AR Sponsor
Posted: 11/2/2015 9:57:33 PM EDT
| Alright, so I recently completed my first build. I have two new bolts, one PSA and one Ares Arms and I put a Green Mountain barrel on it. I bought the Ares for this build and the PSA for another, different build. I finally got my headspace gauges and checked the headspace tonight. The Ares Arms bolt will not close on the Go Gauge or the Field Gauge. I tried it with the PSA and it closed fine on the Go Gauge and not on the Field. My question is this: do I try and get another bolt from Ares? Do I try and chamber live ammunition and, if it chambers, fire some rounds to see if it "breaks" the barrel and bolt in together? It seems that some people do this. I don't really want to buy another bolt at this time as money is tight. Thoughts? |
|
Bolts have tolerances.
Since one bolt passes the Go gage and one does not the chances are the AA bolt is a little tighter than the PSA bolt. Measure the lug length and measure the depth of the face. Subtract the face measurement from the lug measurement the result should be .153” to .156”. New barrel/bolt combinations should also be checked with a No-go gage (1.4706”). In your case if both bolts measure out then your headspace is tight and well within the No-go spec. Ammo is made to a different tolerance range; a chamber that is a little short will probably work fine with typical ammo. Get some ammo in the high end of the tolerance range and you can start having problems. |
|
That just indicates the bolt is within tolerance.
Also the lug lengths should be .278” +- .002”. Every bolt I have measured has had .278” lugs. If for instance the AA Bolt measures .156” and the PSA bolt measures .153” then you know that the headspace problem is caused by tolerance stacking. Until you measure the bolts for all you know the PSA bolt could be significantly out of spec. It may be rare, but a while back a guy found several bolts at his LGS with short lugs. The odds are your chamber is just a little short. Personally I would not use the AA bolt in that weapon. Headspace does get greater over time; fire enough rounds and the AA bolt may pass the Go gage. Keep in mind the chamber and cartridge specs are set so a max tolerance round will work in a min tolerance chamber. Right now the indications are your headspace is less than min tolerance. |
AR Sponsor