Colt F marked barrel on M16A1 upper

[joe scuba]

Hi, I want to make an IDF carbine clone. I have a M4 14.5 barrel that has a F marked barrel. Can I still battle sight zero with the F marked barrel? I know that the front sight post will be taller.

Thanks

[COLT]

Hi, I want to make an IDF carbine clone. I have a M4 14.5 barrel that has a F marked barrel. Can I still battle sight zero with the F marked barrel? I know that the front sight post will be taller.

Thanks


I BELIEVE THE REAR SIGHT IS LOWER THAN THE ONES USED FOR THE F MARKED FRONT SIGHTS.:)

[Robb Jensen]

I BELIEVE THE REAR SIGHT IS LOWER THAN THE ONES USED FOR THE F MARKED FRONT SIGHTS.:)

F FSBs and non F FSBs differ in height. The rear height is the same.

http://img.photobucket.com/albums/v408/gotm4/FshelfColt.jpg

[supertac]

F FSBs and non F FSBs differ in height. The rear height is the same.


The rear height is not the same. The flattop/A3 upper with removable carry handle has a higher rear sight level than the A1/A2 upper.

The exception is Bushy and a couple others. Colt, Stag, CMMG, Novesky, Sabre, etc all use the higher rear sight.

Bushy uses a lower sighted removable carry handle than Colt...they also don't use an F marked FSB.

[Robb Jensen]

The rear height is not the same. The flattop/A3 upper with removable carry handle has a higher rear sight level than the A1/A2 upper.

The exception is Bushy and a couple others. Colt, Stag, CMMG, Novesky, Sabre, etc all use the higher rear sight.

Bushy uses a lower sighted removable carry handle than Colt...they also don't use an F marked FSB.


First I'm going to use the terms A4 for a carry handle and A2 for an A2. A M16A3 (Colt/FN) is a selective fire M16 with a selector with markings SAFE-SEMI-AUTO with an A2 upper receiver (an A2 has SAFE-SEMI-BURST) both share the same upper receivers. Bushmaster and other companies 'not really up to speed nor spec' mistakenly call removable carry handles A3s.

Colt set the standard (mil-spec).............everyone else does pretty much what they want whether it's right or wrong as they have no standard to meet.

What is the rear height difference of an A4 rear sight vs an A2 rear sight when both are bottomed out?

I've never noticed a difference.

I have noticed a difference in the tallness of the elevation drum from an A4 being shorter than an A2 (the A2s has to go through the receiver to assemble), the A4s can't since it's a removable handle. The A4 sight adjusted as high up as it can go won't make it to 8/3 so they made it 6/3. I find the A4 clicks for elevations are roughly half as valuable than they are on an A2.

[Trim2L]

The rear height is not the same. The flattop/A3 upper with removable carry handle has a higher rear sight level than the A1/A2 upper.

The exception is Bushy and a couple others. Colt, Stag, CMMG, Novesky, Sabre, etc all use the higher rear sight.

Bushy uses a lower sighted removable carry handle than Colt...they also don't use an F marked FSB.

I measured the carry handle from a 6920 and a Bushmaster "A3" and both were nearly identical as were the upper receivers.

[supertac]

I measured the carry handle from a 6920 and a Bushmaster "A3" and both were nearly identical as were the upper receivers.

I measured the carry handles on both a Colt and Bushy last week. Yes, they are NEARLY identical. There is a .04" difference in height. That .04" difference is why the F marked front sight base is .04" taller than the A2 FSB.

This is a documented FACT.

[Robb Jensen]

No need for yelling. You said 'document' other than what you posted I can find no other documentation of differences in heights so I'm calling bullshit at this time.

Yesterday at work I measured the bottomed out rear sight heights in 8 different rifles yesterday and found the largest variance between the 8 rifles was 1/64" (or for the decimal junkies 0.015625") or in laymens terms roughly a little less than half of what you found. I measured 2 Colts, 2 RRAs, 2 Bushys and 2 Mutts........The differences were mostly between the Colts and the commercial rifles. I measured from the middle of the windage screw to the center of the selector. So most of the difference is probably is how tight the upper (height wise) fits the lower.

The difference was not enough to make a difference for sight-in as changes in rear sight (windage or elevation) make very little change on paper when compared to the same amount of movement in the front sight would (as any shooter knows or should) and could be called manufacturing variances. A difference like that if the front sight can make all the difference in the world.

So to get back on topic:

Will Joe Scuba be able to sight in a A1/A2 rear sight with an F marked FSB..........YES!