Need help troubleshooting 300 RUM pressure issue.

[IdahoRedneck]

Copy that, well keep at it, I know youll figure it out. Tagging on to keep up with your results.

 

[Barrelnut]

Interesting. Just tagging too, as I use some of the same calibers and powders.

 

[Toptuna]

i shot my 300 today with

winchester magnum primers
remington brass
berger 210 vld
92.5 grains of retumbo

I had no pressure signs at 92 so i loaded in half grains all the way up to 94 grains. Guess ill have to pull the bullets out.

92 grains will not particularly be my accurate powder charger correct?????

Im new at all of this. Thanks.

 

[MontanaRifleman]

i shot my 300 today with

winchester magnum primers
remington brass
berger 210 vld
92.5 grains of retumbo

I had no pressure signs at 92 so i loaded in half grains all the way up to 94 grains. Guess ill have to pull the bullets out.

92 grains will not particularly be my accurate powder charger correct?????

Im new at all of this. Thanks.

I found 93 gr of Retumbo pushing 210 VLD's to be max in MY Sendero 300 RUM. You don't have to pull your bullets if you haven't run into pressure signs yet. Your load and rifle combo will be unique and you have to determine what your max is and what load shoots the best.

This thread isn't about general reloading.

 

[Toptuna]

I found 93 gr of Retumbo pushing 210 VLD's to be max in MY Sendero 300 RUM. You don't have to pull your bullets if you haven't run into pressure signs yet. Your load and rifle combo will be unique and you have to determine what your max is and what load shoots the best.

This thread isn't about general reloading.

Ya I had pressure signs at 92.5 grains and had loaded up to 94 grains. Guess 92 is my max.

 

[MontanaRifleman]

Ya I had pressure signs at 92.5 grains and had loaded up to 94 grains. Guess 92 is my max.

Depending on what "pressure signs" you had, you might want to back off to less than 92. I use brass life as my pressure indicator... less than 4 firings before loosing primer pockets and you are pushing it pretty hard. Take temp into account as well.

 

[MontanaRifleman]

Well... yesterday was an interesting day at the range. Finally some good news.

I cleaned all the rifles and headed to the range with various loads. The plan was to shoot Retumbo loads in a clean bore in the 6-284 and 6.5 WSM. Here are the results.

6-284, 52 gr of Retumbo, 105 Hybrids, 10 rounds, nice moderate light load.
3205
3227
3213
3204
3205
3219
3209
3205
3207

ES, 23, no increasing pressures and velocities.
Ladder pressure test with Retumbo and the 105's
53 3225
54 3287
55 3322
56 3373
57 3445, slightly stiff bolt

All went well so I decided to try the 63 gr RL33 loads that pressured out the other day.
63 gr RL33/105 Hybrids
3516
3528
3566
3566
3584

All rounds had a stiff bolt and ejector marks, but i didn't think they were way over pressure. Not a load i would use but not extremely over pressure. There was a climb in prssure and velocity that seemed to plateau.

63 gr RL33/100 CEB's

3546
3591
3579
3597
3573
3604
3553

The middle 5 rounds have an ES of 25. Overall a fairly stable string. Pressure signs were slightly less than the 105 Hybrid string. So still not a load I would use. I plan to load up a couple of strings with 62 gr and shoot for accuracy. will also load up a string with 56 gr of Retumbo.

6.5 WSM, 64 gr of Retumbo, 130 CEB's, nice moderate light load.
3331
3300
3304
3291
3269
3287
3291
3285
3285

If you throw out the fouling shot and the 5th shot, the 8 round ES is 19.
Ladder pressure test with Retumbo and the 130's
65 3255 unusually low
66 3340 more in line
67 3455 hmmm
68 3499 stiff bolt and ejector mark


Will load up an accuracy string with 66.5 gr of Retumbo.

Will also load up an accuracy string with 73 gr of RL33 and the 130 CEB's

Also decided to try the 98 gr RL33/230 Hybrid load again that pressured out the other day.

3227 - I know this velocity is telling me I am on the edge but I decide to fire another round
3238 - Blown primer

I will pull the rest of these and reload to 96 gr and see what happens.

It looks like the 6-284 and 6.5 WSM have settled down. The RUM is still generating what I consider to be excessive pressure for the charge loaded. Maybe this rifle will end up liking less powder?

Again, the idea was to shoot Retumbo, a less dirty powder than 33, in a clean bore to see if it might stabilize the bore and pressures. It may have done that, or maybe the barrels are just "breaking-in". One way to find out.

 

[Deleted member 46119]

Mark,

I couldn't find neck turning in the thread....

Have you measured the neck area of the chamber?

Have you measured the OD of the fired round?

Will a bullet slip fit into a fired case?

or you could try a set of cases with the necks turned to .013 for the 6-284 and .014 for the 300RUM.

 

[MontanaRifleman]

Good questions Fred.

The reamer neck is spec'd @ .3435

The necks are not turned.

OD of a bullet seated neck is ~ .337 - .338

A bullet will snugly but easily slide in and out in a fires neck.

The fired neck OD's are ~ .341 - .342

There should be more than enough clearance. In fact, if I had the chance to go back and spec the reamer again, I would tighten up the neck a couple of thou.

The 6-284 neck is a little tighter and bullets fit slightly tighter into a fired neck than the RUM

 

[Deleted member 46119]

The last thing I can think of is to slug the bore.

AIUI (AS I Understand It) If it is tight or a tight muzzle end that would mean friction which would mean pressure but lower velocity.

I run my target 300 RUM with 210 VLDs at 3063, I tried faster but it got me nothing for accuracy and wasted cases. I forget the dimensions but I'm sure the neck it is tighter than yours but I turn to .014. 86.5 of H1000 SD=4 ES=11. I'm silly but I carry a bit if paper I punched with 4 holes at 300 yards, around 1/2 inch. I didn't have a 5th round.

I did not build this rifle, I got it off Accurate Shooter forum.

 

[Kiwi Greg]

MontanaRifleman very interested in the outcome of your "issues"

I run this powder in 6.5 wsm & Edge as well as a few others, generally with impressive velocity increases.

BTW which brand of brass do you use in the Edge ?

 

[Pdvdh]

Subscribing. Am hoping you get this resolved soon. What a hassle! Never heard of anything like this before, other than Michael Eichele's problems with his 300 RUMs. I thought Michael's problems developed over a higher number of rounds fired than what you've described. Plus the smith with the bore scope is saying the fire checking isn't overly excessive in your throats, and that was determined to be the cause of Michael's barrels repetitively pressuring out with additional rounds fired.

 

[MontanaRifleman]

The last thing I can think of is to slug the bore.

AIUI (AS I Understand It) If it is tight or a tight muzzle end that would mean friction which would mean pressure but lower velocity.

I run my target 300 RUM with 210 VLDs at 3063, I tried faster but it got me nothing for accuracy and wasted cases. I forget the dimensions but I'm sure the neck it is tighter than yours but I turn to .014. 86.5 of H1000 SD=4 ES=11. I'm silly but I carry a bit if paper I punched with 4 holes at 300 yards, around 1/2 inch. I didn't have a 5th round.

I did not build this rifle, I got it off Accurate Shooter forum.

I've found in my previous RUM that I got good gains in velocity with increased pressure right up to my max working loads. I don't mind loosing a little speed for something that works and good accuracy. I had guestimated all along that I would max at about 3150-3200, with this combo, and I would settle and be happy with 3100.

The unuasual hing about this pressure issue is that it is not constant, so i think that rules out things like a tight muzzle. The gun builder that H&M put me in touch with speculated it might be from a tight bore and that with each firing and laying down of copper and carbon, it might cause increased pressure. But I don't think that's the case with 3 separate barrels in 3 separate cals, although they are all Broughton 5C's. That said, Broughtons are not know to be tight bores like say older Lilja's.

I'm speculating that there may be something in the process and/or products I used to clean the bores up after nitiriding.

MontanaRifleman very interested in the outcome of your "issues"

I run this powder in 6.5 wsm & Edge as well as a few others, generally with impressive velocity increases.

BTW which brand of brass do you use in the Edge ?

Interesting indeed Greg. And quite a relief to see the 6-284 and 6.5 WSM come around... at least so far.

I have a 300 RUM and not an EDGE. I started with 56 hulls of new and once fired RP brass. Not the best stuff by far. I am now down to 34 useable cases and 7 of them only partially held the primers in. Had to use super glue to secure them. Would not have resorted to that if I had more brass. My next lot will be Bertram EDGE brass that I will neck down. I'm done with the RP junk.

Subscribing. Am hoping you get this resolved soon. What a hassle! Never heard of anything like this before, other than Michael Eichele's problems with his 300 RUMs. I thought Michael's problems developed over a higher number of rounds fired than what you've described. Plus the smith with the bore scope is saying the fire checking isn't overly excessive in your throats, and that was determined to be the cause of Micheal's barrels repetitively pressuring out with additional rounds fired.

Paul, I think Micheal had much different problems than what I'm having. I think he might also be snake bit with the problems he's had with the 300 RUM's. I don't doubt him at all, but my last RUM (Sendero) had about 500-600 hardcore max rounds down it before I sold it and it was still holding close to 1/2 MOA without any tuning. Never shot it with a hot barrel though. And to the best of my knowledge, throat erosion had been minimal as I did not have to chase the lands far. Also know of others who have got about a 1000 rounds give or take out the cartridge.

The nitiriding is supposed to increase wear resistance on the throat to slow down erosion, so that's why I had it done. Yeah, i was not surprised that other than some superficial heat checking, the throat and bore were in good condition... other than my lapping it so smooth.

So yes, in the smith's opinion, the fire cracking was not deep or advanced and quite normal for that amount of use in a high pressure overbore cartridge. The RUM showed less checking than the 6-284. No wear on the throats, just early stages of alligator skin pattern heat checking. I saw it too.

 

[Korhil78]

Man, that is some crazy stuff that you have going on.

Trying to break this down to simplify it. It has to be something that was done to all three rifles that was the same.

1. All barrels made by Broughton.
2. All nitride coated by the same company.
3. All rifles put together by the same smith? (doubt that this would be it because different reamers would be used and it is not likely that the chambers are too tight.)
4. You scrubbed the **** out of the barrels (Did the over pressure come before you scrubbed them?)

None of the ones that I have listed would seem to me to be the case. But if I had to make a choice, it would be #2. Can you think of anything else to add to the list?

Have you had the chambers measured and the dimensions compared to one of your loaded rounds for each rifle?

There is light at the end of this tunnel though. You will either get it figured out or you will shoot the barrels out trying to figure it out and will be able to re-barrel them