My **NOT so obvious** question of the evening

Sharkson

Sharkson

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Ontario - yeah, I'm sorry too!
Please enlighten me, perhaps the kids and the lack of sleep are getting to me.

I have been trying to fathom (not too hard obviously) why the SEI gas lock dovetail front sights are a different height for 18" and 22" barrels. I don't get it b/c the actual sight is at the exact same distance from the shooter regardless of the barrel length, aren't they?

I am assuming that the front sights mount on top of the gas lock, no?

Can someone help me out here? Thanks.
 
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I have the same question. In another thread, someone mentioned that SEI would be making a run of metric/Nork gas lock sights and that the first run would be for 22" barrels, "because Norincos weren't made with shorter barrels" .... or something to that effect. So, how is the sight any different if it is the same distance from the rear sight regardless of finished barrel length?
 
girlsgunsandfastbikes said:
Check my third posting of this thread.

GG&FB photos

It has nothing to do with length, the Norcs have metric threading on the barrel, as GI is SAE.
Smith hasn't made metric threading parts......yet.

GG&FB
Click to expand...


GG&FB - sorry, but I don't see where the question about the different height sights is answered in your post. Thanks.

Note: I'm not deliberately trying to be thick. :D
 
The shorter barrels need a slightly taller front site to maintain the same point of impact .
Think about the rear site the front site and the barrel as a triangle .
The barrel and rear site being the 90 degree angle . Think of drawing a line between the rear site and the front site . The standard barrel is 22" I believe, so if you cut the barrel to 18" you will need a taller front site to get to on the same place on the line ( Point of impact ) .
I hope this helps clear things up .
Mike
 
Nope, not clear at all. Sight radius is the same regardless of barrel length. Whether a gas lock sight is used in a 22" or 18" configuration is irrelevant to the sight height, because the sight radius is the same, because the gas cylinder is in the same relative position. The question does not pertain to the difference in threads between chinese and US barrels, it pertains to SEI's nomenclature describing the need for different sight heights FOR THE SAME SIGHT RADIUS. Do AR type carbines with fixed standard location sight blocks have different height sights for a 14, 16, or 18 inch barrel? No! Why? because the sight radius is the same regardless of finished barrel length.
 
I thought you were asking about the the difference in the site radius of the the M305 with a shorter barrel/ taller site and why there was a need for a taller site .
Please clarify ? The taller site is used on the short barrel and the shorter site on the 22" version.
Sorry ,I misunderstood . I was thinking about a 22" with a standard site ,then shortening the barrel to say 18" with a gas lock site .This is what I was trying to explain . I now see what you were asking . I do not know why exactly the site is taller , but I would guess that it has to do with the point of impact of the 7.62 round at longer distances ?
I do not know why . Perhaphs Ron Smith can explain this ?
Sorry ,I misunderstood the original question !
 
J.P. said:
Nope, not clear at all. Sight radius is the same regardless of barrel length. Whether a gas lock sight is used in a 22" or 18" configuration is irrelevant to the sight height, because the sight radius is the same, because the gas cylinder is in the same relative position.
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Nope.

The rear sights are calibrated for a front sight sitting on a flash suppressor at the end of a 22" barrel. Once you move the position of the front sight you either re-calibrate the rear sight (what a mess) or you adjust the height of the front sight to match the existing rear sight calibrations.

Clear as mud :cool:
 
I thought you were asking about the the difference in the site radius of the the M305 with a shorter barrel/ taller site and why there was a need for a taller site .
Please clarify ? The taller site is used on the short barrel and the shorter site on the 22" version.
Sorry ,I misunderstood . I was thinking about a 22" with a standard site ,then shortening the barrel to say 18" with a gas lock site .This is what I was trying to explain . I now see what you were asking . I do not know why exactly the site is taller , but I would guess that it has to do with the point of impact of the 7.62 round at longer distances ?
I do not know why . Perhaphs Ron Smith can explain this ?
Sorry ,I misunderstood the original question !
 
H2O MAN said:
Nope.

The rear sights are calibrated for a front sight sitting on a flash suppressor at the end of a 22" barrel. Once you move the position of the front sight you either re-calibrate the rear sight (what a mess) or you adjust the height of the front sight to match the existing rear sight calibrations.

Clear as mud :cool:
Click to expand...

I understand that, i.e. moving the front sight from the end of the barrel to the gas lock position. This would require a change in the height of the sight. But why does SEI have two different height gas locks, one for each barrel length (JP said it best).

Last try: Is it b/c these dovetail gas locks are designed to re-use the front sights from the issue (i.e. Springfield) 18" or 22" factory rifles, which obviously would each be a different height??

Ahhhh, I believe I see the light.

So, if you aim to put lets say, a Norinco front sight, on the SEI gas lock dovetail sight "base", you'd want to choose the 22" SEI model, because the Norinco sight is calibrated for a 22" barrel?

:dancingbanana:
 
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Sharkson said:
I understand that, i.e. moving the front sight from the end of the barrel to the gas lock position. This would require a change in the height of the sight. But why does SEI have two different height gas locks, one for each barrel length (JP said it best).
Click to expand...

What JP said in my words ~

You are speaking of the GLFS-D-22 and GLFS-D-18.
These are designed to use a standard or NM front sight.
The height of the Dovetail is adjusted to mimic the sight
radius of a standard 22" barreled M14 rifle. The FS-D-18
is taller than the FS-D-22 and both replace the Gas Lock.

Springfield Armory addresses this issue with a taller front sight
on the Scout/Bush 18". I'm not sure how it's done on a SOCOM.


Sharkson said:
So, if you aim to put lets say, a Norinco front sight, on the SEI gas lock dovetail sight "base",
you'd want to choose the 22" SEI model, because the Norinco sight is calibrated for a 22" barrel?

:dancingbanana:
Click to expand...

If you have an 18" barrel you install the GLFS-D-18.
If you have a 22" barrel you install a GLFS-D-22.
 
Sharkson said:
Last try: Is it b/c these dovetail gas locks are designed to re-use the front sights from the issue (i.e. Springfield) 18" or 22" factory rifles, which obviously would each be a different height??
Click to expand...

That makes sense to me. I've been thinking in my head this whole time "Gas lock sights equals Navy sight which has a set height". Switch that to gas lock sight with dovetail and things become more clear. Check out this picture from SEI. The one in the middle is the 22 inch version, the one on the right is the 18 inch version.

gaslocksight.jpg
 
girlsgunsandfastbikes said:
Actually the tight one is for a 22 inch barrel, the middle is for the 18 inch.

Now is everyone comfused again. ????

GG&FB
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That's it - too much speculation on this board from the experts no less! :p

I'm calling SEI and getting the real reason, though I still suspect I'm right. :D

I'll let you all know what I find out.
 
Argh! Ok, GG&FB, should your last statement possibly be corrected to read,
"the one on the right is for a sight that works on a 22" barrel in an original flash hider type configuration" This refererence to a 22" barrel, should actually be a reference to a SIGHT that was for a 22" barrel, but is now being used in a gas lock configuration? Therefore, the type of gas lock sight with a dovetail- of which there are two- comes in two heights, not to accomodate two different barrel lengths, but to allow the owner the option of re-using the sight from a 22" flashhider mounted setup, OR to use a new manufacture dovetail sight that is a different height from the standard one, and therefore requires a different height gas lock base.

Could we just have a problem of semantics causing confusion- ie.: that refering to a 22" gas lock sight should actually read as a gas lock sight that accomodates the reuse of a sight originally designed for conventional flashhider mounting on a 22" barrel? Therefore, when SEI says they will be making gas lock sights for norcs, and that they will only be for 22" barrels, they mean that they will only produce the height of sight that will allow the re-use of the sight that came on the Norc?
 
J.P. said:
Argh! Ok, GG&FB, should your last statement possibly be corrected to read,
"the one on the right is for a sight that works on a 22" barrel in an original flash hider type configuration" This refererence to a 22" barrel, should actually be a reference to a SIGHT that was for a 22" barrel, but is now being used in a gas lock configuration? Therefore, the type of gas lock sight with a dovetail- of which there are two- comes in two heights, not to accomodate two different barrel lengths, but to allow the owner the option of re-using the sight from a 22" flashhider mounted setup, OR to use a new manufacture dovetail sight that is a different height from the standard one, and therefore requires a different height gas lock base.

Could we just have a problem of semantics causing confusion- ie.: that refering to a 22" gas lock sight should actually read as a gas lock sight that accomodates the reuse of a sight originally designed for conventional flashhider mounting on a 22" barrel? Therefore, when SEI says they will be making gas lock sights for norcs, and that they will only be for 22" barrels, they mean that they will only produce the height of sight that will allow the re-use of the sight that came on the Norc?
Click to expand...

Heh, that's what I said! Only explanation that fits the facts. I of course completely agree with you. :D
 
As you guys have suggested......with a gas lock dovetail.....sight radius is the same regardless of barrel length.

These dovetails are different in height to allow for the parallax adjustment for the barrel length differences, hence the tall one is for 18 shorter one is for 22.....don't argue.....these are the parts needed to allow for proper rear sight usage. If you use a 22 in version on a short barrel you won't get any rear adjustment closer than 150m.

GG&FB



GG&FB
 
girlsgunsandfastbikes said:
As you guys have suggested......with a gas lock dovetail.....sight radius is the same regardless of barrel length.

These dovetails are different in height to allow for the parallax adjustment for the barrel length differences, hence the tall one is for 18 shorter one is for 22.....don't argue.....these are the parts needed to allow for proper rear sight usage. If you use a 22 in version on a short barrel you won't get any rear adjustment closer than 150m.
GG&FB
Click to expand...

Thanks! Saves me a call to SEI.
 
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