Sierra Palma Match 155 and IMR4064

[DAVID NANCARROW]

Folks, I have an issue with this particular setup and looking for some guidance.

I know that 4064 is a popular powder for the 308 Winchester although I haven't used IMR in a while, mostly Reloader 15 and Varget.

The load I am trying is 44 grains of IMR4064, Federal 210M primers and new Lapua brass, COAL is 2.815", or magazine length as Rem has a history of using long leades in their chambering. With my chamber gauge, the 155s touch at 2.950" and I would like at least some of the bullet in the case, let alone feed from the mag.

The rifle is a Remington Varmint Synthetic, 26 inch heavy barrel, bolts torqued to 45 in/lb, Leupold Vari-XIII scope on double dovetail rings. 1:12 inch twist. Maybe 800 rounds downrange.

I benchrested the rifle at 100 yards and the groups are 2 to 2 1/2 inches I thought it was me or the rifle/scope combination, but when I launch Sierras 175 MKs over Reloader 15, I get sub MOA.

Is it the barrel, powder, bullet or ????

Your thoughts are most welcome.

 

[Bart B.]

In 1991, I and a couple others tried IMR4064 under Sierra's first batch of 155 prototypes. No loads did all that good. Faster stick powders gave best accuracy at long range. But 4064 should produce MOA at worst on hundred yard paper. Even with COL at magazine maximum length.

There is something else causing poor accuracy. Try another grain or two of powder. Maximum is about 47 grains of IMR4064 under 155's.

 

[DAVID NANCARROW]

Thanks Bart. I was hoping the new Palmas would group well...the bc is advertised at .503 and I was hoping to develop it into something longer ranged. My rifle will normally shoot cheap 150 grain soft nosed Winchester silver box into 3/4 moa so I was quite surprised at this group. Will try moving it up a grain or two and see if anything positive comes of it.

The max load listed is a compressed charge but I don't have experience with such loadings. I sure appreciate the reply.

This rifle has a history of responding well with max or very near max loads, so I will try moving the bar.

 

[HiBC]

I had hopes for that bullet,too.I have no doubt it is every thing we might expect from a Sierra match bullet,but as it worked out in an AR-10 T and a DPMS LR308...I think I used Varget

I got the same results,about 2 moa at 100 yds.

Same day,for comparison,I had some otherwise identical loads with the previous 155 gr Palma bullet,now designated the 155 MK.

Those shot a 3 shot the size of a dime out of the AR-10 T

The DPMS is a 7.9 lb light rifle with a production barrel.They shot well,but more in the 1 MOA + or - range

A very limited experiment for jumping to conclusions,I admit,but I'm not surprised by your experience.
I do not criticize the bullet,I think there is something,whether throat,leade,bore dia,twist or ? that it needs to perform.

I defer to Bart.

 

[DAVID NANCARROW]

HiBC, you certainly echoed some of my concerns. In the past, whenever a bullet/powder combination did not work for me, I changed bullets first. My thinking was that the firearm didn't like it for whatever reason.

I was very concerned about the amount of jump the bullet took to reach the rifling-.130 or so seems like a lot, but when I checked some 175 gr MKs, they jump nearly .200" so something else is amiss I think.

For now, I am going to try a 2 grain step up on the powder and see where it takes me. If the groups don't improve, I am going to go back up to heavier bullets and be happy. This thing just may not like 155 grain match bullets. The odd part is that Hornady BTSP in 150 gr weight is a tack driver, less than 1 MOA and anchored deer a bit too well. I moved up to the 165 Hornadys, same style for less meat destruction.

 

[old roper]

Bryan Litz has done some testing on the Sierra 155gr Palma bullet and he used 1/13 twist barrel and you might want to read that report.

You might want to try 6br site some are shooting that bullet they may have some help for you.

 

[Bart B.]

old roper, how about posting a link to Brian Litz's article on Sierra's 155's? Thanks.

While a 1:13 twist is typically going to produce best accuracy shooting 155's out at 3000 fps from a 30" barrel into 1000 yard targets, shorter barrels with faster twists have proved equally accurate at shorter ranges. To say nothing about some 30" barrels' 1:10 twists have won matches with Sierra's 155 Palma bullets and helped put shooters on the US Palma Team.

Accuracy is more dependant on a bullet's rpm speed than its velocity through the air. Whatever twist spins bullets a the right rate for a given muzzle velocity will work wonders. There's no reason a short, 1;10 twist barrel won't shoot Sierra's 155's into 1/4 MOA at 100 yards from a good barrel decently installed and tested with good ammo. Unless the loads are pretty bad off to start with.

 

[DAVID NANCARROW]

Here ya go Bart. Interesting reading
http://www.6mmbr.com/index.html

 

[603Country]

I recently tried a new bullet in two rifles (223 and 220). Darn thing shot terrible in both guns till I got right at max load, and then they shot wonderfully. I can't explain it, but that's what I saw.

Try Bart's approach and try more powder. That would be my first approach.

 

[firewrench044]

I have had better luck with IMR 4895 with the Sierra 155s

 

[William T. Watts]

It could be your bore is a bit oversize and the longer bullet centers itself in the barrel better. I have only one 30 caliber rifle that measures .300" on the rifling/lands and I presume .308 in the groves. I usually find accuracy improves with the heavier bullet. I picked up a Scott a Duff gauge several years ago and love it for 30 caliber barrels.. William

 

[T. O'Heir]

You work up the Palma load or just pick it and hope? You mustwork up the load from the starting load.
Compressed loads are nothing to worry about. Your 44 grain load is likely compressed.

 

[Grunt96]

I couldn't get good results with 4064 and that bullet either. Haven't had the chance to try other powders yet. Let us know what you find that works.

 

[Jimro]

IMR4064 is best with 165 and heavier bullets in the 308 Win. I've never gotten the accuracy from 150 gr match bullets with 4064 that I have with heavier pills.

For 155's I'd recommend H4895 or as an alternate IMR4895.

Jimro

 

[10-96]

I tried the 155's as well to dismal results. I don't remember the loads, but I did try 4064 and IMR 4895 through my Springfield NM M1A. That'll teach me to buy something just because it's on sale!

 

[Bart B.]

T. O., I don't think it's a 'must' that everyone work up an accurate load for a bullet starting at some charge below maximum. Especially when other maximum loads with similar components have proved safe and normal in ones barrel. Sierra's 155 is their only 30 caliber bullet I worked up a load for. I just used what was popular for all their .308 HPMK's in 30 caliber magnums and .308 Winchester's.

The group of us developing loads for Sierra's first batch of 155's knew tha 45 or so grains of IMR4895 shot Sierra's 150-gr SBT and HPMK bullets very accurate in 200 yard matches in .308 Win's. We tried several powders in the same burn range but 4895 seemed the best for accuracy in spite of AA2520 producing lower spreads of metered charge weights and muzzle velocity. A 45.3-gr charge of 4895 shot those 155's about 1/2 MOA at 600 yards in several barrels with different internal dimensions.

That load also shot about 1/2 MOA at 300 yards in my 7.62 NATO Garand. And it's done well in match M1A's, too.

 

[10-96]

Alright, now I'm curious. I don't have my notes handy, but I don't think I went over 45gr/4895- that sounds about right from memory. I only have 20-25 of the bullets left, but I think I'll give it another whirl.

The bullets were bought on a MidwayUSA Blemish sale. That doesn't effect internal integrity of the bullet- they're just not as shiny- right?

 

[DAVID NANCARROW]

I loaded up 15 rounds of 155 over 46 grains of 4064, 15 more with Varget, 15 of H4895, and 15 with Reloader 15. Maybe I will find out if one of the powders is going to bring me joy, or at least give me groups interesting enough to pursue.

Will also be taking along some tried and true 175 gr MKs so I can break out into my happy dance. Its going to be a few days....the fabulous VA hospital wants to experiment on me for a day or so. Ugh

Will update with results!

TO, 44 grains of IMR 4064 is not a compressed load for my 308, and yes I am working up the load. I just surprised me that the group turned out so large. IMR listed the max load under this bullet at 47.5 grains which is compressed.

 

[Bart B.]

10-96 says the bullets were bought on a MidwayUSA Blemish sale. That doesn't effect internal integrity of the bullet- they're just not as shiny- right?

Maybe, maybe not. I've seen Sierra's seconds that failed accuracy specs with blemishes. Their inspectors also cull out blemished bullets when they see them during packaging. Shoot 'em and see how they perform; the best way to tell if they're good. People who have usually get pretty good ones. There have been exceptions.

 

[Jim Watson]

The Sierra Palma 155 did not show me a lot; the Scenar 155 does very well in MY rifle. But no better than a Sierra 175.

You have to decide how much time, energy, and barrel life you want to put into trying to FORCE it to shoot a different bullet from the ones that you already know are accurate.
Are you shooting for good scores or do you just enjoy the tinkering?