Factory Hornady 123gr AMAX #8150 Velocity

[limafoxtrot2]

Someone may find this interesting.....

I shot a 10-shot string earlier through a custom 700 with a 26" Shilen 1-9". The average velocity was 2515 FPS with a SD of 7.6 . The high was 2525 FPS and the low was 2504 FPS. A MagnetoSpeed was used for the testing.

I will take it out to 1000 yards on Friday and will do my best to follow up the post with any relevant data.

The plan is to cut the barrel back 1" at a time while documenting the velocity at each length. Not sure how far back I plan on going as I want to keep it a "reasonable" length.
-Len

[rabiddawg]

A few questions before you go down this road

Why are you doing this?

What are you hoping to gain?

Are you aware this excersise has been done before?
I went and looked but can't find the article where the guy cut down his barrel inch by inch. If you are determined to head down this path I wish you the best of luck. If you are on a quest for data you maybe able to find it out there somewhere.

Good luck.

[sirriccus]

Subscribing for results. Awesome idea.

[limafoxtrot2]

Wow, I didn't expect a reply like that. What am I hoping to gain? Why am I doing this? Am I aware? Am I determined? Am I on a quest? Geez

The short civil answer is that I hope there is knowledge to be gained. I'm actually doing this so my students can see the results of these tests first hand. I believe in being results based and it simply sounds interesting.

I should have added...When I machined the barrel, I indexed the bore curvature to the 12 o'clock position and as I cut the barrel back I intend to document any point of impact shift from the original 26" zero.
-Len

[rabiddawg]

Please let me explain something Len. I'm not much of a typist, therefore I tend to try and communicate on these forums with as few pecks as necessary. Written communication lacking voice inflection and body language input can be misconstrued.

I'm not trying to be critical of your endeavor rather trying to gain some insight into why you would want to go through what I view as a boring process to gain info that is already out there. Within the last couple years I read an article on the net where a guy did exactly what you intend to do. I thought by informing you of that fact I may be able to save you considerable effort.

[FW Conch]

rifleshooter.com
308Win, barrel length versus velocity

The short story, the loss in MV averaged 27fps/per inch of reduction, from 28" to 16" of barrel length.

[Greyfox]

limafoxtrot2. Do "NOT" let the keyboard nay sayers discourage you from doing your test. What you are doing is sacrificing your time and money to learn something to pass on to others who cannot do it. I for one am looking forward to seeing your results. May I suggest you try some loads with 100gr-107gr bullets too. They are much faster than the 123gr and are a good choice for the Grendel. Thanks.
Greyfox

[sirriccus]

I don't know if you have the means or ability, but I know several others that would be interested in seeing the same test done with a muzzle brake and then with a suppressor as well. I know it would make it more complicated considering you'd need to thread the barrel each time you shorten it, just a thought though.

[LRRPF52]

Just for reference from an older lot from my 16" AA 1/7.5 twist, May 25th, 2013, 80* F:

2365
2470
2422
2470
2460

[limafoxtrot2]

I had the opportunity to take this Grendel out to 1100 today. It was pretty cold at 22 degrees, but the wind wasn't too bad. Windage holds were no more that 1.5 MIL.

The little rifle shot very well, so well that my students are trying to convince me NOT to cut it, but the show must go on....

GF-I want to keep things in check and will only be using the remainder of this lot of factory Hornady 123gr AMAX ammo. (As an aside, I tested many rounds of the lighter weight loads with great result while at AA. Just about any barrel offering would shoot bugholes at 100 yards with one special loading.)

S-I thought about threading the barrel when I cut the initial crown, but it will take too much time and adds too many variables at this point.

L-Thank you for the 16" data. I have had very similar numbers in my notes.

Here is the true come up data from today. This was from the same lot of ammo and coming up from a 100 yard zero.

500 Yards- 12.50 MOA
600 Yards- 15.50 MOA
750 Yards- 24.50 MOA The wind held and I shot a witnessed 3" group at this distance.
780 Yards- 25.25 MOA
825 Yards- 29 MOA
900 Yards- 34.75 MOA
1000 Yards- 44.50 MOA
1040 Yards- 47 MOA
1100 Yards- 52 MOA

More about the rifle....the previously mentioned action was single point trued and then the Shilen CM blank chambered through the headstock with the curvature indexed to 12 o'clock, it is in a McRee Precision chassis, Jewel BR trigger, 20 MOA Talley base, Badger rings, Leupold MK4 8.5-25 Mil-Dot 2nd FP, and a LRA bipod.

The next semester will not start until early Jan. and then there is SHOT, so it will be awhile before I get with the cutting.

-Len

[LRRPF52]

I wouldn't cut it since it's a 1/9" twist. You need as much speed as you can get to keep gyroscopic decay minimized.

You can calculate with a high degree of accuracy how much it will lose using forum member JASmith's shooter's notes velocity estimator:

http://shootersnotes.com/Vel65Gren.php

Just for fun though, if you decide to cut it 1" at a time, your next predicted velocity average should be 2501fps for 25" barrel with the same ammunition lot #, and same temperature.

Your speeds seem really low to me though, within 60-70fps of my 16" and 18" Grendels, as well as the 16" and 18" uppers I have built for others.

They have all been in the mid-high 2400fps range across different barrel sources even.

[Mike Wood]

I averaged 2515 fps today for the first 20 shots through my 20" Satern 1:8.75 using the factory Hornady 123 AMAX Lot Number 3162944

[LRRPF52]

I averaged 2515 fps today for the first 20 shots through my 20" Satern 1:8.75 using the factory Hornady 123 AMAX Lot Number 3162944

That's pretty typical for a 20" barrel. You can find several different hand loads that will take you over 2600fps without exceeding working pressure with a 123gr AMAX or SST.

[cory]

LRRPF52 is correct, with a 9" twist you'll want to keep the barrel at 20"+. I certainly understand the drive to experiment in search of understanding something better. However, in this instance you'll be duplicating an experiment that has been done before on this forum by a member sometime in the last 4 years I believe.

I'm not telling you to not do it, but at the Very least I'd find the thread and see if you can't get some insight before you start chopping on your barrel. If I recall correctly he was in search of the optimal length for accuracy. He stopped when he thought he had found the best length for accuracy.

[Lastchance54]

limafoxtrot2 I just found a post on Facebook where someone did this very test on his 6.5 Creedmoor. If its on Facebook then I can assume its on utube too. You may want to watch the current test. If nothing else, to help you set up the parameters better for your test? The post is from AccurateShooter.com He is starting with a 27 inch barrel and cutting it down one inch at a time to measure the velocity. Best of luck with your project.