16" 308 AR: larue obr or a ga precision gap 10?

[Failure2Stop]

I'm going to try to avoid arguing about velocity, as it is irrelevant to anybody other than the guy shooting, and the only velocity that matters to him is what his ammo is doing in his gun.

The point about wind is pertinent. We have all kinds of neat devices on the market, some better than others, that can tell us range with a pretty good regularity, what we lack is a device that can tell us the wind conditions, at the moment of the shot, and what the wind will be as the projectile is in flight. Wind error is probably the most significant factor in missed shots by those that have the "right" tools. It is not hard to mis-judge wind by a few MPH, which is a significant deviation past mid-range. This is also the real reason that the modern magnum is such a critical tool for long-range precision.

I have no data to suggest that KAC guns are significantly faster than any other 7.62, however, I do have data that shows some wide dispersion in velocity among commercial ammo. With the number of 16" 7.62 guns in military, government, and LE hands, there is a market for ammo companies to more perfectly drive bullets out of 16" barrels. I am optimistic.

When it comes down to it, application is the first question to answer. If I am going to be in a static position and not worried about weight, I'll prefer a heavy gun. Heavy guns shoot softer and if all else is equal (or irrelevant), I'll take the extra velocity of a longer barrel. When it comes to moving around with the gun, I'll prefer a lighter gun. In the end, inherent mechanical precision potential is not a factor of barrel length, but rather of barrel quality and ammunition integration. Extra barrel length does give more velocity, which does indeed help with practically accounting for wind, but 100fps is not enough to gain much of an edge practically, and that is the average of what my data says is gained by going from 16" to 20" in a 7.62. To gain a practical edge in long-range shooting (600-1000), I would need to be 300(+) fps faster than where I am with a 16" barrel and/or increase projectile mass/BC.

.300 WM- 3150fps 180gr
.338 LM- 3340 fps 200gr

Those make a difference. Until you start nearing those velocities/BCs, it's kinda minutia.

[Failure2Stop]

I'm going to try to avoid arguing about velocity, as it is irrelevant to anybody other than the guy shooting, and the only velocity that matters to him is what his ammo is doing in his gun.

The point about wind is pertinent. We have all kinds of neat devices on the market, some better than others, that can tell us range with a pretty good regularity, what we lack is a device that can tell us the wind conditions, at the moment of the shot, and what the wind will be as the projectile is in flight. Wind error is probably the most significant factor in missed shots by those that have the "right" tools. It is not hard to mis-judge wind by a few MPH, which is a significant deviation past mid-range. This is also the real reason that the modern magnum is such a critical tool for long-range precision.

I have no data to suggest that KAC guns are significantly faster than any other 7.62, however, I do have data that shows some wide dispersion in velocity among commercial ammo. With the number of 16" 7.62 guns in military, government, and LE hands, there is a market for ammo companies to more perfectly drive bullets out of 16" barrels. I am optimistic.

When it comes down to it, application is the first question to answer. If I am going to be in a static position and not worried about weight, I'll prefer a heavy gun. Heavy guns shoot softer and if all else is equal (or irrelevant), I'll take the extra velocity of a longer barrel. When it comes to moving around with the gun, I'll prefer a lighter gun. In the end, inherent mechanical precision potential is not a factor of barrel length, but rather of barrel quality and ammunition integration. Extra barrel length does give more velocity, which does indeed help with practically accounting for wind, but 100fps is not enough to gain much of an edge practically, and that is the average of what my data says is gained by going from 16" to 20" in a 7.62. To gain a practical edge in long-range shooting (600-1000), I would need to be 300(+) fps faster than where I am with a 16" barrel and/or increase projectile mass/BC.

.300 WM- 3150fps 180gr
.338 LM- 3340 fps 200gr

Those make a difference. Until you start nearing those velocities/BCs, it's kinda minutia.

[tylerw02]

While I agree with you mechanical accuracy isn't hindered by the shorter barrel, down range dispersion is due to wind differences.

What is the difference in weight between a 16" and a 20"?

The other poster in this thread states his 16" OBR is 2374 FPS. It seems that is normal or the 16" guns outside the KAC realm. My experience shooting precision matches suggests the best shooters have the longest barrels because they want the velocity. Even if it's 226 FPS. They are usually willing to accept 4 or 5 oz of additional weight.


You are right that the magnums are the future for long range shooting. The .308 is anemic but it does have the advantage of logistics, barrel life, etc.

Do you do much precision shooting, personally?


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[why1504]

If 600 yds is your max range why are you going with a 308? Certainly at 600 yds barrel length isn't going to matter much. Last May I went thru the same decision process. I ordered a GAP. Here is why, schedule andflexibility in the build. But, my gun is for 500-800 and maybe 1000 if she can go that far. I am looking to take the 308 as far as I can and I don't plan to carry it very far so a 20" barrel was what I selected. I expect to have my gun in 3 more months. Larue said 24 months. KAC was also Unobtainium at the time and $1500 more money.

For. 600yd gun, I would look hard at a precision 223 with a 20 inch barrel. Shoot 75-80g projectiles using Varget powder. I think you would be pleased with this configuration.

[Failure2Stop]

What is the difference in weight between a 16" and a 20"?

Depends on what models you are comparing.
Lightest 16" is under 8.5, M110 is around 13. Most apples to apples puts the weight delta at around 1/2 lb, however, different guns have different jobs, and therefore have different components and resulting overall weight.
Optics, mounts, bipods, etc, can easily add another 2-6 lbs.
A 10 lb, 38" guns is easier to employ than a 19 lb 47" gun, and if that weight and length does not equal increased capability, I am not terribly interested in it.

The other poster in this thread states his 16" OBR is 2374 FPS. It seems that is normal or the 16" guns outside the KAC realm.

Again, with what ammo?
If this is some point of contention, I stated clearly that I was talking about M118LR, as I did testing with the same lot of ammo, on the same day, with similar wear on both.
168 Rem Prem Match was 2465 out of my 16" on another day:


Lapua has some 170gr stuff that they tested out of 16" barrels at around 2460.
http://www.lapua.com/en/products/new-products/5

M118LR is a bit hotter than usual match ammo, the specific velocity from that round is irrelevant though, as I was comparing velocity spread between a 16" barrel and a 20" barrel with the same ammo, on the same day.

My experience shooting precision matches suggests the best shooters have the longest barrels because they want the velocity. Even if it's 226 FPS. They are usually willing to accept 4 or 5 oz of additional weight.

And if you are talking about most precision matches that involve walking the gun from the car to the line, doing some shooting from a bench or the ground, and then walking the gun back to the car, then I agree that the weight is not a factor and to go with the most precise barrel that you can find and match it with the most consistent ammo you can afford, and a 24-26 inch heavy profile barrel would not be ridiculous. I would also say that for that application you could get a bolt gun at 1/2 the price of a precision semi-auto and get better overall performance.

Do you do much precision shooting, personally?

Not as much as I used to (when I was still in), or as much as I would like to, but I shoot 7.62 precision semi-auto guns with decent regularity. I qualify guns that I send out on T&E and do demos with (ES of 1" at 100 yds), so I am either a mediocre shooter with the most precise rifles ever made or maybe I am a decent shooter with capable guns.
I do not compete in precision competition, I have shot some F-Class, some Service-Rifle, and some other precision-types overseas, but most of my experience is based on practical application/use where a 1 MOA gun is more than enough, and lifespan is more important than 1/4 MOA.

And while I have seen some phenomenal groups out of certain barrels, I have also seen barrels of high regard fail to perform with consistency.
Trying to recommend a "most accurate" gun is nearly impossible.
All you can do realistically is respond to performance requirements with a manufacturer's testing result.

[tylerw02]

We said what ammo above. Most people don't have access to piles of M118LR.

Apples to apples, everything the same, all other components, what is the weight difference? If it's actually 8 oz, I'd be surprised. That seems like more significant a difference, but I'm not in the know. I don't think LaRue OBRs are half a pound difference between the two. We are talking about stripped guns as he has the choice as to what scope and bipod. Nothing is exclusive to one barrel length on an OBR or GAP10.

No, the precision matches I shoot aren't from the car to the line. We shoot two days or so and you're on foot the whole time. Though I do occasionally shoot an F-class match, that is not the norm. They are practical matches. Most guys run 17 lb bolt actions. The gun I mostly use is an Accuracy International because I have discovered reliability and durability are far more important than ultimate accuracy. I learned that the hard way. I have also learned four or five ounces of weight savings isn't worth it.

Also, most of the bolt guns aren't half the price of a semi. I think OBRs are 3600 and GAP10s start at 2800. The base GAP custom bolt gun is 2800. I understand the KACs are significantly more, but no more precise than the later two. Perhaps because of a different level of engineering and target market. At the same time, an Accuracy International AX is close to $7k, and more for some models.

So we've established you're talking about one load. I am talking about the overall scope of loads available to the civilian whereas the availability of M118LR is sporadic at best. So with one set of circumstances vs a vast array, a given tidbit of information is relevant.

Overall the poster above you, back to what I had posted earlier, is more relevant than 16" v 18" v 20". The 5.56 would be even lighter yet, cheaper to shoot, and have a similar 500-600 trajectory, if after all, weight and mobility is the main concern. Otherwise it's all a compromise.



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[mack7.62]

I don't believe the weight difference between 16 and 20 is the driving force in the trend towards the 16, the OAL is. As others much more qualified than me have stated before on a two way range 16" is usable for CQB and also for engaging targets at 600 meters behind cover or wearing body armor. Both options have pros/cons it is up to the individual to decide, I tend to agree with Jack, I am interested in battle rifle first sniper rifle second capabilities.

[Failure2Stop]

We said what ammo above. Most people don't have access to piles of M118LR.

Dude, seriously?
I just stated that the reason I was using the M118LR data was because it showed velocity difference between the barrels under the exact same conditions.
Other ammo shows a similar difference between barrel lengths, but I wanted to use data with as few variables between the data sets as possible in order to frame the data requested.

Apples to apples, everything the same, all other components, what is the weight difference? If it's actually 8 oz, I'd be surprised.

Just weighed two barrels, one 16" non-threaded and one 20" non-threaded, both are barrel profiles that we no longer make;
16"-3.9 lb
20"-4.25 lb
Difference- .325 lbs/5.2 oz

Current 16" barrels are significantly lighter than that, but that's the apples/apples comparison.

The gun I mostly use is an Accuracy International because I have discovered reliability and durability are far more important than ultimate accuracy. I learned that the hard way. I have also learned four or five ounces of weight savings isn't worth it.

Absolutely understood and agreed for that application. Weight is only worth it if it comes with capability. What that weight goes to, and for what capability is up to the user for their needs.

Also, most of the bolt guns aren't half the price of a semi. I think OBRs are 3600 and GAP10s start at 2800. The base GAP custom bolt gun is 2800.

I was more thinking about a decent Rem 700.
Understood that the GAP is a few steps up, especially with a 1/2 MOA guarantee.
I am not a bolt gun expert, so I defer to those that are for discussion on those, but I do know that it is far easier to make a sub-MOA bolt gun than a sub-MOA large production AR-based 7.62 gun.

I understand the KACs are significantly more, but no more precise than the later two. Perhaps because of a different level of engineering and target market.

I tend to avoid talking about products that are not asked about, as I am acutely aware of the perception of a moderator that works for a gun company that busts into a thread touting the company product. KAC's prices are what they are for a reason, and no, they are not going to give a guarantee of a higher degree of precision than the others.

So we've established you're talking about one load. I am talking about the overall scope of loads available to the civilian whereas the availability of M118LR is sporadic at best. So with one set of circumstances vs a vast array, a given tidbit of information is relevant.

Understood, see my first response.
When I get some free time I'll repeat the test with 168gr Rem Prem Match, though, as you can see from the chrono, the SD is higher than I like for precision ammo.

Overall the poster above you, back to what I had posted earlier, is more relevant than 16" v 18" v 20". The 5.56 would be even lighter yet, cheaper to shoot, and have a similar 500-600 trajectory, if after all, weight and mobility is the main concern. Otherwise it's all a compromise.

I have to agree here. If paper/steel out to 600 is the need, 5.56 with good ammo is going to be easier and less costly.
Having a need for 7.62 is the first part of being happy with 7.62, otherwise, the user is probably going to be happier with a smaller or larger cartridge.

ETA: I'm not saying that you are wrong for having the preference that you do, rather that for me, for most folks that I deal with, for 7.62 applications, a semi-auto dual role gun is desired, and the maneuverability of lighter 16" guns meets the needs.

[tylerw02]

I'd be anxious to see the test with perhaps Federal GMM 175 or BHA if you have any available. If not no biggie. Just out of curiosity since one user in the thread is getting really low velocity out of it with his 16", and me about 60-70 FPS faster without a can and 100 with a can.

I also have not had much luck with that particular kind of ammunition. I've pretty much shifted to handloading and Varget exclusively because I get much more consistent ammo.


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[JoshNC]

I'd be anxious to see the test with perhaps Federal GMM 175 or BHA if you have any available. If not no biggie. Just out of curiosity since one user in the thread is getting really low velocity out of it with his 16", and me about 60-70 FPS faster without a can and 100 with a can.

I also have not had much luck with that particular kind of ammunition. I've pretty much shifted to handloading and Varget exclusively because I get much more consistent ammo.


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It was about 30 degrees that day we chrono'd my BH 175s . I'd like to repeat it on a different dayZ and would like to repeat it with different barrel lengths.