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Backup iron sights. Again!

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9 years 4 months ago #45565 by Charlie
Backup iron sights. Again! was created by Charlie
I thought I had the backup iron sight issue sussed, and even went so far as to put a set of Magpul Pros in the shopping cart. Then I got cold feet and trotted out to the shop, got my carpenter level, and set it on the receiver rail of my A4BF. Guess what? The gas block is lower than the receiver rail by a good bit (it looked like about 1/2 inch).

A quick review of the old A4BF web page reveals; "Top of gas block is .398 (+/- .010) lower than top of receiver".

A review of the old A4BNMF web page does not produce information on the height of the gas block. I'm guessing it's the same as the A4BF because both will use the same Armalite detachable carry handle/front post sight set.

An email to Magpul verified that the Mbus Pro sights are "in the same plane". I take this to mean that the receiver and gas block rails need to be the same height.

What do I do now?
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9 years 4 months ago #45566 by jtallen83
Replied by jtallen83 on topic Backup iron sights. Again!
Couple options;

yhm.net/gas-block-riser.html

^I think Sisco went this route so maybe he can elaborate.

Then there is always the trusty MI option;


www.midwestindustriesinc.com/index.cfm?f...play&category_ID=192
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9 years 4 months ago - 9 years 4 months ago #45567 by Siscowet
Replied by Siscowet on topic Backup iron sights. Again!
I'm The

jtallen83 wrote: Couple options;

yhm.net/gas-block-riser.html

^I think Sisco went this route so maybe he can elaborate.

Then there is always the trusty MI option;


www.midwestindustriesinc.com/index.cfm?f...play&category_ID=192

I ran into a problem with the Yankee Hill Machinery adapter on my AR10 T carbine. I was using 45 degree offset BUIS and the recoil consistently would force the adapter up, at a 35 degree angle, making the sights useless. I have since decided to remove the 45 degree BUIS and am contemplating my next move.
By the time of all the screwing around, I would just get the Midwest industries front sight.
Last edit: 9 years 4 months ago by Siscowet.
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9 years 4 months ago #45568 by jtallen83
Replied by jtallen83 on topic Backup iron sights. Again!
Sisco, Do you think it would have had the same issue with a regular same plane sight instead of the offset?

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9 years 4 months ago - 9 years 4 months ago #45569 by GRA
Replied by GRA on topic Backup iron sights. Again!

jtallen83 wrote: Then there is always the trusty MI option;


www.midwestindustriesinc.com/index.cfm?f...play&category_ID=192


This is the option I pursued on my DEF-10. As soon as I get out to the range I'll get back here and report on how it worked. I bought the flip-up rear sight offered by MI, and this special height flip-up front sight.

Although I have not measured yet with a caliper, it appears there still may be some discrepancy with the proper front sight height. This may be correctable with some of the KNS sight posts that are made to correct such issues.

One other option, if I may suggest, is if you have the lower gas block you may be able to swap this out for another gas block that sits higher and matches the proper height / same-plane.

A check with JSE surplus might produce such an item: www.jsesurplus.com
Last edit: 9 years 4 months ago by GRA.
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9 years 4 months ago #45570 by Siscowet
Replied by Siscowet on topic Backup iron sights. Again!

jtallen83 wrote: Sisco, Do you think it would have had the same issue with a regular same plane sight instead of the offset?

I really don't know. Guessing a fifty-fifty chance it would. I may mess around with a standard flip up I have to see what would happen.
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