Im going to get my new 09 Poly headspaced soon and was wondering what is the cutoff point in M14 headspace for it to safely and reliably fire .308 commerc ammo? I have an older M1A that is headspaced to 1.631 and it eats both Nato and commerc without a hitch. My question is at what reading does it become a "use Nato ammo only" rifle?
09 Poly headspace tolerance
- Thread starter J996
- Start date
Ok, I know that an M14 spaced at 1.630 is a tight match chamber and 1.642 is not good headspace. Ergo 1.630 very good, 1.631 very good, 1.632 still good ect, ect. At what point does it turn no-go for factory ammo?
As far as I know military chambers have looser tolerances than say your remmy 700 in .308win. That is why nato brass is thicker so it will stretch safely in the looser chamber. Commercial brass is thinnner and will not take the stretch like nato brass will, if headspace is tight like my M1A's(1.631) commercial ammo is no problem, but if it was out at say 1.638 I would be feeding it nato only.
Update: Ok, I found my answer on a yank site: 1.636 for civ .308 after that use nato. 1.638 is SAAMI field reject and cheap commercial ammo can fail at this headspace. Military field reject is 1.6455
If the Poly mics 1.636 or under im going to feed it both. If it mics over its gonna be fed NATO only.
I hope shes tight
As far as I know military chambers have looser tolerances than say your remmy 700 in .308win. That is why nato brass is thicker so it will stretch safely in the looser chamber. Commercial brass is thinnner and will not take the stretch like nato brass will, if headspace is tight like my M1A's(1.631) commercial ammo is no problem, but if it was out at say 1.638 I would be feeding it nato only.
Update: Ok, I found my answer on a yank site: 1.636 for civ .308 after that use nato. 1.638 is SAAMI field reject and cheap commercial ammo can fail at this headspace. Military field reject is 1.6455
If the Poly mics 1.636 or under im going to feed it both. If it mics over its gonna be fed NATO only.
I hope shes tight
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Most of the USGI M14's I've owned (all four of them) all headspaced over 15 thou
Back then for competition purposes, I just reloaded and neck sized that brass for THAT chamber! That way we minimized case stretch for each firing!
BTW, NATO NO-Go gauge is 25 thou over the 1.630" SAAMI spec... now, yer #### will fall off!
And this afternoon, along with zxcvbn as my witness, I fired a bunch of surplus milsurp ammo out of a spare Poly M14 bolt inside a Norinco receiver and the brass mic'ed 22 thou and 23 thou! I just tossed that brass in the club's brass recycling bin....
Then I dropped my TRW USGI bolt back into that Norinco receiver and it mic'ed 3 thou! Minimum bolt slop!! Life is good!
Make sure yer #### don't fall off!
Barney
Back then for competition purposes, I just reloaded and neck sized that brass for THAT chamber! That way we minimized case stretch for each firing!
BTW, NATO NO-Go gauge is 25 thou over the 1.630" SAAMI spec... now, yer #### will fall off!
And this afternoon, along with zxcvbn as my witness, I fired a bunch of surplus milsurp ammo out of a spare Poly M14 bolt inside a Norinco receiver and the brass mic'ed 22 thou and 23 thou! I just tossed that brass in the club's brass recycling bin....
Then I dropped my TRW USGI bolt back into that Norinco receiver and it mic'ed 3 thou! Minimum bolt slop!! Life is good!
Make sure yer #### don't fall off!
Barney
Just shot zxcvbn's Poly M14 yesterday. His chamber mic'ed to 7, 8, 9 thou! I'm super happy and so is he.
Time to put out an 'all call' to Poly M14 owners to mic their brass..... and do some research! I'll get on that this afternoon when I get out of school!
Barney
Time to put out an 'all call' to Poly M14 owners to mic their brass..... and do some research! I'll get on that this afternoon when I get out of school!
Barney
saskgunowner101
CGN Ultra frequent flyer
- Location
- near Prince Albert
How does one mic their brass, is this somthing that can be done with a digital micrometer? please explain
Curious as well.
Before I start my RANT,
I'll just point out that there is a sticky,
WHICH EXPLAINS ABOUT M14 HEADSPACE IN GREAT DETAIL
AND,
there are several other threads here in the battle rifle section on the subject of headspace in an M14 type rifle.
Why oh why are all the M14 newbies so paranoid about EXCESSIVE headspacing on an M14?
Hungry just posted that his fired 7.62 NATO brass showed a MASSIVE OVERLENGTH .022" - .023", without a Kaboom.
I know of people who have had similar experiences using .308 WIN ammo at similar headspace.
NO,
we don't recommend this massive headspace.
SAMMI lawyer proof headspace RECOMMENDATIONS for .308 is much lower.
but in the real world of M14 rifles,
excessive headspace does not seem to be a REAL problem.
Paranoia is defined as an 'UNREALISTIC' fear ...
and so far, we simply don't have ANY [ NADA .. NOT A SINGLE ONE ] case of too much headspace causing a kaboom in an M14 rifle, if shot with NEW commercially loaded .308 ammo, OR 7.62 NATO ammo.
My bnew UNFIRED 2009 BELL/Poly shows HEADSPACE at .010" over .308 GO, with [ for a bnew unfired bolt ] pretty decent lug bearing on both sides.
Both my 2007 Norcs are tighter, at .006" and .007". over .308 GO, and both have been fired enough to wear the bolts lugs in to near perfect bearing at both sides.
If you want to be afraid, you have lots of other REAL M14 issues that really can really really hurt you ... in the REAL world.
REALLY!
1.] UNTIL you know what proper bolt lug bearing looks like, and can tell at a glance that BOTH lugs are bearing fully, measuring headspace is pretty well just not very relevent. If the lugs aren't bearing fully and equally, headspace WILL change as the bolt lug wear in. A bolt that is bearing ONLY on the right side may give perfect headpace .... but it will only have half the strength as a bolt that is lapped in/fitted up for proper lug engagement at BOTH lugs.
2.] If you want something REAL to worry about,
worry about firing pin extrusion, firing pin/receiver bridge timing, stuck firing pins, etc.
There was a thread about this before, where as a field expedient, we used loose pocket change to measure how much bolt lug bearing there was at the right bolt lug, before the firing pin would fall.
Short answer ...
some of these bolt/receiver/firing pin combinations do have more slop than is desirable.
If any of this concerns you,
the fix is simple:
BUY A GI BOLT AND HAVE IT FITTED!
OR,
if your Chinese bolts otherwise fits well,
BUY A GI FIRING PIN AND HAVE IT FITTED!
So,
how about we NEVER allow another newbie question EVER about headspacing on the M14 and all concentrate our M14 paranoia on firing pins instead.
just for a change .....
LAZ 1
I'll just point out that there is a sticky,
WHICH EXPLAINS ABOUT M14 HEADSPACE IN GREAT DETAIL
AND,
there are several other threads here in the battle rifle section on the subject of headspace in an M14 type rifle.
Why oh why are all the M14 newbies so paranoid about EXCESSIVE headspacing on an M14?
Hungry just posted that his fired 7.62 NATO brass showed a MASSIVE OVERLENGTH .022" - .023", without a Kaboom.
I know of people who have had similar experiences using .308 WIN ammo at similar headspace.
NO,
we don't recommend this massive headspace.
SAMMI lawyer proof headspace RECOMMENDATIONS for .308 is much lower.
but in the real world of M14 rifles,
excessive headspace does not seem to be a REAL problem.
Paranoia is defined as an 'UNREALISTIC' fear ...
and so far, we simply don't have ANY [ NADA .. NOT A SINGLE ONE ] case of too much headspace causing a kaboom in an M14 rifle, if shot with NEW commercially loaded .308 ammo, OR 7.62 NATO ammo.
My bnew UNFIRED 2009 BELL/Poly shows HEADSPACE at .010" over .308 GO, with [ for a bnew unfired bolt ] pretty decent lug bearing on both sides.
Both my 2007 Norcs are tighter, at .006" and .007". over .308 GO, and both have been fired enough to wear the bolts lugs in to near perfect bearing at both sides.
If you want to be afraid, you have lots of other REAL M14 issues that really can really really hurt you ... in the REAL world.
REALLY!
1.] UNTIL you know what proper bolt lug bearing looks like, and can tell at a glance that BOTH lugs are bearing fully, measuring headspace is pretty well just not very relevent. If the lugs aren't bearing fully and equally, headspace WILL change as the bolt lug
2.] If you want something REAL to worry about,
worry about firing pin extrusion, firing pin/receiver bridge timing, stuck firing pins, etc.
There was a thread about this before, where as a field expedient, we used loose pocket change to measure how much bolt lug bearing there was at the right bolt lug, before the firing pin would fall.
Short answer ...
some of these bolt/receiver/firing pin combinations do have more slop than is desirable.
If any of this concerns you,
the fix is simple:
BUY A GI BOLT AND HAVE IT FITTED!
OR,
if your Chinese bolts otherwise fits well,
BUY A GI FIRING PIN AND HAVE IT FITTED!
So,
how about we NEVER allow another newbie question EVER about headspacing on the M14 and all concentrate our M14 paranoia on firing pins instead.
just for a change .....
LAZ 1
BattleRife
CGN Ultra frequent flyer
- Location
- of No Fixed Address
I want a reasonably tight headspace for reasons of brass life. My 2007 Norinco has over a dozen reloads on some cases, with full length sizing each time. It would be nice to keep that feature.
Ok, its my bad that i did not read the sticky first, sorry. I also realize it must be frustrating for the experts to get asked the same questions over and over again (which is why they make sticky's) I have been shooting M1A's for 9 years and this is my first chinese rifle. I dont know too much about them yet. There is alot of bad info about chinese rifles out there (american sites) and it got me concerned about getting a case head separation. This is a non issue in my M1A as it has a match chamber. The info provided on this site has been very helpful in answering most of my questions regarding chinese M14's (now that ive read ALL the sticky's). Thanks.
) I have been shooting M1A's for 9 years and this is my first chinese rifle. I dont know too much about them yet. There is alot of bad info about chinese rifles out there (american sites) and it got me concerned about getting a case head separation. This is a non issue in my M1A as it has a match chamber. The info provided on this site has been very helpful in answering most of my questions regarding chinese M14's (now that ive read ALL the sticky's). Thanks.Do you know your headspace? My norc is 12 - 14 thousandths over and I plan to reload, found collet dies on the way home from the Halifax clinic and will use them to neck size but I'm interested in what other reloaders are doing with their brass/headspace issues.
BattleRife
CGN Ultra frequent flyer
- Location
- of No Fixed Address
Nope. I just shoot stuff and look for stuff to go wrong. I don't generally investigate the stuff that goes right; it's not in my nature.
i can confirm that the rifle mentioned has a measured headspace of 1.637 , 2 thou over match 7.62
AND required no lapping of the lugs for bearing, This poly was a very fine example of an M14s. I've got 4 more customer rifles down on the bench getting match tuned and several more are being shipped in by clients. i will be keeping notes by serial number, recording headspace values and other notable characteristics of the new Poly's, for reference down the road.
