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FTR 308 155.5 or 185 juggs question

Jefferson

if both bullets are shooting to their capabilities how much better at 1000 yards (900 meters) would the 185 be in a 10 mph wind,

what I am looking to see is the actual benefit to the 185 bullet once the wind is in play. everyone uses the 185 over the 155.5 (except maybe the brits from time to time) in FTR but I was wondering the actual target benefit,

everything else being equal, same shooter, same wind, same hold, and so on,


is it only 2 inches at 1000 or what is the benefit
hard for me to quantify

Jefferson
 
not looking for drop persay but looking to see if there can be a smaller "group" formed with the 185's, in other words do they or can they be tuned better on average than the 155.5 is that one of the advantages of the juggs,

Jefferson
 
All I know is my 185 jug/185 hybrid shoot very well and are easy to tune. Hardly can tell which load shoots well at 100 because they all form tiny groups. Had to move to 500 yards to help narrow down load. And still shoots well enough to think about which load to go with
 
Jefferson said:
not looking for drop persay but looking to see if there can be a smaller "group" formed with the 185's, in other words do they or can they be tuned better on average than the 155.5 is that one of the advantages of the juggs,

Jefferson
Click to expand...

What distance are you looking at? You could plug the numbers into JBM or whatever and look at drift as that also forms group size no matter how well tuned for vertical.

On average at 1000, my horizontal group shape is always much larger than my vertical group shape ::)
 
Jefferson said:
if both bullets are shooting to their capabilities how much better at 1000 yards (900 meters) would the 185 be in a 10 mph wind,

what I am looking to see is the actual benefit to the 185 bullet once the wind is in play. everyone uses the 185 over the 155.5 (except maybe the brits from time to time) in FTR but I was wondering the actual target benefit,

everything else being equal, same shooter, same wind, same hold, and so on,


is it only 2 inches at 1000 or what is the benefit
hard for me to quantify

Jefferson
Click to expand...

Using JBM,

155.5 at 3100FPS (probably achievable from a 30" tube, I've never shot them) drift calculates to about 83" in a 10MPH full value wind
185 at 2780FPS (easily achievable and I know it's in a node) drift calculates to about 75.8" in a 10 MPH full value wind

So the difference is 7.2 inches at 10 MPH, or about 3/4 of an inch per MPH which is where you will see the difference. The 155.5 drifts 8.3" per MPH, and the 185 goes 7.6". In realistic terms, with a ½ value wind if you miss a 1 ½ mph letoff then the 155.5 is 1¼ inches into the 9 ring, the 185 calculates to just under 3/4 of an inch into the 9 ring, if you got lucky you might hang that one on the line, or if you were holding over and missed the letoff then you might save yourself an 8 with the 185.

If you can shoot both bullets equally well in your rifle, at the end of a 100 shot weekend the 185 might pick you up two or three points. Take a look at the top 10 from the Berger SWN and see what 3 points would have done for any of their finishing positions.

Nothing is going to magically bring someone's score from the low 180s to the low 190s. At the level of bullet performance we are talking about here nothing is going to move someones scores from the low 180s into the 190s. It will probably get someone less than one point a match on average, but in the agg after 100 or 120 shots it will probably add up to a couple or four points.
 
minnesotamulisha said:
XTR, is that 2,780 fps out of a 30" barrel? I'm shooting the 185s but I havent chronied them yet.
Click to expand...

yes, from a 30. There seems to be a node that the 185s like in just about all rifles, it in the range of about 2775±25 FPS. With an appropriate chamber and throat is pretty easy to achieve w/o pushing the pressures.
 
That's what I measured (Magnetospeed v3) using the RS52 powder and Palma cases. SD is 5 with no signs of pressure (sticky bolt, ejector marks or flatted primer). I'm close to my higher node according QL.
 
XTR said:
...
If you can shoot both bullets equally well in your rifle, at the end of a 100 shot weekend the 185 might pick you up two or three points. Take a look at the top 10 from the Berger SWN and see what 3 points would have done for any of their finishing positions.
....
Click to expand...

Great input. I'd highlight the "If you can shoot both bullets equally well" part. My personal belief is you want to shoot the best BC bullet that you also hold great elevation with. Once your vertical starts to open up, I'd go back to the next lighter bullet that you shot with great elevation. Shooting a bullet at 1000 yards that holds excellent elevation is a tremendous confidence booster. I'd never trade this for a higher BC bullet.
 
How long is your rifle throated? That could increase pressure some with short throat. I am throated long for 215's and my 185 load is at 2830. 4th firing on Lapua and still good with Russian primers.
 
Throat length definitely plays a major role in this discussion.

Rough numbers here, but...

0 to 0.050" throat is good for 155.5's, but way too short for 185's; you'll see pressure at or below 2700.

0.100" throat is still good for 155.5's, and much better for 185's, which you should be able to see ~2750 or a little more with 185's. This is the throat length I recommend if you're planning to run both bullets.

0.150" throat puts the 155.5's way out of the case and makes for fragile rounds. If you drop a box of ammo loaded like this, you might spend the evening in your hotel room rolling the rounds on a desktop to pick out the 'less crooked' ones to finish the match with. Ask me how I know. However, at 0.150" throat, the 185's are perfectly well seated, and far enough out of the case to get you over 2800 without pressure in most barrels.

Note the above are rough results based on my observations of running these bullets in multiple barrels; your mileage may vary but pressure and velocity is affected a lot for the 185's based on throat length. The 155.5's don't see very much more velocity in longer throats (with Varget), and I've never seen serious pressure with any Varget load and 155.5's at any length.

-Bryan
 
broncman said:
How long is your rifle throated? That could increase pressure some with short throat. I am throated long for 215's and my 185 load is at 2830. 4th firing on Lapua and still good with Russian primers.
Click to expand...

.169 Freebore, I get clicks at the top of extraction on anything above 43gr of Varget, Stiller Action. I can shake the case back and forth and here powder moving so it's no where near compressed?
 
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