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1/22/2020 12:12:56 PM
Posted: 11/1/2012 12:48:38 PM EST
hey guys I just built a 300 blackout custom AR with a good 16" stainless Wilson match barrel. It is 1/8 twist. Something I think really weird is going on with it though. It shoots really good if you stick consistently to the same ammo...but if you switch its way off. The first ammo is the Remington UMC 115 grain. Second is Southwest ammunition Barnes hunting ammo...110 grain. I originally had it zeroed with the Remington ammo. Then I shot a couple Barnes through it and it impacted about 8 inches to the left. I didn't know why it was doing that. Then I zeroed it with the Barnes ammo and now the Remington impacts 8 inches to the right... strange huh? why do y'all think it has a huge difference windage wise? Ive never seen that before. Thanks.
Link Posted: 11/1/2012 12:51:37 PM EST
Some ammo will behave drastically different out of certain barrels. Then others will be hardly any change from others.

Try another type of ammo you may see more consistent result your barrel just may not like one of those types.
Link Posted: 11/1/2012 1:28:28 PM EST
Okay good I'm actually glad to hear that! I thought I was going crazy for a few minutes! I was really hoping my build wasnt the problem because I used good stuff. An American defense mount and this brand new 1-4 trijicon Accupoint..

I wonder which one is the problem child.... or if both shoot okay but they just have a windage difference. Because I was getting right at about inch groups with both ammo.
Link Posted: 11/1/2012 4:39:43 PM EST
Anyone else had this experience with 300 blackout or tried multiple different kinds of ammo and hadnt had my problem? thanks
Link Posted: 11/1/2012 6:22:27 PM EST
Definitely subscribing to this as I'm building a 300 right now and was planning on trying out different bullets.
Link Posted: 11/1/2012 6:42:24 PM EST
[Last Edit: 11/1/2012 6:43:32 PM EST by northpark]
I've always been under the impression that this is a rather common variance between the .3 ammos - note that savage dropped the round for accuracy reasons *****


**** which i understand is not for a forum like this that only argues reliability but at some point if savage considers the round to be inaccurate and inconsistent then there are issues above my control
Link Posted: 11/1/2012 6:54:38 PM EST
also 2nd* mine has just been over 1moa no matter what i try at 100 yards
Link Posted: 11/1/2012 7:28:21 PM EST
You might want to try a good copper cutting cleaner (Sweets 7.62, Barnes CR-10 etc.) and clean all the copper fouling out of it E.G. no blue on the patches.
But the truth is some barrels just dont like some bullets
Link Posted: 11/1/2012 7:32:27 PM EST
Originally Posted By rick458:
You might want to try a good copper cutting cleaner (Sweets 7.62, Barnes CR-10 etc.) and clean all the copper fouling out of it E.G. no blue on the patches.
But the truth is some barrels just dont like some bullets


.301x.309 barrels don't shoot anything real well.
Link Posted: 11/1/2012 7:35:32 PM EST
Well, the thing shoots great. I have one inch groups with both types of ammo. Its not a custom bolt gun by any means but pretty accurate. Its just the two ammos have a huge horizontal difference in impact.
Link Posted: 11/1/2012 7:38:17 PM EST
Originally Posted By BadBowtie03:
Well, the thing shoots great. I have one inch groups with both types of ammo. Its not a custom bolt gun by any means but pretty accurate. Its just the two ammos have a huge horizontal difference in impact.


My 262 clone and M193 impact a mil apart from each other at 100 yards. A different POI for different ammo isn't just normal, it's expected.
Link Posted: 11/1/2012 7:52:20 PM EST
I agree its to be expected. I dont think I would of madea post if it was just a couple 2 or 3 inches. But 8 inches?? that just sounded extreme to me! But heck, it happened. So its possible.

I guess Im just thinking its more annoying than anything. I would obviously want the practice ammo and the hunting ammo to be about the same but its not working out for me. I want to do some testing with different bullets and see if the UMC is the oddball or the Southwest Barnes ammo... or if it just changes around alot with different stuff. Maybe Ill try the remington accubond or the Vmax's.

Anyways, thanks for the help guys.

Link Posted: 11/2/2012 1:41:39 AM EST
I have a bolt action .308 that does the same thing. One factory load shoots 8" lower than another factory load. I have another semi .308 that shoots the same two loads into the same group. It just happens sometimes.
Link Posted: 11/2/2012 3:21:00 AM EST
My savage bolt in 243 used to do this, wild poi shifts with different bullet weights. I had the barrel and action cryo'd a long time ago. now it puts every load, cold or warm barrel within the same 2" easily. 55 grain @ 4000 or 105 at 2900.
factory loads and random handloads. I have not, however, tried that with an AR barrel.
Link Posted: 11/2/2012 4:11:47 AM EST
the barnes bullet is lead free so it is significantly longer than other bullets in the same weight range . I shoot them in 5.56 , 308 , and 458 socom weapons and have found that they are a completly different animal they powder charge normally has to be reduced to allow the bullet to seat deeper in the case to retain case over all dimensions , there is nothing wrong with your rifle you just need to try different ammo or reload and find a practice load that will approximate the barnes bullet. or use a scope with ressetable zero and simply dial in the correction when shooting practice ammo.
Link Posted: 11/2/2012 4:41:36 AM EST
It happens ammo from different brands is seated to different lengths, use different bullets, use different powders, and gets different velocities. I see the same thing happen all the time when I work on load development.
Link Posted: 11/2/2012 5:16:13 AM EST
Left to right impact of that magnitude is a bit wierd. Vertical stringing makes sense due to potential differences in velocity.

Any chance you are anticipating recoil and really yanking the trigger? Perhaps there is a slight difference in ignition time between the two and that difference accounts for the left to right spread.

I'm really reaching with that one, but that's all I've got.
Link Posted: 11/2/2012 3:55:56 PM EST
peligro nailed it.
It's amazing how much difference the bullet and powder can make. Makes me wonder how I ever shot different types of factory ammo before I started reloading.
Link Posted: 11/2/2012 4:57:35 PM EST
I've had rifles with vertical stringing with different loads, and had rifles that shot most everything to the same POI, personally never had horizontal stringing more than an inch or so (once I bedded the action and floated the barrels). I'm not doubting you saw what you saw, it would puzzle me also. Apparently it's not as rare as I would have guessed.
Jeez, I can understand the vertical stringing. In my way of thinking, I'd think maybe the barrel was not properly stress relieved, or at least some factor that caused a sideways harmonics. I'm just rambling. 8" horizontal seems excessive, but if you can get 1MOA with some loads, stick to those loads (not meaning to sound smart-ass). It could be worse...
Link Posted: 11/21/2012 9:33:26 PM EST


Hey so here's a picture... I think my barrel hates this Barnes stuff!! Its southwest loaded ammo... no problem there at all! But I think the projectile and my barrel just don't get along. I knew I wasn't going crazy. This Barnes stuff for some reason sometimes will group and sometimes its all over the place like this picture shows. That's two nosler green tips from pnw arms that are 2 in one hole, then two umc target Remington ammo and then the Barnes all over the place but two are far left like I was saying. I went through 50 rounds of this expensive Barnes stuff trying to figure out what was going on!! Anyways, I think I'm gonna stick with green tips cause its almost the same poi as the umc target stuff.
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