M-305 b

M14Doctor said:
simply put, yes. How measurable this would be would depend on just how many degrees or minutes the barrel is out.
tightening a barrel to achieve zero index will shrink your headspace ever so slightly.... and in these rifles.... that's not so bad.
It's when they are over indexed and reading long in the 7.62 headspace that i get concerned, as pulling the barrel, resetting the torque shoulder and threading her in to zero index..... your headspace could grow ever so slightly.
Maybe not a big deal for those shooting Nato ammo.... but for the reloaders using .308 commercial brass and loading to saami specs..... anything over 1.640" is a NO GO for .308 in my opinion, in these chinese rifles. Some might disagree but i like to play it safe.
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You really are the M14 Doctor :) My Clymer gauges arrived today and I have used them to further assess head space of the new M305B. Of interest is the fact that the NO GO in both Forster and Clymer are milled to 1.634 and are identical in dimension. As noted previously, the rifle swallows these with some play in bolt travel. The FIELD gauge by Forster is 1.638 (and the bolt just barely closes on this one), while the Clymer FIELD is 1.640 (and the bolt does not close on this one). The FIELD gauges spec out exactly .002" difference in length, which one would expect, and would suggest IMO that both company's product would be equally good/accurate. The difference in the two company's FIELD dimensions for Winchester .308 is, however, not something I can address.

At any rate, I am now confident that this gun will perform safely with good quality Win .308 brass using appropriate loads and bullet masses, and I will head out to the range with a few starter hand loads and my case micrometer to see what the actual results are in terms of case dimensions for fired cases as soon as time permits.

Thanks again to all who have provided information in this thread.
 
I've been wondering what a NO GO was.
hxxp://www.brownells.com/1/1/8353-go-no-go-gauge-sets-308-win-headspace-gauge-kit-clymer.html
 
I'm certainly not a pro but here is my kick at the ol' rat.

Brass in my M305B mic'd at +0.013" so I probably should stay away from commercial brass. While I'm not too pleased about that I also should have it properly headspaced. Mic'd brass is a nice estimate but with these rifles I believe the case is still partially expanding while extracting so mic'ing the brass may not be a completely accurate indication of headspace.

The rifle is stamped .308 WIN but it probably should be marked 7.62 NATO. I believe the Chinese avoid the NATO designation because many countries (like the USA) will not permit the importation of rifles with the NATO chamber specification. NATO chambers are designed to be generous and case expansion is greater. NATO marked brass is stronger / thicker and able to withstand the larger chambers better - it's designed for this. Commerial brass is thinner and apparently more prone to case head seperations - although I've never seen one (knock on wood). Regardless I still carry a .30-06 case extractor with my gun tools.

If it closes on a 7.62 NATO FIELD gauge, your 7.62 NATO (cough cough cough I mean 308 WIN marked rifle) is a wall hanger or needs some work. I run WCC 7.62 NATO brass out of my beasty. I prefer the thicker case walls for safety purposes. I won't run factory ammo out of this M305B - until I have a better feel for the headspace. Did I say I wasn't too happy about that?


For guns chambered in 7.62 NATO, here are the headspace limits (in inches):
  • GO: 1.6355"
  • NO-GO: 1.6405"
  • FIELD: 1.6455"
And for .308 Winchester chambers:

  • GO: 1.630"
  • NO-GO: 1.634"
  • FIELD: 1.638"
DSCF1306.jpg
 
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woodlotowner said:
I would be extremely interested to hear from anyone who has an M305B from the new Marstar batch and has checked head space. Also, I'd be interested to hear opinions on using .308 Winchester cartridges in an M305B (mine) with a head space measuring SAMMI 'FIELD' length of 1.638". I'm pretty sure I don't want to use this gun.
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Mine was shooting at 1.638 just fine. I reload (full case resize - yeah, yeah, let's hear about it now :p) and left about .005" spacer. It shot pretty good. Really good actually.

I am always tweaking, so I have a new 7,62 bolt, lapped to about 1.631 - just because! Just waiting for the Alberta monsoons to stop for a bit so I can go back out and test it.
 
sobo4303 said:
Mine was shooting at 1.638 just fine. I reload (full case resize - yeah, yeah, let's hear about it now :p) and left about .005" spacer. It shot pretty good. Really good actually.

I am always tweaking, so I have a new 7,62 bolt, lapped to about 1.631 - just because! Just waiting for the Alberta monsoons to stop for a bit so I can go back out and test it.
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Where'd you get your bolt Sobo? Expensive?

Woodlot
 
purple said:
Yes, inquiring minds want to know. I'd be interested in a comprehensive review of these new arrivals vs the previous ones.

What even became of the much spoken of Italian made versions? Current status anyone?
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The only difference seems to be what is stamped on the reciever. Though my M14s has no bayonet lug.
 
Finally fired my M-305B and it was a pleasure indeed. I fired some 110 grain starting loads I had on hand and they fed and cycled flawlessly. With 150 grain bullets, at starting load charges, I expect it will be equally fun. Ready to load up a s*#tload of cheap 150s now. Will be mindful of the need to keep a close eye/gauge on the spent brass as I go along. Still not too thrilled about the head space measurements, but my concern in this regard appears to be much ado about nothing. :)
 
woodlotowner said:
Where'd you get your bolt Sobo? Expensive?

Woodlot
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I got it from 7.62 firearms. I have some previous threads from the problems I experienced. Needless to say, I had to get an oprod from Dlask and oprod springs from Brownells. I now have extra rollers too! I had to do some fine grinding on the oprod to make the roller go into battery smoother, but all in all a very worthwhile and learning experience. Had some of the best on here help me out in trying to figure things out.

The rifle works like a charm and the accuracy is very very good. I have since removed the scope and that lightened it up somewhat. It is a treat to shoot her.
 
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