169g SMK

[gero]

So, are any of you playing with the Sierra 169g smk? I am astounded that I am able to get 2850 fps out of a 26" tube. I have been loading 43.7g IMR 4064 and Fed 210m @ AI mag length 2.890 oal. Produces 1/2" or a little less groups @ 100y.

 

[dk17hmr]

I have been using the 169gr with N150 in my 20" 308 @ 2625. I'm sure I could get more velocity out of it but it's shooting pretty small and I really only shoot that rifle/barrel inside 800 anyways.

 

[Straightshooter1]

So, are any of you playing with the Sierra 169g smk? I am astounded that I am able to get 2850 fps out of a 26" tube. I have been loading 43.7g IMR 4064 and Fed 210m @ AI mag length 2.890 oal. Produces 1/2" or a little less groups @ 100y.

2850 fps!!??? WOW! What brass are you using? With my Lapua brass having 55.9 grs H2O I'm filling my case to almost 103% of capacity with a COAL of 2.890 and I still don't get anywhere near 2850 fps. with that charge of IMR-4064 out of my 26" Krieger barrel with my 169 SMK's . . . more like 2,770 fps. QuickLoad shows pressure at 65,000 psi (not particularly bad, but well above SAAMI max).

 

[gero]

2850 fps!!??? WOW! What brass are you using? With my Lapua brass having 55.9 grs H2O I'm filling my case to almost 103% of capacity with a COAL of 2.890 and I still don't get anywhere near 2850 fps. with that charge of IMR-4064 out of my 26" Krieger barrel with my 169 SMK's . . . more like 2,770 fps. QuickLoad shows pressure at 65,000 psi (not particularly bad, but well above SAAMI max).

I have been using once fired Federal Gold Medal brass. I have tested to 45g and had hard bolt lift, ejector marks on the bases. I also ran a few at 44.5g also having some indications of pressure, tight bolt, marks to a lesser degree. I have been using the Garmin Xero bought at the end of the last year to measure velocities. I am using a V4 to drop powder, the cases are filled to the top of the shoulder and I can feel a crunch when the bullet is seated. Unless something is wrong, I am mistaken, or my equipment is faulty, I have no idea. I did not believe it either. I have captured multiple groups of 5 fired over the Xero and stored in the app on my phone.

 

[gero]

I am going to try to prove my chrono tomorrow. I have a Pro Chrono that I replaced with the Garmin. I will shoot thru the Pro and have the Xero on the bench. Might be interesting for shits and giggles. I pulled a bullet from some of the batch that data came from and weighed it on my Fx and also a Scott Parker Redding, powder checks @ 43.7g....more tomorrow.

 

[Straightshooter1]

I have been using once fired Federal Gold Medal brass. I have tested to 45g and had hard bolt lift, ejector marks on the bases. I also ran a few at 44.5g also having some indications of pressure, tight bolt, marks to a lesser degree. I have been using the Garmin Xero bought at the end of the last year to measure velocities. I am using a V4 to drop powder, the cases are filled to the top of the shoulder and I can feel a crunch when the bullet is seated. Unless something is wrong, I am mistaken, or my equipment is faulty, I have no idea. I did not believe it either. I have captured multiple groups of 5 fired over the Xero and stored in the app on my phone.

I thought maybe you were using something like Winchester brass. I've fired a lot of FGMM brass and they tend to be pretty close to the same case volumes (on average) as my Lapua's. I know that compressing the charge like that tends to produce a little higher velocities, but I wouldn't think it'd be that much. Now I'm wondering what the moisture content of your powder is, as that can be a contributor??? Most likely, it's probably a combination of things.

I am going to try to prove my chrono tomorrow. I have a Pro Chrono that I replaced with the Garmin. I will shoot thru the Pro and have the Xero on the bench. Might be interesting for shits and giggles. I pulled a bullet from some of the batch that data came from and weighed it on my Fx and also a Scott Parker Redding, powder checks @ 43.7g....more tomorrow.

I have a ProChrono that I haven't used in several years now. . . mostly because I shot it! I was running a ladder of dots across and down a large piece of butcher paper and not thinking where the bullet was traveling compared to what I was seeing through my scope, aiming at a lower dot I skimmed a bullet across the top, in the middle, for the length of the ProChrono and kinda made a mess of it. A little duct tape and put the sensors back in place, and I could still get good reading. That's when I went to a MagnetoSpeed. Now I've replaced that with the Xero.

It'll be intereing to hear how your ProChrono compares to the Garmin. I know my MagnetoSpeed v3 was very very closer to the same as my Xero. But my ProChrono was never as consistent as or as close to my MagnetoSpeed.

 

[gero]

....a quick one before the range. I had bought some Hornady 168 eldm ammo to try. The advertised velocity on them is 2840 fps. I ran 10 thru the same gun and it produced 2896 fps on the Garmin. As far as moisture, I am in Boulder City, Nv near Las Vegas and moisture iin the house is 21% now....more later

 

[Straightshooter1]

....a quick one before the range. I had bought some Hornady 168 eldm ammo to try. The advertised velocity on them is 2840 fps. I ran 10 thru the same gun and it produced 2896 fps on the Garmin. As far as moisture, I am in Boulder City, Nv near Las Vegas and moisture iin the house is 21% now....more later

I tried IMR-4064 a couple of times with the 169 SMK's, but found my best results with AR-Comp. Here's my data for using IMR-4064 behind the 169's:


Note: even if I use the same COAL as yours, the velocity isn't a great deal more.

 

[gero]

This is all so very interesting and by God it IS rocket science! So I went to my range and set up both chronos, the Pro Chrono a measured 10 feet from the muzzle and the other on the bench.I shot 10 rounds of the Hornady 168g eldm factory. The Pro averaged 10 shots @2901 fps and the Garmin 2924 fps. I have no idea what would account for the 24fps difference but maybe the distance in front of the muzzle of the Pro. I next shot my 169g smk handload but only averaged 5 rounds. The Pro showed 2821 avg and the Garmin 2853 so a difference of 32 fps. I think the data is solid and can't account for why the Quickload prediction is low other than the moisture content listed on the spreadsheet. I am thinking the powder that is in the V4 never gets returned to the 8#'er and the humidity here is 16% with the windows open now.

I believe the data is solid and that both chronos are working properly. I know it is strange to get this kind of speed on a .308 but makes me lick my chops to be able to shoot next to the darlings of the Creedmore. I did one more test with a Bergara with a 20" tube and showing 2682 fps on the Pro and 2714 fps on the Garmin.

 

[Straightshooter1]

This is all so very interesting and by God it IS rocket science! So I went to my range and set up both chronos, the Pro Chrono a measured 10 feet from the muzzle and the other on the bench.I shot 10 rounds of the Hornady 168g eldm factory. The Pro averaged 10 shots @2901 fps and the Garmin 2924 fps. I have no idea what would account for the 24fps difference but maybe the distance in front of the muzzle of the Pro. I next shot my 169g smk handload but only averaged 5 rounds. The Pro showed 2821 avg and the Garmin 2853 so a difference of 32 fps. I think the data is solid and can't account for why the Quickload prediction is low other than the moisture content listed on the spreadsheet. I am thinking the powder that is in the V4 never gets returned to the 8#'er and the humidity here is 16% with the windows open now.

I believe the data is solid and that both chronos are working properly. I know it is strange to get this kind of speed on a .308 but makes me lick my chops to be able to shoot next to the darlings of the Creedmore. I did one more test with a Bergara with a 20" tube and showing 2682 fps on the Pro and 2714 fps on the Garmin.

Yup, you do have to account for that 10 feet out where the ProChrono sits. And yes, there can be that much different in 10 ft. as recorded by the ProChrono. . . as you've well demonstrated.

Leaving that powder in you V4 in that low humidity pretty much explains a lot of your additional velocity. But, I'm really surprised that you're not getting obvious pressure signs. I do think you're pressure is way more than you think??? You might try a loading a couple cartridges using the powder from your 8 lb jug to see the difference???

That QuickLoad calculation is simply base on my velocity results, where I adjusted the burn rate up from what was QL's default rate to get the numbers to be consistent with my various results for the IMR-4064.

 

[gero]

I will continue down this path. I did read Brian Litz, an article about how the moisture content of powder could affect velocity by as much as 200fps. ....aand please let me say thank you for your well received non snarky or humor attempting real deal want to help. Kudos to you sir! Maybe there is an advantage to living in a DRY climate! Dry skin and eyes not being a couple of them!

 

[dk17hmr]

When I had a 26" 308 barrel my hunting load was a 178gr at 2775fps. I was using CFE223 it was a bit spicy but I could reload the brass a handful of times before the primer pockets were gone.

 

[bks22345]

 

[bks22345]

That was January 2023. 5 shots, 26” criterion prefit, alpha SRP. CCI 450 I think.

 

[Dolomite]

That was January 2023. 5 shots, 26” criterion prefit, alpha SRP. CCI 450 I think.

Nice group