Double digit ES

[Wile E Coyote]

Has anyone else experienced this? A wide ES with Retumbo? Briefly, here's what I have and have done yet I still get extreme spreads of 30 or more; never in the single digits.

100 pc of Hornady brass divided into boxes of 20 with 1 to 4 firings through each lot. All cases were trimmed to the same length after the first firing and none has exceeded .010" over that length since then. After the first firing all the necks were turned to the same thickness, .013." Most needed only a partial turning to achieve this and any that needed more than about 80% are not included in the boxes in question. Flash holes were reamed to be uniform. And before reloading, the brass is cleaned with a tumbler and SS media.

I FL size to move the shoulder back .0015 to .002" and use a neck bushing to achieve a neck tension of no more than .002," usually a .307" or 308". I don't use the expander ball.

All reloadings have been 71 to 73 gn of Retumbo powder with 72.6 being the lowest ES (28) and has shown to be the most accurate without pressure signs.

CCI-250 primers and Berger 168 VLD Hunting bullets;the bullet seated .020 off the rifling. (Seating determined using a method written about by someone at Berger and posted elsewhere here on LRH.)

Bullets are sorted and seated as shown in Shawn Carlock's video so thet the OAL - may vary but the base to ogive dimension is within .001". The necks are brushed and lubed similarly too. After the first firing of the cases, concentricity is usually within .001" of both cases and assembled ammunition.

The rifle barrel is a Hart, 26" 1/9 twist and the remainder of the rifle has had all the customary squaring, truing, bedding ect. The rifle is a Remington 700 in 7mm RM.

I couple weekends ago, I shot the last of the batch where I has the ES of 28. I've reloaded 20 the other night and yesterday I fired 5 through the chrono (CED M2) and the ES of those 5 was 67. I stopped right there. Routine was my norm; 1 shot every 5 minutes or so after 2 foulers (not counted)

Now here I am trying to figure out what's going on so I could adjust but my head has cramped. Anyone have any ideas?

Thanks.

 

[rscott5028]

[...]
I FL size to move the shoulder back .0015 to .002" and use a neck bushing to achieve a neck tension of no more than .002," usually a .307" or 308". I don't use the expander ball.
[...]

It's my understanding that .303, .304, .307" all result in about the same neck tension.

But, .308" could be sufficiently less neck tension so as to cause your problem.

This could especially be an issue after springback and settling.

You might want to try stepping down .001" with your bushing.

-- richard

 

[Tikkamike]

It's my understanding that .303, .304, .307" all result in about the same neck tension.

But, .308" could be sufficiently less neck tension so as to cause your problem.

This could especially be an issue after springback and settling.

You might want to try stepping down .001" with your bushing.

-- richard

I dont like retumbo because it seemed pretty inconsistant when I tried it in my 300 rum. One thing that should help you is if you anneal the brass before you size it. it will bring all the brass back to the same state. It may not fix the problem but it should help considerably

 

[rscott5028]

Also, don't forget muzzle blast and other things can skew your chrony readings. If it groups well, try some at long range.

I'm not a fan of annealing unless you have a valid reason for it. ...which you may. In fact, I may need to do it with my 300WM load using 225 Hornady's and 230 OTMs. H1000 has been more cosistent MV while Retumbo gives me more MV and better groups.

My son fired these 2 shots at 953 yds last Sunday after an equally centered cold bore shot at 650 yds. These were 225 Hornady's on top of a compressed 79 grains of Retumbo at 2785 and 2794 fps.

 

[Tikkamike]

why are you not a fan? IMO its just one more step toward consistancy that is easy to do. But I would like to hear the argument against it.

 

[runshort]

Your experience with Retumbo and the Berger 168 sounds a lot like what I got into.
Your case prep and reloading routine sound pretty much like mine except we don't turn case necks. We did anneal cases after every second firing. We changed up brass and primer brands hoping that would help. I was never able to get ES under 40. We finally started load development with H1000 and found a load that worked with ES running around 14. The velocity also went down but the load was accurate and decided we could live with it. Dont know if this helps but good luck with the Retumbo.

 

[rscott5028]

why are you not a fan? IMO its just one more step toward consistancy that is easy to do. But I would like to hear the argument against it.

No argument against annealing when it's needed.

I prefer to use good brass, moderate cartridges, moderate loads, no turn neck, and no annealing as much as possible.

Like I mentioned, I've got a 300wm with Win brass and a stout load of Retumbo that could probably benefit in order to achieve more consistent neck sizing/tension for lower ES/SD on my MV.

On the other hand, I seriously doubt I'll ever need to anneal my 6br Lapua brass.

-- richard

 

[Wile E Coyote]

Only have a moment here to reply to comments thus far... in no particular order. Thanks for the input all

Regarding bushing selection: when I mention .308" or .307" bushing, those are the two I seem to use most often. I'm not set on any particular one and I could have worded that a little better. my fault. One thing I do differently and failed to mention is AFTER neck sizing. I measure the ID of the finished neck with a shopmade plug. After struggling to accurately measure the ID of the cases, a machinest friend made up a set of 'plugs' turned to .0005" increments. She made 6 for me for the .284 including .2835, .283, .2825, .282, and .2815. Fitting the tightest one without forcing is how I determine a .002" or a .0015" neck tension. Don't know if this is correct but this is how I do it.

Regarding H1000: It may be on the horizon but I have 5 or 6 pounds of Retumbo yet to burn up.

As for annealing: It's on the radar but resource$ are not there at the moment.

and lastly, the muzzle blast affecting the chrono result: I made a plywood blast shield that is placed between the gun and the chrono. I set the chrono at the max distance the cables will allow and set the blast shield about mid way. the plywood is 30" wide by 40" tall (I had the piece cut to that dimension already) with a 3" wide x 8" tall hold cut in the center. The panel is canted away from the gun at about a 45 deg. angle with 2x3 legs to support it. I learned this trick with my old Shooting chrony Beta Master chrony. That unit was actually accurate BUT very succeptable to outside influences.

Again, thanks

 

[rscott5028]

Only have a moment here to reply to comments thus far... in no particular order. Thanks for the input all

Regarding bushing selection: when I mention .308" or .307" bushing, those are the two I seem to use most often. I'm not set on any particular one and I could have worded that a little better. my fault. One thing I do differently and failed to mention is AFTER neck sizing. I measure the ID of the finished neck with a shopmade plug. After struggling to accurately measure the ID of the cases, a machinest friend made up a set of 'plugs' turned to .0005" increments. She made 6 for me for the .284 including .2835, .283, .2825, .282, and .2815. Fitting the tightest one without forcing is how I determine a .002" or a .0015" neck tension. Don't know if this is correct but this is how I do it.

Regarding H1000: It may be on the horizon but I have 5 or 6 pounds of Retumbo yet to burn up.

As for annealing: It's on the radar but resource$ are not there at the moment.

and lastly, the muzzle blast affecting the chrono result: I made a plywood blast shield that is placed between the gun and the chrono. I set the chrono at the max distance the cables will allow and set the blast shield about mid way. the plywood is 30" wide by 40" tall (I had the piece cut to that dimension already) with a 3" wide x 8" tall hold cut in the center. The panel is canted away from the gun at about a 45 deg. angle with 2x3 legs to support it. I learned this trick with my old Shooting chrony Beta Master chrony. That unit was actually accurate BUT very succeptable to outside influences.

Again, thanks

I misunderstood the OP.

I assumed 30 cal with a measured ID after sizing = .308". That would be a problem.

Sorry.
-- richard

 

[Bart B]

2 digit extreme spreads are not necessarily bad for accuracy. For example a Berger 7mm 168 gr Match Grade VLD Hunting bullet leaving at an average velocity of 2785 fps with a 30 fps spread will have vertical shot stringing at 1000 yards of about 6 to 7 inches if all the bullets leave at the same angle and are perfectly balanced and shaped. As bullets ain't all perfect, the shot stringing will be a couple inches more from the very small spread in BC.

Most barrels producing best accuracy have their bullets leaving just before the muzzle axis reaches its highest angle up from the barrel whipping when its fired. This lets those with faster muzzle velocity leave when the angle's a bit lower than slower ones that leave later. This is called positive compensation and typically masks vertical shot stringing at the longer ranges.

You might try some Wolff primers; a favorite of competitors. Magnum primers oft times do not produce best accuracy with belted cases. My 30 caliber mag's shot more accurate with milder primers than hot ones. And when all else is equal, different lots of primers will produce different levels of accuracy.

Ask someone else to shoot your bullets through a chronograph's screens. If their spread's lower than what you get, you're not holding the rifle against your body with the same pressure for each shot. I've been a victim of that problem. It can easily cause a 20 to 40 fps spread in muzzle velocity.

 

[Joe King]

Sounds like the only things you have left to try is different primers and play with your seating depth again if you find a primer that works better. But you may also just have to live with it, I've alsways heard Retumbo is known for wide SD and ES

 

[Tumbleweed]

I've been fighting an ES problem working up a load for a friend in 300Win. We're using 215 hybrids and we started with Retumbo. First of all the load data was way off for Retumbo and we got a sticky bolt at relatively low velocity. As in everything else I've loaded Retumbo for, it had wide ES numbers too. Switched to H1000 and did a lot of load testing. In this rifle it did not like H1000 either, never had any ES's under 17fps consistently. Could not find the .5 to .75 moa accuracy we were after either. Out of desperation and wanting to stay with Hodgdon's extreme powders we tried H4831SC. I quickly saw the ES shrink way down and accuracy immediately improved. I realized that we had 3 firings on most of the cases so I annealed as well. Picky as I am, it wasn't quite good enough. I switched from Fed215GM primers to CCI 250's and shot a .5 moa group at 300 yards running 2800 fps with very low ES. Bumped up the load .5 grains to max for this rifle and shot 3 with an average of 2834fps and an ES of 6. The biggest contributor to the ES problem in this case was definately the powder. This week I will stretch to 750 yards and see how she does. You may just need to get away from Retumbo and find what your rifle likes.

 

[Joe King]

you might look at RL22, I'm working up a load right now with Matrix 168 VLD that so far is well under 1/2" at 100. 65gr and both REm 9 1/2m and Fed 215M where .3 seated 0.020 off the lands I'm going to use the 9 1/2m's for now since I have a bunch, and next is to try different seating depths, to see what it likes.

 

[Bart B]

In talking with folks shooting belted 28 and 30 caliber magnums in long range matches, every single one of them mentioned they had problems getting good accuracy with the slower powders and hottest primers that shot bullets out the fastest. When they used powders in the 4350 to 4831 range and milder primers, they got much better accuracy.

I had the same issues and quickly learned that winning the race to the target wasn't nearly as important as getting all the bullets to arrive there at the same place was. That works best for paper punching and I doubt any animal nor hunter will see any significant difference between bullets arriving on targets a long ways away a hundred fps slower.