Advice on switching from 175 SMK to 175 TMK in .308

[hockeyref]

I have an older Remington 700 with factory 24" heavy varmint barrel that shoots the #2275 SMK well, but I just ran out of them and I want to try Sierra 175 TMK's for better windage. I never had a chance to run the Stoney Point in to determine touch point so just for grins I pushed the OAL for the #2275 SMK's out to 2.965" and measured velocity at 2605fps. I figure I have room to add powder to get velocity back up. I know I can just get more of the #2275's and carry on, so the ultimate goal of this experiment is to find a faster load with the TMK's.

Current load holds ~1/2 moa at 500yds:
Chamber: Remington factory wide x huge!
175 SMK #2275 (Just ran out of the 175 SMK's)
OAL 2.825
LC 64 Match case 53.7g water
Re 15 43.8g
Primer: WLR (circa 1990's)
Velocity:2705fps
ES:9

What would I like help with?
- With the info I have, can anyone give me an idea if it's realistic to try to to get 2800+ fps with TMK's from my 24" barrel?
- What pressures am I estimated to be running at now with the #2275 and what might I expect with the TMK's?
- Looking at the difference between bullets, is it reasonable to start at 44g Re15 with the OAL at 2.970"
- Predicted max load?
- Suggestions with all of the above using IMR 4895
- Please do NOT suggest VARGET, it's against my religion. I quit using it 15 years ago.

 

[shortthroat]

I ran QL to your suggestion for H4895 and it predicts ~2660 with 42gr, and just below max. pressure. You probably cannot get to 2800 with that short barrel. The load you suggest with RL15 is calculated by QL to be way over max pressure. Here are the QL suggested powders. Varget isn't even on the list. As they say, you gotta get a bigger (longer) barrel.

Keep in mind that these are calculated internal ballistic results. You should NEVER start loading to these maximum loads, but always drop a couple of grains and work up to pressure signs.

159 loads produced a Loading Ratio below user-defined minimum of 95%. These powders have been skipped.
Powder type Filling/Loading Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gram fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Alliant Reloder-17 104.9 47.1 3.05 2696 99.1 52667 8033 1.196 ! Near Maximum !
Elcho 17 104.9 47.1 3.05 2696 99.1 52667 8033 1.196 ! Near Maximum !
ReloadSwiss RS 60 105.0 47.2 3.06 2692 99.5 51564 8122 1.204 ! Near Maximum !
ReloadSwiss RS 52 100.0 44.3 2.87 2652 99.7 52667 7405 1.213 ! Near Maximum !
Hodgdon CFE223 99.0 46.3 3.00 2643 97.6 52667 7644 1.210 ! Near Maximum !
Hodgdon H414 103.9 47.1 3.05 2640 94.4 52667 7790 1.211 ! Near Maximum !
Winchester 760 103.9 47.1 3.05 2640 94.4 52667 7790 1.211 ! Near Maximum !
SNPE Vectan SP 11 102.2 45.2 2.93 2637 98.6 52667 7494 1.212 ! Near Maximum !
Ramshot Big Game 98.9 45.1 2.93 2630 98.5 52667 7407 1.213 ! Near Maximum !
IMR 4895 98.1 42.0 2.72 2621 98.8 52667 7395 1.229 ! Near Maximum !
Bofors RP3 101.6 44.0 2.85 2617 99.3 52667 7297 1.236 ! Near Maximum !
Norma 203 old 101.6 44.0 2.85 2617 99.3 52667 7297 1.236 ! Near Maximum !
Vihtavuori N550 105.0 46.0 2.98 2612 96.8 50162 7711 1.242
PB Clermont PCL 511 105.0 47.9 3.11 2612 94.8 50466 7783 1.231
Norma 203B 99.4 42.6 2.76 2611 98.7 52667 7308 1.230 ! Near Maximum !
IMR 3031 98.9 39.6 2.57 2611 100.0 52667 6642 1.225 ! Near Maximum !

 

[hockeyref]

Thanks for the info, Much Appreciated. What pressure was RE15 calculated at?

 

[Texas10]

Sierra has advised that the TMK has a longer bearing length than the SMK, so drop powder charges accordingly as you start load workup.

https://sierrabulletsblog.com/2015/06/22/do-you-have-load-data-for/

http://bulletin.accurateshooter.com...ad-data-for-latest-high-bc-sierra-matchkings/

 

[JFrank]

I have an older Remington 700 with factory 24" heavy varmint barrel that shoots the #2275 SMK well, but I just ran out of them and I want to try Sierra 175 TMK's for better windage. I never had a chance to run the Stoney Point in to determine touch point so just for grins I pushed the OAL for the #2275 SMK's out to 2.965" and measured velocity at 2605fps. I figure I have room to add powder to get velocity back up. I know I can just get more of the #2275's and carry on, so the ultimate goal of this experiment is to find a faster load with the TMK's.

Current load holds ~1/2 moa at 500yds:
Chamber: Remington factory wide x huge!
175 SMK #2275 (Just ran out of the 175 SMK's)
OAL 2.825
LC 64 Match case 53.7g water
Re 15 43.8g
Primer: WLR (circa 1990's)
Velocity:2705fps
ES:9

What would I like help with?
- With the info I have, can anyone give me an idea if it's realistic to try to to get 2800+ fps with TMK's from my 24" barrel?
- What pressures am I estimated to be running at now with the #2275 and what might I expect with the TMK's?
- Looking at the difference between bullets, is it reasonable to start at 44g Re15 with the OAL at 2.970"
- Predicted max load?
- Suggestions with all of the above using IMR 4895
- Please do NOT suggest VARGET, it's against my religion. I quit using it 15 years ago.

I don't think you'll get to 2800 FPS with a 175 smk or tmk
44 gr of RL-15 is pretty stout load I've ran that in my Tikka
Have you looked at IMR 4064

 

[2506]

If you want to get 2800 fps with that bullet sale the 308 win and get a 300 Win mag because it will not happen with the 308 win.

 

[284winner]

I'm with 2506, a 24" barrel won't give you those numbers. Don't even think you'll get them with 168s and a 24" barrel. I'm getting 2880 in my 26" barrel running 168s. That's probably about the best I'll get. The 308 has it's limitations and I'd say you are gonna fall short of the 2800 by about 50+ fps no matter how hot you push it..

 

[10XSHOOTER]

Moly coat your bullets. 45.0 RL-15 With 26" barrel will run you close to 2900 fps no pressure. should beable to hit 2800 with the shorter barrel.

 

[hockeyref]

I knew the bullets are different, just couldn't lay my hands on a comparison - my google-fu sucked when I was looking so I aske for asistance here. I knew I would need to give them a "Palma-ish" kick in the ass to get them up to 2800 fps in my barrel if it were possible. I KNOW I can get 2700fps from a 175 SMK as I have been doing it for 10+ years. I should at least be able to equal that with the 175 TMK, and JBM predicts 1.3 moa wind advantage at 1k at 2700 - apples to apples comparison. If that's what I get, so be it.

I have 5 firings from my rifle on this set of 100 LC64 Match cases & have not lost a primer pocket yet. I will prep another set of cases for the TMK's after I narrow down the load. I literally have a 5 gallon bucket of them that are once fired. If\when I shoot out this barrel I will look at Lapua or Peterson SRP cases. Until then, these do just fine.
I have not used Molly in almost 20 years.... none of the other loads for this rifle are coated so that would necessitate reworking multiple other loads - makes it a no go

FWIW - I have old load dev notes from when I had a decent\fast lot of Varget 44.5g that had the 175 SMK going 2750 at 62* temps, I wound up using 44g @2700. Notes also say that I got over 2800 with sticky bolt lift. When that lot ran out the next lot of Varget maxed out at ~2600 so I tried the RE15 that I was using for the 90 JLK's in my AR. The 43.8g RE15 load @2705 was more accurate than the previous Varget load with low ES. I ran with it and have shot it without issue in temps as high as 90*.

 

[shortthroat]

QL calculates 53120 psi and 2639 fps for 43.8gr RL15, and is below 60191 psi maximum for NATO brass. The calculation shows 32.4% ballistic efficiency for the load which is high, indicating that it might well be an accurate loading.

If you use RL17 and up the charge to 47.1 gr (a 100% case fill) , QL shows the pressure much reduced to 47210 psi with almost the same calculated 2634 fps. The efficiency reduces to 30% owing to the additional powder loading. These figures are for 175 SMK #2275 G7 bullets.

The QL calculation with RL15 gets to 2806 fps but with 65485 psi; above the 60191 maximum, and about 104% compressed loading for 53.7 case capacity. In theory you could get close to 2800 fps with RL15, but you will certainly be seeing pressure signs. Work up from about 44 gr RL15 VERY slowly and definitely don't switch to the 175 TMK #7775 bullet. Just changing to that bullet puts the pressure up to 72989 psi, well above the maximum and above what your action or the shooter would like to see.

Moly coating isn't going to accomplish your objective. As stated by others, you are looking for 300 Win Mag performance from a .308.

 

[hockeyref]

ShortThroat,
Yup, #2275's 43.8 RE15 out of my rifle give ~2.75" @ 500 yards prone with BiPod depending on how much coffee I had and how stiff my neck is that day. I might need to try some RE17......

Like I said, I ran out of #2275's and wanted to see what the #7775's might do....
Since we seem to have bounced around between the #2275 and #7775, I just to make sure which QL report is for which bullet. Is the info posted in your original reply above is for the #7775 or the #2225? I am reading the second post above to be QL for #2275. correct?

One more question for reference, what kind of pressures are frequently quoted Sierra and Berger 155.5 Palma loads (Lapua\Varget ~46g) predicted at when they push those pills upwards of 3k?

 

[shortthroat]

My post #10 refers to 175SMK #2275. The last comment referencing Sierra TMK refers to the same loading/OAL that was used for the #2275; just switching to that bullet QL calculates as way too hot.

The calculation for Varget/46gr with the 155 Palma MK shows 55984psi, just below the maximum, and 2800 fps. Just switching to the 168SMK takes calculated pressure up to 59676 and knocks speed down to 2750 fps. Keep in mind that these are calculations, not measured values. The results are internal ballistic calculations and therefore depend on all the variables such as starting pressure (jam or jump), powder burn rates, etc. QL is usually excellent to find a good starting load, one that is safe for a powder and bullet combination without any loading manual references and if you are careful not to start close to maximum calculated pressure. Hence, the caution to not make switch from the SMK to the TMK without reducing the load accordingly.

 

[hockeyref]

Thanks for the info, no way I was going to just swap the bullets onto the same load. I've done my share of developing nuclear loads and living on the bleeding edge, It is good to have an idea of the pressures before starting. I wish I had QL 15 or so years ago when i was one of the first shooters running the JLK 90's in a 20" AR service rifle at 2750 fps and 2900 fps from an AR match rifle. Developed the load without a functioning gas system to mimic developing it in a bolt gun, then made changes to the rifle to keep it from trashing the brass too fast....

 

[hockeyref]

Minor update, I called Sierra to try to get info "from the horses mouth" so to speak. Not exactly sure which end was talking to me ,,,, I was told to just drop my RE15 load down .8gr and work back up from there. Would not discuss - at all - any differences between the bullets that can be measure and quantified. Would not discuss any powders. Definitely different from the Sierra guys that I talked to about the JLK 90's at Perry in 2003.

 

[shortthroat]

Nice to know that Sierra gives out all the assistance possible, short of actual help.

 

[hockeyref]

Yeah, I wondered if maybe a lawyer was listening to the call.....

 

[hockeyref]

Well. I tried to rush out and get some chronograph data last night after work in from of the cold front (temp was 88*) Got numbers on my .223 80gr SMK load and then switched to the .308 as the shadows started to get long. Switched scopes from vari-x III 6.5-20 EFR to the LRM3 as the 6.5-20 was zeroed for 500 yards and the LRM3 had a BDC on it that was zeroed at 100 yards. What I didn't remember or notice was that I didn't turn it down to 100 yard zero. the last time I had last shot it was at 500 yards..... You know what happened next:

Yup, I killed my Chronograph.

 

[Lone Hunter]

Well. I tried to rush out and get some chronograph data last night after work in from of the cold front (temp was 88*) Got numbers on my .223 80gr SMK load and then switched to the .308 as the shadows started to get long. Switched scopes from vari-x III 6.5-20 EFR to the LRM3 as the 6.5-20 was zeroed for 500 yards and the LRM3 had a BDC on it that was zeroed at 100 yards. What I didn't remember or notice was that I didn't turn it down to 100 yard zero. the last time I had last shot it was at 500 yards..... You know what happened next:

Yup, I killed my Chronograph.

One Shot, One Kill...