POI differences between ammo question.

[Jaysop]

So today I was at the range trying out some bulk IMI M855.
Ive been using American eagle M855 in the past. And switching between the two I had about a FOOT of elevation difference at 50 yards.
Has that ever happened to anyone before? Ive mixed in different mags of multiple types of ammo and never had something noticeable let alone 12inches...
My windage was dead on and oddly enough both types of rounds were grouping perfectly when I went to the bench to figure out what was going on, except that there was a major difference in elevation.
I didn't try out my irons, I didn't think of it at the time. But its was consistent threw the scope so I cant figure that it would make a difference.

My rifle is a factory built Noveske Lo pro with a 16 inch barrel with a battlecomp installed. I'm also using a Vortex pst 1-4 on a larue mount.
I apologize if there is a simple answer to be found threw the search function, I haven't found it, maybe I don't know what to look for.

Any insight?

[Failure2Stop]

12" at 50 is not usual.
I have seen differences up to 6 inches at 50, but they are rare.
FWIW- the biggest shifts I have seen is going from M855 to Mk262 in issued weapons. With all of my ammo and weapons the shift between ammo has never exceeded 3" at 100 meters.
Shift is common and unpredicatble, but 12" is excessive in my experience. Could there be any other contributing factors?

[Jaysop]

I really cant think of anything that couldn't think of anything else that could be causing that. I wouldn't believe it unless I saw it.

Could there be that much of a difference of the rounds?

Ive heard that IMI was good quality so I figured id give it a go.
Now I'm gona buy a few boxes of some random stuff and see what happens. I wish I could measure my velocity, could that be it?

At first I thought maybe my barrel was loose but ruled at out because of the consistency of what was happening.
I did notice that there was A LOT of fouling and lube coming out the front of the receiver visible on the gas tube. I never noticed that before but I also just finished putting my first 1K threw the rifle without issues.
I doubt the fouling on the gas tube is any kind of indicator but its the first rifle Iv had where the gas tube in that position is that visible.

The only thing that's different from any other Novekse is that it has a Novekse marked MUR1a I believe it is called. The one that has the cut out so you can mount a rail like a DDRISII which is the plan for down the road...
Other Noveskes don't normally come with that upper.

I'm not to concerned with something being wrong because it ran fine but that just in no way seemed normal.

[CarlosDJackal]

...Could there be that much of a difference of the rounds?...

Yes. Even when purchasing ammo from the same manufacturer, there can be differences between lots. A lot of times the manufacturer ends up using different components between lots out of necessity. This is why Snipers are supposed to list the Lot Numbers they are using and re-check their zero when changing lots.

FWIW, I ordered a 1200-round case of IMI M855 ammo last Spring and ran into extraction issues. It seems that the brass they were using may have been too soft and was deforming instead of allowing the extractor to properly grip the rims for extraction. I have not had a single issue with over 3,000-rounds of Wolf but can't make it through a whole magazine of that IMI ammo. FWIW.

[markm]

That is way beyond normal. A foot at a hundred yards and, I'd be stunned.

[Belmont31R]

I have shot tons of different types of ammo and they are all usually within 2" of each other center of group to center of group. Thats at 100 yards not 50.


The only times Ive had large POI differences is changing a muzzle device.

[Jaysop]

FWIW, I ordered a 1200-round case of IMI M855 ammo last Spring and ran into extraction issues. It seems that the brass they were using may have been too soft and was deforming instead of allowing the extractor to properly grip the rims for extraction. I have not had a single issue with over 3,000-rounds of Wolf but can't make it through a whole magazine of that IMI ammo. FWIW.

Yea I ordered the same amount. With the other stuff I used I was getting feeding issues, but ran threw about 300 IMI today and it never felt smoother. Thankfully with that amount in my closet.

[Atg336]

In Basic Training ('98) we were doing Basic Rifle Marksmanship and we were using one type of ammo for most of the range time. All was well until on the day of qualification when for whatever reason in the middle of the day they switched up the ammo type and literally everybody on that half of the day in the platoon couldn't qualify, including yours truly.
Eventually everyone passed BRM, but they wasted an extra two days of range time just because they switched ammo types.
I don't know what ammo was switched to what, but its not unheard of to have such a difference in POI.

[Iraqgunz]

I had the exact same issue a few years back in Iraq with some commerical loaded Black Hills 77gr loadings. The difference between it and the M855 was huge.


12" at 50 is not usual.
I have seen differences up to 6 inches at 50, but they are rare.
FWIW- the biggest shifts I have seen is going from M855 to Mk262 in issued weapons. With all of my ammo and weapons the shift between ammo has never exceeded 3" at 100 meters.
Shift is common and unpredicatble, but 12" is excessive in my experience. Could there be any other contributing factors?

[ST911]

Did this hasty exercise last year to illustrate POI deviations. The point was to show that a troop picking up a mag from a partner with different duty ammo could still be expected to deliver good hits at likely ranges. 40 rounds total, a few of each 52 through 75gr in weight, fired at 50yds, a little faster than 1:sec. IIRC, it was just under 30 seconds. That target zone is ~4" in diameter.

I've also done this several times with various loads at 25yds, where most have little to no discernible deviation from each other.

Optimal choice is always to zero for the load in the gun, verified at all ranges expected. Less optimal, but still acceptable is to data card others and do the adjustments, assuming you have a quality optic with reliable adjustments. If you had to switch without verification, you're likely good at close ranges.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/374a4065.jpg

[markm]

I had the exact same issue a few years back in Iraq with some commerical loaded Black Hills 77gr loadings. The difference between it and the M855 was huge.

The more we play with, measure, and examine Black Hills Ammo, the less I like it.

[Moltke]

I shoot M193 or M855 almost exclusively because it's cheaper, but I thought that Black Hills was the good stuff. I've read numerous times here on M4C that most people either praise BH or TAP ammo as being their preferred load. What don't you like about it?

[markm]

I've read numerous times here on M4C that most people either praise BH or TAP ammo as being their preferred load. What don't you like about it?

That's what's puzzling to me. I've not tried that Mk262 whatever load... but I've tried blue box and red box.

Blue box had grossly untrimmed brass in .223. Function was fine though.

In their "match" ammo, I was given a box of 168 SMK in 308. And I don't think one round in that box had less than .007" runout in it... and as much as .010".

We also had some primers seated so deep that they wouldn't fire in a Rem 700 308.

The same Match 168s were loaded with Ball powder.... Shit... I can do that at home. If I'm paying up money for match, It'd better come with good, temp stable, extruded powder.... Varget, IMR, etc.

I know the balls can shoot decent too. But it just strikes me as "WTF?"

I've just seen nothing to convince me of BH's fanboy following. Fed GMM 308 loads run rings around anything BH pukes out.

[Moltke]

Thanks for the insight, I understood most of what you said. So, I'll just chalk it up to "I've just seen nothing to convince me of BH's fanboy following." and think to myself about a lack of attention to detail on their loads, and not getting the components you feel you're paying for.

I'm guessing you handload alot and have some strict accuracy requirements?

[markm]

I'm guessing you handload alot and have some strict accuracy requirements?

Not that strict... but yeah... we've been starting to produce precision loads. Thus we have some nice Sinclair toys to measure for these things.

With the runout issue I mentioned... it's typically agreed upon that anything more than .003-.004" in bullet runout will impact accuracy. No one can get every bullet perfectly straight in the case neck every time.... but running at .007" and more??? Not in a "match" box.