major velocity debockel question

[vendetta333]

i found this in the archives when i was doing a google search for a comparison between the 123 SMK and Scenars. >>>>>>>06-20-2011, 02:49 PM
sititunga,

I would look at Lapua's radar data with Quick Target Unlimited or Viking Ballistics. You don't need to mess with theoretical BC drag models anymore with Lapua bullets now.

Either way, I wouldn't be taking any drop data from those programs and expecting 1000yd performance with those weight of projectiles at those anemic velocities. I'm not even happy pushing the 123gr Scenars out of my .260 Rem past 600, and I'm throwing them at 2960 fps. Too much wind drift when the winds get over 10mph. I even know some Norwegian Snipers that hot-loaded their 6.5x47's with the 123gr Scenars at well over 3300 fps, and I'm not sure it helped them at even 900 meters.

I think for 1000 yds, you really need a heavier/longer 6.5 projectile going pretty fast if you want to get your money's worth, unless there are no winds.

You should be able to get more velocity than the 2500's with a 22" pipe. I get 2520 with the 120 SMK's and TAC out of my 16" Grendel. Maybe you need a slower powder...

LRRPF52<<<<<<<

i am building a practical/tactical competition gun and wanted to stick with a 24" barrel for weight and manuverability's sake. my mind is pretty made up on that fact, but i also would like to (if my barrel ends up liking them) run the 123 SMK's as that would be one less type of bullet to buy (my swede uses them). but the stated bc's and velocities found on hodgdon's page and AA's page have me worying that if the atmospheric conditions dont line up, i may go trans/sub sonic at or befor 1000 forcing me to use scenars. however trans sonic boundary aside, i would like flatter as well. but if i had the velocities stated above (or higher from the extra 2" of tube) i would feel better. ok, now the QUESTION; are those realistic Grendel velocities? would you all say those are "moly" numbers, or "beyond mag length" or could i really expect those or better numbers out of a 24" bolt gun? thanx for all input!

P.S. i am disregarding the opinion part, i am purely interested in the numbers! no disrespect tho!

[txgunner00]

I get 2500 from 123 SMKs and 8208 in a 20". I agree with LRRPF52 on the practical range limitations. I shoot to 1000 yds with my Grendel on a regular basis but I really have to pay close attention to the wind. I stick to 600 and in when it's gusty or over 15 mph. How far are you shooting in these competitions?

[bwaites]

Are you building a bolt gun or a semiauto AR chassis?

From your post it appears to be a bolt gun. If so, the brass and your action will take a lot more pressure than the 50,000 the AR Grendel is limited to.

I shoot 123's at 2700 FPS out of my 28" Grendel without issues, so I would expect to be in that range plus some with a 24" bolt gun and higher pressures. The real issue you run into will be finding a powder that you can stuff enough of into the case to get the velocity you want.

[JASmith]

Alexander Arms reloading data for the 123 gr SMK suggests that you can get 2630 ft/sec from a 24" barrel using Accurate 2520.

If txgunner's load is safe in your rifle, then you should get almost as much velocity as above out of a 24" barrel.

You can use this tool to get estimates for changes of velocity when going to different barrel lengths, bullet and charge weights than the data you have: http://shootersnotes.com/calculator/velocity-estimator/

[Drifter]

Trajectory calculator on JBM site using Litz data indicates that the 123 SMK should stay above the speed of sound out to 1000 yards if launched at or above 2510 fps.

I won't pretend to be a player in the 1000-yard game, but I think it's preferred that the bullet stay supersonic to ~1300 yards for best results in 1000-yard competitions. For the 123 SMK, that would require a 3050 fps MV, which is unreasonable to expect from the Grendel. (123 Scenar would need ~3015 fps MV.)

For 1000 yards using the AR-15 platform, the Grendel isn't a bad choice. (6mm wildcats based on Grendel case might be better.) But if you're using a bolt rifle, you are limiting your potential compared to other cartridges that will likely work in the same platform.

[vendetta333]

thanx for all the great replies. i meant for the mods to delete the original post actually. i made a huge oversight when i was looking on google. and the AA page. i was looking at the 14.5" barrel page on the pdf, not the 24". super silly!! but thanx for all the info guys! well with that figured out, how about this: is ther a real practical difference between the bc's of the two 123"s? how do they stack up against one another at a grand? thanx!!

o, and drifter, thanx for that. i am choosing the grendel for a few reasons: NUMBER ONE, i love the cartridge! two brass is cheaper than 260, use less powder, longer barrel life, small rifle primers tend to be more consistent and cheaper, and itwill fit the cz 527! so thers's my logic! am i crazy? lol

[bwaites]

I actually think most of the 123 Scenar BC numbers are a little optimistic, and targeted at higher velocities than the Grendel will support.

If I recall correctly Bryan Litz's numbers indicate that the 123 SMK actually has a higher real BC than the Scenar. Since he doesn't work for either company, I tend to believe his numbers vs. the manufacturers.

Lapua is now publishing actual numbers based on radar data, so I think those newer numbers will be closer to Litz's.

[Drifter]

is ther a real practical difference between the bc's of the two 123"s? how do they stack up against one another at a grand? thanx!!

Instead of attempting to decide which bullet is best based on numbers, it might be beneficial to let the barrel decide. Perhaps it will show an accuracy preference with some testing. I would include the 123 A-Max in the mix along with the SMK and Scenar.

o, and drifter, thanx for that. i am choosing the grendel for a few reasons: NUMBER ONE, i love the cartridge! two brass is cheaper than 260, use less powder, longer barrel life, small rifle primers tend to be more consistent and cheaper, and itwill fit the cz 527! so thers's my logic! am i crazy? lol

I understand. The CZ-527 chambered for the Grendel is certainly an appealing setup.

[vendetta333]

yea i like the less is more kinda thing. y carry a long action when u can carry a short, and why carry a short when you can carry a micro lol? thanx for reminding me of the amax! i had almost forgotten that one. i am really hoping when i get the barrel it will like the smk'd tho, just as i already buy a lot of them, and they are supposed to work wonders on cyotes! again thnx for all the info! from all the guys! i am also not yet a player in the 1000 yrd game but this is what i want to build! so drifter, what is your cal of choice? just curious, u and i got kinda a back and forth thing goin here on this thread.