Re-barreling to a 7 SAUM with a 28" Bartlein 1-7.5 and interested in both bullets. The question I have is simply this. Hornady is posting a g7 bc of .401 which I am not about to dispute as others have verified as being true or even a bit conservative with the right twist. Sierra's 183 gr is longer by .075-.080 and pointed so maybe someone can educate be as to how its bc is much lower?
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Range Report 183 gr Sierra or 180 gr Hornady ELD-M
- Thread starter nick338
- Start date
what is the ogive profile of the two bullets? That will be the major factor here, especially if they are both pointed.
You also need to evaluate what velocity the various BCs apply to. 3000fps v 2000fps very different drag profile vs the G7 model projectile. Manufacturers really should state two numbers: avg BC and the velocity band it applies to. If the Hornady profile is a BC at 3000fps and the Sierra one is for something less, that could explain the entire difference right there.
You also need to evaluate what velocity the various BCs apply to. 3000fps v 2000fps very different drag profile vs the G7 model projectile. Manufacturers really should state two numbers: avg BC and the velocity band it applies to. If the Hornady profile is a BC at 3000fps and the Sierra one is for something less, that could explain the entire difference right there.
Hornady has a secant ogive profile but not sure on the Sierra. Best guess would be somewhat of a hybrid design. Hornady does list the avearge g7 bc throughout the velocity range of .404 and Sierra lists there's as well but only g1 which is .702 or ~.360 g7. That is a huge difference that doesn't make sense to me but I'm not an engineer either.
I've shot the two side by side at 1000 at 3040 or so fps.
Drop was very close with the Hornady needing maybe .1 mil less.
The main difference is accuracy. I can get the Hornady to shoot sub 1/2 MOA. Not so much with the 183 SMK.
Drop was very close with the Hornady needing maybe .1 mil less.
The main difference is accuracy. I can get the Hornady to shoot sub 1/2 MOA. Not so much with the 183 SMK.
I posted on this in another thread here but if you go into the Hornady 4DOF app and use the plain BC calculator and generate a drop chart, then Scroll to the right across the top where all the inputs are you will see the G1 BC listed at 0.71 which is lower than advertised. Then if you run the 180 ELDM in the 4DOF calculator you will see the drops are much more optimistic vs the BC calculator. I took the 180 ELDM to 1535 the other day with my last 3 rounds of load development. 1:8 twist at 3080 FPS and I hit 0.8 to 1 Mil low with the 4DOF data. DA was 2250 and I had synced kestrel to the app. Made a correction and got 2nd round hit. 3rd shot: elevation good, missed off left edge. Called it a day. Obviously I have more shooting to do as this was just 3 rounds, but I did have single digit SD on the previous 7 I put on paper prior.
Figured out all of the above later that evening and the BC calculator matched my dope. Even when I changed the axial form factor to 1.1 in 4DOF I still needed more elevation to match what I had previously seen in the field. Plugged 0.71 into Coldbore and it matched right up too. The bullets bughole, but something seems off between 4DOF data and the fact that Hornady is publishing a 0.71 BC in the app vs what they are advertising. I figured my set up would be taking advantage of the higher BC range, maybe not max, but higher.
Figured out all of the above later that evening and the BC calculator matched my dope. Even when I changed the axial form factor to 1.1 in 4DOF I still needed more elevation to match what I had previously seen in the field. Plugged 0.71 into Coldbore and it matched right up too. The bullets bughole, but something seems off between 4DOF data and the fact that Hornady is publishing a 0.71 BC in the app vs what they are advertising. I figured my set up would be taking advantage of the higher BC range, maybe not max, but higher.
I'm getting amazing results from the 183 sierra, in my 7mm-300wsm, i have not shot any of the 180 bergers. Is anyone shooting a 7SST, im curious about the speeds that they are pushing, with these same pills.
I had the 180 eldm blow up 7mm rem mag 1-8 twist 28 inch barrel from 2950 to 3068. My buddy has a 7mm saum 180 eldm doing 2970ish maybe alittle faster and he had blow ups. We now shoot the 197 smk with no problems. Faster twists i would stay clear of 180 eldms which bc is off from little data we had. 190 berger 183 smk or 197
