'Clumping' Retumbo--Kirby/anyone?

[jmden]

Shot some 338AX rounds loaded with 100g Retumbo under a 300 Berger lit by a 215M. These had been loaded last spring with no pressure signs evident upon shooting at that time. I use dry lube in the necks before seating. Now they are showing pressure signs with every shot. Temp controlled as I keep them in a 40F cooler if I'm shooting in warmer weather than that to try and simulate more typical hunting temps in an effort for consistency. Haven't gotten the over pressure loads over the chono yet.

I decided to pull a bullet to see if I somehow put too much powder in. Right at 100g with same scale--checked with flashlight to make sure no powder left in case. But, to measure this, I had to wack the edge of the case head pretty hard several times to loosen the powder so it would drain out. Only one kernal came out before doing this.

What is going on? Is this contributing to my over pressure issues? This is the second 8lb jug of Retumbo that I've had clumping. When I called Hodgdon several months ago, their tech said it's not a problem, but that was before I had this overpressure issue after having powder sit in the case for several months.

Perhaps I should give every loaded case a couple of good wacks on the edge of the case head...??

 

[Franklin]

If this is a compressed load, clumping is normal with extruded powders, when you pull the bullet and tap the powder out.

 

[jmden]

That may be it. This load is 100% density. Still not sure of why the load is doing what it's doing in terms of pressure. Gave the barrel, lugs (bolt and action) and chamber a good cleaning. Chamber and action lug area was more dirty than I like to see.

 

[royinidaho]

My load of 101 gr of 50 BMG in a 338 RUM is compressed behind the 300 OTM and does cake pretty solid.

However, pressure isn't a problem either immediately loaded and shot or if they set for as much as several months.

With Retumbo in the 375 AM with Kirby's std load of 142 grains and the 350 SMK which has been quite a moderate load considering my nature , the last time I was in Townsend and not on a very hot day, she blew a primer.

It's no way a compressed load.

I haven't shot her since.

Maybe there's something going on with Retumbo???

We'll see next week.

 

[jmden]

I'm starting to wonder about Retumbo as well, Roy.

I loaded some Kirby fireformed Lapua brass tonight to 99g (dropped 1g) and -.015 (standard load, just dropped a grain), same as the other load that ave. 2954fps MV. After two foulers to foul a clean barrel it went 2930fps 3x. Still had too much pressure. Will drop to 97g and try that tomorrow. Quite frustrating. It's as if the powder became a faster powder, whether loaded in a case or in the powder container, in the last 4 months since I worked with it. Seems to be pressuring out at lower charges and velocities.

Is this a Retumbo thing? Anyone else besides Roy and I noticing anything with Retumbo lately?

 

[royinidaho]

If it ain't one thing it's another!

My problem is going to be, if things are wonky, I have a several hundred loaded and ready to go.

 

[Greyfox]

I use Retumbo exclusively in my 300WM and 6,5x284. The caking at the mouth of the case has always occurred, particularly of the load is compressed. There was definitely a a change in the Retumbo formulation 2-3 years ago that required a decrease in charge of 1.5gr in my 6.5x284, from 59 to 57.5 to get my velocity of 2970 FPS. There were no pressure signs, just the velocity change. This has maintained constant for the last few lots I have purchased since then. Having read this post, I'm a little suspicious that I might have a problem as well. My 300WM loads are OK, but they have been only recently loaded up over the last couple of months. I recently shot some of my 6,5x284 ammo that was loaded two years ago and noticed a velocity increase of 30-40 FPS. My recently loaded ammo is fine. I wrote it off the higher velocity loads as lighting effects on my chronograph, but will now go back and double check it. There were no pressure signs and the loads gave the same POI and group size. If there is a change over time it's not good news.

 

[jmden]

The strange thing is that 100g load from this jug of 8lbs purchased last Sept. were fine in April. Normal MV and no pressure signs. But the pressure signs went way up when these same loads were fired a few days ago.

From running some 99g loads over the chrono yesterday and having them chrono the same as when I worked up with this new jug of powder last Sept., it appears that the velocities per load are the same, but pressures have increased. That's only chrono-ing one load, 99g, but the appearence is there.

Pulled the bullets on the rest of the sixteen 99g loads and reloaded at 97g and -.020 vs. my typical -.015 using the Forstner micrometer seating die and Davidson seating depth checker...

Strange. Not happy about losing the velocity, but must find a load here very soon. High buck starts 9/15...

 

[jmden]

This morning at 97g Retumbo (normal load was 100g last spring with same jug at 2954fps) and -.020 instead of the normal -.015, I'm still getting pressure signs, though less. First round through dirty, cold barrel went 2824fps, then the next three went 2879, 2872, 2867 and grouped well under 1/2 MOA prone at 205 yds on paper, but the first was 2" to the R of the 3 shot group and why the low MV. ??!! But still a shadow of ejector mark on 338 Lapua Brass. This thing should be doing 2950fps with no problems.

I do have some left over Retumbo from an older 8lb. jug that I switched from last year. My load with that was 101g and 2979fps. Perhaps I should investigate if anything has happened with that. Regardless, it sure appears to me at this point in time that something happened to this lot of Retumbo over the last few months....

 

[jmden]

My load of 101 gr of 50 BMG in a 338 RUM is compressed behind the 300 OTM and does cake pretty solid.

However, pressure isn't a problem either immediately loaded and shot or if they set for as much as several months.

With Retumbo in the 375 AM with Kirby's std load of 142 grains and the 350 SMK which has been quite a moderate load considering my nature , the last time I was in Townsend and not on a very hot day, she blew a primer.

It's no way a compressed load.

I haven't shot her since.

Maybe there's something going on with Retumbo???

We'll see next week.

Roy, What's your plan going forward with this issue...?

 

[royinidaho]

Roy, What's your plan going forward with this issue...?

This is a very busy week so won't get anything done regarding shooting.

Next week I'll take'r to the hills along with the chrono and validate things.

The expectation is that that blown primer was a "fluke". Donno. I haven't checked primer pocket expansion yet. Will most probably do this first.

This is the powder and charge weight that Kirby validated accuracy with, with an anticipated velocity of 3250.

I have good base line data. They have been chrono'd right at 3250 average.

 

[jmden]

Well, I hope you figure it out and all is OK.

 

[bigngreen]

Have you guys taken an abrasive cleaner to your barrels at all, like the KG or JB, and made dang sure your carbon has not built up. I use a lot of Retumbo and I'll start getting pressure signs if I don't address carbon aggressively once in a while.

 

[jmden]

Have you guys taken an abrasive cleaner to your barrels at all, like the KG or JB, and made dang sure your carbon has not built up. I use a lot of Retumbo and I'll start getting pressure signs if I don't address carbon aggressively once in a while.

I have wondered if there's a barrel change as the same issue came up when I used a reduced load of an older lot of Retumbo as a test yesterday. So two different lots of Retumbo from two different 8lb jugs purchased 3 years apart or so, the newest purchased last fall and each showing significant pressure at reduced loads that should be very pedestrian and have proven to be in the past for this rifle. The odd thing is this barrel was shooting well 3.5 months ago, sat in the safe and the loads seem to have changed significantly even after doing a thorough cleaning.

I have not used abrasive cleaners on my barrel. Just BoreTech Eliminator (do use brass brushes as I've talked to folks who scope a barrel after using nylon brushed and then compare to using brass brushes and say theres a quite a difference) and then a pass with gun oil and then patch dry. More to it than that, but that's the basics.