17" .308win 208 Amax 2500fps

[RedGoat]

Working up a load for my 17" .308win Krieger 1:10" melonite coated DTA barrel that I recently had Mark @ SAC cut down from 26" for me.

208 Amax / RL-17

pictured here suppressed (30BA TBAC) next to a fully extended 16" 300 Blackout

Goal is to find an accurate load close to 2500fps
Step 1: Pressure Test
Step 2: Accuracy Test

<span style="text-decoration: underline"><span style="font-weight: bold">Initial Pressure Test:</span></span> temp=low 80s

COAL = 2.975" (2.194" to ogive); just kissing the lands
Once fired Win brass FL sized and match prepped

45 = 2328
45.5=2338
46 = 2349
46.5=2403
47 = 2423
47.5=2457
48 = 2473
48.5=2492
49 = 2518 (feint swipe)
49.5=2578 (swipe)
50 = 2592 (swipe)
50.5=2606 <span style="color: #FF0000">(heavy swipe)</span>

Since the range was packed I didn't bother doing a ladder test with these like I had planned to do @ 300y. Instead I went down to the 500y range were no one else was and just fired all the shots at steel; was nice hearing it hit harder every shot. Step one complete now onto accuracy.

The rounds are too long to mag load in the DTA mag (2.93" overall mag length). Going to jump the next loads .045" to accomodate mag feeding. I have read that the 208 likes to be jumped, and I don't think case capacity should be a problem since not even the heaviest load I made for the pressure test had any crunch to it. Plan is to load up some in the 47.5-49 range in .3 increments and see if I can find something accurate.


<span style="text-decoration: underline"><span style="font-weight: bold">Accuracy Test (100Y):</span></span> 68F - Elev=39ft - Humidity=100%
COAL=2.93" (2.149" to ogive); .045" jump to lands
Once fired Win brass FL sized and match prepped

47.5x5 = 2442/2478/2478/2458/2421 SD:24 ES:57
47.8x5 = 2458/2474/2477/2485/2469 SD:10 ES:27
48.1x5 = 2486/2477/2503/2497/2503 SD:11 ES:26
48.4x5 = 2512/2512/2497/2503/2506 SD:6 ES:15
48.7x5 = 2521/2518/2536/2522/2526 SD:7 ES:18
49.0x5 = 2545/2536/2554/2552/2545 SD:9 ES:18 <span style="color: #FF0000">*very feint extractor mark</span>

None of them grouped that well @ 100y, but when I was finished shooting 100y groups I had 4 loads of 48.8 left over that I took to the 500y range and they grouped at around 3" (best I could tell from my scope, range was busy, and I was getting pressed for time so I didn't drive down to look).



<span style="text-decoration: underline"><span style="font-weight: bold">Accuracy Test (300y):</span></span>
Temp stayed in the mid 70s; wind was 0-20mph running left to right
COAL=2.9" (2.119" to Ogive); .075" jump

47.5 - 2439/2453/2429/2457/2450 - SD-11/ES-28
47.7 - 2455/2480/2469/2480/2498 - SD-15/ES-43
47.9 - 2487/2498/2498/2488/2507 - SD-08/ES-20
48.0 - 2496/2487/2493/2490/2505 - SD-06/ES-18
48.3 - 2493/2503/2522/2506/2506 - SD-10/ES-29

Was running short on time so didn't get any pictures. The wind played hell on getting groups, but was still able to get sub MOA (2.8") results from 48.0, the best of the five loads. All rounds mag fed 100%.

I plan to load more with 48.0 and go out and see how it shoots at 100-1000y soon. I'll post results as I get them.

 

[Onemoretime]

Re: 17" .308win 208 Amax 2500fps

Have you tried 4350 yet?

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

I have not

 

[Onemoretime]

Re: 17" .308win 208 Amax 2500fps

I tried some when the RL17 was too Temp Sensitive for me... it worked really well but sacrificed some velocity for stability.

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

I'll put it on my list, and give it a shot after I finish load development with the RL17. How much velocity did you lose and out of what length barrel?

 

[gcoulsey]

Re: 17" .308win 208 Amax 2500fps

Awesome rifle mate, and good velocity from your 17" too!!
Just what I need for standing/kneeling shots

How do you find running the bolt quickly when prone? I have only handled/dry fired a DTA at shot show this year, it had a 16" .260 barrel on it, and felt fantastic just stood up. My friend test fired the .338 version (prone) for a day, and said it felt a bit awkward running the bolt fast on rapid fire strings. (Some of our competitions have rapid fire stages mixed in with snap shooting)

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

I have a TAB gear sling and with the short barrel off hand shooting has never been so easy. The first weekend I got the new 17" barrel from Mark I went to the 500y range and fired standing/kneeling/seated - I was shocked at how well it handled, every shot connected with steel.

As for the bolt manipulation, just like with any new (different) system it will take time and practice to get used to it, slow is smooth... smooth is fast. At this point I don't even notice the bolt being further back, I have no issue emptying a mag in seconds without breaking my cheekweld.

**hoping to make it out Friday morning to do the accuracy test - will be bow hunting the rest of the weekend**

 

[gcoulsey]

Re: 17" .308win 208 Amax 2500fps

Well a DTA is on my wish list for sure, 90% of the guys on the firing line are using AR's (quite rightly so.. They are the sensible tool for the job)
But I like to be different and use long rifle.
Any points I lose standing/kneeling/sitting I get back on the long range prone stages, so it all balances out nicely. I use the TI quick cuff sling, works very well for sitting shots, and easy to pop the buckle when dropping into prone.

Good luck on your 208 amax load, I shot them all this year as my competition load, they worked great jumping from AICS mag length (2.890"..front plate removed in the mags) but I was only running them at 2400fps with Varget.
I never tried rl17 because of the temp stability issues people have reported.
I don't need fliers from chamber cooked rounds

If you can stay at 2500fps and keep the recoil under control they will be awesome!

Keep us posted!

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

Updated OP with Accuracy Test (100y) results

 

[ChadTRG42]

Re: 17" .308win 208 Amax 2500fps

The 208 is a great bullet. But I have seen some issues with stability out of several 308 Win short barrel rifles (18"-20"). I have had 2 rifles that would shoot 1/3 MOA out to 600 yards with ease. Once you got to 800 yards, it would open considerably and at 900 and beyond, was out of control. All the calculations show it to be stable, but the bullet was tumbling. These were 1:10" twist custom barrels. Velocity was 2500 and 2520 for them using R17 powder. So, just keep an eye out for this issue. I still have no answer for this problem.

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

Thanks for the input Chad, very interesting. I was thinking that they might not be fully stabilizing till past 100y since they were shooting so well @ 500y and not @ 100y.

 

[ChadTRG42]

Re: 17" .308win 208 Amax 2500fps

Yes, that is correct. I would not test them at 100, until you have your load developed at 300 yards. If it shoots good at 300, then run with that. It should then shoot good all the way out, hopefuly. When I tested my 208's in my 300 WM, my best load at 300 shot about 3/4" at 100. But my .4" load at 100 shot BIG groups at 300 plus. So, pick which one you will use it for the most.

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

Updated OP with Accuracy Test (100y) photos.

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Yes, that is correct. I would not test them at 100, until you have your load developed at 300 yards. If it shoots good at 300, then run with that. It should then shoot good all the way out, hopefuly. When I tested my 208's in my 300 WM, my best load at 300 shot about 3/4" at 100. But my .4" load at 100 shot BIG groups at 300 plus. So, pick which one you will use it for the most. </div></div>

Is low SD/ES indicative of an accurate load? I know it reduces vertical stringing, but do you normally find better accuracy with the low numbers?

 

[wchartz]

Re: 17" .308win 208 Amax 2500fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RedGoat</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Yes, that is correct. I would not test them at 100, until you have your load developed at 300 yards. If it shoots good at 300, then run with that. It should then shoot good all the way out, hopefuly. When I tested my 208's in my 300 WM, my best load at 300 shot about 3/4" at 100. But my .4" load at 100 shot BIG groups at 300 plus. So, pick which one you will use it for the most. </div></div>

Is low SD/ES indicative of an accurate load? I know it reduces vertical stringing, but do you normally find better accuracy with the low numbers? </div></div>
Not necessarily. One load I tested a few months ago had a SD of 4 and an extreme spread of 12 in a 10 shot string.It was the lowest SD I had ever recorded, it also was the worst 2 sets of 5 shot groups that my 308 had ever shot. I chronograph a lot of loads and I have not noticed a direct correlation between accuracy and SD at 100-200 yards. Of course your observation of vertical stringing is quite important at longer ranges. Just run the ballistics on a load with 50 f.p.s. difference at 1000 yds. The difference in drop will be significant.

 

[ChadTRG42]

Re: 17" .308win 208 Amax 2500fps

I have found that most of my sweet spot loads will have a low or the lowest ES numbers out of the 5 or so test groups I do. Most often the best load does have the lowest ES. One of these days, I want to just shoot my test loads through the chronograph and pick the lowest ES and see what I get.

 

[VJJPunisher]

Re: 17" .308win 208 Amax 2500fps

Is 600 plus yards realistic in the 17 inch? I mean all the numbers say sure to around that 800 zone. My 16.5 inch bieber was load developed with a 208 amax and RL-17 getting 2520 FPS, but all I want it to do for this short rifle is shoot well at 600 and BELOW, for my purposes that's all I need outta this rifle. Just curious as y'all's experience of the true max effective range on the shorty with 208's

 

[Bruiser_Joe]

Re: 17" .308win 208 Amax 2500fps

I've nailed a 5" swinger constantly at 750 with a 16.5" 308. People do not give the shorties enough credit

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VJJPunisher</div><div class="ubbcode-body">Is 600 plus yards realistic in the 17 inch? I mean all the numbers say sure to around that 800 zone. My 16.5 inch bieber was load developed with a 208 amax and RL-17 getting 2520 FPS, but all I want it to do for this short rifle is shoot well at 600 and BELOW, for my purposes that's all I need outta this rifle. Just curious as y'all's experience of the true max effective range on the shorty with 208's</div></div>

I haven't gotten it over 550 yet, but I can say so far it shoots better at 550 than it does at 100. I'm doing another accuracy test @ 300 and if I find something I like I will stretch it out to 1k+.

Also I know coldbore has shot out to 1200 with his 16" shooting 175smk.

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

Added 300y results

 

[Belisarius]

Re: 17" .308win 208 Amax 2500fps

Are you using RL-17?

 

[RedGoat]

Re: 17" .308win 208 Amax 2500fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Belisarius</div><div class="ubbcode-body">Are you using RL-17?</div></div>

Correct