Who is shooting 34" barrels in F Class TR?

[Marksman63]

Moved to this board:

Building up my new F TR rifle for shooting heavies 208 Amax, 210 and 215 Bergers.
Long .250" throat but still deciding if switching to 34" barrel (current 32").

I have room for weight but worry about its balance and armonics issues. Stock is a Shehane FG ST1000.

Any thoughts? Feedback?
Thanks

 

[Rustystud]

There are several FTR shooters already shooting 34" tubes.
Good luck
Nat Lambeth

 

[Down South]

Moved to this board:

Building up my new F TR rifle for shooting heavies 208 Amax, 210 and 215 Bergers.
Long .250" throat but still deciding if switching to 34" barrel (current 32").

I have room for weight but worry about its balance and armonics issues. Stock is a Shehane FG ST1000.

Any thoughts? Feedback?
Thanks

If weight isn't a issue go for it.....I run a heavy custom contour 32 inch barrel but if i could make weight with the same contour in 34 inch i would do it.

 

[savagedasher]

The good part of a longer barrel it is free horse power. You can gain 10 to 30 Fps depending on the powder per inch.
If it is too long you can shorten it . Nothing can be done with one too short.
Larry

 

[chkunz]

Here's mine:

In all seriousness, if you can make weight AND have a sufficiently heavy contour to satisfy your needs, it won't hurt you. The only other question to consider is what you will really get out of an extra 2-4" of barrel (depending on the current barrel length). This is one area where having Quickload can really be of benefit. You can input your current numbers and get a very good idea of whether having the extra barrel length will allow you to hit the next higher velocity node, for example. In some cases, it becomes apparent that the extra barrel length won't produce much extra velocity (i.e. you'll still be hitting the same node), although it might lower the pressure a bit. In that case, I would much rather have the extra weight devoted to a heavier contour.

In any case, the longer the barrel, the more weight needs to be sacrificed elsewhere in order to make the 18.18 lb limit. With a medium weight stock and bipod, my F-TR rifles with 30" MTU contour barrels come in at just a fraction under 18 lbs. I would have to dramatically lighten my bipod and/or stock and/or scope and/or go with a much lighter barrel contour in order to use a 32" barrel, let alone a 34". So I would consider what you expect to get out of the extra 2-4" of barrel very carefully before committing to a specific length.

You make a very good point. What is an approximate increase in velocity in the 30 to 34 inch range?

 

[savagedasher]

Using QL in my dasher with my seating depth and 60 000 psi average

30'' barrel 34''
varget 3049 3120
H 4350 3072 3142
N 550 3147 3219
By just changing barrel length I gain more FPS then I did changing from a 6MM BR to a Dasher.. The big advantage I see you can use slower burning powder and shoot less pressures. Larry

 

[Marksman63]

Good suggestion playing with QL. I will report my results

 

[Laurie]

I have considerable doubts over going with barrels much over 30 inches in FTR. As noted, any extra weight due to the additional inches has to come off the barrel profile and/or the other components. The guys I know running the highest velocities mostly use 30-inch but very fat and hence stiff barrels, often fluted for weight reasons.

A friend who is very innovative in rifle design and is into making his own stocks ran a Barnard P action with a good heavy profile 34-incher on a long forend lightweight own design and build stock for 210gn bullet loads. It was a disaster - you could literally watch the barrel and forend flex during the shot. Cutting he barrel down by four inches and beefing up the stock using the extra weight allowance this provided improved things remarkably. The 2013 GB FTR Champion Paul Crosbie won a lot of our league rounds and stage matches running a very heavy and stiff 28-incher and 215s including top results in our annual 'Long-Range Trophy' league round at Bisley. This included a runaway win in the 1,200 yard stage in the 2013 matches.

Look too at F-Open. These guys are allowed 22lb all-up weight (and no bi-pod to be included) and run cartridges whose expansion ratio is far higher than for 308 Win and which will therefore benefit more ballistically. I don't see many 34 inch tubes fitted.

Finally, whilst a great fan of QuickLOAD, I wouldn't trust it for a minute on this measure once one gets past the optimum barrel length for a cartridge. Just to test my thoughts out here, I ran it with six different barrel lengths for the 7mmBR with the 130gn Sierra MK and a stiff load of H4895. Here's what it predicts:

24" ............. 2,724 fps

26" ............. 2,765 fps ........ + 41

28" ............. 2,802 fps ........ + 37

30" ............. 2,836 fps ........ + 34

32" ............. 2,866 fps ........ + 30

34" ............. 2,895 fps ........ + 29


The reason I chose this combinatgion is that I read an article some years ago (most likely in Precision Shooting) on 'Effective Expansion Ratio' in which the 7mm calibre was used and barrel lengths wree progressively reduced in two-inch increments for several different sizes of 7mm cartridge starting with the BR.

The experimenter found that there was no worthwhile benefit in exceeding 28 inches with this cartridge as each extra inch only produced another 4 or 5 fps MV above this and even less above 30. Conversely QuickLOAD forecasts an additional 93 fps for 34 over 28 inches, an average of 16 fps / inch.

 

[Marksman63]

I have just run QL with my current calibrated loads, keeping my bullet (185 jug) and powders (VV N150 and RS52), changing the barrel length (from 32 to 34") and cartridge OAL (according the new required throat), playing with new nodes and around same pressures.

The load with VV N150 gave me 60 fps more at 67.000 psi (2840 fps vs 2780 fps)
The load with RS52 gave me same velocity (2900 fps) at lower pressure. I could not reach a higher node

 

[jsthntn247]

Your looking at the wrong end if you want to run a 208 at 3k, your reamer needs to read wsm not 308 win.

 

[Marksman63]

Looking at 2600/2650 for the 208 amax!

 

[Marksman63]

I have considerable doubts over going with barrels much over 30 inches in FTR. As noted, any extra weight due to the additional inches has to come off the barrel profile and/or the other components. The guys I know running the highest velocities mostly use 30-inch but very fat and hence stiff barrels, often fluted for weight reasons.

A friend who is very innovative in rifle design and is into making his own stocks ran a Barnard P action with a good heavy profile 34-incher on a long forend lightweight own design and build stock for 210gn bullet loads. It was a disaster - you could literally watch the barrel and forend flex during the shot. Cutting he barrel down by four inches and beefing up the stock using the extra weight allowance this provided improved things remarkably. The 2013 GB FTR Champion Paul Crosbie won a lot of our league rounds and stage matches running a very heavy and stiff 28-incher and 215s including top results in our annual 'Long-Range Trophy' league round at Bisley. This included a runaway win in the 1,200 yard stage in the 2013 matches.

Look too at F-Open. These guys are allowed 22lb all-up weight (and no bi-pod to be included) and run cartridges whose expansion ratio is far higher than for 308 Win and which will therefore benefit more ballistically. I don't see many 34 inch tubes fitted.

Finally, whilst a great fan of QuickLOAD, I wouldn't trust it for a minute on this measure once one gets past the optimum barrel length for a cartridge. Just to test my thoughts out here, I ran it with six different barrel lengths for the 7mmBR with the 130gn Sierra MK and a stiff load of H4895. Here's what it predicts:

24" ............. 2,724 fps

26" ............. 2,765 fps ........ + 41

28" ............. 2,802 fps ........ + 37

30" ............. 2,836 fps ........ + 34

32" ............. 2,866 fps ........ + 30

34" ............. 2,895 fps ........ + 29


The reason I chose this combinatgion is that I read an article some years ago (most likely in Precision Shooting) on 'Effective Expansion Ratio' in which the 7mm calibre was used and barrel lengths wree progressively reduced in two-inch increments for several different sizes of 7mm cartridge starting with the BR.

The experimenter found that there was no worthwhile benefit in exceeding 28 inches with this cartridge as each extra inch only produced another 4 or 5 fps MV above this and even less above 30. Conversely QuickLOAD forecasts an additional 93 fps for 34 over 28 inches, an average of 16 fps / inch.

Mmmm. Interesting!

 

[Marksman63]

I agree with you as my QL simulations confirm that.
However it seems that the OBT theory is independent from barrels' contour but practice says that the whole action/barrel/stock system would react in different ways.

Is there an empirical rule which correlates barrel lenght and its contour with OBT theory?

 

[savagedasher]

Moved to this board:

Building up my new F TR rifle for shooting heavies 208 Amax, 210 and 215 Bergers.
Long .250" throat but still deciding if switching to 34" barrel (current 32").

I have room for weight but worry about its balance and armonics issues. Stock is a Shehane FG ST1000.

Any thoughts? Feedback?
Thanks

I would build it. Balance can be a factor. OBT is a theory that hasn't worked for me. When I changed to a different burn rate powder OBT didn't work.
To tune a load u increase or decrease bullet speed for vertical.
Nice thing about a long barrel is if it works nobody will have one for 6 months or more.
I have a 35'' that hasn't arrived yet. The 32'' shoots better then my 28'' and 30'' does. Where I see the difference is when I shoot over 600 YDS.
With a longer barrel you can shoot slower burning powder .Most slower burning powder you get 95 % of bullet speed farther down the barrel . The chamber and throat erosion decreases.. Let me know your finding I will do the same.
Larry

 

[savagedasher]

You can shoot 215 Bergers Hybrids at 61000 PSI 2660 Fps with a 308.
Larry

 

[savagedasher]

I have 5 loads with different powders. OBT 1.295 1.284 1.289 1.321 1.381 Bullet speed 3050 to 3095. All shoot .250 at 100. What barrel time is correct?
Larry

 

[XTR]

My experience with a 34 was shooting side by side with a 30" barrel chambered with the same reamer, shooting the same load of Varget with 185 Juggs the 34" tube was 30 to 40 FPS slower than the 30. Now, the 34 was new and the 30 had a thousand or so through it, but in a 308 case I think you are running out of OOMPH to keep acceleration going unless you are running a whole lot of something slow.

I cut two inches off after the first match.

 

[savagedasher]

;D

My experience with a 34 was shooting side by side with a 30" barrel chambered with the same reamer, shooting the same load of Varget with 185 Juggs the 34" tube was 30 to 40 FPS slower than the 30. Now, the 34 was new and the 30 had a thousand or so through it, but in a 308 case I think you are running out of OOMPH to keep acceleration going unless you are running a whole lot of something slow.

I cut two inches off after the first match.

;D Why would you cut 2'' off a oversize tomato stake? ;D Larry

 

[DL1979]

Using QL in my dasher with my seating depth and 60 000 psi average

30'' barrel 34''
varget 3049 3120
H 4350 3072 3142
N 550 3147 3219
By just changing barrel length I gain more FPS then I did changing from a 6MM BR to a Dasher.. The big advantage I see you can use slower burning powder and shoot less pressures. Larry

Larry you seem to know your stuff and I was hoping to ask you a few questions on an FTR set up. I’m new to the game and just entered my first match at the Canadian nationals in Ottawa. I used. Savage 12 FTR 308 and lol I was shooting 155.5 Fullbore’s against everyone’s 200x grain projectiles with 30 years experience on me ! anyhow looking at this post regarding barrel length and pressures & velocity has me thinking of stepping up to heavies and if possible a 32” barrel. Would you suggest a shilen barrel for the job to go onto the savage target action? I’ve owned a shilen in 6.5 and it was well made. Thanks.

 

[memilanuk]

You might be better off addressing your question to Wade, aka @XTR

...he not only actually shoots FTR, which to the best of my knowledge Larry never has, but he's also on the current US team, *and* has experience shooting @ Connaught.

Just sayin'...