F/TR freebore

[AusFclass]

What sort of freebore do you find works well for berger 200/215 hybrids? Has anyone set one up for the new lapua 175 or 220L bullets?

Any assistance would be greatly appreciated.

 

[Steve Blair]

I use .280" freebore for 230 Hybrids. Berger lists the bullet as 1.640" long but they actually average ~1.665". 215 Hybrids are listed as 1.564" and 200's as 1.500". Providing the nose profile is the same, a little arithmetic tells us that freebore for 200 and 215 Hybrids should be .115" and .179", respectively. My .280" freebore is predicated on the possibility that I will jump the bullet as much as .030" in a new barrel and still want to keep the shank away from the neck shoulder junction.

 

[Laurie]

Has anyone set one up for the new lapua 175 or 220L bullets?

This pair are in a rather different bracket from Berger's Hybrid big-three. G7 BCs are modest to low for the bullet weights:

GB550 175gn Scenar-L ........ 0.247

GB551 220gn Scenar-L ........ 0.303

By comparison, the competent but not ballistically startling 175gn SMK is 0.243 (but the 168 Berger Hybrid is 0.266) and the antediluvian 220gn SMK is better than the Lapua at 0.310. Having looked at the 220 Scenar-L, like the 220 and 240gn SMKs, it has a very long parallel bearing section, so will likely generate a lot of in-bore friction and higher chamber pressures reducing potential velocities and possibly increasing the likelihood of barrel copper fouling (the 240 SMK's great bugbears in .300WM usage).

I'm not really sure who Lapua designed this pair for, but it's not the 1,000 yard F/TR competitor. I suspect it's more likely the law enforcement and military ammunition markets.

 

[paulT]

Was going to ask same question but for the berger 210 BT LR bullet also what would be good to go measurement for throating new ftr build for the 210g.

 

[gsg5pk]

Just wonder what method you calculate freebore for each projectile?

My FTR reamer from PTG for unturned Lapua Brass was .342"nk , .168" fb , 1-30


So, how many type of projectiles that suitable for my chamber?

List of Projectiles that I had on hand;

168 smk
175 smk

Berger 155.5 FB
Berger 168 Hybrid
Berger 175 LRBT
Berger 185 LRBT
Berger 185 Hybrid
Berger 215 Hybrid



My tube was 32" Bartlein 5T with 1:10"tw

 

[stgw77]

gsg5pk,
I have the same reamer as you do w. same FB, but with .340" neck.
My method for freebore calculating: I try with chosen bullet to touch lands. I need to know the length of bearing surface. You can get data on internet or you can measure it (Sinclair tool). I write down how much of length of bearing surface (bullet s biggest diameter whitout optional pressure ring) stay in neck (for example .140" using 185 Juggernauts in my chamber). For other bullets you only need to know the length of bearing surface. If it is longer, more will stay in neck.
You will not reach lands with .168 FB using Berger 155.5, with 168 SMK will be probably minimal (not sure), have no experience with 168 Hybrids, with 175 and 185 Bergers LRBT, 175 SMK and 185 Hybrids will be perfect - half of the length of neck, and using 215 Hybrids your freebore will not be optimal (read as too short, will take space for more powder).
Hope it helps you.

 

[Erik Cortina]

Has anyone set one up for the new lapua 175 or 220L bullets?

This pair are in a rather different bracket from Berger's Hybrid big-three. G7 BCs are modest to low for the bullet weights:

GB550 175gn Scenar-L ........ 0.247

GB551 220gn Scenar-L ........ 0.303

By comparison, the competent but not ballistically startling 175gn SMK is 0.243 (but the 168 Berger Hybrid is 0.266) and the antediluvian 220gn SMK is better than the Lapua at 0.310. Having looked at the 220 Scenar-L, like the 220 and 240gn SMKs, it has a very long parallel bearing section, so will likely generate a lot of in-bore friction and higher chamber pressures reducing potential velocities and possibly increasing the likelihood of barrel copper fouling (the 240 SMK's great bugbears in .300WM usage).

I'm not really sure who Lapua designed this pair for, but it's not the 1,000 yard F/TR competitor. I suspect it's more likely the law enforcement and military ammunition markets.

Through my testing with 220's, I found they have a .700 G1 BC, not the advertised .608 BC that Lapua published.

 

[Laurie]

Through my testing with 220's, I found they have a .700 G1 BC, not the advertised .608 BC that Lapua published.

I'm delighted that you're apparently getting good results from the new 220 Scenar-L. (How are velocities and their precision?) But. I'm intrigued by this comment. First, I personally would be very leery of challenging either Berger or Lapua company quoted BCs by such a large amount. Both put considerable effort with a rigorous scientific and experimental testing regime into producing figures that are meaningful and useful to the LR shooter for their primary LR match bullet designs. Moreover, their results are (a) averages over long distances, and (b) are corrected from those ambient conditions appertaining during the test to 'standard ballistic conditions', ie 59-deg F 0% humidity, 29.92 inches Hg atmospheric pressure.

I regularly have friends say to me that the calculated come-ups produced by some Berger LR BT designs are overly 'pessimistic' compared to what they experience on their first shots. ie the BC is higher than that quoted because they have to bring elevation down by a couple of MOA from their initial calculated level for 900 or 1,000 yards. The likely reasons for this are well known and include different atmospheric conditions - the range this usually occurs on is ~1,000 ft ASL and lies in a region that regularly sees low pressure weather conditions - the actual scope mounting height above the bore greater than the default 1.5-inch in ballistic programs, and scope adjuster click values not 100% accurate, so 30-MOA of on the gun adjustment being something a few % different at the muzzle.

Anyway, looking at the new 220 Lapua and putting it alongside the 215gn Berger Hybrid, or even 210gn LRBT, I really find it difficult to see how the former has a considerably higher BC than either of the other pair, Bryan Litz quoting the 215 Hybrid's G1 average BC as 0.696, and the 210 LRBT's as 0.626. The Lapua has a very long central bearing surface by today's standards and a correspondingly short and relatively sharply radiussed nose section compared to competing designs. Since it's the nose shape that determines ~60% of generated drag during supersonic flight, this doesn't look at all promising for this design. (Anyway, why use the G1 metric which sees the effective BC vary by around 15% depending on speed when the G7 form is far more accurate and less variable?)

 

[Erik Cortina]

Laurie, I'm not challenging anyone, I'm just telling you what my findings were in my gun with my load. I use G1 because that's all my phone app had before I upgraded it.

Personally I don't get hung up with BC, I look for accuracy above all.

 

[Laurie]

Erik, I didn't mean 'challenge' in any aggressive sense, perhaps 'query' or 'question' would have been a better choice of word.

Personally I don't get hung up with BC, I look for accuracy above all.

I agree there. BC is just one factor, albeit an important one to LR shooters especially F/TR with both 308 and 223 having to be optimised for 900 and 1,000 yards shooting. I also regularly emphasise to people that there are other factors that sometimes seem intangibles to us mortals who aren't former rocket scientists (maybe to them too for that matter) which make bullets perform better (or worse) than their paper specifications suggest. The old-model 155gn .30 SMK, the ancient 190, 200, and 220gn SMKs too all do better at long distance than people might expect. Since I don't understand the minutiae of bullet design factors and their interraction, I can only sum it up as being 'ballistically well balanced', a very unscientific description.

I'm still very interested in your experience with the 220 Lapua. Since I've given up on heavies, I've not got anything throated for this bullet length, so won't shoot the 100 that the UK Lapua importer, Hannams Reloading generously gave me as samples in any great hurry. I am genuinely puzzled though why Lapua has adopted this design as it's obviously not intended to challenge the equivalent weight Berger Hybrids. With law enforcement and military sniper sales important parts of Lapua's business, I did wonder if it's geared to the .300 Win Mag or similar as a long-range design. The new 175 model appears to be squarely aimed at the ammunition market currently served by the same weight Sierra MK and Berger Tactical OTM designs, loaded into M118LR specification cartridges and similar. I've bought a few hundred and while I've not tried them yet, expect them to perform very well in the shorter-distance F/TR role and in non specialist HBar 308s used in various disciplines loaded at around magazine length.

 

[Erik Cortina]

Erik, I didn't mean 'challenge' in any aggressive sense, perhaps 'query' or 'question' would have been a better choice of word.

Personally I don't get hung up with BC, I look for accuracy above all.

I agree there. BC is just one factor, albeit an important one to LR shooters especially F/TR with both 308 and 223 having to be optimised for 900 and 1,000 yards shooting. I also regularly emphasise to people that there are other factors that sometimes seem intangibles to us mortals who aren't former rocket scientists (maybe to them too for that matter) which make bullets perform better (or worse) than their paper specifications suggest. The old-model 155gn .30 SMK, the ancient 190, 200, and 220gn SMKs too all do better at long distance than people might expect. Since I don't understand the minutiae of bullet design factors and their interraction, I can only sum it up as being 'ballistically well balanced', a very unscientific description.

I'm still very interested in your experience with the 220 Lapua. Since I've given up on heavies, I've not got anything throated for this bullet length, so won't shoot the 100 that the UK Lapua importer, Hannams Reloading generously gave me as samples in any great hurry. I am genuinely puzzled though why Lapua has adopted this design as it's obviously not intended to challenge the equivalent weight Berger Hybrids. With law enforcement and military sniper sales important parts of Lapua's business, I did wonder if it's geared to the .300 Win Mag or similar as a long-range design. The new 175 model appears to be squarely aimed at the ammunition market currently served by the same weight Sierra MK and Berger Tactical OTM designs, loaded into M118LR specification cartridges and similar. I've bought a few hundred and while I've not tried them yet, expect them to perform very well in the shorter-distance F/TR role and in non specialist HBar 308s used in various disciplines loaded at around magazine length.

Accuracy was amazing, at 500 yards I was shooting groups under an inch out of my 300 WSM.

At 1000 yards with well prepped brass (I was experimenting) it would hammer the X ring over and over. I shot a 199-? with them at 1,000 yards my first time out with them. I cleaned the 600 yard target 3 out of 5 times during a regional match.

I measured bullets and as always, the Scenar L line was impressively consistent. I was shooting mine between 2,880 - 2,900 fps.

 

[Laurie]

Excellent! That's very good to know. I'll pass that on to our small but growing number of .300WSM F-Open and Heavy Gun LR bench rest shooters on our side of the pond.