.

1. Were all these cases only fired in your rifle? Or did you pickup some range pickup .300 BO brass.
2. Did you make these cases from .223/5.56 cases yourself or did you buy them already made.
3. Are only one brand of case causing the problem?
4. Lake City and other brands of 5.56 cases are made of harder brass and will spring back more after sizing.
5. The "shorter" .300 BO case made from 5.56 brass will have thicker case necks, and the thickness varies between case brands.
Below my Hornady cartridge case headspace gauge that lets you measure a "FIRED" case and then set the die for the correct shoulder bump.

Below a Redding neck thickness gauge, and one twist of the wrist tells you all you need to know.
I buy bulk once fired 5.56 Lake City cases fired in a multitude of different chambers, and size them the first time with a small base die.
And a small base die reduces the case to minimum SAAMI dimensions. Meaning .002 to .003 smaller in diameter and also push the case shoulder back .002 to .003 mor
This case neckse than a standard die.

If you are now using a small base die and having chambering problems my guess is your case necks are too thick. The .300 BO case is shorter than the parent 5.56 case and the case neck and shoulder area of the newly formed case is thicker. And the thicker case necks can cause chambering problems.

You need to measure some factory loaded .300 BO case necks vs your cases formed from 5.56 cases.

Thicker case necks is a problem anytime you use a longer case and form it into a shorter case. The same thing happened to me forming 30-06 cases into 7.65 Belgian Mauser cases.
WARNING, if the case necks do not have room to expand you can have pressure spikes and exceed max chamber pressure.

Read below, you need a neck thickness gauge and a Hornady cartridge casse headspace gauge.


Forming .300 Blackout Brass

Forming .300 BLK Brass - MassReloading


Below a Redding neck thickness gauge, and one twist of the wrist tells you all you need to know.


Below my Hornady cartridge case headspace gauge that lets you measure a "FIRED" case and then set the die for the correct shoulder bump.



Below not all case gauges are made the same, the red JP Enterprise gauge is smaller in diameter and made with a finish chamber reamer. The reversed 5.56 cases dropped further into the Wilson and Dillon gauges showing they a larger in diameter. Meaning they check shoulder location but not case diameter. And if the case fits the red JP enterprise gauge the loaded cartridge will fit in any chamber. I use the Hornady gauge to check the shoulder location on fired and sized cases. And the red JP Enterprise for checking case diameter in a plop test.

 

[ckcollins2003]

Are you trimming your cases after full length sizing?

Also, try turning your die in another twist after it touches the shell holder. I had a problem chambering my .308 when I first started and this solved it. I don't know why, since the die was touching the shell holder, but another turn and it seemed to maybe go in just a touch more.