i have 2 custom ar 20-223 nitride barrels. when i installed them they both shot fine, BUT the cases came out 1.472 to 1.473 headspace. this is causing some case head seperation. the barrel maker said the headspace problem was my bolts. they told me their rubber city bolts headspaced ok .they sold me 2 for 200.00 but the cases come out of my guns the same lieght 1.472 to1.473. now they say there is nothing they can do as the barrels headspace ok and can't take the new bolts back. i would like any ideas as what can cause the case problem.
ar 15 head space
- Thread starter jb
- Start date
There may be no problem at all.
If you are using a 20 Tactical chamber then the shoulder angle is 30 degrees vice 23 degrees and that will change the headspace.
If you are using a 20 Practical chamber then the headspace is the same as a .223 and your headspace values are within the SAAMI specs for that cartridge.
How do you measure your headspace? If you are using a Hornady style headspace tool then you can't really say what your actual headspace is, that type of tool is a comparator and not an actual measuring tool. The only way to truly know the headspace is by using headspace gauges.
Headspace on an AR is built in to the barrel and as long as the bolt/bolt carrier and extension are all standard sizes then the headspace will be correct.
If you are using a 20 Tactical chamber then the shoulder angle is 30 degrees vice 23 degrees and that will change the headspace.
If you are using a 20 Practical chamber then the headspace is the same as a .223 and your headspace values are within the SAAMI specs for that cartridge.
How do you measure your headspace? If you are using a Hornady style headspace tool then you can't really say what your actual headspace is, that type of tool is a comparator and not an actual measuring tool. The only way to truly know the headspace is by using headspace gauges.
Headspace on an AR is built in to the barrel and as long as the bolt/bolt carrier and extension are all standard sizes then the headspace will be correct.
Some dies really shove the shoulder back if you adjust them to touch the shell holder. Measure a new piece of 223 brass and see if your dies are setting the shoulder back. If it is just adjust it until it doesnt.
You could also do a false shoulder on first firing to put a stop to the seperations.
You could also do a false shoulder on first firing to put a stop to the seperations.
new brass is .015 to .017 shorter than a fired case. both of my dies will size to 1.460 with a .125 shell holder. using a redding .135 shell holder they are still .003 short. the only thing i can think of is the headspace is .010 to long. i need 3500 cases for each gun. these looong chambers mean many casehead seperations and then many hours checking each case for seperations. i have already necked all the cases to .204
Sounds like you have a wildcat cartridge. Do you have actual headspace gages to go with your reamer? That is the only way to accurately check both rifle and brass.
If you are necking down 223 cases to shoot 204 bullets, only size part of the neck so the case will headspace off a false shoulder for the first firing. That will let the case blow out without causing a head separation
If you are necking down 223 cases to shoot 204 bullets, only size part of the neck so the case will headspace off a false shoulder for the first firing. That will let the case blow out without causing a head separation
The false shoulder is a great idea ( all most) , but necks have been sized already.
And not good if the rounds dont chamber or action close fully, in an auto loader. Most all AR 15s will not fire if the bolt is not locked.
3. ways to fix-
1. A light oil on the case body may keep the brass from grabbing the chamber on firing? This is said to let the brass form to the chamber without separation?
2. Smaller chamber.
3. Jam bullets into rifling to fire form. Load 1 at a time. Use long, base to ogive bullets. May not work when firing? Firing pin strike reseats bullets, deeper into case.
https://sierrabulletsblog.com/2016/09/14/reloading-101-fireforming-cases/
Annealing first may help, but with 1000s of brass, not possible.
Ask the experts on here what lube to use when fire forming. And if they think it may work. I have never used lube or oils.
Last edited:
Coyotefurharvester
Silver $$ Contributor
New 20p BHW AR barrel. Measurements using my Hornady 330 comparator body. I purchased 300 LC formed to 20p these are 1.4510-1.4485(haven't check many seems typical) fired(2-3x) 1.4595-1.4585 new 223 rem brass 1.4545. This is my first experience with a non factory available cartridge, have not had any case separation. I have not necked down from new 223 or 556 brass. Using this rifle for coyote and don't want to lose brass in the snow, the formed LC brass I purchased for 15$/100.
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