IMR 8208 XBR Performs Well in .308 Win Testing with 155s
We have a “Palma/Tactical” project gun in the works built with an Eliseo chassis, Borden action, and one of Krieger’s very first 5R barrels. Initial load testing with Hodgdon Varget showed excellent accuracy potential, but we weren’t achieving the velocity we hoped to get from the 30″ medium-Palma-contour barrel. With Lapua brass and Varget we ran short of case capacity when seating bullets to mag-length, and the best accuracy came at about 2860 fps, well under competitive Palma velocities.
Mark LaFevers with .308 Win Eliseo Tubegun on SEB NEO front coaxial rest. Mark made the wood front bag-rider.
Chris Hodgdon kindly shipped us some H4895 and some of the new IMR 8208 XBR powder, lot #1022510-4798. In beautiful 70° conditions yesterday, we did a quick pressure work-up with both powders to determine “practical max” loads with the Berger 155.5gr Fullbore bullets (#30416). The 155.5s were loaded in once-fired Lapua brass with CCI BR2 primers, to a COAL of 2.860″, which is about .010″ short of land contact.
Varget-beating Speeds from Both IMR 8208 XBR and H4895
We loaded up two rounds at each charge weight, starting with the Hodgdon’s recommended starter load for a 155gr Sierra HPBT, as found in Hodgdon’s online Reloading Data Center. (There was no load listed for the 155.5gr Berger). It’s good that we started low because we saw immediately that both the 8208 XBR and the H4895 were yielding much more velocity, grain for grain, than Varget. Though we were not shooting for groups, the 8208 XBR also seemed to have a very large accuracy load window. Moreover, the velocity spreads for each two-round 8208 charge (above 43.0 grains) were remarkably low — none were more than 6 fps, and the velocities on our two 44.0-grain shots were exactly the same — 2992 fps. (This was NOT an error — the chron registered both shots #7 and #8.)
Of course, you can’t conclude much about ES/SD from just two shots, but the speed consistency in the 8208 was notable as you can see from the chart above. By contrast, each pair of H4895 shots varied in speed much more. For example, the two-shot ES for 43.0 grains of H4895 was 14 fps, while the two-shot 8208 XBR spread (for 43.0 grains) was 4 fps. It will be interesting to see if further testing confirms the low ES/SD potential of IMR 8208 XBR in the .308 Winchester.
We dispensed charges with an RCBS ChargeMaster calibrated and leveled on a granite bed. The 8208 XBR has smaller kernels than either Varget or H4895 and, as we expected, 8208 XBR dispensed very easily. The H4895, with longer kernels, dispensed fine in the ChargeMaster, but it took the machine more time to trickle the H4895.
As noted, we didn’t shoot for groups, but the IMR 8208 looked like it would shoot really well at anywhere from 43.0 to 44.0 grains. The H4895 proved accurate as well, at least in the high pressure ranges. We need to do 5-shot testing, over flags, before drawing any real conclusions. But right now we can say that, if you’re shooting a .308 with 150-155 grain bullets, you should definitely try the IMR 8208 XBR. It looks like a near-perfect match for the Palma-class bullets. The velocity is great, it appears the ES will be very low, and 8208 XBR packs more densely than Varget so you won’t have to run compressed loads.
Our most important discovery was that both 8208 XBR and H4895 offered significant velocity gains over Varget, at least in this rifle. It looks like 8208 XBR can run 2990 fps in this gun without pressure issues, while H4895 may top 3000 fps. Varget struggled to get much past 2900 fps.
IMPORTANT WARNING: The stated max load for IMR 8208 XBR with a Sierra 155gr HPBT was 45.3 grains, while the stated max load for H4895 (same bullet) was 46.0 grains. Note that, in this rifle, which has a tight 0.298″ Palma bore, we hit pressure limits well before reaching Hodgdon’s “book max.” Read that again carefully folks. Our 44.0 grain “practical max” for 8208 XBR was a FULL GRAIN less than the stated max load with a Sierra 155-grainer. Likewise we started getting stiff bolt lift at 44.3 grains of H4895 — a long way from the 46.0 grain stated max. So, the combination of a different bullet, and a tighter-than-normal bore made a significant difference in pressures. This is why, if you change ANY component in a load recipe you MUST start low for safety. And never assume that a factory “Max Load” is safe or “conservative”.
Similar Posts:
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- Yes Both Velocity and Pressure Can Vary with Primer Choice
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Thanks for the reports. Be interesting to try some of that new propellant for Palma shooting… once I’ve located some.
My experience today was similar. Conditions in San Diego were 80° and windy. Two five-shot groups of Lapua .308 brass with Wolf KVB-7 primers, Lapua 155 Moly Scenars and 44.0 grains 8208 from a 30″ McGowen-barreled Savage 12F produced 2915.1 and 2916.9 average with ES/SD 7.1/2.9 & 16.4/7.0 respectively. Groups were ~1.5″ at 300 yards.
These groups were validating load development done on 5 March. The only oddity is that the identical load, in the same weight-sorted brass, averaged 2935 with 14.3/5.8 at 55° during the previous series. I dropped 20 fps at 25° warmer. Number of rounds fired prior to those groups was similar and all components are from the same lot. I know it is said to be temperature insensitive, but I did not expect an inverse relationship.
These results are very similar to my experience with this powder. My load is 43.4 gr. in LC 84 brass using FGMM primers pushing 155 Lapua scenar out of a 24″ Krieger barrel. Extreme spread is 2898 to 2903 for 5 shots. Groups reflect the low SD. Shot it last week in a 600 yd. F-TR match and was very pleased. 44 gr. started to get sticky bolt lift. Hope it is as temp insensitive as they say.
Test like this are of little value.
Shooting groups while testing will greatly increase the value of an article like this. Otherwise your just selling a new powder.
Phase 1 of testing was to establish max velocities and pressure limits efficiently with low round count. We have proceeded to do accuracy testing at 100/200 yards. It appears that 43.2 and 44.0 are both promising, but this powder has a wide accuracy window. Readers will need to do further work for their own rifles. But we did try to establish low/high load points for the 155.5 Berger in a Palma gun.
Request loading tables for IME 8208 in different calibers Thanks Don
Thanks for the article. I tried and have been very happy with IMR-8208 for my Palma rifle. My accuracy load turned out to be 44.0 gr with a 155 gr. for 2965 fps with an average SD of 6 and ES of 17 for 2, 10 shot strings. This enabled me to shoot some excellent scores at 1000 yds. I also found that 42.5 gave very similar results for SD/ES at 2840 fps for an excellent 600 yd prone load.
Who is the maker of the front rest in the picture ?
Editor: That is a SEB coaxial rest from http://www.SebRests.com . US Dealer is:
Ernie Bishop
Gillete, WY 82716
ernieemily [at] yahoo.com
307-257-7431
Hi I am hoping you may be able to assist. I have a 308 Sako and a 3006 FN Sauer rifle. I have been using ADI 8202 Benchmark powder for reloading my 308 ammunition.
I have been using Sierra 30 cal 308 dia 180 gr hpbt match 2220 bullets.
I was able to find reloading data for the “ Bench Mark 8208 .308″ 2.800″ 36.0 2,340 fps 51,600 PSI 40.0 2,497 fps 60,100 PS” powder.
Unfortunately, I cannot find any data for using the same powder and bullets for my 30 06 FN SAUER rifle.
Could you please recommend some reloading data options to use for the same powder and Sierra bullets.
If not recommended what alternative Powder would you recommend I use?
Your assistance will be greatly appreciated.
Inus