LR-308

erwos said:

Only? For a 20" barrel, 2600 out of a 175gr SMK is a pretty hot load, arguably into questionable pressures. I only do like 2560 or so with 168gr FGMM with my RPR. What exactly are you putting in there?

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pcfixer said:

point of aim is circles...1st 4 center... 2nd 4 top left...3rd 4 top right, 4th 4 bottom right.. last 4 round bottom left.

43 thru 46 grains IMR 4320 at 100 yds.


Need to adjust left 1 1/2 on scope. 6 or seven clicks.

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erwos said:

Only? For a 20" barrel, 2600 out of a 175gr SMK is a pretty hot load, arguably into questionable pressures. I only do like 2560 or so with 168gr FGMM with my RPR. What exactly are you putting in there?

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Pinecone said:

Yeah, my .308 load is 2600 out of 24"

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erwos said:

With a 24" barrel, sure, you can get 2600fps without too much drama. I don't want to flat-out say "no way you're getting 2600fps out of a 175gr SMK with 43.5gr of Varget", but I'm basically saying that. Hodgdon's own data says 2690fps with a max load of 45gr, and you're going to lose ~80-100 FPS from going to 20". If we revise the number to ~2550fps, yes, that's believable. The OP has a bigger problem, which is that he's gonna have to fight some velocity loss from being a semi-auto, too.

(And before people jump on me over 50fps being negligible, if you're using one of the many BDC scopes out there calibrated to 175gr SMKs @ 2600fps, it's not a negligible difference at longer ranges.)

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Pinecone said:

1) What step sizes? 5 steps in 43 - 46 is almost a grain, which is over 2%. Since nodes are only 3% apart, the step size is too much.

2) If doing an OCW, you should fire round robin. 1 round of Load 1, 1 round of Load 2, ... 2nd round of Load 1, 2nd round of Load 2. Evens out changes due to heating and fouling.

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Speed3 said:

Ok....you don't have to believe me, I don't care either way. I can tell you that my father shot that rifle at Ed's class and the Strelok data matched real world data out to 1150 yards(he ran out of elevation). We measured the scope height over bore.

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Pinecone said:

1) What step sizes? 5 steps in 43 - 46 is almost a grain, which is over 2%. Since nodes are only 3% apart, the step size is too much.

2) If doing an OCW, you should fire round robin. 1 round of Load 1, 1 round of Load 2, ... 2nd round of Load 1, 2nd round of Load 2. Evens out changes due to heating and fouling.

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I began with three rounds each of five different charges, graduating in .3 grain increments. The tested charges were 39.2, 39.5, 39.8, 40.1, and 40.4 grains.
I cleaned the rifle, and shot two fouling shots and allowed two minutes for it to cool. I had five targets posted at 100 yards, one target for each charge variation.
I shot one round of the 39.2 grain charge at target 1, allowed two minutes for cooling, and then fired one shot of the 39.5 grain charge at target 2, cooled, one shot of the 39.8 grain charge at target 3, cooled, you get the idea...
This is basically a "round robin" system of grouping each charge, which precludes disadvantaging late groups due to fouling, or heat build up.
When finished, I had three shots on each of the five targets, BUT (!)... I don't look for the tightest group of the five and call that my load.
Here's what I do instead, and I'll explain why later: I look for the three groups of the five that come the closest to hitting the target in the same position. I noted that in this case, the three groups from the middle of the string were the ones which happened to hit the same POI, (all within about a 3/4" overlay, and all at a 2 o'clock position with relation to the bull) with the 39.2 grain group hitting low and left from that common POI by an inch. The 40.4 grain charge, in addition to moving high and right of the common POI for the three center charges, opened up in size to about 7/8". The 39.2 grain charge shot just under 1/2", but as I said, it wasn't near the common POI that the 39.5, 39.8, and 40.1 charges shared.
So I concluded that the best charge for this application was 39.8 grains of IMR 3031. This was the charge that would allow 39.5 grain charges and 40.1 grain charges to group right with it.

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This is basically a "round robin" system of grouping each charge, which precludes disadvantaging late groups due to fouling, or heat build up.

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erwos said:

With a 24" barrel, sure, you can get 2600fps without too much drama. I don't want to flat-out say "no way you're getting 2600fps out of a 175gr SMK with 43.5gr of Varget", but I'm basically saying that. Hodgdon's own data says 2690fps with a max load of 45gr, and you're going to lose ~80-100 FPS from going to 20". If we revise the number to ~2550fps, yes, that's believable. The OP has a bigger problem, which is that he's gonna have to fight some velocity loss from being a semi-auto, too.

(And before people jump on me over 50fps being negligible, if you're using one of the many BDC scopes out there calibrated to 175gr SMKs @ 2600fps, it's not a negligible difference at longer ranges.)

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Speed3 said:

Zero pressure signs in my rifle. I'd have to go look at the book, but should be right around 43.5gr of varget. I've loaded 45gr and started to see cratered primers but they didn't shoot.

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Pinecone said:

I shoot 175 SMK, 4.35 grain Varget, in Lapua brass, and get 2600 out of 24"

Just saying.

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ted76 said:

I don't know if 4.35 grains of Varget will push the bullet out of the barrel.
Are you sure that you aren't loading 43.5 grains of Varget?

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