Question about BDC reticle

[Mickster]

I've been reading up on the Burris 1x4 and IOR 1.1x4 BDC reticles. What I've learned is that the reticle is approximately pre-calibrated for the M855 62 grain bullet out of an AR -15 at 3050fps. The word "approximately" comes up often.

Has anyone mounted one, gone out and shot groups at varied distances and verified how "approximate" the BDC reticle in these scopes would be?

I've searched all over and couldn't find anything.

[Y. Koester]

I have the burris 1x4 xtr and i must say that the 300 dot is on at 300 if you sight in the 100 dot at 100. I shoot mostly 69 smk's. I don't know about the IOR.

[Trail3]

The Black Hills 69 and 77 Gr. Blue box are only a about an inch low at 300 after sighting in at 100.

Great scope.

[abn-rgr]

I have the Burris XTR. Im shooting 55 grain Montanas with 26 grains of Win 748 with a 18" barrel. Out to 300 its on. 400 and out it starts to get squirelly. I havent chronoed the load yet, so I couldnt say what the FPS is.

[ERIC]

I called up Valdada a few months ago and asked them about how they calibrated the reticle because my friend was about to buy one of their scopes. The guy told me they used a muzzle velocity of 2,750 fps for the 62 gn bullet and a scope height of 1.5". The 2,750 seemed a little on the low side but that's what I was told.

My buddy is using Win 62 gn factory ammo which we chronoed at 3,010 fps. We were having a hard time hitting a 12" square at 300 yards using the 1st hash mark.

I have their older scope with the M-SeriesCQB reticle and like that a lot more because you don't have to do any backwards math if you want to use the BDC and a different bullet.

[Mickster]

I just got off the phone with a customer service rep from IOR/Valdada.

The data he gave me was IOR calibrated the 1.1x4 BDC based on a muzzle velocity of 3000 fps for the 62 grain M855 ammunition. Sight height was the standard height of an AR-15 zeroed at 100 yards. He didn't say but I believe that would be about 2.6 inches.

So, if I had some M855 ball ammo and drove to the nearest range that could accommodate 300 to 500 yard shots (100 miles from my house each way) I would set up a paper target and zero at 100, then shoot some groups at 300, 400 and 500 to verify the BDC stadia.

But because I suffer from L.A.Z.Y. syndrome I'm hoping that somewhere out there is an Enos forum member that has already done that.

As a side note, he also said that scope with the BDC will work very well with 140 to 150 grain ball ammo in .308. That would be interesting too.

[outerlimits]

I just got off the phone with a customer service rep from IOR/Valdada.

The data he gave me was IOR calibrated the 1.1x4 BDC based on a muzzle velocity of 3000 fps for the 62 grain M855 ammunition. Sight height was the standard height of an AR-15 zeroed at 100 yards. He didn't say but I believe that would be about 2.6 inches.

So, if I had some M855 ball ammo and drove to the nearest range that could accommodate 300 to 500 yard shots (100 miles from my house each way) I would set up a paper target and zero at 100, then shoot some groups at 300, 400 and 500 to verify the BDC stadia.

But because I suffer from L.A.Z.Y. syndrome I'm hoping that somewhere out there is an Enos forum member that has already done that.

As a side note, he also said that scope with the BDC will work very well with 140 to 150 grain ball ammo in .308. That would be interesting too.

what you were told is accurate. i have a GSRC with a BDC designed by the man that did the IOR CQB reticle. he confirmed that data to me. all you have to do is plug in that data into ballistic software and play with the bullets and muzzle velocity and you will find a load that will match the BDC. i have confirmed mine out to 400, and that's as far as i care for our game.

[apriav]

I have IOR 1X4 and 1x8 scopes. The short answer is with SMK 69s@2800 if you zero 300 line at 300 yards your 400 will be right on. Check where you hit at other distances, but I have found my scopes hit where they should. That being said, you have to check your ammo/scope at yardages. No free lunch.

[ERIC]

I just got off the phone with a customer service rep from IOR/Valdada.

The data he gave me was IOR calibrated the 1.1x4 BDC based on a muzzle velocity of 3000 fps for the 62 grain M855 ammunition. Sight height was the standard height of an AR-15 zeroed at 100 yards. He didn't say but I believe that would be about 2.6 inches.

So, if I had some M855 ball ammo and drove to the nearest range that could accommodate 300 to 500 yard shots (100 miles from my house each way) I would set up a paper target and zero at 100, then shoot some groups at 300, 400 and 500 to verify the BDC stadia.

But because I suffer from L.A.Z.Y. syndrome I'm hoping that somewhere out there is an Enos forum member that has already done that.

As a side note, he also said that scope with the BDC will work very well with 140 to 150 grain ball ammo in .308. That would be interesting too.

what you were told is accurate. i have a GSRC with a BDC designed by the man that did the IOR CQB reticle. he confirmed that data to me. all you have to do is plug in that data into ballistic software and play with the bullets and muzzle velocity and you will find a load that will match the BDC. i have confirmed mine out to 400, and that's as far as i care for our game.

So the 2.6" scope height is correct? Why don't they just put that info on their website instead of us having to call them and getting different answers depending who answers the phone.

[mpeltier]

I just got off the phone with a customer service rep from IOR/Valdada.

The data he gave me was IOR calibrated the 1.1x4 BDC based on a muzzle velocity of 3000 fps for the 62 grain M855 ammunition. Sight height was the standard height of an AR-15 zeroed at 100 yards. He didn't say but I believe that would be about 2.6 inches.

So, if I had some M855 ball ammo and drove to the nearest range that could accommodate 300 to 500 yard shots (100 miles from my house each way) I would set up a paper target and zero at 100, then shoot some groups at 300, 400 and 500 to verify the BDC stadia.

But because I suffer from L.A.Z.Y. syndrome I'm hoping that somewhere out there is an Enos forum member that has already done that.

As a side note, he also said that scope with the BDC will work very well with 140 to 150 grain ball ammo in .308. That would be interesting too.

what you were told is accurate. i have a GSRC with a BDC designed by the man that did the IOR CQB reticle. he confirmed that data to me. all you have to do is plug in that data into ballistic software and play with the bullets and muzzle velocity and you will find a load that will match the BDC. i have confirmed mine out to 400, and that's as far as i care for our game.

So the 2.6" scope height is correct? Why don't they just put that info on their website instead of us having to call them and getting different answers depending who answers the phone.

Both numbers are probably correct. The 1.5 height is most likely the mount height as in the larue 1.5 which places the center of the scope at 1.5" above the reciever rail. Which in turn is 2.6" from the center of the bore to the center of the scope.

[outerlimits]

with a larue spr-e, mine is 2.7" above the boreline.

[ERIC]

Both numbers are probably correct. The 1.5 height is most likely the mount height as in the larue 1.5 which places the center of the scope at 1.5" above the reciever rail. Which in turn is 2.6" from the center of the bore to the center of the scope.

Both numbers are correct to different questions. What we need is the sight height - the distance from the center of the scope to the cenber of the bore.

[mpeltier]

My appologies, I missread your post.

I thought you were looking for the sight height (distance from the center of the bore to center of the scope) which is 2.6" (or maybee 2.7", .1" makes no differance).

Which also happens to be 1.5" from the top of the rail. Which is probably more relavent as most rings/mounts will be expressed in this number.

It would be impossible for it to be 1.5" from center of bore to center of scope.