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Discussion Starter · #1 ·
Has anyone tried the Sierra MatchKing #2123 .308 135 gr. HPBT. I plan on working up a load using the IVI brass I got from scharch's. (Did not want to start from scratch with my GGG.) With IMR 8208XBR powder, CCI BR2 primers. And shooting out of my Socom 16.
These bullets have only been out for a few years and a Google search was not much help.( Calls to Sierra ended with persons being told to load them like 150 gr..) The bullets are shorter than the SMK 150 and 155 gr. HPBT. I will probably shorten the OAL, 2.775 recommended by Sierra for the 150/155 gr.. Starting load will be 38.5 grains of IMR 8208XBR and increase in .3 grain increments.

This will be interesting, new powder, new bullets, in new cases. The fun I'll have!
I am on call and will not be able to shoot till November 6th, so any input would be appreciated.

Glenn
 

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keep us posted, I've worked up a very good load using 8208 for my 168 grain Barnes TTSX bullets but I haven't tried anything lighter.
 

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keep us posted, I've worked up a very good load using 8208 for my 168 grain Barnes TTSX bullets but I haven't tried anything lighter.
RAMMAC, can I assume you've had no port pressure issues?

Would you mind sharing your load data? I just bought a couple of pounds of 8208, but I've yet to hear back from IMR as to questions about port pressures.

TIA
 

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Ya' know that all the standard warnings apply and any load should be worked up to in increments to ensure safe conditions.

The data below is what I got when I last checked all of my results in detail. I have made two changes since this data was collected, specifically I am now using Lapua brass and Barnes Tipped TSX bullets. The COAL is a little longer using the TTSX bullets but I actually go by the ogive for my length dimension (2.181" if memory serves). The TTL is the same.

With those changes my 100 yard bench groups are about 1" plus or minus about a quarter inch depending on how careful I am but most often I get 1" or better groups.

As for pressure issues, I have not had anything unusual show up except the primers are definitely flatter than what I'm used to with my other powders but then I usually run about 2540 fps with the other loads in my 22" barreled standard.




Current best load using IMR 8208 XBR with my SOCOM 16.

COAL - 2.81" (2.181" at the ogive)

Powder - IMR 8208 XBR 42.4gr (I was able to fire 43gr but I groups and pressure signs started getting worse after 42.4gr, pressure signs at 43gr included ejector marks on the base of the brass and I would get head separation after only two or three reloads).

Bullet - Hornady 168gr A-Max

Case - WCC, TTL 2.005" (cases were sorted by weight, all primer pockets were uniformed and flash holes uniformed and chamfered on the inside).

Primer - Winchester Large Rifle

Muzzle Velocity Info -
42.4gr
Chrony at 15 feet from the muzzle
5 shot Average - 2587 fps.
41 fps extreme spread
15 fps standard deviation
Hi 2606 fps
low 2565 fps

I also tested velocities using 41.1gr and got an average of 2501 fps with 5 shots.
 

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Discussion Starter · #6 ·
Just got back from IMR's website, and I'd say you are good to go with the 8208 XBR. According to their burn rate chart, it's just one rate faster than H4895, and three faster than IMR 4895. Go for it!
For reference:
http://www.imrpowder.com/burn-rate.html
Kevin
Thanks Kevin,
I have all the IMR info., I was trying to find out any recommendations for OAL of the finished cartidges. The bullets are a little shorter. I will start at 2.750" and work from there. My Federal XM762D uses what looks like a M59 bullet (150 gr) with an OAL of 2.715. I had a Federal bullet that I pulled put aside somewhere, I just have to find it or pull another.
The fun part will be the accuracy. I had to skim on some bedding on one side of my stock to get good barrel tension. And while I was at it, I put on a USGI extractor, ejector, (with springs), and a USGI rear sight aperture. Have only shot it once and I still need to get use to the smaller sight window.

Thanks again for the input,
Glenn
 

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I called Sierra recently and they recommended starting at 2.725" C.O.A.L. for the 135 SMK. They also saw no benifit in running them over 2700 fps.

I'm using LC '74 brass/ case wt = 176.1-181.9 gr./ trim length 2.005"
135 gr. SMK/ seated 2.134" at the ogive/ 2.722-2.730" C.O.A.L
CCI #34 primer
VV N-140 powder

Temp 86F

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

Both of the above loads will shoot inside the x ring off the bench on a calm day with my Super Match.

I started at 41.5 gr. and worked up in 1/2 gr. increments.

IVI brass is heavy, so work up accordingly. The IVI '01 brass I bought from Scharch weighs 183.8-186.3 gr. If I were using the IVI brass in the above load, I would have dropped the starting load at least 1 gr. GI3

Chuck

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Discussion Starter · #8 ·
Thanks for the heads-up, Chuck.
Looks like a good OAL to start at. I have to start with a lower charge weight and work up for my Socom. It shows pressure signs sooner than most other rifles.(Tighter chamber or rifling) And IMR 8208XBR is a bit faster than what your using.
Great info and thank you,
Glenn
 

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I just loaded the new update to my QuickLOAD software (ballistics info for reloaders) and WOW!

BE ADVISED THAT (according to QuickLOAD data) 39.4 GRAINS OF IMR 8208 XBR WILL, IN MOST CASES, PUT YOUR CHAMBER PRESSURES RIGHT AT 50,000 PSI AND JUST OVER 40 GRAINS WILL PUSH THE PRESSURES TO RIGHT AT 60,000 PSI (assuming a 168gr Hornady A-Max bullet, a COAL of 2.81", a TTL of 2.005", and a case with a 54.2 gr water volume capacity).
I had previously posted that I was using 42.4 grains of this powder with the Barnes 168 gr TTSX bullet, COAL 2.864", case TTL 2.005", case capacity of 54.2gr H2O in my SOCOM 16. According to QuickLOAD the muzzle velocity should be around 2579 fps (I got a chronograph speed of 2587 fps) and since that came out pretty close to the real world I think the rest of the numbers are pretty scary. These are what QuickLOAD predicts for my load...YIKES1

Compressed load - 104.4% of the usable case volume
Chamber Pressure - 69023 psi
Approx Port Pressure - 12963 psi
Muzzle Velocity - 2579 fps (man I love that speed!)

I am so glad that I didn't blow my face off!! dance2 It looks like I need to re-work my loads and they should end up somewhere in the range of 37.8 - 39.8 grains of powder.


geepee, I ran some of your data to see what would come up and this is what I saw;

135 SMK
Case TTL 2.005" and assuming a volume of 54.2gr of H2O
COAL 2.725"
38.5gr of IMR 8208 XBR
Chamber pressure 35034 psi
MV 2306 fps
Case volume used 85%

It seems that good loads use about 93% - 98% of the case volume so using this as a standard here are the numbers;

AT 93%
42.1gr
2524 fps
44798 psi

AT 98%
44.4gr
2664 fps
52432 psi

Hope this helps.
 

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Discussion Starter · #10 ·
Thank you RAMMAC.
I will be taking it slow. I have to keep an eye on loads for my rifle anyway. That's the thing with new powder, not all the variables are in yet. It is also why I am testing the powder with lighter projectiles. I did hear when IMR 8208XBR came out that it was better suited for lighter weight bullets.

I am also glad you and your rifle survived your initial testing.

Thanks again for the update.
Glenn
 

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Well my load did prove that the rifle is one tough cookie. I will work on the 168gr load and post my results, please let us know how your loads work out too, it will be nice to have some loads for bullet weights across the board.
 

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Discussion Starter · #12 ·
Update

I first want to thank everyone for their input.

I feel like a mad scientist. ChuckE gave me the basic set-up and I fine tuned it for my equiptment. I took a fired case, removed the primer with my Lee primer punch. and sized the case to give me my actual headspace and trim length but was able to have enough neck tension to be able to hand seat the bullet and make adjustments.

With a GGG 03 case, sized, trimmed to 2.005" length, this is what I can up with.
Using the Hornady bullet comparator and .308 caliber insert it gives me an ogive of 2.145".
And a total lengths between 2.724"- 2.730" ( yes, the bullet lengths vary that much.)


SMK 155gr. (L.), SMK 135gr. (C.), Win. 147gr. FMJ (R.)
The black lines on the bullets show seating depth.


SMK 135gr. test cartridge


Federal XM762D 150gr. (L.) SMK 135gr. test cartridge (C.) Win. 147gr. FMJ handload (R.)

Will be loading them up this week and weather permiting will be shooting this weekend.

Thanks
Glenn
 

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Sierra 135s

Not the same powder but I have used the 135s in my M1 Garand and M1A rifles for a couple of years now.

LC Case 3006 47.5 4064 CCI LR 3.160 OAL

LC Case 7.62 44 4064 CCI LR 2.775 OAL

Very accurate and soft recoil. Jesse
 

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Discussion Starter · #14 ·
rounds Loaded

Thanks again for everyones input.
Have eight different loads(sets of six) ready to be tested out.
Loads from 38.5gr. to 40.6gr. in 0.3gr increments. Stopped at 40.6gr. because that's where IMR 4895 loads starts showing pressure signs with 150-155gr. bullets.



"03" IVI cases trimmed to 2.006"
Sierra MatchKing 135gr. HPBT bullets
IMR 8208XBR powder
CCI BR2 primers
2.145" length to ogive
2.724"- 2.730" C.O.A.L.

IMR 8208XBR in an extruded powder. Smaller in length and diameter than IMR 4895,and it has a coating like H 4895.


IMR 8208XBR (L) and IMR 4895 (R)

Will be picking up a chronograph before I shoot on Sunday. The reloading shop next to my work has the Chrony ones for a fair price. They also had one somebody shot, I don't want to do that.
So I will keep you all posted after I test the loads.

Thanks again,
Glenn
 

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Discussion Starter · #15 ·
Shots Fired....... it was only me.

Finished testing my loads today.
Let me first say, no chrony's where harmed in todays test.
It looks like the combination of SMK 135gr HPBT and IMR 8208XBR from a 16" barrel is a bust. Extreme spread and standard deviations are high. Lowest of the group was at 38.8gr. load with an ES of 39.87fps and an SD of 15.16fps, with an average velocity of 2177fps . Highest of the group was at 39.7gr load with an ES of 143fps and an SD of 61.74fps with a average velocity of 2342fps. I used CCI BR2 primers to keep the ignition of the powder constant. Here is the data I that I have for the record.

Air temp; 62 degrees F.
Wind; NNE 10-15mph.
Cloudy skies

Chrony set at 13' from shooting bench

Socom 16 rifle, 16.25" barrel
SMK 135gr HPBT bullets
IMR 8208XBR
IVI "03" new cases trimmed to 2.006"
CCI BR2 primers
Length to ogive; 2.145"
COAL; 2.724-2.730"

6 shot strings.

38.5gr
AV; 2168fps
ES; 87.74fps
SD; 37.81fps
Lo.;2124fps
Hi.; 2212fps

38.8gr
AV; 2177fps
ES; 39.87fps
SD; 15.15fps
Lo.;2155fps
Hi.; 2195fps

39.1gr
AV; 2250fps
ES; 61.36fps
SD; 21.72fps
Lo; 2217fps
Hi; 2278fps

39.4gr
AV; 2260fps
ES; 114.8fps
SD; 4356fps
Lo; 2195fps
Hi; 2310fps

39.7gr
AV; 2342fps
ES; 143fps
SD; 61.74fps
Lo; 2268fps
Hi; 2411fps

40gr
AV; 2359fps
ES; 82.09fps
SD; 30.06fps
Lo; 2308fps
Hi; 2390fps

40.3gr
AV; 2399fps
ES; 104.6fps
SD; 41.47fps
Lo; 2337fps
Hi; 2441fps

40.6gr
AV; 2433fps
ES; 62.81fps
SD; 29.01fps
Lo; 2396fps
Hi; 2459fps

I also tested three shots (before it started to rain) of PMC Bronze 308b cartidges.

PMC was a surprize with the best numbers.
#1; 2604fps
#2; 2607fps
#3; 2608fps
AV; 2606fps
ES; 4.49
SD; 2.00
147gr FMJBT

I will be trying the IMR 8208XBR with 147-155gr bullets later on. Will not be able to shoot for three more weeks. So I will start a new thread when I put them together.

Thank you all again for all the input.
Glenn
 

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Finished testing my loads today.
Let me first say, no chrony's where harmed in todays test.
It looks like the combination of SMK 135gr HPBT and IMR 8208XBR from a 16" barrel is a bust. Extreme spread and standard deviations are high. Lowest of the group was at 38.8gr. load with an ES of 39.87fps and an SD of 15.16fps, with an average velocity of 2177fps . Highest of the group was at 39.7gr load with an ES of 143fps and an SD of 61.74fps with a average velocity of 2342fps.
Are you serious? You should be able to get something like 2800 fps with a 135. Max safe loads didn't even come within 600 fps of that?

I'm wondering if your high ES and SD numbers are because the loads are too light for this powder, and pressures were not high enough to promote a consistent burn of the powder...?
 

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Are you serious? You should be able to get something like 2800 fps with a 135. Max safe loads didn't even come within 600 fps of that?

I'm wondering if your high ES and SD numbers are because the loads are too light for this powder, and pressures were not high enough to promote a consistent burn of the powder...?
I'm wondering the same thing. That software that I use estimates that charge weights of 44gr - 46gr should be good loads with the 46gr recipe getting you up to about 2700 fps and about 54000 psi for chamber pressure.
 
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Discussion Starter · #18 ·
Are you serious? You should be able to get something like 2800 fps with a 135. Max safe loads didn't even come within 600 fps of that?

I'm wondering if your high ES and SD numbers are because the loads are too light for this powder, and pressures were not high enough to promote a consistent burn of the powder...?
My thoughts exactly. That's why I am going up to a 147-155gr bullet. I have more of that grain bullets to play with right now. Then up the load when I know more about this powder. This is the first time I have tried it.

Glenn
 

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Curious to see if you get something you like worked up here. I'm also playing around with 8208 with 150 and 168gr Sierras. Might get a chance to shoot tomorrow with 150s, will start a new thread when I do.
 

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Discussion Starter · #20 ·
Curious to see if you get something you like worked up here. I'm also playing around with 8208 with 150 and 168gr Sierras. Might get a chance to shoot tomorrow with 150s, will start a new thread when I do.
Please let us know how you do. I will continue to work up loads for the SMK 135gr. I just need to jump up the loads.
I am practicing what I preace about starting low and working up. To me, even the load data so far is good data. Since there is very little data avalible for IMR 8208XBR, every little bit helps.
I only have 52 bullets left of this grain, thats why I want to work with the 147gr. (I have over 400 of these, and they are cheaper)
One thing this tells me is my Socom gas system is fine. All these shots with under powered cartidges and not one FTF or FTE.

Thanks,
Glenn
 
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