Need help me with my F-Class build, which 7mm cal to use????

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elmerdeer

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Hi guys I am going ahead with an F-Class build, and my main problem is which 7mm caliber should I use? Has anyone used a 280AI for F-Class as I have the reamer and my gunsmith can throat it for the 180 Berger hybrid or another bullet with extremely high b.c, like the new Sierra's? I would like to be able to get speeds of 2950 to 3100 maybe, can I achieve that with the 280AI? Or do I have to go bigger?
Anyway I am just looking for the best option, that expierenced F-Class shooters are using.
Thank you
Elmer
 
Unfortunately, no way you'll get the .280 AI anywhere near those speeds, you might kiss the low end of your speed range with a 162gr AMAX or 168gr Sierra out of a 28" barrel. Honestly though this cartridge is perfect for F Class, and would be a 'big boy' on the firing line, you don't even need that much gun. There is nothing a Berger 180gr can't do between 0-1000 yards on paper even with a 2,650-2,700 MV. To reach 2,950 look to a straight .284 Win with RL17.
 
Why a .284? given everything being the same, barrrel and so on, Is'nt the 280AI more capable of achieving higher speeds than the straight .284 win? Out of my custom hunting rifle with 24" Krieger barrel Rl-22 max charge I am getting 2780fps, add another 4-6inches of barrel and It could be possible, also go to a slower powder and maybe add a few more fps. Is my thinking flawed?
Thx
Elmer
 
If you want to get a 180 Berger up to 3100 FPS you will have to go 7WSM, 7 Rem Mag or something similar. I just don't think the 280 AI has the case capacity to push it that fast safely.
 
elmerdeer said:
Why a .284? given everything being the same, barrrel and so on, Is'nt the 280AI more capable of achieving higher speeds than the straight .284 win? Out of my custom hunting rifle with 24" Krieger barrel Rl-22 max charge I am getting 2780fps, add another 4-6inches of barrel and It could be possible, also go to a slower powder and maybe add a few more fps. Is my thinking flawed?
Thx
Elmer
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That's a hot .280AI load if you're doing that with 180grs... .284 is more efficient, and on the same weight of powder, will out run the .280AI.
 
Well, that hasn't been my experience, and I have a few examples of each. In 22-24" barreled rifles, they come within about 25-50 fps of each other, and neither will push the heavier 7mm bullets (175-190) that fast (nor will my 7mm Gibbs, though it comes about the closest of the three). A longer barrel will buy you some more velocity, but if you want to push these bullets at those speeds, you're looking at a 7 WSM and larger in terms of case capacity, and a 26" barrel or longer will help. Sure, you sometimes come across a "faster" barrel, but you can't count on it. FWIW - dan
 
Ardent said:
My mistake, to clarify 2,950 with 162gr AMAX in .284, not 180gr Berger.
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Yes thats what I thought, I get 2920 out of my 280AI 24" barrel with the 168bergers and rl-17 or rl-22.
The guys I met at F-class competions this year were getting 2920fps with the 180's and the .284 but barrel was at 30" or maybe a touch longer but 30" for sure.
Thx
Elmer
 
I built my version of the 280improved and called it a 7 mystic. The shoulder is pushed forward relative to the 280AI so there was a bit more case capacity.

I shot 180gr Bergers to 2850fps out of a 24" Shilen. Yes, it was hot but I use the cases many times with little issue.

Case volume is the 'same' as the 7RSAUM and performance mimics this cases. Was a wonderful 1000m plinker for sure.

The straight 284 Win is a small case and a few grains smaller then an improved 280. It is the slowest of the commonly used cases and if pushed hard is a PITA to tune.

Bottom line, pick your velocity, ease of tuning and lack of bore life.

I have also shot the 7RM with this bullet and it is so easy to get speed from this case. 3050FPS out of another 26" Shilen. In 30" tube, 3100fps is certainly viable BUT you are going to have a very short throat life.

Most will find the RSAUM/280AI/Mystic case volume to be the best compromise between speed, ease of tuning and bore life.

Let me know if I can help you put some parts in place.

Jerry
 
elmerdeer said:
Yes thats what I thought, I get 2920 out of my 280AI 24" barrel with the 168bergers and rl-17 or rl-22.
The guys I met at F-class competions this year were getting 2920fps with the 180's and the .284 but barrel was at 30" or maybe a touch longer but 30" for sure.
Thx
Elmer
Click to expand...

And I would bet dollars to donuts that they were loading quite hot as well, a not uncommon thing in competition, oddly enough. 2900+ with 162 Amax bullets is possible with hot 284 loads (with 28-32" of bbl), not as hot 280 AI/7mm Gibbs/7mm Mystic loads (24-26"), or average 7mm Mag loads (24"). - dan
 
I was hitting almost 3000fps with the Berger 180's in my 284 Shehane using 56.5gr of H4831SC and a 30" barrel.

These loads though are far to hot and will need to be backed down quite a bit to sit in the 2850-2900 range.

I was hoping to achieve 2920-2950 to take advantage of the extra velocity over the straight .284 but looks like I will have done all the extra work for naught.

Going to try the Berger 175 XLD's as well since they are only 1 point less in BC than the 180's.

I saw a 284 shooting 162 Amax bullets set a new US record in Oregon last year in pair shooting.
 
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yea i guess but you get better brass with the 300 rcm.... maybe i'd go with a 338 rcm necked down. the 338 rcm case looks a little smaller, not a hundred percent sure tho
 
What makes you say you would get better brass in the RCM?

hrn is the only manf and although decent stuff, tends to be soft. Given the reduced case volume, there would be a trend to hot rod it and that could reduce brass life.

Personally, I have found it better to use a larger case at lower pressures. WAY easier to tune and the difference in bore life is small.

At the end of the day, there are several ways to get from 2800 to 2950fps. They all work and the bullet doesn't care what case it was booted out of.

But your wallet will if going with a wildcat.... ask Cyan1de. If you are looking for the different Bergers to try, let me know. Sierra has a new entry too.

Jerry
 
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