Muzzle Velocity

[1911man]

I am wondering if we have any guys on here who have had the opportunity to use a chronograph to test the muzzle velocity on their rifle? Specifically 18" barrels as I know most published velocities are for 24". The reason I started thinking about this is I was looking at my box of SSTs and the velocity listed on the box says 2620 fps while the Hornady website says 2580. It says on the website the barrel tested is 24".

I realize that the best way to get data is to Chrony it myself and I will once I purchase one, but I am wondering what results others are seeing. Specifically on Hornady Factory loads like the Amax and SSTs and if there is a formula for converting those 24" numbers down to 18". Another thing I am aware of is that velocities will be different for the different chambers like the Grendel 1, Grendel 2, and .264 LBC because of the pressure differences in these chambers.

Thanks guys.

[cst]

I have a 18.8" lilja barrel with the tighter neck before they got the correct reamer...I chronoed the Hornady 123SSt at 2430fps. (magnetospeed V3)I shoot 123gr scenars ..my reloads at 2530fps.

[Jakal]

got a 20" Lilja (second chambering run with the correct reamer) and the Factory SST's run about 2465 fps for me. Type II bolt (.136 depth). You can lose about 25-50 fps per 1 inch of barrel lost or you can gain about the same FPS per 1 inch added.

[Klem]

It will be about 25fps for each inch of barrel.

So approx 2,430fps in an 18" for your Hornady website specs.

Testing differences between throats of the same barrel length is a more precise and small difference. Probably best done at the same time, same conditions and same Chronograph.

[LRRPF52]

There's a laundry list of muzzle velocity data in the reloading handbooks, as well as a velocity estimator graph based on accurate modeling.

Everything from 16" to 24" velocities are included in Volume II.

The published manufacturer data varies from one to the next.

AA's original data was for 24", but there was also a breakdown of 20", 18", 16", 14.5", and 10.5" data with several of the factory loads.

Hornady's 8th Edition published data for a 14.5" AA carbine, while their 9th Edition has 18" data, to include CFE.

Hodgdon's published 24" data, as did Lapua/Vihtavuori.

Western Powders published 20" data.

There isn't a linear rule for muzzle velocity and barrel length, but rather a curved rule. As the barrel gets past 20", the increase per inch produces less speed, although each barrel has its own characteristics.

My 16" AA barrel gets 2460fps with the 123gr A-MAX factory load. Depending on how tight or loose the bore is, and how the chamber is cut, you can see 100fps variation easily, although from all the mv data in Volume II, most are really close.

[JASmith]

Here is a running average taken over a period of nine months with an 18" TC Encore with SAAMI chamber and 123gr SST Hornady factory ammunition:

Count 29
Average 2473
SD 23
ES 91

[1911man]

Thanks alot guys, there is alot of useful information here. I definitely need to get a chronograph but until I do this helps me get an idea of what i can expect. I was really hoping the muzzle velocity of the factory loads would stay above 2500 fps but it really doesn't effect what I am going for anyway. When I decided to build this rifle I decide to sacrifice the extra velocity to save weight since I will be carrying this rifle in the field.

[Klem]

Sounds like a plan.

In the meantime you can get a idea of your velocity by zeroing at 100, noting the ambient conditions, shooting groups at another distance like 200 or 300 and noting the drop. Enter the conditions, bullet, zero into a ballistics calculator like JBM online and look for the same drop by varying the muzzle velocity. It'll be pretty close.

[1911man]

Thanks for the suggestion Klem, I think I will do exactly that.

[jiml]

I just got in from the range at about noon today. I have a 20 inch Black Hole Weaponry barrel from Precision Firearms. I chrono'd the Hornady 123gr Amax which says 2580FPS on the box and my average was 2626FPS. BHW barrels are polygon and supposedly faster so I hear. According to my chrono may be something to it.

[san antonio fj]

I just got in from the range at about noon today. I have a 20 inch Black Hole Weaponry barrel from Precision Firearms. I chrono'd the Hornady 123gr Amax which says 2580FPS on the box and my average was 2626FPS. BHW barrels are polygon and supposedly faster so I hear. According to my chrono may be something to it.

Awesome I just got the same barrel yesterday(still waiting on gas block and bolt) have you chrono'd any of the wolf gold? I have 100rnds of it and was woundering how fast they would be out of my 20" BHW

[jiml]

No, I have only chronoed the Hornady factory load and the reloads I made. They are Hornady brass, hornady 123 Amax, CCI 41 primers, and Alliant AR Comp powder. I have eased them up to 27.9 gr with an average of 2560 fps. The two groups I have shot with that load were .406 and .461. I was shooting off a bipod with a small sand bag under the grip. It has a 3# trigger in it. I have a cheapo 6-24 Tasco varmint scope on it but that's all I can muster right now. You are going to like it. It kicks less than a .243 and is super sonic to about 1250 yards per Hornady calculations at that speed.

[sneaky one]

jiml,,, pm tools of the trade,we have same bbl. length as you. He has the BHW tube. We compare notes from his- to my 20" AA tube. He's always a tic faster.

His is a 9 twist, mine an 8.

[san antonio fj]

Nice I bought the wolf for cheap brass then realized it was large primer, eventually I will spring for lapua but want to come up with a load first. I have a cheap primary arms FFP 4-14x on it with ALG EMR 15" rail so im doing a pretty cheap build, I have the exact same setup in 6.8. I built both rifle as relatively cheap hunting/target setups for when my Saker is free from jail. I really need to get a chrono so I can stop asking people what my velocity should be or just guessing lol, anyway thanks for the info and Im glad to here it shoots well!

[kmon]

Was a little disappointed with the Hornady factory SSTs when I ran them across the Crono 15 feet from the muzzle they measured 2372 to 2442 from a 22 inch boltaction barrel, 70fps extreme spread. Reloads that were actually mild with the same bullet beat that by over 100fps at 2550 with much smaller ES.

[mxmaniac2004]

10 shot strings through my 18" Brux barrel gave me

Hornady factory 123 AMAX
2471 fps average
36 fps extreme spread

PPU factory 120 hpbt
2476 fps average
35 fps E.S

[RangerRick]

We've had some discussions about chrono results on here before, and there seems to be quite a variance from chrono to chrono even with the same barrel length.

Some of that could be altitude, temp, humidity, twist rate, rifling, barrel age, etc., but they do tend to vary. Mine reads slow compared to most when measuring the Hornady factory 123 AMax.

But it's a good relative measure. My hand loads with AA2520 and CFE are about 25-30 fps faster than the factory ammo, and just as accurate, or more so.

RR

[LRRPF52]

Yesterday, I chrono'd many loads from two Lilja-barreled 6.5 Grendel's.

17.6" Lilja barrel:
123gr Hornady SST factory 30JUN2015
2441
2467
2477
2489
2481

18.5" Lilja barrel:
123gr Hornady SST factory 30JUN2015
2468
2441
2421
2495
2453

16" AA/Shaw barrel:
123gr Lapua Scenar Precision Firearms factory 03APR2012
2447
2451
2454
2450

123gr Hornady A-MAX factory 25MAY2013
2365?
2470
2422
2470
2460

These have all been with a Chrony Beta model, 15ft from the muzzle. The 6.5 Grendel Reloading Handbooks have a ton of data and barrel length estimator graphs.

[keystone183]

17.6" Lilja barrel:
123gr Hornady SST factory 30JUN2015
2441
2467
2477
2489
2481

18.5" Lilja barrel:
123gr Hornady SST factory 30JUN2015
2468
2441
2421
2495
2453

This correct, or backwards? And if correct, care to elaborate?

[LRRPF52]

It's correct. Not much to elaborate on really. Different barrels have different personalities. My 16" averages faster than the 17.6" and 18.5" Lilja's. Could be the tighter twist rate, rifling type, or just bore surface. The Lilja's are one of the smoothest, if not the smoothest barrels I have ever seen.

My Lilja's are 1/8 twist. My 16" AA is 1/7.5 or 1/7.75.