Range Report Bullet trajectory help-Remington 150gr Core Lokt

[melloyello]

The 150gr Remington Core Lokt cartridge is advertised at 2820fps with a 14.7" drop at 300yd. I don't know what length barrel they are firing this out of though. My AAC-SD 20" 1:10 twist has is zeroed at 100yd on a 55°F day with this exact round.
I fired my first round and of course was way low. I was thinking per the advertised velocity I was going to be somewhere around 14.5" drop. I actually got a 19.5" drop as I had to dial in 1.8mil on my scope to hit the bullseye. Todays temperature was 65°F with a steady 5mph headwind.
My question is, is the advertised 2820fps way off or is my 20" barrel slowing this bullet down that much? I would think the velocity would be close to 2500fps with that kind of drop. Has anyone ran this bullet through a chronograph?
Or am I way off b/c the BC of this particular bullet is so low at .314?

 

[40xs]

Re: Bullet trajectory help-Remington 150gr Core Lokt

You are real close to being right on point with your estimated exit velocity. My info on a bullet with a B.C of .338, using reverse math based on your drop at 300 your bullet is leaving the barrel right at 2500fps. Not surprising with a 20" bbl. This can be improved upon with some judicious reloading. ( my source is taken from the Hornady book on long range ballistics)which for me has proven very close to actual field experence.

 

[melloyello]

Re: Bullet trajectory help-Remington 150gr Core Lokt

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Old Seabee</div><div class="ubbcode-body">You are real close to being right on point with your estimated exit velocity. My info on a bullet with a B.C of .338, using reverse math based on your drop at 300 your bullet is leaving the barrel right at 2500fps. Not surprising with a 20" bbl. This can be improved upon with some judicious reloading. ( my source is taken from the Hornady book on long range ballistics)which for me has proven very close to actual field experence.</div></div>

The SHOOTER software I have on my phone shows about 2475fps to give 1.8mil. Took a lot of playing with the numbers to come up with that. My brothers 1:12 twist 26" barrel needed 18" elevation which equaled 5.6moa for his Marlin. This would give him a velocity of about 2600fps.
I plan on reloading some 175smk for this rifle. I will be looking for the fastest/most accurate round I can get without pressure signs. I was just amazed there was a 1.5" difference between his gun and mine at only 300yds b/c of 6" of barrel. And yes, we shot the same ammo just b/c we had the question, how much effect does barrel length have.

 

[gstaylorg]

Re: Bullet trajectory help-Remington 150gr Core Lokt

Depending on how "fast" your barrel is, it's a rough estimate to expect 20-25 fps loss in muzzle velocity per inch of barrel length lost in the overall barrel length range you're talking about. Might be a little more or less, depending on a number of factors. The standard test barrel length used to determine factory load MVs is 24". I would have expected somewhere in the neighborhood of 2720 to 2750 fps for a 20" barrel. If you're only getting ~2500 fps, seems to me like something is amiss. That is 320 fps slower than the factory value, which is a much greater loss compared to the factory value than you probably should have expected.

According to the Remington Ballistics Calculator webpage, the G1 BC for that projectile is 0.331.

http://www.remington.com/pages/news-and-resources/ballistics.aspx

Using an MV of 2475 fps with the parameters listed below, the predicted drop at 300 yd from a 100 yd zero is 18.5" (1.7 mil) [JBM Ballistics: G1 BC = 0.331, Alt. = 1000 ft, temp = 65 F, Hum. = 50%, Press. = 30.15, Sight height = 2.19"]. Given that your 100 yd zero was determined at 55 F on a different day, it's probably safe to assume it could have been just slightly off compared to what it would have been the day you required 1.8 mil to reach center POI at 300 yd. With that in mind, the estimated 1.7 mil is pretty close to what you actually needed to dial (1.8 mil), suggesting 2475 fps is pretty close to correct as you calculated also. Maybe it's just me, but that seems extremely slow for that ammo out of a 20" pipe. Have you tried other factory loads, and if so, how does your rifle's MVs with them compare to the 24" (box) test values?

 

[melloyello]

Re: Bullet trajectory help-Remington 150gr Core Lokt

Didn't try any other ammo at the 300yd range. I should have and probably will another day. Hopefully I will have a chronograph by then. I want to get some real numbers instead of having to figure it by bullet drop. I would love to chrono a couple of Core-Lokts to get an average out of my barrel.

 

[john_1182]

Re: Bullet trajectory help-Remington 150gr Core Lokt

I have shot thousands of these projectiles as i got them real cheap (4c each)in my tikka T3 1/11 twist, 24 inch, 2880 fps.

but what you will want to know is the BC.

G7 0.160

i have worked out the BC of the thousands of rounds and shoot very accuratly and shhot them to 1070 meters all the time.

The BC is an averaged from 3000 fps to 750 fps