.338 Win Mag/250 TSX low velocity

[Tac Beard]

I'm seeing velocities way too low with the following loads in my 26" M70:

Hornady .338WM brass, once fired
Barnes 250 TSX @ 3.320"
72.0 gr AA Magpro
CCI 250
Book velocity 2619 in a 24" barrel, Actual velocity 2407-2458 over 10 shots in a 26" barrel.

This is a max load in the Barnes book. I worked up very carefully, as I'm stuck with different primers than Barnes used-- I just can't find Fed 215s anywhere. I'm also using different brass (book lists W-W) but I can't see that making a 200-fps difference.

I've had some great success with Magpro in the past; but it's cold-ish here in AK, so I switched to the less temperature sensitive H4831sc, with the following loads using the same bullets, brass, and primers:

Bullets seated to 3.370 (.030" off lands, and more room for powder)
65.0gr -- 2439 avg
65.5gr -- 2456 avg
66.0gr -- 2463 avg
66.5gr -- 2480 avg -Very nice one hole group
67.0gr -- 2481 avg
67.5gr -- 2417 avg--:banghead: Yes, really. I guess that's the pressure limit? I don't see any other signs.

I'm really annoyed that I can't even reach the book's 24" barrel velocities with my 26" barrel. All the primers have a slight ridge around the indent (this rifle does that with all loads), but there's no flattening at all, and no hint of stickiness in the bolt.

I fully realize that I don't "need" any more velocity. I know this load will kill moose and brown bears just fine under 200 yards. But this is a .338 Win Mag, if I wanted a 338-06 I would have bought one!

It's probably time to switch to A-Frames at this point and give up on these bullets that I know are too long for the .338WM case. But Barnes got MUCH better numbers, and I really want to at least match them.

Any suggestions?

 

[Andrew Leigh]

Nope, you are far from the pressure limit in my opinion. Feeding in your 66.5gr load (assuming the standard H2O case capacity of 86.0gr and that indeed your barrel is 26" as measured from bolt face to crown and not taken from the spec sheet) Then this load is probably running at 43 000psi according to QL.

Something looks odd though. You velocities look rather overstated for the powder burn rate of the Magpro. Your best load (65.5gr) looks like it is 130fps faster than what would be expected from the Magpro.

To get QL to calibrate to your shot velocities required a significant change in the original powder burn rate which makes me wary. So there could be a couple of things causing this;
- Internal case volume of your cases is less than specification.
- Barrel length different to what was stated.
- There were issues with your Chrony.
- The powder batch is indeed faster than specification.

Given the existing components you should be able to get 72.2gr into the case to give 2 713fps at the muzzle and about 2 704fps at the Chrony if 5 yds away. I would load this only if I can confirm your internal case volume of fire formed cases and your measured barrel length. ELSE DO NOT LOAD

 

[Tac Beard]

Thanks Andrew, I really appreciate the info.

To be clear, only the original load that I listed of 72.0 gr was with Magpro, and it was giving me 2407-2458 as compared to Barnes' listed 2619 for that load.

All the loads listed from 65.0-67.5 gr were with H4831SC.

72gr Mapgro left a fair amount of room in the case; H4831SC was starting to crunch very slightly at 67.5gr. I believe I could compress a couple more grains in the case, but when velocities dropped off so much at 67.5 compared to 67.0, I decided to bag it for the day and regroup.

I'll measure the barrel today to be 100% sure on the length.

These Hornady cases seem pretty roomy compared to others, but I'll do a capacity check as well.

Assuming everything checks out, do you think it would be wise to continue increasing charge weight with H4831SC? Given what I'm seeing so far, I have my wonders about ever reaching my goal of 2650-2700.

Thanks again.

 

[ArchAngelCD]

Most, if not all load data shown in manuals will have higher velocities than any of us can achieve. They do their testing under laboratory conditions we can't duplicate.

Best I can tell you, go with the published load data. Don't load below the starting charge weights and work up to the Max watching for pressure signs. Usually you will find an accurate load before you hit the Max, I go with that.

 

[Tac Beard]

Accuracy is no problem. As stated I had a couple excellent groups, and no bad ones.

The problem is that my velocities are 200 fps below standard, accepted velocities for this caliber. I don't want to push the envelope or break new ground, I just will not accept 338-06 performance from my 338WM.

I should add that my Chrony seems to be accurate. It's fairly new, and other loads give readings that are pretty much in line with expectations.

 

[Andrew Leigh]

I have remodelled with the actual powder H4831 SC.

Much closer now, the results are more or less as per expected. Generally powder burn rates will tend to be lower than spec as an additional safety factor. Yours is the case.

With the 66.5gr load believe it or not you are very close to optimum barrel time OBT which would explain your good group. The node closest for a 26" barrel would be 1.416ms and your calculated barrel time on your load was 1.439ms The load of 67.3gr should have been on the money.

To get to the next OBT accuracy node would require a charge of 70.0gr which will result in a slightly compressed load, 104.7%. Do not change anything else not COL, nothing else. This should deliver 2 626fps at the muzzle at a pressure of 55 900psi.

Lets check those two measurements and remodel before loading.

 

[Tac Beard]

Thanks Andrew, that really helps.

I just wet-checked 4 of my cases. They measured 86.0, 86.7, 87.5, and 88.2. I guess I'll need to sort these things before loading more... Should have done that before, I suppose. What do you think?

My barrel is indeed 26", at least as near as I can measure, guesstimating the exact location of the bolt face.

 

[Andrew Leigh]

I just wet-checked 4 of my cases. They measured 86.0, 86.7, 87.5, and 88.2. I guess I'll need to sort these things before loading more... Should have done that before, I suppose. What do you think?

More spread than I would like. At 86.0gr (standard) H2O you measure 2 626fps, increasing the volume to 88.2gr. H2O drops the velocity to 2 587fps too much in my books.

My barrel is indeed 26", at least as near as I can measure, guesstimating the exact location of the bolt face.

Remove your firing pin, close the bolt and place a rigid cleaning rod down the barrel. mark where the crown is, remove the rod and measure.

 

[jmr40]

Have you checked this rifle's speeds with other loads? I've seen individual rifles shoot much slower than expected. I own 3 different 30-06 rifles. The best rifle is always within 20-30 fps of what the manuals say I should be getting. Which is expected with the shorter 22" barrel. Another rifle is consistently 25-50 fps slower than the 1st and the 3rd is 75-100 fps slower. It depends on the individual load.

A friend and I were shooting at the range a couple of years ago when he tried my chronograph and got MUCH slower speeds than expected. When we tried the same loads in my rifle they were 130 fps faster than from his rifle and right where they should have been according to the load data. Both with 22" barrels.

Having an individual barrel be 100fps slower would be rare, but not unheard of. Somewhere around 50 fps difference between barrels of equal lengths would be pretty common.

 

[Tac Beard]

jmr40-- I've checked other loads with this barrel and it usually runs slightly slow, but nowhere near what I've seen with this load. For example, my 225 TSX load chronos around 2720-2740, which is a little lower than book velocity for that charge weight but close enough that I haven't tried to mess with it.

Andrew-- My barrel measures 25.875". Close enough?

Just finished wet checking this lot of cases; most of them hold between 86.5-86.9 grains. Do you think that calls for a change in charge weight, or would you stick with 70.0?

 

[Andrew Leigh]

Andrew-- My barrel measures 25.875". Close enough?

Nope I needed it bang on thanks. The length alters the nodes.

Just finished wet checking this lot of cases; most of them hold between 86.5-86.9 grains. Do you think that calls for a change in charge weight, or would you stick with 70.0?

I have used 86.7gr as the average. Cull the extreme cases or make up a new batch. I download them and use them to foul the barrel.

70.2gr. should give you 2631fps (2 623fps at the chrony) at a pressure of 56 082 psi. You cannot get to the next fastest node safely.

 

[Tac Beard]

I can't thank you enough. I'm loading up a batch now, will post results after the range trip.


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[Andrew Leigh]

You need to chrony the load for one last tweak. As the case gets fuller and the load gets hotter the internal combustion alters.

 

[Tac Beard]

Andrew--

Just got back from the range, I chrony'd 10 rounds @ 70.2 grains of H4831SC:


Avg 2579.5
High 2600
Low 2555

Much better results this time, if still a little bit on the slow side. Guess it's just a "slow barrel"... The first couple 3-shot groups were sub-MOA, the last one opened up a bit but I'll take the blame for that. I'll shoot better groups with a fresh shoulder in a couple days, I'm sure

Now I'm wondering why the large deviations. I haven't done any match type brass prep, like uniforming primer pockets, deburring flash holes, annealing necks, neck turning etc. Actually, I tossed one case with a cracked neck during prep for these loads. It had only been fired 3x so that was surprising. I infer from that that maybe the brass is hardening pretty fast and possibly affecting neck tension? I haven't had any luck with annealing in the past, but it might be time to give it another try.

At any rate, my velocities are much more in line with expectations now, and pressures seem fine. Anything else I need to know? Many thanks for all the help!

 

[Andrew Leigh]

Lets for a moment accept that the QL data is correct and that the data was supplied by the powder manufacturers.

Your powder batch is extremely lethargic, and when calibrating the powder burn rate to the velocities shot this batch of powder is 4.7% slower than specified. Going back to your original velocities of 2 480fps you will note that 4.7% will increase the velocities by some 116fps. So this is all adding up and we appear to have explained some of the velocity drop.

So why am I telling you this? Simply because your next batch of powder may not be the same and may be on or slightly over spec. For this reason any change in component should result in a new load development process.

So where does this leave us. As you have filled the case with a little more powder I was expecting the load to "liven" up a little, it did not. I have recalibrated the burn rate down from 0.4301 to 0.4100 in order to align with the chronied average velocity. As velocities were not as expected the consequence is that the actual elapsed barrel time has shifted and moved you off the node.

Next time you load then 71.3gr. should be your target to give 2 632fps at a safe 56 170psi.

I am assuming that you are checking as a matter of course for flattened primers, stiff bolt opening etc. I would doubt if you have experienced any of this so far.

I am curious. Do you leave the powder tin open for extended periods? Just wondering if there has been some slight moisture ingress. Are you in a very humid climate? This powder batch is odd, the V/C ratio (Velocity/Charge) generally increases as the charge increases, yours is decreasing, albeit slightly. We appear to by battling to ignite the powder efficiently hence the inability to get the desired result.

Are you using the CCI250, or any other magnum primer for that matter?

Regards

 

[Tac Beard]

I am using an older lot (red box) of CCI 250 primers. They've been completely reliable so I've never questioned them.

The powder has never been left out in in the open. I bought this 8 pound jug about a year ago; my routine is, pour some in the powder measure when loading, then empty the powder measure back into the jug immediately after loading. I even keep the styrofoam seal between the lid and the jug. I'm in south central AK, which is pretty mild, humidity wise.

I haven't seen any primer flattening, only the ridges around the indent that seem to be this rifle's signature with any load. I'll try to post some pictures, the more info the better. The bolt lifts easily every time.

I do have a newer batch of CCI 250s, should I try those? Maybe better not to change anything until I get the charge weight sorted out?


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[Andrew Leigh]

I think we are good to go, just some lazy powder. Have you ever tried Reloader-17? Don't change anything now only the charge weight.

 

[Tac Beard]

I've never tried the Reloder powders, as they've been really scarce around here the last couple years. I've heard good things about them though, might have to try RL-17 now that it's becoming more available again.

Will load up a few rounds tonight at 71.3 gr H4831sc and report back with what I find.

 

[Andrew Leigh]

The other thing that confuses me a little is that you are 0.030" from the lands. Now in my limited mono experience that results in a little more pressure due to the close proximity of the lands, we appear not to be seeing this here.

To avoid excessive range time and given the lethargy of the powder I would recommend, assuming you have the components available, that you load up 3 x lower charge rounds to foul the barrel if the barrel has been cleaned. The 3 x 3 sets of 71.3gr +-0.50gr. All the loads are safely within pressure limits.

3 x 70.8gr.
3 X 71.3gr.
3 x 71.8gr.

My motivation for the above is simply that we are compacting the load a little more and in my experience this increases the burn rate. So if the load finally starts behaving like I normally would expect, and the burn rate increases, then it would be prudent to download by 0.5gr. On the upside if the powder continues being lazy then another 0.5gr to the recommended load may prove to be required. 0.3gr steps with a case this size makes little difference.

Care to try something different?

Shoot the fouling rounds and allow the barrel to cool for 10 minutes. Create a target with three bulls, one for each load.

Shoot round 1 load one into the first target, followed by round 1 load two into the second target and then round one load three into the last target. Allow 2min between shots and time it for consistency. After the first sequence allow the barrel to cool for 10 minutes and repeat. It may sound odd but I have found that this method to be rather effective. The reasoning is that as the barrel heats the shots string. With this method it negates that as each shot on each target will be shot at roughly the same temperature. With the last target being the hottest, but they will all be hot so the group should be more indicative. Watch your chrony as you move from target to target.

After the initial shot from each group take not of the primer and the bolt opening, the normal routing stuff.

Make sense?

Cheers

 

[Tac Beard]

Sounds like a good plan. I didn't have time to get anything loaded up tonight but I should be able to tomorrow.

I like that approach, I think it'll work well because these higher end loads really heat the barrel. It definitely needs to cool after three shots.

 

[Tac Beard]

Here's what the primers from the last load look like, for what it's worth.

 

[Andrew Leigh]

I have been known to keep my rounds in group order in the box and to return each fired case in order so that I can tie these back to the actual velocity per cartridge and where possible record the sequence of the shots to correlate back to the case capacity and speed. Just helps to better understand the process.

 

[Tac Beard]

Finally got to the range this evening. I followed your recommendations as closely as possible, my results were as follows:

70.8 grains:
2615
2605
2633

71.3 grains:
2630
2616
2613

71.8 grains:
2633
2625
2624






I can't explain that wild flyer on the final shot of the 71.8 group. I didn't think I pulled it, but it must have been my fault given the small velocity spread and the first two right on top of each other. Maybe I psyched myself out and got stage fright after seeing the first two when I went down range during the cool down period. Also, I forgot to wait 2 minutes between shots so that might have been a factor.

Otherwise pretty happy with the results this time! Maybe 71.8 is my load. Thanks Andrew for all the help on this project.

 

[Tac Beard]

BTW, I did start with a clean barrel and fire three fouling shots, I just used them to blow up water jugs instead of paper. More fun that way

 

[Andrew Leigh]

Hi,

could I have the average velocities for each of the three groups please.