.308 SMK 135g. HPBT load data?

[dsv424]

I recently bought this bullet and just my luck it isn't in my Sierra 5th Edition manual. Does anyone have load data for this one. It must be new since I can't find it in the manual. The closest I can find is in my Hornady book for a 130 g. SP. I tried looking for it in different 30 cal guns but no luck there either.

 

[kludge]

E-mail Sierra tell them you have the 5th Edition and ask them for a recommended load with your choice of powder.

 

[MEHavey]

This type/bullet weight is made for a faster powder.

QuickLoad likes.....
Cartridge : .308 Win.
Bullet : .308, 135, Sierra HPBT MatchK 2123
Cartridge O.A.L. L6: 2.800 inch or 71.12 mm
Barrel Length : 28.0 inch or 711.2 mm

Powder %Fill Grains Vel %Burnt Press
IMR3031 97.4 43.8 3000 100.0 45,213
AA 2495 98.7 44.9 3000 100.0 46,735
AA 2520 95.9 47.6 3000 99.30 47,098
RL-15... 98.2 47.3 3000 96.20 47,117
H4895... 94.7 45.6 3000 97.50 47,754
IMR4895 96.9 46.7 3000 96.70 46,212

 

[dsv424]

Are those Max loads you posted. I have IMR 3031, H4895, and RL-15 but not sure from what you posted where I should start. Thanks for the data though.

 

[MEHavey]

The 308Win is a 57-60,000 psi cartridge.
From Quickload calcs, those are relatively "soft" loads akin to what you would load up for an Garand or M14/M1A. The particular powders here, though, fill the case and efficiently burn in normal rifle-length barrels.

Pay attention to the 2.800" COAL, however.
If you seat only 1/10 inch deeper, you will raise pressures ~4,000 psi

....and start a grain or two lower until you see how your rifle reacts.
(Out of curiosity, what does your Hornady Book list as max for that 130 grainer?)

 

[dsv424]

In the Hornady book they are talking about 130g. SP non BT bullets and the OAL is 2.690(which I definitely can't use for this long bullet) but some of the Max loads are:
H4895 48.2g.
RL-15 50.1g.
H 322 44.0
IMR 4895 49.4
AA 2495 45.9
Win 748 52.6

BTW, I sent an e-mail to Sierra for load data so I may get some info on Monday. If I do I will post it in this thread. I'm sure I'm not the only one who has purchased this bullet lately.

 

[MEHavey]

Looking over Sierra data for their lighter BT/NonBT bullets, it looks in all cases like they are setting OAL to numbers that give them 0.200"-0.205" shank depth minimum. For their particular 135-SMK, that means OAL=2.695 in a case that's trimmed to 2.010".

For that shorter OAL, a mild (under 50,000psi) loadout still reaching decent velocity (3,000fps), filling the case with powder that burns close to completely in a 28" barrel....
Quickload suggests....

Cartridge : .308 Win.
Bullet : .308, 135, Sierra HPBT MatchK 2123
Cartridge O.A.L. L6: 2.695 inch or 68.45 mm
Barrel Length : 28.0 inch or 711.2 mm

Powder. %Fill Grains Vel %Burnt Press
H4895 .. 96.80 44.8 3000 97.40 48,920
RL-15 .. 100.0 46.5 3000 96.10 48,279
IMR3031 99.50 43.1 3000 100.0 46,179


[post: If you want a real screamer, go get some BL-C(2)/Win748 ]

[post post: Those Hornday loads -- even for their lighter 130SP -- calculate out as (in the W748 case, incredibly) hot.]

 

[dsv424]

Thanks for the data MEHavey. I think I will start out with either RL-15 46.5g. or IMR 3031 42.0g. and go from there and see how they perform. Also, set the OAL as you stated to 2.695.

 

[dsv424]

FYI, here is the response I got from Sierra for load data on this bullet. Not exactly what I expected but it will help me get started. Hopefully this will help anyone else that may purchase this bullet.

"Due to the demands of production we haven't been able to shoot any new data
for many months so I don't have any supplements to share with you . However
I would suggest you use 150 grain data as a basis for your load development
with complete safety. Please stay in touch and when I do have data to share
I'll be more than happy to do so."
Rich

 

[ChuckE]

I called Sierra recently and they recommended starting at 2.725" C.O.A.L. for the 135 SMK.

I'm using LC '74 brass - trim length 2.005"
135 SMK seated 2.134" at the ogive/ 2.722-2.730" C.O.A.L
CCI #34 primer
VV N-140 powder

M1A with a 22" barrel

Temp 86F

42.0 gr. N-140 = 2705 fps/ SD = 8.20/ ES = 29 [my current 200 yd target load]
42.5 gr. N-140 = 2749 fps/ SD = 7.68/ES = 24

Chuck

 

[dsv424]

I tried a recipe from the 150 g. data.

43.2 g. IMR-4064
COAL 2.770
CCI BR primers
R-P Brass trimmed to 2.005

Very good grouping at 100 yds.