Experience of 308 Hornady interlock 150 sp (flat base) and n140

DCG

Well-Known Member
Hi all
Ive been loading some Hornady interlock 150gn sp (flat base) for 308, using Norma cases and Cci br2 primers. Currently seated at 2.740" col, I've got up to 48gn of n140 without showing any signs of pressure . However in a 20" barrel I'm only seeing about 2540 ft/ps over the chronograph.
I'm concerned to go any higher with the powder and was wondering what the experiences and thougts/ observations were of anyone else using this combination of components.
​dcg
 
if you are seeing no signs of pressure just keep going until you do then back off,provided you still retain a good level of consistant accuracy,at the end of the day speed dosent kill accuracy does
 
Hi see it shoot it
problem is I'm starting to crush the load and from what I can tell 48 grains seems excessive, for that level of powder I was expecting to see about 2950 to 3000 ft/ps and then back down a bit.
dcg
 
Hi see it shoot it
problem is I'm starting to crush the load and from what I can tell 48 grains seems excessive, for that level of powder I was expecting to see about 2950 to 3000 ft/ps and then back down a bit.
dcg
its called a compressed load,if you think your at your max FPS and you cant get no more in the case its time to change powders but I don't think you will see 2900 FPS with a 150 bullet
 
+1 on the suggestion that seeing 2900/3000 fps for a 150g out of a 20" .308 barrel may be unlikely. I'm not familiar with the powder you are using, but the most recent Barnes manual lists 3 max loads at 2900+ fps. Two of the three are compressed loads, and all are from a 24" barrel. Nosler (#4) says max loads of RL 15, and IMR 4064 will push a 150g at 2900+ fps, but again, out of a 24" test barrel. Hornady (5th ed.) shows a couple max loads at 2800 fps from a 22" barrel.
I would guess that it's been done - probably more often than I like to think, but I am not one to mess with loads beyond published maximums.
 
My mate gets about 2950 with n140 and the 150 gameking out of a 22" barrel. Im getting 2770 with varget and the 150 from a 21" tube.


Nutty
 
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Why don't you try Viht 540 - a double base powder with higher energy content.
2540 fps sounds quite satisfactory to me unless you want to shoot deer at 1000 yards!
 
hi dcg your bullet speed of 2540 is giving you 2148 ftlb of energy, well above the legal requirement for stalking if the round is accurate leave well alone.
cheers Geoff
 
DCG, what type of speeds are you getting with factory loads? What barrel is on the rifle? Speed sounds very very low for that load.
Normally hear of 44gr N140 being a magic number for that bullet.
edi
 
DCG, what type of speeds are you getting with factory loads? What barrel is on the rifle? Speed sounds very very low for that load.
Normally hear of 44gr N140 being a magic number for that bullet.
edi
:thumb:
 
Speed seems low, I was getting 2900 from 46 g 140 but from a 24 in barrel. Is there a monster muzzle flash when you take the mod off? I wonder if you are not getting full combustion in the short tube. Faster powder would be worth a try. My 308 seems to like H4895 too
 
44gr and 46.5gr are the node points with N140 in my sako which has 20inch barrel. Worked well for me out to 180yards.
is you chronological correct?

BE
 
Hi Guys,
Thanks for all of your replies, I'm going to try the Chronograph against another this weekend, and put some factory over them both. I rather suspect its out of calibration.
Definately compressing the load which, in my opinion, is rediculouse for a hunting load. But I expected to see signs of pressure before now, especially as I'm seating it slightly shorter than book.
Quickload gives 47gn a 100% burn in a 25 1/2 " barrel so I would think that I'm wasting a bit of powder in a 20" barrel.
Conclusion at the moment , especially as the accuracy is good and the power is adequate, is that it'll do for the time being, until I get the time to try some other powders.
Once again thanks for your help.
​dcg
 
Hi all
Ive been loading some Hornady interlock 150gn sp (flat base) for 308, using Norma cases and Cci br2 primers. Currently seated at 2.740" col, I've got up to 48gn of n140 without showing any signs of pressure . However in a 20" barrel I'm only seeing about 2540 ft/ps over the chronograph.
I'm concerned to go any higher with the powder and was wondering what the experiences and thougts/ observations were of anyone else using this combination of components.
​dcg

You're using 48.0g of N140? The Hornady Manual (6th ed.) recommends 45.8g as the maximum charge and for that you should get around 2700fps. You are therefore 3.0g above the recommended maximum charge. QuickLoad indicates that you should get just over 2800fps but at a peak pressure of 61.5 kpsi - the maximum permitted pressure for the .308 Win is 60.1 kpsi.

Three points to make. One, you are exceeding the recommended powder charge. Two, your load is at or exceeds the maximum permitted pressure (I'll bet your brass is suffering). Three, your chronograph is duff and/or getting whacked by muzzle blast since it is under-reporting by 250fps. Try firing your loads over two chronographs simultaneously and compare the two.

Footnote: Vihtavouri Manual (2nd ed) lists 42.3-46.8 of N140 for the Sierra 150g SPBT, but you are above that maximum too. Ah, 9th ed states 41.8-47.1g N140 but that's for the Sierra bullet not the Hornady bullet.

-JMS
 
I'm using 44gr with BTSP hornady 150gr in lapua brass and getting 2770fps which is more than adequate and very consistent. Speeds seem slow for such a high load
 
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