Velocity vs Barrel length on TRG

[Killbox Alpha]

Frankly I know this has been dicussed but I was unable to find the discussion thread.

Has anyone ever checked the velocity difference on a TRG 22 308 with a 20" barrel vs a 26" I realize there are several things that come into play here, bullet weight, powder charge, etc. Is there a rule of thumb? 1"=20 ft per second.

 

[hugo121175]

Re: Velocity vs Barrel length on TRG

Here is a good read: http://www.chuckhawks.com/rifle_barrel.htm

 

[spot69221]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kill Box ALPHA</div><div class="ubbcode-body">...TRG 22 308 with a 20" barrel vs a 26" I realize there are several things that come into play here, bullet weight, powder charge, etc. Is there a rule of thumb? 1"=20 ft per second.</div></div>

It's not quite linear but that is close. From the 26-20 range, I'm sure it increases more below 20".

 

[SScott]

Re: Velocity vs Barrel length on TRG

Just for estimation I think that you aren't far off, I generally use 25fps per inch.
I am able to get 2725pfs for 175 SMK pushed with Varget in an RP case, with a 26" barrel.
Maybe someone will chime in and give you their numbers for a 20" barrel.
SScott

 

[Bacarrat]

Re: Velocity vs Barrel length on TRG

20-26 is about right. I chopped mine down from 26 to 18" and lost around 200 FPS. I was pushing 155s 2950FPS to 2740FPS now.

 

[bohem]

Re: Velocity vs Barrel length on TRG

My 20" 308 spits the following bullet/velocity combos out very well without any kind of pressure signs. Quickload pressure prediction says they're all below 58ksi:

168 Amax ~ 2645fps
178 Amax ~ 2600fps
175 SMK ~ 2600fps
155 Amax ~ 2800fps

It's an 11.27tw Rock Creek, and while everything rifle barrel is different this will give you an idea what you're looking at.

 

[hgr2]

Re: Velocity vs Barrel length on TRG

I was thinking that my TRG 22 with it's 26" barrel might give more velocity than the some of my 24" 308s. It seems a little on the slow side by compairison.

 

[Stubb]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bacarrat</div><div class="ubbcode-body">20-26 is about right. I chopped mine down from 26 to 18" and lost around 200 FPS. I was pushing 155s 2950FPS to 2740FPS now.</div></div>

Is that a difference that you've noticed at the range?

I ran some quick calculations for 155 Scenars at those velocities. At 600 yards, I'm getting 10 MPH wind drift of 29" (1.3 mRad) vs. 32" (1.5 mRad). At 1000 yards, I get 97" (2.7 mRad) vs. 109" (3.0 mRad). It seems like your wind calls should be within ~2 MPH before worrying about that difference.

I'm planning to get a TRG-22 later this year and will be following this thread with interest.

—Andreas

 

[Killbox Alpha]

Re: Velocity vs Barrel length on TRG

I appreciate the information gentlemen.. I guess the only decision still is either to go with a 20" or a 26"

 

[Bazgab]

Re: Velocity vs Barrel length on TRG

I have the 26", if I had a choice I would go with a 20" or 18" (wasn't an option to get the 20" with the new digital camo patterns from EuroOptic). I am on the east coast though and am in more wooded areas so the 20" or less seems like it would be handier.

Plus I would like to get a suppressor in the future so that too would push me to go with the shorter barrel. I am not too concerned with the velocity loss as I rarely get to push the rifle to its range limits as is.

 

[Flynn]

Re: Velocity vs Barrel length on TRG

I have a 20" TRG on the way. I chose this barrel length because I intend to hunt with and pack this rifle long distances. I'm hunting in fairly open country...

 

[tt350z]

Re: Velocity vs Barrel length on TRG

My 20'' 1-11.25'' Bartlein spits out:

175gr SMK at an avg of 2697 FPS with 43.5 gr of IMR 4895

168gr Nosler CC 2735 FPS

All at 10' in front of muzzle with a CE ProChrono

 

[Stubb]

Re: Velocity vs Barrel length on TRG

The 20" TRG-22s appear to cost ~$300 less than the 26" models. I'm planning to get a can for mine and am thinking to get a 26" TRG and have the barrel cut to 22" and threaded 5/8-24. It comes threaded M18x1, which just doesn't seem that common in the US. An AAC Cyclone threaded 5/8-24 seems like it would be handier than one threaded M18x1.

—Andreas

 

[mavrick10_2000]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sunnyside Scott</div><div class="ubbcode-body">Just for estimation I think that you aren't far off, I generally use 25fps per inch.
I am able to get 2725pfs for 175 SMK pushed with Varget in an RP case, with a 26" barrel.
Maybe someone will chime in and give you their numbers for a 20" barrel.
SScott </div></div>

I get 2570fps with this load combo in Win brass from my 20" TRG22

 

[cardboardkiller]

Re: Velocity vs Barrel length on TRG

Sako TRG-22
26" 308
Black Hills 180 Accubond Ammo
43 feet above sea level
86 degrees
70% Humidity
Shooting Chrony Alpha Master Chrono 10ft from muzzle
No can average - 2691fps
AAC Cyclone average - 2728fps

Black Hills lists 2550fps for this load, but I have no idea what rifle they used, if any, to get that number.

 

[Numn]

Re: Velocity vs Barrel length on TRG

I just so happen to have side by side velocity data (10-shot strings) for both 20" and 26" TRG's with the following load:

175 SMK
2.865 OAL (.020 jump)
44.4 gr Varget
Lapua Case
GM210M Primer
78 degrees

20": AVG 2579 fps, SD 10.7
26": AVG 2656 fps, SD 11.1

 

[Killbox Alpha]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Numn</div><div class="ubbcode-body">I just so happen to have side by side velocity data (10-shot strings) for both 20" and 26" TRG's with the following load:

175 SMK
2.865 OAL (.020 jump)
44.4 gr Varget
Lapua Case
GM210M Primer
78 degrees

20": AVG 2579 fps, SD 10.7
26": AVG 2656 fps, SD 11.1</div></div>


Thanks Numm..
This is good info and exactly what I am looking for.

 

[jbell]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Numn</div><div class="ubbcode-body">I just so happen to have side by side velocity data (10-shot strings) for both 20" and 26" TRG's with the following load:

175 SMK
2.865 OAL (.020 jump)
44.4 gr Varget
Lapua Case
GM210M Primer
78 degrees

20": AVG 2579 fps, SD 10.7
26": AVG 2656 fps, SD 11.1 </div></div>

Im getting 2650 fps out of my 26" TRG with 43.5g Varget and every thing else exactly the same. Strange I would of thought 1g would of made a bit more of a difference.

 

[Numn]

Re: Velocity vs Barrel length on TRG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jbell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Numn</div><div class="ubbcode-body">I just so happen to have side by side velocity data (10-shot strings) for both 20" and 26" TRG's with the following load:

175 SMK
2.865 OAL (.020 jump)
44.4 gr Varget
Lapua Case
GM210M Primer
78 degrees

20": AVG 2579 fps, SD 10.7
26": AVG 2656 fps, SD 11.1 </div></div>

Im getting 2650 fps out of my 26" TRG with 43.5g Varget and every thing else exactly the same. Strange I would of thought 1g would of made a bit more of a difference. </div></div>

Is your OAL 2.865? If you're running shorter your velocity at 43.5 makes sense. I have data with 44.0 Varget and an OAL of 2.800 and a velocity of 2692 from the 26" TRG. This velocity was measured with my now non-functioning Pact chrono where the data above was collected with an Oehler 35P. My confidence in the Oehler is high. Oehler data combined with Litz G7 data has produced very accurate elevation data.