6.5 Creedmoor load issues

[D13REW]

Evening all,
Would be interested in your opinions and pointers on the issue below.

I've been developing loads for my 6.5CM for an upcoming shooting course. Due to difficulty in getting some powders I've been working on a few different loads and had finally settled. Today at the range I thought I would take the opportunity just do some confirmation shots. It was about 15 degrees and pouring with rain.
First load
130 ELDM, 42.2grns vit N550. New brass chamfered and deburred, mandrel expanded, measured with the comparator at 1.550" before loading.
20 shots all with heavy bolt lift and slight ejector marks. Av 2818 fps, sd of 5, es of 17

Second load
140 ELDM, 42.3 grns vit N550. New brass, chamfered and deburred and mandrel expanded, measured with the comparator before loading at 1.550" 5 shots , not as heavy a bolt lift but a much bigger ejector smear. Av 2793 fps , sd of 5 ES of 14.

Third load
140 ELDM, 43.0 grns of RS60. Once fired, full length resized, chamfered and deburred, mandrel expanded, brass I think measured at 1.552" 40 shots. No heavy bolt lift but on inspecting as I was depriming I noticed some ejector marks with a raised sharp edge. Av 2824fps, SD 9 ES 25

Now, I shot the same loads inside just 2 weeks ago and had no issues. So I've checked the h2o grn weight and found that although the new cases have a .5 h2o grn less capacity. According to quick load I should be well within the pressure limits.

So I'm thinking possibly a carbon ring which I will checkout tomorrow night with a borescope or the cases are to short for the chamber and are getting slammed back into the bolt. How would I check this? or is there anything else to check or clean.

TIA

 

[jthyttin]

Quickload is just a mathematical tool, and if you want to use it you have to learn to tune it. I've never used it or any other similar tool.

Your VV loads sounded quite high (from the perspective that I've loaded for 260 Rem for long time) and just checked you're way over VV data so I'm not surprised you encountered pressure marks.

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BTW I have a recent experience, was loading the 260 Rem to new Lapua cases. Did expect a mild difference compared to fireformed, but the accuracy was "completely" lost. Like 5x group size or more (although I don't measure by group size). Was blaming this and that, checked and double-checked everything. Proceeded to load a small sample to the old decommisioned brass. Hey ho, close to previous accuracy. Proceeded to load test sample to fireformed Lapua cases, and they were also accurate (might need some tweaking but I don't know if I bother).

 

[Utectok]

I bought quickload and very quickly realised that actual testing and real world data is more useful than theoretical pressures. Maybe tuning the app helps but if there are pressure signs there and pressure signs. Difficult to evaluate without seeing pictures of the case heads?

 

[jcampbellsmith]

@D13REW

Why didn't you stop testing as soon as you encountered issues? Firing one test shot I can understand, after firing two shots, what was your objective? Destroying your rifle?
Regards
JCS

 

[ChesterP]

43gr of RS60 with that class of bullet imho is getting rather warm. It's nothing to do with carbon rings. For LR brass I would expect safe loads to be closer to 41.5gr with RS60 and up to 42.5 with RS62 and perhaps up to 1.5gr more is using SRP Brass. Less case capacity only makes that situation worse and you don't always get a sticky bolt lift on high pressure loadings. Anyone loading up to that point is asking for trouble, especially when the weather (eventually!) turns warmer. In your shoes, I'd be starting from scratch when changing anything, especially brass and never loading that hot to begin with, instead working up. Is there a reason you want such high velocities from the 140 for hunting? The 6.5 is a slippery bullet and I've shot SSTs to very long ranges with little compromise on precision at just 2650fps. You really don't have to push those rounds as hard for any UK hunting distances.