SMKs slower than A-Maxs?

[McLarenross]

Ive been doing load work ups with 155gr bullets and with 46.3gr of RL-15 and a 155 A-Max I get 2775fps outta my 20" Remington barrel, but 155 SMKs(2155) with the same charge only move 2650fps. It took a full grain more powder to get the same 2775fps. Also with 175 SMKs I dont seem to be getting nearly the velocities others are, even taking into account my 20" barrel. With the 175 SMKs and 44.2gr of RL-15 I only got 2600fps and was getting a stiff bolt and slightly flattened primers. Those were pretty accurate though.

 

[308sako]

Re: SMKs slower than A-Maxs?

deleted in protest!

 

[McLarenross]

Re: SMKs slower than A-Maxs?

LOL!!! Thats just frustrating!!!! Thanks though.

 

[Niles Coyote]

Re: SMKs slower than A-Maxs?

Also keep in mind a lot of shooters on here are using after market barrels. My 21.5" rock creek barrel surpasses what I see in my other 308 with 26" factory Rem barrel with like loads, the Remington tube generally shooting 50 to 75 fps slower.

 

[sawgunner2001]

Re: SMKs slower than A-Maxs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">Also keep in mind a lot of shooters on here are using after market barrels. My 21.5" rock creek barrel surpasses what I see in my other 308 with 26" factory Rem barrel with like loads, the Remington tube generally shooting 50 to 75 fps slower. </div></div>

What he said. My Remington barreled .308 (when I had it) was slower than most customs.

 

[MitchAlsup]

Re: SMKs slower than A-Maxs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: McLarenRoss</div><div class="ubbcode-body">155 A-Max I get 2775fps outta my 20" Remington barrel, but 155 SMKs(2155) with the same charge only move 2650fps. </div></div>

This is yet another demonstration that different bullets of the same weight still need their own individual load development process.

 

[Rust]

Re: SMKs slower than A-Maxs?

What other people get is only a rough, very rough guideline for what you can expect out of your rifle. Simply too many variables to accurately predict your results.

If I remember right, the older 2155 Sierra has a bit more bearing surface in comparison to the 155 A-max, and that extra bearing surface will affect velocity. More drag down the barrel. Then the differences in lead core hardness, jacket hardness, jacket drag coefficient....

You might want to scope out the newer Sierra 2156 155 gr bullet and the new Berger, better ballistically than the old 155. The old 155 is still and excellent bullet though, just not as well suited for long range as the newer stuff.

 

[Grump]

Re: SMKs slower than A-Maxs?

Exact same bullets, .308, and a 22-inch barrel.

My velocity differences were more like 30 fps, but I was using only Varget and 4064 powders. First noticed it with the Winchester primers.

125 fps is a pretty extreme difference. If not from the same day of shooting, I'd look into possible lighting/battery issues with the chrono.

I suggest you invest in QuickLOAD. Once you get all those variables loaded in from YOUR chamber (and corrected if needed), it can be quite eye-opening to see the chamber pressure predictions.

You don't necessarily need to take load/velocity data from reports here on the Hide with a grain of salt--you just have to realize that a LOT of these reported "safe in my rifle" loadings are almost certainly over SAAMI pressure specs. How much someone else is willing to live with is mostly their business, until and unless they hurt one of the neighbors.