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185 Burger Hybrids-Load development

300 RUM

Gene Nowaczyk
Ok I have been playing around with the Burger 30 cal 185's. I've done my Load development home work and I am down to one load and trying to figure out seating depth. There are some obvious +'s when looking at the numbers. I guess I am looking for some comments on results shown below, I have beaten myself up looking for bliss and currently brain dead :-) (see photos below)

The tests conducted were from seating depth of .010 jamb to .050 jump, the winners are the photos below.

Rifle info:
Ar-10
Bisley chamber 308
.298/.308 bore
26.5" barrel length

Load:
42.3gr Varget
Lapua brass
CCI br#2

I would like to hear all comments and attempt to answer all questions.

Thanks in advance

Gene
 

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jbpmidas said:
What distance were you shooting? I would prefer the .005 jump target, but I'm biased towards a jump.

Now that I am a bit rested :-)

200 yards was target range, I really like the ES and SD on the .005 jump myself.
Vel seems a bit low?
Oh and actually both groups are the exact same size.
 
I shoot the 185 Hybrids as well. My velocity is a little higher at 2660. I'm also jumping .010, well, 500 rounds ago I was. I haven't remeasured. I shot Master level scores last weekend with that load. I think you'll love them in the wind and they don't recoil bad at all!
 
I back mine off .030 and was shocked, start on the lands, back off in .010 increments to .050 and see what the best grouop is!

I learned this a long time ago, when you get a decent group, try the above. Again, I was shocked when I found my 185 Hydrids like being .030 off the lands!

I have another gun, different caliber, it likes being .050 off and I FOUND THIS OUT BY MISTAKE!

All VLD's like to be in a little!

Dennis
 
The Berger 185 Hybrid is the class leader in BC terms and 2,600 fps is more than usable at any sensible range. For instance that combination far outperforms the popular 175gn Sierra MatchKing at a considerably higher MV at 1,000 yards

185 Hybrid (G7 BC 0.291) / 2,600 fps: 1,284 fps remaining at 1,000yd; 8-MOA sideways movement in a 10 mph 90-deg crosswind
175 SMK (G7 BC 0.243)/ 2,800 fps: 1,207 fps / 9.4-MOA wind drift

My concern would be about maintaining the 0.005" jump. Being as close as that you risk most bullets being just out, but with a few kissing the lands. The latter will usually produce fliers. This is why most advice on the subject says use a minimum jump of 10 thou' as many makes / models of bullets used out of the box allied to press / die quality traditionally risked the some out / some in situation if a smaller jump value was used.

So you need to be sure the bullet ogive is in the same place on each and every round to within a couple of thou'. This is difficult if there are a lot of minor shape variations between bullets. the good news is that current Bergers are very good indeed in this respect within each production lot - buy a new supply though and they may be marginally different from what you're working with now.

The only way to be 100% sure you've got enough jump each time is to measure each loaded round using callipers and a bullet comparator and adjusting the COAL of any that are marginally loo long. A seater die with micrometer top makes this tedious task a LOT easier - I use the Forster Ultra BR seater in my 223 and 308 L-R match ammo where one gradation on the top really does change COAL by 0.001" or a figure very close to it, and the top turns easily and smoothly so making minor changes isn't too onerous. By setting the die up to give a marginally long round, quick measure and adjust/reseat, keeping comparator-COALs to within plus or minus 0.001" is quick and easy, returning the die to to the original setting after each re-seat operation.
 
Had an opportunity to get started with the 185 Hybrid during our recent early spring 'heat wave' a couple weeks back. Seem to like N550 & Palma brass, seated to 0.020" off the lands. Great SD's at a node right at 2,800 fps with excellent accuracy. Will be using them for the season's Fullbore opener at Winnequah Saturday after Easter.
 
spclark said:
Had an opportunity to get started with the 185 Hybrid during our recent early spring 'heat wave' a couple weeks back. Seem to like N550 & Palma brass, seated to 0.020" off the lands. Great SD's at a node right at 2,800 fps with excellent accuracy. Will be using them for the season's Fullbore opener at Winnequah Saturday after Easter.

what are your barrel specifications I could push the 185 to 2835 what I was seeing some flat primers very flat primers
 
300 RUM said:
what are your barrel specifications I could push the 185 to 2835 what I was seeing some flat primers very flat primers

30" Broughton 1:11 5R chambered long by Mike Ross back in 2005 when I bought my Gilkes-Ross rifle from him. Since new I've probably fired ~ 2,000 rounds thru it in testing, practice & competition.

@ 0.020" off the lands those bare 185's average 2.950" OAL. (Meplats appear to vary as much as +/- 0.004" but as I'm just starting with them I chose not to trim or uniform in any way.)

Was comparing H4895 & N550 that day, similar results with the nod to H4895 but as I have eight pounds of N550 on the shelf figured I'd best use that up before buying any more propellants. Test rounds fired over three-cell Oehler 35P.

Obviously what's safe in my equipment may not be in yours! I'll ask those wishing to discuss this in greater detail please contact me off-forum via e-mail.
 

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