Benchmark 8208 / 155.5 / 308 FTR

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UL1700
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Benchmark 8208 / 155.5 / 308 FTR

#1 Postby UL1700 » Fri Dec 14, 2018 4:28 pm

So I'm going to be pulling the FTR rig out in the new year and have been hearing rumours and reading a bit about using 8208 behind the 155.5 Bergers. I have been running 2208 and had a good accuracy node around 44.4 grains but have been struggling to find a sweet spot with anything much hotter. Does anyone have any experience with this combo (I'm using Lapua Palma Brass and CCI450) or similar. Not looking for specific loads just experience regarding pressure, velocity ES etc.

Also for anyone in the FTR game, do you do your load development of the bi-pod or use a front rest (I have a SEB MAX for F open)?

Cheers,

James.


Image20181209_184242 by James Elphick, on Flickr

williada
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Re: Benchmark 8208 / 155.5 / 308 FTR

#2 Postby williada » Fri Dec 14, 2018 5:26 pm

James, I have used those sand bags and found unless packed correctly you will get bounce and so it makes it very difficult to find a tight spot. You are better off with a bit of plate welded in a frame topped with marine carpet. Do load development in .2 grain increments. Get a set of calipers and measure around the extraction groove for .001" excess expansion. Any more stop. Check for pressure signs like flattened primers, then cratering and sticky bolts etc . This powder will generate well in excess of 3000 fps in .308 with 45 grains or a tad more. At the moment I think the load could be increased but it depends on your pressure signs. Maybe you could get up 3040 fps or a tad more but safety and barrel wear could become issues. You simply have to test. Those with long barrels do not have the same pressure issues so beware of people giving out loads for your own safety. Chamber dimensions should be true SAAMI for this class and tight bores or custom chambers with tight throats will raise pressure.

UL1700
Posts: 149
Joined: Sat Sep 16, 2017 5:39 pm

Re: Benchmark 8208 / 155.5 / 308 FTR

#3 Postby UL1700 » Fri Dec 14, 2018 6:18 pm

williada wrote:James, I have used those sand bags and found unless packed correctly you will get bounce and so it makes it very difficult to find a tight spot. You are better off with a bit of plate welded in a frame topped with marine carpet. Do load development in .2 grain increments. Get a set of calipers and measure around the extraction groove for .001" excess expansion. Any more stop. Check for pressure signs like flattened primers, then cratering and sticky bolts etc . This powder will generate well in excess of 3000 fps in .308 with 45 grains or a tad more. At the moment I think the load could be increased but it depends on your pressure signs. Maybe you could get up 3040 fps or a tad more but safety and barrel wear could become issues. You simply have to test. Those with long barrels do not have the same pressure issues so beware of people giving out loads for your own safety. Chamber dimensions should be true SAAMI for this class and tight bores or custom chambers with tight throats will raise pressure.


Yes I have a 6mm steel carpet covered plate as well which i like as long as I can get it to sit on the mound without wobbling. I have had good results with both but interstingly my wife hates the sand bags. Chamber is to SAAMI and machined by David Brewster. I have run upto 47 grains 2208 without presure signs and was looking for a node arround 46.4 and 47.2gn when last used.

williada
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Re: Benchmark 8208 / 155.5 / 308 FTR

#4 Postby williada » Fri Dec 14, 2018 8:02 pm

James, David is a great guy and an excellent gunsmith. He is a person who shoots 8208 well and would be my first port of call having chambered the rifle. Give him a bell. It is essential that you realize 8208 is not the same powder that is 2208 and requires significantly less than 2208 to be effective. Don't think it would be wise to run 47 + of 8208. You must work up a load and chronograph it and look for stability areas. You should find an upper node (shooter speak) within a 1.4 grain range from max. safe pressure. ps James, the secret to staying in front of your wife is to load her ammo. Just an old man's advice. :shock: [-X

UL1700
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Re: Benchmark 8208 / 155.5 / 308 FTR

#5 Postby UL1700 » Sat Dec 15, 2018 9:21 am

williada wrote:James, David is a great guy and an excellent gunsmith. He is a person who shoots 8208 well and would be my first port of call having chambered the rifle. Give him a bell. It is essential that you realize 8208 is not the same powder that is 2208 and requires significantly less than 2208 to be effective. Don't think it would be wise to run 47 + of 8208. You must work up a load and chronograph it and look for stability areas. You should find an upper node (shooter speak) within a 1.4 grain range from max. safe pressure. ps James, the secret to staying in front of your wife is to load her ammo. Just an old man's advice. :shock: [-X


I don't think Sophie is volunteering to take over the reloading any time soon in the same way I don't clean horse tack :lol: I will pester DB to see what he thinks! Don't worry I'm well aware of the difference between 8208 and 2208 and I have the ADI data. Fingers crossed that Sophie has got the we (I) need a Chronograph and Christmas is coming...

williada
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Re: Benchmark 8208 / 155.5 / 308 FTR

#6 Postby williada » Sat Dec 15, 2018 10:36 am

Good luck to you James. Put a suggestion in for a Lab Radar. Don't run with things that hang off the muzzle, they can distort group shape which is vital for understanding tune as you become more sophisticated with this stuff. Had the opposite problem with my horses. Had to get rid of the stallion who bit the missus on the boob years ago. Have a great Xmas.

Tim L
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Location: Townsville

Re: Benchmark 8208 / 155.5 / 308 FTR

#7 Postby Tim L » Sat Dec 15, 2018 2:53 pm

Hi James,
I'll leave Dave to deal with the loading side of things. Far more experience in his tool bag than mine.
With regards to doing load development off a rest or bipod. Go with the bipod. The rifle reacts very differently and you will get different results. Also don't do your final load tuning off the bench. Its ok to get close but that final tune needs to be with everything like it will be when you want the best results.

I am wondering why you're using 115.5s. These are a very capable projectile and used to great effect buy F std. But when you swap that rest for a bipod you will need every advantage you can get, and once you get back to the longs the bullet bc becomes a definate advantage.

UL1700
Posts: 149
Joined: Sat Sep 16, 2017 5:39 pm

Re: Benchmark 8208 / 155.5 / 308 FTR

#8 Postby UL1700 » Sat Dec 15, 2018 3:27 pm

Tim L wrote:I am wondering why you're using 115.5s. These are a very capable projectile and used to great effect buy F std. But when you swap that rest for a bipod you will need every advantage you can get, and once you get back to the longs the bullet bc becomes a definate advantage.


It was on the advice of David Brewster, I was just starting out in F class, both local ranges top out at 600 and are very sheltered. It was a good place to start both in terms of recoil management, the wealth of information about the round and there was some questions regarding limiting the bullet weight for FTR at the time. My next barrel will be chambered for something closer to 200gn but going to get this tuned in 1st.

tonic4u
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Location: SA

Re: Benchmark 8208 / 155.5 / 308 FTR

#9 Postby tonic4u » Wed Dec 19, 2018 8:58 pm

Hi James: my experience with 8208 in a range of target rifles all 308, with
30-32" barrels has been positive. My best empirical loads are between 43.5 - 43.8gr, but adverse
pressure evident at 44gr. Speeds in vicinity of 2990fps, but more temperature sensitive than 2208 I suspect.
TimB

SteveL
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Joined: Thu Jun 14, 2012 9:29 am

Re: Benchmark 8208 / 155.5 / 308 FTR

#10 Postby SteveL » Thu Dec 20, 2018 9:28 am

Hi James,
I have used the 155.5 and 8208 quite a bit and have had some amazing results.
My load was quite hot 45.7g in lapua small primer brass, BR4 primers 25th jump for around 3080 fps.
However, for reasons i have moved away from this powder and now use 2206H and would not go back to 8208.

Steve

UL1700
Posts: 149
Joined: Sat Sep 16, 2017 5:39 pm

Re: Benchmark 8208 / 155.5 / 308 FTR

#11 Postby UL1700 » Thu Dec 27, 2018 9:27 am

Well the hints worked! So now I have another tool in the arsenal to help me on my journey to ballistic enlightenment [-o<

Image2018-12-26_07-16-04 by James Elphick, on Flickr

ShaneG
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Re: Benchmark 8208 / 155.5 / 308 FTR

#12 Postby ShaneG » Thu Dec 27, 2018 10:11 am

My .02C - my go to powder for 155gr in 308 has been 2206H. I feel 8208 is a tad fast in burn rate.
Any of the heavier pills such as Juggs it becomes 2208 obviously and my opinion on 2208 and 155 is that it is too slow for that combo.
FWIW


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