IMR 8208XBR

44marty · Posted: Mon May 24, 2010 9:20 am Post subject: Re: IMR 8208XBR

Another interesting target.
After the OCW test for IMR8208 powder, I shot a 25 round group with a mix of my three go-to loads. I moved 3/8 MOA up and right, then let fly. These were 39gr Blitz Kings loaded with my OCW charges of IMR4064(3rounds), IMR4895(5rds), and IMR3031(17rds). I feel good that I can pick up any of these and demolish a varmint at any range I'm likely to shoot.
The 7 rounds inside the black outline were "foulers" shot earlier.
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44marty · Posted: Mon May 24, 2010 9:21 am Post subject: Re: IMR 8208XBR

Hope it worked that time . . .

I must be a REALLY OLD dog.

slimjim · Posted: Mon May 24, 2010 4:53 pm Post subject: Re: IMR 8208XBR

Ok, after all the pictures of the groups, I think I need to see a picture of this rifle! What was the time interval on your shots?

44marty · Posted: Mon May 24, 2010 8:10 pm Post subject: Re: IMR 8208XBR

I'll have to take a picture for you, Slimjim. It's an off-the-shelf Ruger 77 Mark II stainless steel varmint rifle, standard bull barrel and laminated benchrest style stock. Lots of clearance between the stock and free floating barrel.
Barrel heating doesn't seem to be an issue - groups don't really grow much. The 25 round group in the previous photo was shot with very little cooling.

8208 OCW results from today:
26.0 gr powder was both the OCW choice and the tightest 3-round group, at 5/16" center-to-center (125 yds). The one round that registered was 3697 fps

The clouds rolled in again just after I started shooting, but I did get some chrono results:
25.8 gr - - - - - - - - - 3675 fps, 3686 fps
26.0 gr - - - - - - - - - 3697 fps
26.4 gr - - - - - - - - - 3808 fps

No rounds registered for the 25.6 gr or 26.2 gr loads.

The primer cratering issue did not appear with charges 26.0 gr or less. At 26.2 gr it was apparent, but minimal. The 26.4 gr (and higher rounds in the earlier post) all showed cratering as in the photo.
This surprises me with the 8208. Pushing the same bullet faster with IMR 3031, 4895, and 4064 doesn't show the same degree of primer deformation.

Again, bullets were 39 gr Sierra blitz king, neck-sized Win brass, and
Rem 7 1/2 BR primers.

slimjim · Posted: Tue May 25, 2010 4:42 am Post subject: Re: IMR 8208XBR

I'm jealous! It typically takes me two months to accomplish what you've done in a couple of days. Very predictable accuracy. Some day I'll have a rifle like that. Great shooting with a great (unseen) rifle!

44marty · Posted: Tue May 25, 2010 3:11 pm Post subject: Re: IMR 8208XBR

slimjim wrote:

Ok, after all the pictures of the groups, I think I need to see a picture of this rifle! What was the time interval on your shots?

The 25-round group was fired last thing before leaving. Timing: five shot strings at 20 to 30 second intervals with about 1 to 2 minutes between the five strings. I wanted to see how much the group would grow with barrel heating. NOT MUCH !!!

During the OCW testing, I would feel the barrel and wait to shoot until it was only slightly warm. (Tried to wait 1 to 2 minutes between rounds, but cheated some.) I cleaned the barrel after each 10 rounds and fired a fouler before continuing.

I'll post photos in a minute - - have to grab them off my camera . . . .

44marty · Posted: Tue May 25, 2010 3:20 pm Post subject: Re: IMR 8208XBR

The scope is a Barska 10X - 40X 50mm

The rifle is stock off-the-shelf

44marty · Posted: Tue May 25, 2010 3:21 pm Post subject: Re: IMR 8208XBR

Cool . . . You really CAN teach an old dog new tricks!

44marty · Posted: Tue May 25, 2010 3:26 pm Post subject: Re: IMR 8208XBR

PS - That beanbag is what I am using as a rest. I set up the gun at the bench as shown here in the photos.

slimjim · Posted: Wed May 26, 2010 2:17 am Post subject: Re: IMR 8208XBR

44, that is one beautiful rifle!! I love the laminated wood stocks! Thanks for taking the time to take and post the pictures.

44marty · Posted: Wed May 26, 2010 7:47 am Post subject: Re: IMR 8208XBR

Yeah, I love this rifle. Can you believe that someone bought this rifle and then sold it to Datillio's gun shop (S. Burlington, VT) after firing only 16 rounds? He saved me a few hundred bucks.

Next up - comparing Frozen with normal ammo in IMR 4895 and IMR 3031.

Then, accuracy comparison between OCW loads of IMR 3031, 4895, and 8208.

And then, finally, more testing with my 300 WBY mag. Looking forward to some real recoil. I don't care for the barrel cooling time, though. I really get spoiled shooting the 204.

Grumulkin · Posted: Wed May 26, 2010 2:50 pm Post subject: Re: IMR 8208XBR

I've got to shoot some more with IMR 8208XBR and even got velocity data! The pressure is not high; I could push the load further but am leaving it as is because accuracy is best there. This 3 shot group was shot at 200 yards.

I've found this powder to be very clean burning and it meters very well. In fact, though I usually weigh all powder charges individually, after getting a couple dozen charges that were right on fresh from the powder measure, I started just throwing charges which makes reloading with this powder quite a bit faster than with most of the others I use.

Using the Point Blank software with a knowledge of the ballistic coefficient of the bullet and drop data, I calculated the velocity to be about 2,900 fps. That turned out to be close; measured velocity over an average of 11 shots came out to 2,850 fps.

It was a gut wrenching decision but I decided the target has been patched enough and am going to discard it.

shrpshtrjoe · Posted: Wed May 26, 2010 3:23 pm Post subject: Re: IMR 8208XBR

I might have to try this powder for the .223

44marty · Posted: Wed May 26, 2010 5:04 pm Post subject: Re: IMR 8208XBR

Well, that's a sweet 200 yd group, grumulkin. Yes, the 8208 meters like a dream.

Follow-up comparison to the 8208 "Frozen ammo" test this afternoon is too small a sample, but the results are just about what I expected.

IMR 3031 FROZEN at -10 F
3872 fps
3868 fps

IMR 3031 at 70 F
3888
3864

IMR 4895 FROZEN at -10 F
3765
3746

IMR 4895 at 70 F
3812
3832

Both the 3031 and 4895 (from the same batch of reloads) have averaged right around 40 fps faster than today's 70 F results. Today I was shooting offhand, possibly at an angle to the chrono.

Not that it matters for the comparison, but:
neck-sized Nosler brass, CCI 450 primers, 39 gr Sierra blitz king bullets, .204 Ruger M 77 Mark II

slimjim · Posted: Wed May 26, 2010 6:20 pm Post subject: Re: IMR 8208XBR

Grumulkin wrote:

It was a gut wrenching decision but I decided the target has been patched enough and am going to discard it.

At least you have the photographic record!