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Problem_Child
June 10, 2007, 11:16
Imbel barrel on a DSA receiver.

I want to be able to shoot both 7.62 NATO and .308 ammo.

I'm using Forster Go/No-Go gauges.

Chamber and gauges are clean. Extractor is removed from bolt.

Bolt will close on "GO" gauge with firm pressure on a .257 pin...
will close with moderate pressure on a .256 pin.

Bolt will not close at all on "No-Go" gauge with .255 pin.
Bolt will close with firm pressure on "NO-GO" gauge with .254 pin.

If I use .257 as my spec...

Add .001 for set-back = .258
Subtract .002 for NATO spec = .256 LS

If I use .256 as my spec...

Add .001 for set-back = .257
Subtract .002 for NATO spec = .255 LS

Should I install a .255 LS or .256 LS?

I'm pretty sure I have it right, but just want to verify it with the pros.

Mosin Guy
June 10, 2007, 11:24
lots to read here http://www.falfiles.com/forums/showthread.php?s=&threadid=119640

W.E.G.
June 10, 2007, 12:38
Use a locking shoulder of the same dimension as the pin that allows you to close the bolt with easy two-thumbs pressure on a 1.630 headspace gage.

Use a locking shoulder of the same dimension as the pin that allows you to close the bolt with easy two-thumbs pressure on a 1.630 headspace gage.

Use a locking shoulder of the same dimension as the pin that allows you to close the bolt with easy two-thumbs pressure on a 1.630 headspace gage.

Got that?


Almost without exception the .308 and 7.62x51 ammo I have checked has been well short of the 1.630 dimension touted as the "ideal" new-gun headspace dimension.

If you want to know the comparative specs of your ammo versus your headspace gages, you need to get a tool to measure the gages and the ammo.
You nee an RCBS Precision Mic
see http://www.realguns.com/archives/035.htm

Until you measure your gages and your ammo - and you compare the specs - you are pretty much talking out your ass when it comes to headspace discussions.

Radio
June 10, 2007, 17:43
That's quite a switch for you, Gary, you have long been a proponent of a looser headspace than a tighter one. I still remember your dissertation about shooting at 1.636" with a calm conscience.

The math in question looked fine to me. I'd better trust the .257" GO figure if his NO-GO fits a .254". The final locking shoulder of .256" is what I would put in there myself.

Are you saying we should now be shooting (haha) for 1.630" headspace instead of 1.632"?? That certainly seems to contradict many years worth of experts saying otherwise. Reminds me of the proper way to oil a piston pin; hole through the top, then that was verboten and hole from the bottom along the rod wall was the only recommendation, then back to hole through the top. Confusing. So who shortened the headspace standard????

--Radio

torquemada055
June 10, 2007, 17:58
Dang, I thought he was trying to figure out his hat size!!!:tongue:



:whiskey: :rofl: :beer: :rofl:

I think it's time to stop the drink.

W.E.G.
June 10, 2007, 18:39
Originally posted by Radio
That's quite a switch for you, Gary, you have long been a proponent of...

I've given up trying to tell people what the headspace dimension should be on their rifle. Everybody seems to agree that 1.630 is the standard "match" spec. for .308 Winchester.

How you achieve that spec, or whether it is correct to set a FAL to that spec is the cause of more hand-wringing than I want to get into on the internet these days.

Nowadays I just try to get people to be straight up about what they are saying.
I don't argue the right and wrong of it.

Powderfinger
June 12, 2007, 23:55
Your gauge pins are belong to us.:]

owlcreekok
June 13, 2007, 13:52
Whatever you do, don't let gunnut1 in here.

Radio
June 14, 2007, 03:08
:rofl:

richbug
June 15, 2007, 13:11
Originally posted by W.E.G.


I've given up trying to tell people what the headspace dimension should be on their rifle. Everybody seems to agree that 1.630 is the standard "match" spec. for .308 Winchester.

How you achieve that spec, or whether it is correct to set a FAL to that spec is the cause of more hand-wringing than I want to get into on the internet these days.

Nowadays I just try to get people to be straight up about what they are saying.
I don't argue the right and wrong of it.

I think he is now of the opinion that the fired brass is worth something, and it is even more valuable if it doesn't need that .006" worth of resizing and trimming(lasts much longer to boot)...

Jon Frum
June 20, 2007, 20:38
I make mine tight--they will loosen up, a file stroke will do the trick if not-follow the angle (on LS).

dougjones31
June 25, 2007, 14:12
Did somebody say Locking Shoulder?????

What is the angle on it? HA HA :tongue:


Old WEG has sure tightened up over the past year or so......he used to say headspace to 1.632" +.002"........and justified it with "It will not be dependable if it is too tight......you might have problems chambering a round....:


I think I was the only one here promoting "tight headspace of 1.630" then. Oh how times have changed..... :biggrin:

Rich@CGW
June 25, 2007, 14:22
You fella's crack me up.

All the: Add this much , Subtract this much..

And you always end up right back to what the dumb guage told to use the first time.

dougjones31
June 25, 2007, 15:09
Yeah Rich....it is easier just to tell people to use what the guage tells you. Your guage is 1.630" so use the same size LS as the pin you use to measure with.

I think that there are some 1.632" go guages out there. Somebody can verify but Clymer guages may be big. I use a Forster guage that is 1.630"

I even go one further on my builds now.....I ADD .001" to my pin size to allow for setback. So my headspace is 1.629" before setback and 1.630" after. I have a rifle that is 4-5 yrs old that I set the headspace to 1.629" initially and it has not missed a beat ....ever. Not a jam, even with several thousand round of Indian ammo. (Sorted of course!)

dougjones31
June 25, 2007, 15:20
I have found that most people under-estimate 2 thumbs pressure.
2 thumbs pressure is when you put both hands beside the receiver and hook your thumbs on the back of the carrier and your birdie fingers on the front of the receiver(where the barrel screws in) then use only your hand strength the force your fingers together and close the bolt. It is a pretty good amount of force.....It is a crisp snap when the bolt drops.

I think the .256 locking shoulder probably best = 1.632"


.257 locking shoulder = 1.631"
.258 locking shoulder = 1.630"

Use any of the 3 sizes they are all safe and will allow you to shoot commercial or milsurp ammo. You probably already have one of the 3 sizes in the kit.

dougjones31
June 25, 2007, 15:27
Originally posted by Raspeguy
If you want your headspace somewhat on the "tighter" side go with a .256 locking shoulder. If your GO gage is on the money this will equate to about 1.630/1.631 headspace. The Imbel has a mil chamber and the force of the bolt/carrier closure will slightly shorten or resize a cartridge that might be a tad over this amount. And this would most likely only be encountered or experienced on a reloaded case - avoidable of course. It's all what you want. Personally, I'd go for the tighter setting. You can always find a more worn bolt, or modify one, if you want more headspace for adverse operating conditions.

OOOOOOOOOOHHHHHHHHH! NOOOOOOOO! did he suggest grinding the locking surface on the bolt? :eek: :rolleyes: Century did that on their guns.....or did you do that on their guns?:wink: :p

dougjones31
June 25, 2007, 15:29
Originally posted by dougjones31
I have found that most people under-estimate 2 thumbs pressure.
2 thumbs pressure is when you put both hands beside the receiver and hook your thumbs on the back of the carrier and your birdie fingers on the front of the receiver(where the barrel screws in) then use only your hand strength the force your fingers together and close the bolt. It is a pretty good amount of force.....It is a crisp snap when the bolt drops.

I think the .256 locking shoulder probably is closest to = 1.632"


.257 locking shoulder = 1.631"
.258 locking shoulder = 1.630"

Use any of the 3 sizes they are all safe and will allow you to shoot commercial or milsurp ammo. You probably already have one of the 3 sizes in the kit.

Powderfinger
June 26, 2007, 10:27
Who shoots .308 Win in their FAL?
I headspace for the 7.62x51 Nato that I keep on hand. 1.633
http://www.falfiles.com/forums/showthread.php?s=&threadid=49526
Of course .308 Win can be used.

Radio
June 26, 2007, 15:04
DOUG!!!!!!!!! YOU'RE STILL ALIVE!!!!!!!!

:beer:

This has got to be the first time you've posted in over a year.

Originally posted by dougjones31

Old WEG has sure tightened up over the past year or so......he used to say headspace to 1.632" +.002"I noticed the same thing.

I think that there are some 1.632" go guages out there. Somebody can verify but Clymer guages may be big. I use a Forster guage that is 1.630"It depends. Forster is USUALLY 1.630"; Clymer is USUALLY 1.632", however, they also produce a 1.630" GO gauge. The final arbiter is what the blinkin' gauge says on the side.

I have found that most people under-estimate 2 thumbs pressure.
2 thumbs pressure is...HIGHLY SUBJECTIVE. This is not something you can teach over the internet or through a book or video. All I will say is that your pressure should be FIRM, but you aren't going to gain anything by raunching down harder. After all, you wouldn't dare do this with your fine precision measuring tools like a micrometer.

I will still headspace to 1.632", the old standard. Has served me well so far.

--Radio [edited one word the next day for clarity]

Problem_Child
June 26, 2007, 17:25
Thanks for the responses. :cool:

The reason I asked the question in the first place is that there seems to be varying degrees of opinion and methodology (as demonstrated by the differing responses posted here).

Trust me... before I even posted the question I searched for and read at least a dozen or more threads regarding head spacing.

Seems like the consensus so far leans towards using a .256 locking shoulder. After literally checking and rechecking (with varying degrees of thumb pressure), a .256 LS appears to be the proper choice.

Thanks again.

Now another question (in another thread :biggrin:).