Sniper & Sharpshooter Forums banner
1 - 10 of 10 Posts

·
Registered
Custom Aero Precision M5E1, 18” .308 Win. Criterion barrel, Trijicon CREDO HX 2.5-15x56 scope
Joined
·
8 Posts
Discussion Starter · #1 ·
I am getting some very odd groups with my new custom Aero Precision M5, in .308 Winchester. With several match grade factory loads at 100 yds., I am getting three rounds of a five round group that are a cloverleaf measuring ~ .25” center-to-center, with the other two rounds high and expanding the overall group to ~ 1”x1”. I have gotten these virtually identical groups with Federal 175 7.62x51 MK HPBT, Nosler 175 Custom Competition, Barnes 168 TTSX and Lapua 175 Scenar-L.

The groups are fired semi-auto, magazine fed. The groups have all been fired at about the same pace: one round every 30-60 seconds, so no significant heat-cycling of the barrel. I am getting the same results from multiple different magazines — all Mag-Pul — 10 round, 10 round with -5 round limiter and 25 round M118LR magazines, so I can’t attribute it to a specific magazine. The barrel is a Criterion 18” Hybrid; comp is a Precision Armament M4-72; BCG is JP Low Mass with a JP Enhanced bolt; optic is a Trijicon Credo HX 2.5-15x56mm. I have duplicated the same results on different trips to the range.

I am at a loss as to explain how I could be getting 3/5 rounds in essentially one ragged hole and the other two high “flyers”, with multiple different factory loads. Any ideas?
Plant Wood Grass Groundcover Natural landscape
 

·
Registered
Joined
·
28 Posts
Just my opinion but I suspect it is mostly attributable to you. Your setup is probably changing between firings and that is resulting in the high fliers. It could be your grip or your placement of buttstock in the shoulder pocket or bipod loading or ???, I would ask someone you that is a good shooter of that type of firearm to shoot it and see if the problem repeats.
 

·
Registered
Joined
·
6 Posts
Large frame ARs are not the same as their little cousins. So I agree with the reply above. I don't know what bipod that is (Magpul?) but it is not one I own or recognize from precision rifle use. You have to drive these guns and if you're not consistent from shot to shot your groups will reflect it.

In my mind I'm not convinced that all Criterion barrels will shoot. And that's a pretty skinny barrel. I know you're saying it isn't getting hot but it's hotter, and weird things sometimes happen to steel. That being said, 1 MOA is plenty useful. Finding a solid .75 MOA .308 gas gun shooter is not a given.
 

·
Registered
Joined
·
4 Posts
I am getting some very odd groups with my new custom Aero Precision M5, in .308 Winchester. With several match grade factory loads at 100 yds., I am getting three rounds of a five round group that are a cloverleaf measuring ~ .25” center-to-center, with the other two rounds high and expanding the overall group to ~ 1”x1”. I have gotten these virtually identical groups with Federal 175 7.62x51 MK HPBT, Nosler 175 Custom Competition, Barnes 168 TTSX and Lapua 175 Scenar-L.

The groups are fired semi-auto, magazine fed. The groups have all been fired at about the same pace: one round every 30-60 seconds, so no significant heat-cycling of the barrel. I am getting the same results from multiple different magazines — all Mag-Pul — 10 round, 10 round with -5 round limiter and 25 round M118LR magazines, so I can’t attribute it to a specific magazine. The barrel is a Criterion 18” Hybrid; comp is a Precision Armament M4-72; BCG is JP Low Mass with a JP Enhanced bolt; optic is a Trijicon Credo HX 2.5-15x56mm. I have duplicated the same results on different trips to the range.

I am at a loss as to explain how I could be getting 3/5 rounds in essentially one ragged hole and the other two high “flyers”, with multiple different factory loads. Any ideas? View attachment 29509
Do the flyers occur as the same shot number during each grouping? Or random?
 

·
Registered
Joined
·
4 Posts
Same question as RobertM^^^ . I have a DPMS LR308 with low round count, and it throws the first (hand-chambered) round one inch high. I am hoping this will stop being an issue when everything "wears in", but as of now, it is consistent enough that I can compensate if I need to.

Triangle Rectangle Art Font Red
 

·
Registered
Joined
·
4 Posts
Noah, just curious, What config is the LR308, Barrel length and material. GEN 1 GEN 2 AT4 etc..
I also had the same question as Robert M
Gen 1 Sportical, their least expensive model. 16 inch unlined HBAR contour 4140 chromoly barrel w/ six groove 1:10 twist. High Picatinny receiver with no dust cover or forward assist. Oval handguard ("Glacier Guard"). The load I use that averages .43" groups (excluding the first hand-chambered round) is Remington brass, 44.0 grains of Varget, Remington 9 1/2 primer, and a 168 grain Nosler Custom Competition bullet seated to 2.800" OAL. Velocity averages 2,481 FPS.
 

·
Registered
Joined
·
18 Posts
I know that the heat from one shot should not ne enough to garner a 1/2 MOA change at 100 yards when the subsequent shots are all so tightly grouped... but what else is could it be? all human error aside, it would seem more plausible if the shots continued their movement in a predominate direction as the barrel continued to heat up. But this is exactly the opposite of what is being described. (I think) I believe that RobertM's question needs to be answered in order to categorically put both of these problems squarely in the same box. I have a friend with a Gen1 20" heavy stainless barrel and I do not know if it is capable of sub MOA groups neither he nor I are good enough to get those kind of groups consistently so measuring beyond my own capability is splitting hairs. Your groups appear to illustrate somewhat of an anomaly. Have you tried letting the rifle get very hot before firing it? say by leaving it in a hot car for an hour or two prior to shooting? I am trying to wrap my head around what changes from shot one to shot two. Another question I have for you, Does this happen on the first cold shot only and if so how long dose it take before the rifle will duplicate this spread and at the point in time which it dose has the rifle cooled completely or is this occurring at different barrel temps.
 

·
Registered
Joined
·
4 Posts
I know that the heat from one shot should not ne enough to garner a 1/2 MOA change at 100 yards when the subsequent shots are all so tightly grouped... but what else is could it be? all human error aside, it would seem more plausible if the shots continued their movement in a predominate direction as the barrel continued to heat up. But this is exactly the opposite of what is being described. (I think) I believe that RobertM's question needs to be answered in order to categorically put both of these problems squarely in the same box. I have a friend with a Gen1 20" heavy stainless barrel and I do not know if it is capable of sub MOA groups neither he nor I are good enough to get those kind of groups consistently so measuring beyond my own capability is splitting hairs. Your groups appear to illustrate somewhat of an anomaly. Have you tried letting the rifle get very hot before firing it? say by leaving it in a hot car for an hour or two prior to shooting? I am trying to wrap my head around what changes from shot one to shot two. Another question I have for you, Does this happen on the first cold shot only and if so how long dose it take before the rifle will duplicate this spread and at the point in time which it dose has the rifle cooled completely or is this occurring at different barrel temps.
I don't believe it has anything to do with heat. I'm sure it has to do with the difference in lockup between chambering a round by letting the bolt forward by hand (either dropping from hold-open or operating the charging handle to cycle the bolt), or the bolt being reciprocated more vigorously by firing a round. If I load six in the mag and put the first one into the backstop, the next five will shoot into less than a half inch, even with the barrel quite warm. I suspect as the bolt lugs/chamber and/or the buffer and tube wear in to one another this phenomenon will lessen or go away entirely. This rifle has fewer than 150 rounds through it.
 

·
Registered
Joined
·
18 Posts
Yes that is an extremely low round count to be making any assumptions. It still seem that dropping the bolt from a newly inserted mag would have the same effect as reciprocal operation... unless you are experiencing some sort of bounce affect in the buffer system. But this seems unlikely as well. Have you tried loading 10 rounds and manually clearing 4 while letting the bolt ride into battery under its on force. Just a thought. I hope it goes away completely.
 
1 - 10 of 10 Posts
Top