120gr 7mm08 troubles- #62 potential issue

WhelanLad

WhelanLad

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I rekon I had another thread askin about seating depths and such to see if it would help Bring a 120gr Sierra into reasonable contention for a Hunting Load....

So I shortened up the COAL and re-loaded a few Charges wich showed promise.. I didn't gain too much but had one group at a bit over 1.5 inch ..

there seemed to be a common trend, few close an one out. So I continued loading and shooting Groups of 3, incase it was me. but seemed often than not I couldn't improve.


So Today I've started on a New Batch of Brass, to work out a load for these 120gr... NNY Brass - Kimber Montana 84m -

The Data I have says from about 42.5 - 44 gr ? of AR2208 (VARGET to You)
so I tip toed around 42gr after none of the above charges worked, an now have dropped right down to 41gr too see if that can slow things up a bit but give me a decent accuracy.


This wouldn't be unsafe?

also this wouldn't be unheard of if my particular Rifle didn't like said 120 bullets? ey?

good evening from Australia

WL
 
Two close and one out?

Try this...

I imagine you are going shoot,shoot,shoot

Try going shoot , wait , shoot , shoot

or shoot , wait , shoot, wait , shoot wait.

or shoot, shoot, wait shoot.

See if you find a pattern.

Could also try a ladder test to see if you can find some accuracy nodes at different velocity, start at 42 and go up in .3 increments, load up to 45 grains but stop at pressure signs.
 
Two close and one out is common with any caliber, so have a cool down period beween shots, so yes wait and wait some more between shots might cure the problem.
 
Actually I have had some bad experience with under loading. Hogdon (which markets the ADI powder here) has some bad data on the internet for loads in my .264 which are too light, and I followed it. See the results below. As your man Crocodile would say, "That's not a dent, this is a dent!"

Dents.jpg


My thoughts are that not enough pressure was developed to seal the neck. Pressure leaked by and collapsed the case. Three loads at a too light load of H3831 (AR2213), and all with the same result. Would that happen with AR2208? Not sure. However, if you want to pursue lighter loads you may want to try H4895 (AR2206H). Apparently you can go down to 60% of normal loads with it. No personal experience though...
 
My loads suggest 43.0 gr +/-0.2 in a 22" barrel. However, suggest you work up in 0.3gr increments. Some items you should first rule out are scope and mounts, paralax, bedded rifle, crown condition, overall length to touch lands, Brass prep, others....

IME I have found the 120 sierras to be very good performers and you should be expecting sub moa in your rifle. You will be surprised some times that a node is rather short in its behavior. I have run 120s using 60 jump in order to have enough bullet in the case neck, you may need even up to 120 jump. If you have a long throat then this makes tuning more difficult with lighter and shorter bullets. My 2c
 
I have use a lot of 2208, but usually in quite hot loads.

It would be safe to try lighter.

But before I went lighter, I would load 44, 44.3, 44.6, 44.9 & 45.2. Shoot 3 each, with lots of cooling time between strings.

If you get any bolt lift resistance, stop shooting.

And yes, some rifles just won't shoot some bullets. Can you get some Hornady or Nosler 120s?
 
Have you tried IMR 4064 with the 120 gr bullet. In my 7/08 bullets heaver than 160grs work best with H-380, H-414/ww760, but with lighter ones IMR 4064 works for me. Also if you are getting 2 shots in and one out, try a primer change. This has worked, at times, for me before .
 
Two close, and one out? In a Montana?

Quick question..... Have you bedded this rifle? Or is it running on the factory bedding? Annnnnd have you had it out of the stock since you started this load? Is it assembled correctly? (Serious question) Meaning, is your mag box binding anywhere in the stock?
 
My 7.08 prefers 140 grain bullets and I don't run them hot. I tried 120's and had pressure issues when they were grouping the way I wanted so gave up on them (Wby VGII).

Anyhow, as far as your charge weight goes I have the Sierra manual and for their 120 grain bullets their starting powder weight for Varget is 37.6 grains with a max of 43.8 grains - COAL of 2.780" (developed/tested with Federal cases trimmed to 2.025" and Federal 210M primers)

For the best accuracy, Sierra suggests 40.3 grains of H4895 making 2900 fps from a 26", 1:9 barrel
 
oh yeah fellas, look before we get into the wild west of 'scope an mounts, bedding, assembly etc..... shoots 139 HORNADY & 140 WOODLEIGHS no dramas into an inch using 2208 .


Even with these 140s i cant get much more than 2 grains over max before primers flatten and BOLT lift is Difficult..... so proberly last thing I'm goin to do is keep pushin more powder in the case ay.

Cheers for other infos, will try this 41gr load an then may Fk around with seating them even deeper in the case.... without seein my numbers first loads were out around mag length then pulled them back in, didn't notice much difference but the lower charge was better..
 
Ron AKA said:
Actually I have had some bad experience with under loading. Hogdon (which markets the ADI powder here) has some bad data on the internet for loads in my .264 which are too light, and I followed it. See the results below. As your man Crocodile would say, "That's not a dent, this is a dent!"

Dents.jpg


My thoughts are that not enough pressure was developed to seal the neck. Pressure leaked by and collapsed the case. Three loads at a too light load of H3831 (AR2213), and all with the same result. Would that happen with AR2208? Not sure. However, if you want to pursue lighter loads you may want to try H4895 (AR2206H). Apparently you can go down to 60% of normal loads with it. No personal experience though...
Click to expand...

that's odd dents, mine are in the actual shoulder angle before the neck.
you must of been well under min tho?? not just a grain. I cannot see a grain doin anything wild
 
Ganderite said:
I have use a lot of 2208, but usually in quite hot loads.

It would be safe to try lighter.

But before I went lighter, I would load 44, 44.3, 44.6, 44.9 & 45.2. Shoot 3 each, with lots of cooling time between strings.

If you get any bolt lift resistance, stop shooting.

And yes, some rifles just won't shoot some bullets. Can you get some Hornady or Nosler 120s?
Click to expand...

Hi mate,
yeah I get hard Bolt lift pretty quickly in this rifle, I kind of covered that in above post but I think a tight chamber .. initial load development when I got it I loaded up a few charges, after the first 2 weights I shot a 3rd an immediately had resistance, I did finish those 2 shots "just too see" but the group was wild .. so back down.

my loads are
40gr 2208 140gr Woodleigh - Sambar load 1.2-1.5 inch group.
40gr 2208 139gr H I-L - Fallow and other game.
both only 1mm difference in COAL.

I picked up these 120s from down the big town Gun shop as I wanted something 'cheap' to plink with I suppose over summer, but with the possibility of - if it shot well- to take Fallow deer, Foxes and mid sized critters..
I'm getting the trigger time LOL but not the results..
 
I'm thinking it may be a component combination, I have seen major accuracy changes just in switching powders all else staying the same.

If the 150's are shooting that means the rifle is good to go , going heavier yes, that can pose some issues but moderately light as you are no so much.

If you have a slightly faster powder available I would try that , load up a 10 or 12 shot ladder test and see where your nodes are.Might be surprised.Might change your pressure signs as well.That 120 will need more of a pop than a push I am gathering.

It will shoot the 120's, eventually.

WhelanLad said:
oh yeah an Federals 150s shot sweet as.

I'm really thinking it don't like 120s...
Click to expand...
 
You have done what I would do, if I had poor accuracy. Change the powder charge.

Since going lighter did not help, I would go hotter, as I suggested. Load all the way to 45.2 as I suggested, and stop if you feel that bolt lift issue you are familiar with.

You are using the right powder. 2209 would be too slow for 120s, but about right for the 140s.
 
Your rifle has a 1-9" twist right? 120gr is light for that twist rate. I can't see getting much better than 1.5" groups out of it.

Maybe tweaking your loads might gain some improvement, but that's pretty much what I would expect.

Edit- I also noticed the bullets you are using are soft point. I think you are realistically doing pretty good.
 
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Tagged for interest. Interested in knowing more about your testing Whelan. (flat bases have worked well here in -08. No experience to offer in 120gr)

Regards
Ronr
 
I used that sierra 120gr Prohunter quite a bit 15-20 years ago to make some reduced recoil practise hunting loads for young teenagers. I didn't spend a lot of time on load development, just tried some different powders I had on hand and settled on the best one. According to my notes H4350 and IMR4895 weren't great, and IMR4064 worked best. Maybe could have gotten a bit smaller groups if I had spent more time tweaking, but it was "good enough". Rifle was a Rem 788.

For the reduced recoil loads 38gr IMR4064 for just over 2500 fps, 1.5"
Hunting load 44gr IMR4064 2950 fps 1.3"
 
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