155gr Lapua Scenar load for F Class

[MichalS]

I want to develop light recoil load for my F Class Rifle, so started to experiment with 155gr  bullets. I tried Berger 155.5FB and Sierra Palma (new) but they are too short for my chamber. 155gr Scenar fits perfectly, but seems a bit erratic. 45.4gr RS52 at 2.89" COAL (0.010" jump) is best I found and it shoots 0.3-O.4MOA @2965fps in 12*C. The problem is 45.2gr and 45.6gr are much worse, so the window is really small. I also noticed bullets differ quite a lot in BTO lenght (I get different COALS with the same die setting). Velocities seem OK. Would You use that load? Groups from the left: 45.2gr (around 0.6MOA), 45.4 gr (0.33MOA), 45.4 gr with mandrel (0.42MOA), 45.6gr RS52. Barrel is 28" 11.5 twist.

Michal

[Popsbengo]

How are you measuring COAL?  I use 155 Scenar and find them to be very consistent when measured with a Hornady ogive gauge.

[MichalS]

I measure with Mitutoyo caliper. 185 Bergers are set +/-0.002", Scenars +/- 0.005".

[Popsbengo]

To the meplat (tip)?  That's not a good way of doing it.  For .308 an annular ring of 0.40" is the standard place - a Hornady gauge attached to your calipers.

[MichalS]

That would not be COAL if You measure it like this though? I don't have a comparator, thats why I measure COAL, I know it's less than perfect...

[Popsbengo]

OK, you will struggle to get a meaningful consistent measurement your way.  The idea is to gauge your particular rifle chamber/throat and then calculate from that reference.  There's plenty of examples of how-to on Youtube.  COAL is not about the tip to head, that's a rough n' ready measure (obviously COAL does impact on loading a magazine).

How do you know you have 0.010' jump without measuring ?

 

[MichalS]

AFAIK cartridge overall length (COAL) is a measurement from the base of the brass shell casing to the tip of the bullet, seated into the brass casing. How else would You know if it fits in a magazine if Yopu don't measure to the tip? I know I have 0.010" jump because I measured max COAL in my rifle using the split case method.

[Popsbengo]

16 minutes ago, MichalS said:

AFAIK cartridge overall length (COAL) is a measurement from the base of the brass shell casing to the tip of the bullet, seated into the brass casing. How else would You know if it fits in a magazine if Yopu don't measure to the tip? I know I have 0.010" jump because I measured max COAL in my rifle using the split case method.

OK, you carry on pal.

[MichalS]

Popsbengo, I just started reloading so may be doing it wrong. How should I measure COAL the right way? Do I need some kind of special comparator? My knolwledge is prettt much from manual, forums and YouTube, so I wouldn't be surprised if I got something wrong

[Popsbengo]

13 minutes ago, MichalS said:

Popsbengo, I just started reloading so may be doing it wrong. How should I measure COAL the right way? Do I need some kind of special comparator? My knolwledge is prettt much from manual, forums and YouTube, so I wouldn't be surprised if I got something wrong

OK, we all need to learn.  Let's assume that the problem is over-long COAL as it's not likely you would want to make a deliberately short round (which is not safe).  COAL is important for fitting rounds in the magazine so if you want to use a mag (and many do not) then you need a finished COAL that fits.  Now to get an accurate and repeatable COAL it's better to measure from a datum on the bullet ogive (curved bit) rather than the meplat because that's not necessarily finished accurately in the manufacturing process.  To do this a special gauge that fits on the caliper measures from the bullet ogive to the case head (that's the end with the primer). As the bullets are accurately made, the ogive will give the best measuring datum.  The actual measurement when using the gauge is less important than the repeatability.  The gauge is normally used to measure a test round that's been made to just touch the lands, that becomes the starting measurement - you then take off "X thou" and set the die to seat to the new measurement standard.

If you ignore the need to fit into a mag you may get more flexibility in sizing your rounds, this is what I do, I hand feed each shot as they are well oversize with Lapua 155 Scenars. My rounds are within 0.5 thou every time (possibly better but I can't measure more accurately than 0.5').

Hornady make a gauge set and you fit the correct size for your calibre (all makes of bullet of the calibre will fit).  A headspace gauge is also very useful but not essential if you can use the split case method (if done very carefully).  Do repeat your measurements a few times to get consistent sizes.

[MichalS]

On 3/31/2019 at 8:51 PM, Popsbengo said:

 Now to get an accurate and repeatable COAL it's better to measure from a datum on the bullet ogive (curved bit) rather than the meplat because that's not necessarily finished accurately in the manufacturing process.  

Isn't it Cartridge Base To Ogive (CBTO) that You describe?

[Popsbengo]

6 minutes ago, MichalS said:

Isn't it Cartridge Base To Ogive (CBTO) that You describe?

Well yes - it amounts to the same thing doesn't it?  The cartridge base as you call it is the head - hence 'headroom'.  The bottom line is COAL is not accurately measurable because of the meplat errors.  Ogive datum will result in a COAL of course.

[Re-Pete]

OK, I just measured 10 cartridges from a recently reloaded batch of 6BR as in the photo's:

The variation in ogive measurement, (cart 1) was 0.02mm, and meplat (cart 2) was 0.14mm.

Make of this what you will..................but I'll stick to ogive.

Pete

 

[Popsbengo]

A picture speaks a thousand words..

[MichalS]

I agree this is a better method, but I cannot find a comparator anywhere so I have to stick with COAL. For what it's worth COALS with Bergers are much more consistent than with Scenars, which means Bergers have more uniform tips/meplats.

[Popsbengo]

2 minutes ago, MichalS said:

I agree this is a better method, but I cannot find a comparator anywhere so I have to stick with COAL. For what it's worth COALS with Bergers are much more consistent than with Scenars, which means Bergers have more uniform tips/meplats.

Where do you live? Hornady Comparators are widely available in the UK - try "1967SPUD" for one.

[Bianchi]

On 3/31/2019 at 7:50 PM, MichalS said:

Popsbengo, I just started reloading so may be doing it wrong. How should I measure COAL the right way? Do I need some kind of special comparator? My knolwledge is prettt much from manual, forums and YouTube, so I wouldn't be surprised if I got something wrong

I guess that this could be a convenient address for your location. Like @RePete demonstrated, you would also require the Hornady comparator body and (alternatively) the anvil base that is attached to the calipers to increase the contact area for the bases of your brass. Makes my life easier 😊.

[VarmLR]

Pops is correct.  The only meaningful way to set COAL is from the case head to the ogive...that's all that matters provided it will mag feed.  The Hornady bullet comparitor will help you here.  It doesn't matter that the meplat to base is different as that isn't referencing to the lands, your ogive is.

Also, if I may offer some observations Michal.  Your conclusions RE the loads are a little wayward.  You can't judge a load purely on group size.  At distance, vertical dispersion matters, not just group size unless it is quite obviously opening up.  There can be many reasons for increase in horizontal grouping from trigger technique to wind effects etc.  Look instead at group centres, ES and vertical dispersion.

Re-assessing your groups this way, your centre two targets look to be on the node, so if this correlates to 25.4/25.6 then you have a wider latitude than you think, and try the centre of this and then play a little with seating depth if you must, but to my eye, your ES figures look pretty good (are they in M/s?).

There's another thread going that discusses accuracy discrepancies and tolerances.  Your chronograph and scales both have tolerances of probably 0.5 to 1% or thereabouts so applied to your MV, your ES could be half as much in reality or twice as much.  Look for patterns, and read the groups...your tightest vertical ones on the photos are the two centre ones.  That's where I'd be concentrating.

[Richiew]

Factory Berger ammo is 2.9 inch coal for all 308 match weights ie 155.5,175,185 . Found my sweet spot at 2.234 to 2.237 case base too ogive this gives me a 60 thou jump with plenty of bullet in the neck . 155’s be they amax lapua  or Berger give 0.5 moa with 42.5 g of N135 or 46g of N140 ,      175 burgers like 44 or 45 g of N150/N550 and same for the 185 jugs  . Loads built up to these figures and tested at 100 and 300 yards .

hope this helps 

accuracy int 308 ...26” barrel 

[MichalS]

18 hours ago, VarmLR said:

Also, if I may offer some observations Michal.  Your conclusions RE the loads are a little wayward.  You can't judge a load purely on group size.  At distance, vertical dispersion matters, not just group size unless it is quite obviously opening up.  There can be many reasons for increase in horizontal grouping from trigger technique to wind effects etc.  Look instead at group centres, ES and vertical dispersion.

Re-assessing your groups this way, your centre two targets look to be on the node, so if this correlates to 25.4/25.6 then you have a wider latitude than you think, and try the centre of this and then play a little with seating depth if you must, but to my eye, your ES figures look pretty good (are they in M/s?).

Thanks for Your insight. I understand the value of MV SD and ES at long range, but coming from sport (ISSF type AR and FR) I always think first about group size. I can call my shots really well, the groups I posted do not have more than 0.1MOA of shooter induced error, there was almost no wind.

The 2 middle group You mention are actually both 45.4 grain - one without (2nd from the left) and the other with mandrel neck expansion (3rd from the left). Groups 1 and 4 (left and right) are 45.2 and 45.6 respectively. All velocities in meters per second. Also note there is an error in descriptions - I've put 25.x instead of 45.x everywhere because I have exactly this load in .223...

With 185gr Berger Jugg I have almost identical good/brilliant groups (0.25-0.4MOA) anywhere from 42.5gr to 44.2gr... From 43.0 to 43.5gr I have ~0.25-0.3 MOA with velocity plateau - much better than with Scenars.

Richiew - thanks for the info on Berger factory ammo, I will try to replicate the 155.5 as I can't "reach" the lands with this bullet in my rifle.

Michal

[Richiew]

Hi Michal 

for info the 155 amax and 168 amax if used at 2.9 coal are jammed into rifling in my rifle . Found by chambering a round and finding it tight fit , removed cartridge and re-seated them all to 2.235 inch case base to ogive and now all ok . Amaxes also very accurate at 2.8 coal even though its a big jump to the rifling . Also try bushing dies to get consistent neck tension it’s only took 3 years to get to a load I’m happy with         Enjoy 

[MichalS]

9 minutes ago, Richiew said:

Hi Michal 

for info the 155 amax and 168 amax if used at 2.9 coal are jammed into rifling in my rifle . Found by chambering a round and finding it tight fit , removed cartridge and re-seated them all to 2.235 inch case base to ogive and now all ok . Amaxes also very accurate at 2.8 coal even though its a big jump to the rifling . Also try bushing dies to get consistent neck tension it’s only took 3 years to get to a load I’m happy with         Enjoy 

I use Redding Competition dies and was fortunate enough that my first load with Berger 185 Jugg is brilliant (see photo @1000y). I experiment with Scenars because I want lighter recoiling and cheaper option for training and when there's less wind.

M.

[VarmLR]

8 hours ago, MichalS said:

Thanks for Your insight. I understand the value of MV SD and ES at long range, but coming from sport (ISSF type AR and FR) I always think first about group size. I can call my shots really well, the groups I posted do not have more than 0.1MOA of shooter induced error, there was almost no wind.

The 2 middle group You mention are actually both 45.4 grain - one without (2nd from the left) and the other with mandrel neck expansion (3rd from the left). Groups 1 and 4 (left and right) are 45.2 and 45.6 respectively. All velocities in meters per second. Also note there is an error in descriptions - I've put 25.x instead of 45.x everywhere because I have exactly this load in .223...

With 185gr Berger Jugg I have almost identical good/brilliant groups (0.25-0.4MOA) anywhere from 42.5gr to 44.2gr... From 43.0 to 43.5gr I have ~0.25-0.3 MOA with velocity plateau - much better than with Scenars.

Richiew - thanks for the info on Berger factory ammo, I will try to replicate the 155.5 as I can't "reach" the lands with this bullet in my rifle.

Michal

In which case why not load some more up at that plus 0.1 either side...pick the best and play with seating depth?  I must admit, every time I use some neck tension uniforming (Lee factory crimp) it almost always results in better consistency of shots.