IMR 8208 in 6BR

[6BRinNZ]

Steve,

I am curious about using this powder in my 6BR and the Berger 88s. After your testing I would be keen to know what your opinion would be. I have tried ADI 2206H with 75grn V-max. 31grns was too hot at 3189 fps and the best load came in at 30.0 grns with an avg of 3065 fps.

Thanks

Wayne

 

[savageboy]

Anyone try this powder in a Dasher or BRX? I am putting a BRX together to shoot 105's/ 108's for 1000yd F class. It gets very hot here in NC in the summer and if this is as temp insensitive as it is claimed to be, it should be a winner. My concern is of course accuracy and velocity 1st, temp 2nd. Any early experimenters?

 

[limbic]

Any new data on the 8082?

 

[Moderator]

We have tested an early lot of IMR 8208 XBR in a 6BR with Berger 108s and the max usuable velocities were very similar to those obtainable with H4895. It may work best with the 95-100 grain bullets, but it is worth testing with heavier 105-108 grain 6mm bullets.

I have removed posts referencing velocities, the pursuit of which, I believe, will get people in serious trouble.

I'll never say that a Forum member didn't see what he saw over HIS chronograph with HIS barrel. But 8208 XBR (at least the lot we tested) is NOT a powder that will miraculously make your standard 2880 fps 6BR (with 105s) into a 3000+ fps BRX.

FYI, the Hodgdon data center lists a MAX IMR 8208 XBR load as follows (in 24" bbl):

107gr Sierra SMK IMR 8208 XBR 2.250" COAL 26.7 grains 2555fps 50,400 CUP

Yes, the above may be considered "conservative." However, Hodgdon has pressure gauges. Most of our forum readers do not. FYI the max velocity of Varget with the 107 SMK was listed at 2620 fps at 29.0 grains at 50,100 CUP. Max Vel with 107 SMK and H335 was listed at 2649 fps at 28.0 grains at 50,400 CUP. That gives you some idea of the velocity potential of IMR 8208 XBR compared to some other powder. 8208 XBR is not a miracle powder (in terms of velocity).

What this tells me is that you should expect to end up fairly close to the velocities currently allowed by Varget and H4895... which can vary considerably gun to gun. But I don't know any human that is driving a 107 safely at 3050+ using a standard 6BR, NOT a BRX or DASHER.

 

[Steve Blair]

I have been able to achieve just a few fps over 3000 with a slightly compressed 6BR load of Reloder 17 and Sierra 107s from a 30" barrel. Some other folks have reached the same velocity but are not seeing the accuracy I am with that combo. As our Moderator said, all the anecdotal results are great, but specific to a given rifle. I use a Kurzzeit chronograph and feel confident of the velocities but cannot speak to pressures other than by empirical means.

8208 has performed well for me with 155 and 155.5 bullets in .308 and with 69 grain Sierras in .223.

 

[Moderator]

Steve...

I should have put an asterisk in my preceding message regarding 3050+ velocity. The asterix would reference Reloder 17. That, virtually alone, is a powder that, in some cartridges, has demonstrated velocities not achievable with any other propellant.

The bottom line is safety. I know a couple guys that are getting close to 3000 from a standard 6BR throated very long, in 30" barrels. But they are running extremely high pressures, and their barrels are comparatively speaking, much faster than average.

For the 105-108gr class of bullets, with powders other than RL17, the "practical max" will likely be between 2850 and 2950 fps, and probably closer to the lower number. If a shooter is getting a distinct ejector mark, he is pushing his brass at very high pressures and needs to be careful. There is a darn good reason why the 6BRX and 6mm Dasher have been developed to shoot 105-108gr pills at 3000-3050 fps. If you could reach those velocities reliably and consistently with the parent, unimproved 6mmBR cartridge nobody would go to the trouble of forming BRX and Dasher cases just to go that fast.

Another thing to keep in mind when tossing around FPS numbers is that two different functional chronographs can read up to 70-80 fps different. We tested five chronos in a parallel lineup and we saw the variance in read-outs.

My main reason for posting here is that I really don't want people venturing into "over-pressure territory" just to try to match a velocity somebody else is getting, or thinks he getting because he has an optimistic chrono. When developing loads, every shooter has to find the practical max in HIS OWN GUN, through careful loading, moving up in small increments.

 

[Steve Blair]

You are correct, as usual. My most accurate load with Varget and 107s was an even 30.0 grains averaging 2876.3 and providing ES/SD of 11.0/4.6. Pressure was reasonable and the load very consistent. I saw no reason to push it harder.

 

[limbic]

I'm gonna try some in my BRX tomorrow. It usually is about 3g more than a br load. roughly. With the published max at 26 - 3 more grains will leave me at 29-30 and that leaves plenty of room in the case for the powder to slosh around in. I like my loads a bit more full. 33.5 of VV550 is just about perfect for me. Ill let yall know.

 

[limbic]

96deg, 280 asl
105 lapua scenar and cci Br4. Seated .20 in the lands.

32.1g showed heavy ejector marks. 3023fps
32.4 had pierced primer and heavy marks from the ejector and extractor.

May try 30-32g but that leaves a bit more room in the cas than I typically like.

 

[spclark]

8208 has performed well for me with 155 and 155.5 bullets in .308....

Interesting... where RL17 may be a bitt too slow, 8028 may have an application? You have an opinion as to how it was to clean up after?

Varget's been my standard Palma propellant for several years but I'm always on the look-out for something that works - accuracy-wise - but may offer an advantage when barrel condition (after 40 or 50 rounds or more) is an issue. I understand N150 is good in this regard & was to be my next choice. Right now I have a few pounds of 8028 but no N150 & no $$ to spend on propellants.

 

[Steve Blair]

Funny you should ask...

I went to the range today and, among other things, shot a 100-round series in my Borden/Eliseo RTM. The series comprised 100 Lapua Palma cases loaded with 44.0 8208 XBR, Berger 155.5 BT-FB seated 2.867, just touching. The barrel is a 31" Bartlein 10" twist MTU with a PT&G Palma chamber. I used a Nightforce 12-42 BR for this test with the forend and rear bag riders running in a Farley Co-Ax and Edgewood Minigater. Brass prep consisted of running all cases through the Sinclair expander die with a neck-turning expander. That provided ~.0025 tension. Case mouths were lightly deburred. 20 each cases were primed with Rem 7½, Wolf KVB-5.56M, Fed 205M, CCI 450 and CCI BR4. QuickLOAD predicted 2884 fps.

This rifle is a pain for me on bags. It handles really well prone with irons but I just cannot get a groove with it on the bench. It is very muzzle-heavy and does not ride bags well. My best results come from grabbing it very hard and pushing the butt down into the rear bag and back into my shoulder. It would not have been a pleasant day if I did this for all 100 rounds. So, I made a full effort on at least one group per primer and the rest somewhat less so. The best groups for each set were:

Rem 7½ .334 Wolf KVB-5.56M .246 Fed 205M .290 CCI 450 .297 CCI BR4 .345

I would not take any of these as definitive, it was a long day and I did not clean the barrel until afterward. It was, by the way, remarkably easy to clean and had almost no copper. Gotta love those Bartleins. Also possibly affecting my result was a group of 25 Russian exchange students shooting next to me. No, I am not kidding. They were all college kids and very enthusiastic. They fired a number of rifles, among which was a semi-auto AKM. Call me old-fashioned but I was always taught that giving a loaded AK to a Russian is a bad idea. The kids really behaved well, seemed to have a great time and some actually hit the targets regularly. Their presence did not help my concentration, however.

The attached text file lists each 5-shot group for velocity statistics. A summary is at the bottom. Several interesting results emerged. The missing chrono items were caused by me. I unplug the unit to conserve battery power when idle and stupidly did not plug in before restarting. Maybe I can blame that on the Russians.

1. The velocities were remarkably consistent and ES/SD better than LR primers and the same load.
2. Even though it was only a few fps difference, the CCI 450 gave the lowest mean velocity. That could easily change with more rounds fired. This is a small sample.
3. CCI BR4 primers gave an extreme spread of 13.8 fps for 20 rounds with SD of 3.8! I have never seen a result that low on this size sample.
4, Accuracy was very good with all primers, better overall than any LR I have tried with this combo.
5. I will be using Lapua Palma brass in this rifle, henceforth.

 

[savageshuter]

In regards to the Moderators comments on 7/22/10, the information quoted is for the 6 BR Rem. which has an overall length of 2.25". Is there any difference in the Rem. and the Norma other than the OAL? I shoot a Savage LRPV in 6 BR Norma and usually load mine to 2.44" COAL. Since I am new to reloading, I stay on the safe side of things with 29.5 grains of Varget. I currently do not chrono loads but will later this year but I can say with some confidence that I am not getting any where near the velocities mentioned by the forum members. Are there any real differences in the two chamberings? Thanks.

 

[Heavies]

6BR Norma can be loaded longer than 6BR Rem. From what I understand, this lessens pressures and allows you to bump up charges from that of 6BR Rem, thus allowing greater velocity. I know my barrel can get 2900+ in a 24" with 105VLDs with HBN, but I do feel I have a 'fast' barrel.
YMMV

 

[savageshuter]

Heavies: Thanks for the info. Do you know of anyone who publishes data for the Norma chambering? Also, what charge and powder are you using? Thanks again for the info.

 

[Heavies]

Lapua/VV powders has some data, but limited selection of components.
http://www.vihtavuori-lapua.com/pdfs/Rifle-Reloading-Data-2006.pdf

6mmbr section of this site has the only other info that I know of.

In regards to seating depth. Much depends on your throating. Some folks have long, some short. This will determine where you can run your bullets. You don't have to run them at 2.25", that is just a minimum seat depth.

I have used Varget and RL-15. I am now working on IMR 8208 XBR with promising results so far. I have had very good groups with 29.4 grains, CCI450, lapua brass with HBN coated 95 grain SMKs. Now, I am very close with 105 Hunting VLDs HBN coated. I worked up from 28.5 to 30.3 grains, now settling on 30 grains of 8208. This load is on the hot side so if you try it work up watching for pressure. Also, using uncoated bullets you may find pressure alot sooner. When F-class season starts the proof will be on paper. I have also played with RL-17, but this needs more development.

When working up watch for your signs of pressure, and stop when you get the indications.