Some thoughts on barrel length for F-TR

[memilanuk]

Monte,
What is your free bore for the 200's?

In theory, it should be 0.170", as it was chambered with the 2013 US FTR reamer. OAL with a 200 touching the lands is approx. 3.078".

 

[Dos XX]

In theory, it should be 0.170", as it was chambered with the 2013 US FTR reamer. OAL with a 200 touching the lands is approx. 3.078".

Mine is supposed to be .168 FB. OAL with 200 touching is 3.060. Sounds like they are close.

 

[rap36case]

Easy enough to know, anybody who's running 215 hybrids in 30" barrel, on any sane pressures is running them between OBTs. Slow node with any stable powders(Varget or H4350) is around 2450-2490 fps, higher node is not achievable unless they are using brass once and throw it out.
Bryan Litz posted his load here, he is running 2550ish fps. The general trend is these bullets shoot around 2550-2570 or 2630-2640fps.
I haven't run any numbers yet but I doubt we can run 200s or 210s on OBT at safe pressures.
That's just one example, I can give more accurate answers if I was sitting in front of Quickload. Quickload is not always 100% but it can't be that off either.

Again I'm not disagreeing that OBT exists, it's just that it is possible to NOT be at OBT and be accurate, atleast accurate enough to be able to hold waterline in a F class match.
I'm not arguing in case we are discussing benchrest here.

Thank you for this bit of information! If 2550fps is the muzzle velocity, then running the applied ballistics calculations shows a terminal velocity of 1488fps at 1000 yards and WEP of 91.9%. This might be better, with a 30" barrel and 1 to 9 twist, as found in articles here. However, the brass my be blown at the pressure this generates. A muzzle velocity of 2490 gives 1422fps at 1000 with WEP estimate of 90.4%. The lower node in a 30" barrel may be acceptable and save some brass.
I use Varget at 2400fps in a 24" barrel with little sign of over pressure. This calculates to 1373fps at 1000y and WEP of 87.6%. I think this is adequate for my level of shooting.

 

[shootmore]

I'm building out a new .308 FTR for Max (12yrs. a little fellow). Our .223 FTR weighs in at 11.3 lbs. with Heavy Palma 30" barrel, action, trigger, scope, rings bi-pod etc. everything but the stock. McMillan says the stock will weigh in around 5lbs.
18.2lbs. - 11.3lbs. - 5lbs. =~ 1.65lbs to spare.

The 30" Brux Heavy Palma reports 6.5lbs. We could go up to an 8lb. barrel
Can I get a heavier barrel? What type. Scott mentioned a 5" breech. What contour?

 

[Jennb]

I just started running Palma brass last year, so I can't comment on how many loadings I will get yet.

If you travel to shoot larger matches, like the Berger SWN, or FCN's, you need to be able to take almost 400 rounds to a match. I am running 450 pieces of brass on each of 2 barrels right now. I would estimate 3000 is rounds is about max on a 308 barrel for match accuracy, so if I can get 7 loadings that would be 3150 rounds or enough to retire a barrel. It will be interesting to see.

I am running 200’s at 2700 fps in palma brass and have 14 firings on my oldest brass and it still holds a primer quite nicely. No signs of stress in the brass.

 

[Medic505]

I'm building out a new .308 FTR for Max (12yrs. a little fellow). Our .223 FTR weighs in at 11.3 lbs. with Heavy Palma 30" barrel, action, trigger, scope, rings bi-pod etc. everything but the stock. McMillan says the stock will weigh in around 5lbs.
18.2lbs. - 11.3lbs. - 5lbs. =~ 1.65lbs to spare.

The 30" Brux Heavy Palma reports 6.5lbs. We could go up to an 8lb. barrel
Can I get a heavier barrel? What type. Scott mentioned a 5" breech. What contour?

A 30" .308 HV (Heavy Varmint) with 4 inches of 1.25" tapered to .940" will run 7.6 pounds give or take a little. I weighed one this morning.

 

[shootmore]

Hi Medic505, what Barrel brand?

 

[swadiver]

I shoot 200 Berger Hybrids in my F/TR barrels. one is a 30 inch 5R Bartlein, the other is the same barrel and chambering but at 28". with Palma brass and Varget, the 30" gives around 2690 fps MV. the 28 inch around 2680 fps MV. both chambered with the same reamer, they both shoot the same load. the 28 inch MAYBE shoots a tad better. my next barrel will be a 28"

 

[Medic505]

Hi Medic505, what Barrel brand?

For the most part I shoot Bartlein 5R's. The barrel I weighed this morning is a Broughton. Pick a brand you like or one you can find if you don't want to wait on one. I really don't think you'll go wrong with any major brand. I've shot Kreiger 4 and 5 grove barrels also that have performed well. The best barrel I've ever owned was a Rock Creek.

 

[Jennb]

Hi Medic505, what Barrel brand?

Krieger. Tell Max high!

 

[Warren Dean]

The best barrel I've ever owned was a Rock Creek.

What??? not your Savage barrel??? HERESY!!!!

 

[Bill K]

I get it. That would be a cool experiment. I would be curious to know if as the barrel gets shorter does the pressure increase even if the velocity stays the same?

My understanding is the pressure in a chamber is due to the case and it's load, and what it exerts to the sides and base of the case in the chamber. That is why, when they check pressure in a chamber the gauge's read at the chamber and not in the bore. The FPS is what is effected by the length of the barrel.

 

[Ned Ludd]

Don't ever let anyone tell you that it is the length of the barrel that matters...



it's the diameter .




Shootmore - some commonly-used barrel contours for F-TR (in order of increasing weight for a specified finish length) might include Med Palma, Heavy Palma, M24, MTU, and Heavy Varmint, among others. Here are a couple more actual weights for chambered .308 barrels, Bartlein 5R: 30" MTU - 7.47 lb, 28" M24 - 6.31 lb. MTU and HV contours usually end up pretty close in weight for a specified length; however, the weight is distributed a bit differently. M24 contour uses a 1.20" shank, rather than 1.25". You might want to take a look at Bartlein's Barrel Contour page: https://bartleinbarrels.com/contours/. If you do a search, various outfits offer online barrel weight calculation tools, or you can contact the manufacturer directly and inquire about the weight of a given contour/finish length.

I would also suggest that your subtractive approach for estimating the weight you have to add to a barrel based on the existing .223 Rem rifle is extremely rough, at best. It is much better to weigh the actual components themselves, or get a weight from the manufacturer. It's also a good idea to give yourself a bit of headroom in case you ever want to use the rifle in a match where the weight might actually be checked. I try to keep my F-TR builds at, or just slightly under 18.0 lbs. You never know how accurate someone else's scale might be.

 

[memilanuk]

The best barrel I've ever owned was a Rock Creek.

I've had several over the years in various calibers that were just stupidly accurate, right out of the gate, and they always cleaned up easy. Don't know why I've never used one for F/TR...

 

[memilanuk]

A 30" .308 HV (Heavy Varmint) with 4 inches of 1.25" tapered to .940" will run 7.6 pounds give or take a little. I weighed one this morning.

I thought I'd take a couple inches off my Bartlein HV in 2017 - down to 28" - to make weight. Still ended up having to run a super light-weight carbon-fiber bipod (Talon) to get under the weight limit with a steel action (Savage TA) and McM XIT stock - along with changing out the scope rail from a Farrell (steel, 6 oz.) to a NF (aluminum, 2.4 oz), finding an aluminum trigger guard (not a big deal for a Remchester action, but a freakin' unicorn for Savage), etc.

 

[avidflyer]

I am running 200’s at 2700 fps in palma brass and have 14 firings on my oldest brass and it still holds a primer quite nicely. No signs of stress in the brass.

What powder? H4895?

 

[Jennb]

What powder? H4895?

Varget

 

[Jennb]

I get it. That would be a cool experiment. I would be curious to know if as the barrel gets shorter does the pressure increase even if the velocity stays the same?

I have a 31" and a 32" chambered with the same reamer. They also run almost the same velocity. Again, I wonder if the pressure is the same? I may can judge by brass life.

Given no changes other than barrel length!

Max pressure does not change because it happens in the ignition process
Velocity will decrease based on shorter barrel length
Powder efficiency changes based on what barrel length the load was developed for
Obviously barrel timing will change due to length of barrel