IMR7383 and the 300 Win Mag

[Sur5er]

Had the opportunity to start to work up some loads with IMR7383 for my 300 Win Mag and wanted to share my findings. I know there can be some pressure issues with the triple base powder, so please take the info as info and not gospel when it comes to your rifle or your loads.

When fired it smells of ammonia...........badly! The range was in the mid 80's, no wind, so-so humidity and I was shooting from overhead cover. The smell permeated my shirts. At first, I thought I forgot to use the underarm poof-poof but then I got a wiff of the sleeves. It brought tears to my eyes! That being said, it was the ony drawback I have run into:bigsmyl2: .............so far!

OK, all data was collected using my Remington 700 XCR, Harris bipod, PACT Chrono @ 15', Win once fired cases, CCI Large Rifle (NON Magnum) Primers and fired from a bench. After playing around with some 147FMJ, 168HPBT, and 175 FMJ Match bullets to get a feel for the powder, it seems that this lot of 7383 likes heavier bullets in the 300 Win Mag although I did get decent velocity, 3050+/- FPS, with the 168 and 175 bullets.

I used a Sierra 190gr SPBT seated to nominal max OAL and not crimped. i.e the canelure was exposed. After working up from a starting load of 60gr of IMR7383 I am now at 69gr and that provided an average of velocity 2880 with ES of 76FPS. Groups are OK, nothing to write home about, but not bad either There are no signs of pressure so my next step will be to seat the bullets to the canelure and apply a medium-heavy crimp.

Keep you posted.

[Ben]

Very Interesting, please keep us posted.

Have you done any work with the 30/06 with IMR 7383 ?

Ben

[Lead Fred]

I just switched from using IMR-4350 in my 06 for years to H4350.
Loading 180 A-Max, Im doing 2990fps at 58 grains with a inch group, and cutting the same holes when I backed it down two grains to 56, got 2912fps.

This is up from 2880 with IMR, and Ive the best groups ever

[Shiloh]

I just switched from using IMR-4350 in my 06 for years to H4350.
Loading 180 A-Max, Im doing 2990fps at 58 grains with a inch group, and cutting the same holes when I backed it down two grains to 56, got 2912fps.

This is up from 2880 with IMR, and Ive the best groups ever

I love it when somebody finally gets it all put together and discovers the magic.
Good for you!!

Shiloh

[Sur5er]

It may be a week or two. I just dropped the rifle off at my friends shop to have one of Holland's Radial Baffle QD Muzzle Brakes installed. It'll be nice to be able to get back on target again!

[Ricochet]

I use it in .300 Weatherby, .30-06, 8mm Mauser, 7.62x54R, 7.5 Swiss and .22-250. Tried it in .45-70 and quickly abandoned that idea. There's been much written about 7383 on this board. Search the archives.

[Jim]

I've used this weird stuff in all kinds of calibers. I even figured out a load for .45 Colt.
Ric, I've been using it in several .45-70 loads and it seems to be working for me.

[madsenshooter]

It may be a week or two. I just dropped the rifle off at my friends shop to have one of Holland's Radial Baffle QD Muzzle Brakes installed. It'll be nice to be able to get back on target again!

Let us know how the muzzy effects your zero, over the years I've read articles about rifles with removable brakes and their change of zero when the brake was removed and/or replaced.

[Ricochet]

Ric, I've been using it in several .45-70 loads and it seems to be working for me.
The unburned powder jammed up my 1895 Marlin.

[Jim]

When I first started using this stuff, I went through all kinds of problems. One thing I found out was, you gotta run the load density up high enough to get mildly flattened primers before it starts to burn completely. Kinda' like, 820, it likes pressure. What's dangerous about it is, you can sure 'nough load too much and the pressure will spike like a rocket. Years ago, I ruined a Sharps repro buffalo rifle 'cause I didn't know what I was doin'.

[Sur5er]

Jim,

With 69gr of powder filling the case just below the bottom of the neck, the primers are still rounded. The bore has no unburned powder but it is definitely a much dirtier burning mix than I have used. I anticipate that seating lower and crimping will improve the burn, raise the pressure a tad and may be just what I'm looking for as far as velocity and accuracy. Time will tell.

[Jim]

That's the trick. Bring it up a grain at a time and watch it. Eventually, it'll start burning and acting right.

[Sur5er]

I'll let you know what happens after I get my thunderstick back.

[Ricochet]

Be careful about compressing it. That makes the pressure rise very quickly, probably because of crushing powder kernels. (You won't safely get up to full capacity loads in your .300 WM anyway.)

[Sur5er]

Be careful about compressing it. That makes the pressure rise very quickly, probably because of crushing powder kernels. (You won't safely get up to full capacity loads in your .300 WM anyway.)

That's what I figured too. The Hornady 190gr SPBT canelure sits about .250" above the top of the case lip when loaded to MOAL. There should be minimal compression of the powder. Since the 700 is a bolt action, I'm just neck sizing the brass and monitoring for case stretch and any indications of case head separation. I'll be very happy if I can get <MOA in the 2950FPS range.
One problem I have noted is the inconsistancy of the Dillon powder measure I'm using. This is from a first generation Dillon that had the manual push handle bar that I've adapted for rifle use. I have an XL650 for the pistol. It is normal to have .5 grain variation of weight from throw to throw. The IMR7383 kernels are large and don't like being cut or squeezed. If this works out, I may have to opt for one of those digital powder measure and scale combos. Yeah, more toys!

[Sur5er]

Well I may finally have my XCR back for the weekend. Weather permitting, we'll see how well the Holland Radial Brake tames the muzzle jump from a bench rest position. BTW, the size Holland brake required for the Rem XCR in 300 Win Mag is ¾”X28, not the standard 5/8”X28 used on most .308 muzzles. It will be nice to have the scope looking in the same county as the target! I also want to experiment with the placement of the Harris bipod on front and rear sling points and just using rolled carpet under the stock. Even with a free floated barrel, leaning on the stock can cause the barrel to contact the channel of the stock and change POI. I glass bedded my XCR and the barrel is free floated .010” from the front of the recoil lug forward; the tang has also been set in glass. The XCR is quite comfortable to shoot from the bench, even without the muzzle brake. I have to give a lot of credit to the designers of the XCR’s stock and recoil pad, for a mass produced factory rifle, it ain’t too bad. Now if they would only use Jewell triggers the out of the box XCR would really be the “cat’s ass”

[Sur5er]

It's back and what a difference in the felt recoil! I swear the kick is less than a .223 bolt action and the muzzle jump is almost non-existent. Now I have to sort out some other issues.

Rifle/Scope: Rem 700 XCR 300 Win Mag; Konus 8.5X32 AO scope mounted in 30mm Leupold hardware; action bedded and barrel free floating from recoil lug forward, Holland Radial Baffle muzzle brake.

Load: 70gr IMR 7383 Sierra, 190gr BTSP crimped at cannelure, CCI 200 primer.

The first is I'm not sure the scope is holding a constant zero. All the screws and rings are tight, the rifle action is solidly bedded and action screws are tight. The adjustments will move the POI around, but the grouping sucks. At 50 yds, I'm almost ashamed to admit this, the group is more than 1.5". Sometimes the rounds will hit on top of each other and sometimes they fly. If it were the new muzzle brake, I'd have flyers all the time and there would be contact indications on the brake. The other thing I noticed is a tendency for the image to get fuzzy after a few shots. By turning the parallax adjustment it comes back into focus. This may be the main problem. If anyone else is using a Konus 8.5X32 I'd be real interested to hear your thoughts.

Secondly, I don't know if the new load is exacerbating the lousy grouping, but I know I shoot better than this. The 70gr seem to be real close to the ideal charge weight for the 190 Sierra. The fouling was substantially less than with the 65 gr load and the primers still look good. No I didn't bring the chrono this time. Some dope:oops: managed to stuff the case behind a load of lumber and other assorted crap. I've already made a note to myself.

I also shot my .308 using both mil surp FMJ and 147gr FMJBT over 47gr of IMR4064. The 3X9 Redfield kept the groups a lot tighter than the 300 Win, but nothing I'd be willing to pose with!

I think my first course of action will be to send the scope back and have them look it over.

More info as it becomes available.

[Sur5er]

Just a quick follow-up. I sent the scope back to KONUS in Miami, FL. last week. They received it on Friday along with a letter explaining that I felt the scope wasn't holding a zero. Got an email from them today: "New scope went out in UPS today, you should have it by Friday or Monday". I called to try and find out what happened to the scope and was told that if I thought the scope wasn't holding a zero, that was good enough for them and all they needed from me! They don't check them out in CONUS, they just send 'em back to Italy along with my notes.
"WELL PICK ME UP AND DUST ME OFF"! That's what I call customer service. I don't know of ANY other firm that would that for you.

No, I don't have a vested interest in KONUS or affiliated with them in any way................but maybe I should!

[Sur5er]

Got the Konus scope installed, colomated, and took the thunderstick to the range. Pretty good velocity results from both the IMR7383 and WC860 with 190gr BTSP.

IMR7383. Seems the higher the pressure, the less the ammonia smell and fouling. I used 71.5gr IMR7383 and 190gr BTSP which yielded an average 2862FPS with a ES of 34 for three rounds. Chrono was set up 15' from muzzle. Bullet was seated to cannelure and crimped. Before moving up in charge, I'll try seating the bullet out until it is just short of the lands. The bullet has about 1/4" jump to and may be causing a drop in pressure as well as imparting some wobble. This load is a fairly clean burn but I may try to move up to 75gr about .5 grains at time if seating the bullet out further doesn't help.The 50yd group was one ragged hole and 2" above point of aim. 100 yd group was off the point of aim by 24" left and 14" high. I can understand a verticle change in impact, but 24" laterally???????????? Something be very wrong.

85gr WC860 and 190gr BTSP was 2655FPS with ES of 15FPS. Bullet seated to cannelure and crimped. Good clean load, not compressed. Can probably go another 2-3 grains before compressing the charge. I found that if I touch the loaded case to my Lyman tumbler, the vibration will settle the charge quite nicely! Group was, as my Basic Traning Sergeant would say, a "Ballentine" shot group that was 1/2" from edge to edge @50yds.

I will try seating the bullets out further before I do anything else. If that doesn't work I will move my Leupold V-III 6.5X20 from my .243 to the 300 Mag just to eliminate any external factors.

[Ricochet]

IMR7383. Seems the higher the pressure, the less the ammonia smell and fouling.
I agree. But watch out, it does go up quickly as you approach the limits.

[Sur5er]

For those of you that have been following this thread on IMR 7383, I believe I have found, most, if not all of the problems I have encountered trying to find "the" load for my 300 Win Mag.

I remounted the new M30 8.5X32 scope Konus sent me under warranty. Not a bad scope, but not in the Leupold Vari X III league either. OK, on with the findings.

The 190gr Hornady BTSP (J bullet) has a cannelure and I had previously tried the same powder loadings with a an OAL of 3.362, heavy crimp in the cannelure. The velocity was somewhere in the 2700-2800FPS area....................I'm still trying to find some of the holes! I've had better groups with a 12ga and 00 at 50yds!

As many of you know, IMR 7383 can be mighty quirky when working up loads. The trouble seems to be that the powder burns so slowly that the bullet is moving down the tube long before all the powder can be efficiently burned. The result is low velocity, horrible grouping, dirty residue and an ammonia smell that could fetch the EPA!

I loaded up a batch of rounds with 72, 73, 74, and 75 gr of IMR 7383 under a Hornady 190gr BTSP and a CCI LR primer. This batch was loaded to an OAL of 3.4870". This places the bullet right at the start of the rifling in MY RIFLE and requires higher pressure to start it on its way. The higher pressure will also result in a cleaner, more uniform burn of the powder. Yesterday, I did some pressure testing, all anecdotal, and decided that 73gr of IMR7383 was my max load for this particular set of components.

The 72 gr was OK but only measured in the 2850 FPS range, 73gr put me over 100fps faster and just slight flatening of the primers; 74gr resulted in mildly sticky extraction and 75gr cratered primers and caused very hard extraction. I only fired 2 rds each of the 74gr and 75gr loadings to verify that the loads were too hot.


Here is the data from my PACT Chrono for today (+10F, 0 wind 0900 local, screens 15' from muzzle): Glass bedded Rem 700 XCR, Konus 8.5X32, Holland muzzle brake, Harris Bipod mounted on rear sling swivle. I left the rifle and rounds out for 30 min to acclimate while I set up the target and chrono. Six rounds were fired from the bench, thru the chrono screens and into a 100 yd target. Last three rounds fired measured 1"X1/2", and zeroed 2 1/2" high.

2929
2994
2955
2967
2986
2936
SD 29
ES 64.7

AVG 2961

Fouling was almost non-existant and the ammonia smell wasn't really that noticible either! A SD of 29 along with the MOA group made my day.

My cursory findings are that a heavy crimp doesn't have the required effect to restrain the bullet while the slow burning powder gets up steam. The bullet then has to make a minimum .125" jump to the rifling and now the volume suddenly expands, pressure drops, pressure builds, bullet moves again, volume expands and you don't get an efficient burn of the powder. Not to mention that the bullet has a pretty good chance of not entering the barrel squarely.

My recommendation for IMR7383 would be to seat your bullets at or just shy of the rifling and work the loads up from there.

[Multigunner]

The US Army recently ordered 50 million dollars worth of .300 Winchester Magnum cartridges at $1.60 per round.
I will be watching for the reaction when cheap .300 Magnum milsurp ammo starts showing up about ten years from now. We can expect a greater interest in the chambering then no doubt with many tired .30/06 barrels being rechambered and bolt faces opened up to put new life in them.

[wiljen]

Just a word of caution, as temperatures rise above the 10F you tested at, so will the pressure produced by that load and you may find that at 80-90F this summer that 71gr is a maximum. 7383 does show some temp sensitivity so remember to rework your load when dealing with significant temperature changes.

[Sur5er]

Just a word of caution.............................

Words of caution are always accepted and respected.

[Sur5er]

Just a word of caution, as temperatures rise above the 10F you tested at, so will the pressure produced by that load and you may find that at 80-90F this summer that 71gr is a maximum. 7383 does show some temp sensitivity so remember to rework your load when dealing with significant temperature changes.

Well founded advice! The 73gr of IMR 7383 is too hot for the warmer weather. Hard extraction and flowing primers. I would surmise that 71gr would be the max load in temps above freezing and would even go so far as to say that you may have to adjust when the temps get over 90F. OTOH, the WC860 loads don't seem to have the same temperature sensitivity. 90gr of WC860 under a Sierra 190gr BTHP Match give better than MOA at 300 yds and no signs of pressure.

[wiljen]

You found the same thing I did. 7383 is more temperature sensitive than most commercial powders. I think it ranks right next to H450 as the most temperature picky stuff I've used.

[StarMetal]

If you want to try a better powder then that in that mag cartridge try the new out surplus 867. Wiljen Wideners has it and I've bought and have been fooling with it. I'm impressed and might buy them out.

[onceabull]

for those west of the Rockies,there is a gent in Tooele,Ut.advertising that he has 59,268 Lb of 867 and 872 for sale... Says $4.50 /Lb.. no mention of how many Lbs of ea.,or whether or not the price is only applicable to the whole lot..does state the obvious--"Shipping not included"..call 949-645-3815 (ph # as stated in the ad) maybeso the ultimate "group buy" Onceabull

[StarMetal]

for those west of the Rockies,there is a gent in Tooele,Ut.advertising that he has 59,268 Lb of 867 and 872 for sale... Says $4.50 /Lb.. no mention of how many Lbs of ea.,or whether or not the price is only applicable to the whole lot..does state the obvious--"Shipping not included"..call 949-645-3815 (ph # as stated in the ad) maybeso the ultimate "group buy" Onceabull

I'm really amazed as how fast this powder is for it being used in 50 cal and 20mm. It burns absolutely clean. It's suppose to be new, not a pull down. I'm curious about the 872 because the two are claimed to be very very close and use the same load data.