Cold bore?

[Nipp]

Hi there,

I have a precision build AR15. 18" Wylde, cut from Batrlein by Craddoc Precision. Mounted to Radian upper, adjustable gas.

It's bit weird - from a cold bore it consistently shoots 2MOA high and then impact migrates downwards, with almost perfectly straight line. At 50+ rounds it is 2MOA lower than aim point. The ammo is not exactly precision stuff - a plain Winchester white box, 55grain.

As far as I understand, the "cold bore" is not supposed to act this way. It might throw off first shot or two, but for me it takes way more than couple shots.
Or is it something else?

Thank you.

 

[Molon]

Hi there,

I have a precision build AR15. 18" Wylde, cut from Batrlein by Craddoc Precision. Mounted to Radian upper, adjustable gas.

It's bit weird - from a cold bore it consistently shoots 2MOA high and then impact migrates downwards, with almost perfectly straight line. At 50+ rounds it is 2MOA lower than aim point. The ammo is not exactly precision stuff - a plain Winchester white box, 55grain.

As far as I understand, the "cold bore" is not supposed to act this way. It might throw off first shot or two, but for me it takes way more than couple shots.
Or is it something else?

Thank you.

You are using some of the shittiest ammunition ever produced for use in an AR-15. Unless you are using significantly large sample sizes for your groups and firing your AR-15 under variable-controlled conditions, nothing can be accurately surmised about supposed shifts in points-of-impact with that barrel and that ammunition.

 

[drewthebrave]

Molon has spoken. This is the way.

 

[Nipp]

You are using some of the shittiest ammunition ever produced for use in an AR-15. Unless you are using significantly large sample sizes for your groups and firing your AR-15 under variable-controlled conditions, nothing can be surmised about supposed shifts in points-of-impact with that barrel and that ammunition.

Well, at least it's not Hornady Frontier I have some Blackhills 77gr stashed for a better day. It would be interesting to see the difference.

 

[Gustav7]

Well, at least it's not Hornady Frontier I have some Blackhills 77gr stashed for a better day. It would be interesting to see the difference.

Unless you're just screwing around at the range, I wouldn't ever fire bulk or cheap crap out of your gun. The entire point of putting together a good rifle like that is to shoot good ammo.

You basically took a Shelby GT500 and put old lawnmower gas and cheap Walmart tires on it and then got mad when it didn't handle well lol.

 

[Nipp]

Actually, it's quite good, even with the worst ammo. I wish there was a steady supply of quality ammo, but where I am at, even the worst stuff is impossible to get. I won't call myself mad or disappointed with what I am getting out of that barrel. It's just that weird POI downwards creep, that I can't explain.
If I do my part carefully, it shoots sub-MOA groups quite reliably (yeah, even with WWB ammo).

Speaking of bad ammo, what can it do to a high quality barrel? As I understand, it's the copper and carbon. More work to clean it up, but at the end - it doesn't really matter to barrel, right?

 

[Molon]

Actually, it's quite good, even with the worst ammo.

The best barrel on the planet isn't going to magically transform shitty ammunition into ammunition that shoots "quite good." The 10-shot group of Winchester White Box pictured below was fired from my bench-rest setup at a distance of 100 yards using an AR-15 barrel that has produced sub-MOA 10-shot groups when using match-grade hand-loads. The 10-shot group of the WWB has an extreme spread of 4.08".

Three 10-shot groups of the WWB fired in a row from my bench-rest set-up at a distance of 100 yards had a mean radius of 1.34" for the 30-shot composite group. That is equivalent to an average 10-shot group extreme spread of 4.3".

If I do my part carefully, it shoots sub-MOA groups quite reliably (yeah, even with WWB ammo).

..

 

[Nipp]

May be I got an unusually consistent batch

 

[XLR308]

May be I got an unusually consistent batchView attachment 7414546

Was this after your 2moa shift or is your first shot in that group ?
The first AR I ever built in the mid 90's with a WOA 24" 1-8 twist straight bull contour surprisingly will shoot Winchester white box varmint 45 grain hollow point into an elongated diagonal hole of about 1.125".
The worst ammo I could think to run in it and kind of expected them to come appart.

 

[Nipp]

It was a last group for the day. I was not even trying to shoot for a group, so I was sending it, as soon as I was reasonably well aligned. This was after 70 shots, POI migrated down almost 4 MOA since the first shot. Initial was 2MOA high, and that group is 1.5-2 MOA low from aiming point.

Again, it might be a fluke.