308 bullet questions

[tommyc279]

I am building a 308 winchester for long range tactical shooting. I am using a Pierce custom action in a AI AX chassis and a Broughton standard 12 Palma 1-10 twist. I am trying to determine how to chamber this rifle and what bullets and ammunition I am going to use. Most important it must work with the twist and second is getting good ballistic coefficients. I would sometimes like to use factory loads to compare against other rifle builds and for competition I will use reloads. The reason I want to compare rifles is due to many people building rifles with the Pierce action and reviewing the rifles with factory loads. Thanks for the help.

 

[teflonhunter]

You could use 175 SMK's , affordable and kind of the old standard. Federal loads them in Federal Gold Medal Match , good round that works in alot of rifles. I have a load using 175 SMK's and IMR 8208 that works real well. Berger VLD's also work well.

 

[tommyc279]

What reamer should I use for the 175 factory loads and reloads with the 175's?

 

[RMulhern]

What reamer should I use for the 175 factory loads and reloads with the 175's?

Call Jon Beanland, Gould, Oklahoma and talk with him!

 

[Bart B]

With a 1:10 twist, you'll probably get best accuracy with bullets heavier than 190 grains. I say this because when the .308 was "the" cartridge to use in high power competition, a 1:11 twist was about perfect for 190's with max loads. And a 1:12 was about perfect for 168's and 180's as well as 175's. 1:13's the one to use with 150's and 155's. shot at faster speeds.

Spinning bullets too fast typically causes accuracy to suffer. As all bullets are unbalanced to some degree, the best match ones are close to, but not quite, perfectly balanced. Uneven jacket thickness, core position and outside profile all vary a tiny amount. So spin bullets just fast enough to stabilize them all the way to the target.

So, with that barrel, use Sierra 200's and maybe 220's with a case packed full of IMR4350 at about 48 grains for the 200 and 47 for the 220. I'd bet these will be the most accurate.

 

[rscott5028]

I'm trying to help a friend with a similar situation. He's bringing the rifle over tonight so that we can take some measurements.

My concern is whether you can seat the big bullets out far enough with magazine constraints rather than waste limited case capacity.

He's got a 20" barrel. So, MV will already be down although he may get some back with the suppressor.

-- richard

 

[liltank]

I'm currently in the process of doing load development to try my hand at F-T/R class shooting w/ the .308. I have tried the 175 Berger Tactical OTM with good results on a windy day at 975yds. Two loads stood out. One was with 48.0grn of Alliant Power Pro 2000MR (3" vertical with 3shots) and the other was 45.0 grains of RL15. I know that German Salazar over at accurateshooter.com is using the 185's in his builds along with some others. You might want to look up his blogs. For tactical shoots, I would think the 168 Berger Hybrid, 178 A-max, 175 Berger OTM, and 175 SMK will do all you need for that application. I have a sneaking suspicion the 168 Hybrid with a healthy dose of powder will do all you want. I will suggest going with a minimum of a 24" barrel to maximize powder usage and velocity. I crunched the numbers using JBM and the 168 Hybrid will stay mach 1.2 through the 1000yd line at a speed of 2800fps. This speed is very doable with most powders.

You'll want to stay with PP 2000MR, RL15, Varget, H4895, IMR4064, and TAC. These are all used with good effect. Chamber size is personal preference. I had a match chamber once, and will never have another one. It was a pain in the neck to get the brass right every time. I don't like too tight of tolerances.

Tank

 

[Bart B]

What reamer should I use for the 175 factory loads and reloads with the 175's?

The most accurate rifles I know of chambered for the .308 all have used SAAMI spec chambers. The guy whose rifles used by a bunch of record setters in high power competition have them. Sierra Bullets; they use the .308 to test all their 30 caliber bullets and their rail guns all have SAAMI spec chambers.

Reamers made by Henricksen seem to be the favorite. An old Elliott reamer is also great, if someone's got one that's been resharpened the right way.

 

[Kevin Thomas]

Bart B,

A correction on that last; Sierra uses a number of different 308 chamber configurations, but not the SAAMI 308 Win Standard reamer. The 308 Obermeyer was the standard that I used (and favored) for many years, along with one of Jim Hull's old Red Elliot reamers. The Palma bullets are fired using a designated 308 Palma chamber, complete with the short throat common to that configuration. Lastly, the 308s were only used for bullets up to 190 grains most of the time. The heavier bullets, 200s, 210s, 220's and 240's were all done in 300 Win Mags.

 

[Bart B]

Kevin, I'd belive your info on chambers in .308 Win. test barrels. So thanks for the update.

When Jim Hull was giving me a tour of their production line in the late '60's, he told me their .308 Win. test barrel was chambered with a Red Elliott reamer that was made to SAAMI specs. While Mr. Elliott made many of the best reamers back then, it's normal that he might change one or two dimensions a tiny bit. Henricksen did the same thing.

I've no idea what the "standard Palma chamber" is; several have been used. The one Mid used to chamber my Palma barrels were SAAMI spec's except for a shorter throat for those short Palma bullets. Which one are you referring to?

And it makes sense that 30 caliber heavier bullets would be better served by testing them in a larger case.

Now I'm wondering why two Tech's at Sierra a few years ago told me they used SAAMI chambers for their .308 Win. test barrels. Maybe they were "virtual" ones with a couple of minor differences.

 

[Kevin Thomas]

The very same. Mid chambered up my personal Palma gun, too, and I followed his recommendations for setting up the Palma test barrels. Undersize dimensions (.2985" bores, .3065" grooves, if memory serves) 1x13" and finished off at about 30". Essentially the same thing the US Palma team shooters were using. I want to say the reamer was a PTG, but it was specifically what he suggested. The throat's substantially shorter and has a shallower leade angle that matched up with the 155s seated at 2.800" OAL.

I ran across the Obermeyer chamber many years back, and tried it in a couple test guns. Had consistently excellent results, so that just became the "default" go-to reamer when I was setting up new 308 test barrels. I think I got these reamers through PTG as well, but the profile (hence the name) was done to Boots' original specs. Again, different leade angle played into that one, and man did they shoot well!

Just for clarification to others who may read this thread, no, we never used anything that would be considered a tight neck chamber, or a true BR design. Far too much shooting and far too little time to mess with such nonsense in a lab environment.

 

[rscott5028]

I'm trying to help a friend with a similar situation. He's bringing the rifle over tonight so that we can take some measurements.

My concern is whether you can seat the big bullets out far enough with magazine constraints rather than waste limited case capacity.

He's got a 20" barrel. So, MV will already be down although he may get some back with the suppressor.

-- richard

The 175 Berger OTM fits this rifle like a glove. I'm not sure that a longer VLD would clear the magazine. Of course, we haven't shot any loads just yet.

This is a 700 trued and rebarreld by Stiller. I don't know what reamer they used.

Measured OAL to ogive using Hornady tool with 175gr Berger OTM touching rifling. Ogive OAL = 2.268"

Subtracted .010" (desired jump to the lands to start load workup) = 2.258"

Measured COAL to bullet tip = 2.876" to tip with .010" jump

Made dummy round matching desired ogive OAL = 2.258" (COAL=2.876" to tip)

Measured AICS magazine length = 2.888"

~.012" clearance for cartridges in this magazine.

Confirmed dummy round just fits in 3 AICS magazines cleanly and stacks all the way to the bottom without rubbing.

The bearing surface uses just over half of the neck and the boat tail sits just below the neck.

-- richard

 

[Kevin Thomas]

Bart,

In re the last sentence, I hate to burst any bubbles here, but I'd venture a guess that they simply didn't know any better. The guys on the 800 line Tech Service do not work in the range, and most have little more than a passing accquaintance with what goes on down there. They work for the Sales and Marketing dept, while the range is handled by an entirely different crew that comes under the pervue of the Engineering dept.. Frankly, most of them don't know the details of what goes on down there in the tunnel.

Back in Jim's day, and when I started working for him, he was both the 800 Tech guy you'd speak to on the phone AND the guy who did all the QC firings. The 800 room and the range were one in the same, literally located in the same room. As the tech service was better advertised, it expanded dramatically, to the point where we hired several additional guys just to answer phones. The firing scheduled in the range also expanded dramatically over they years, to the point where Jim wouldn't have recognized it any longer. I used to routinely do more firing in a month down there than Jim used to over the course of a year, literally. One of the unfortunate (and probably unavoidable) consequnces of that was a gradual widening of the gap between the 800 service and the range itself. Very different entities today, and little transfer between the two.