Thread: Pressure issue resolved 7mm08

I thought I'd share a recent reloading experience in case it helps anyone else out - I certainly spent a lot of time scouring forums to find a solution.

I recently got back into reloading after about at 10 year hiatus. I'm running a fairly stock standard 7mm08 Howa, surpressed, trigger tweaked, bedded, with an Arken scope. Due to a move, most of my current hunting is in the Ruahine tops, with shots ranging from 150+ metres. Furtherest to date is 325m.
As I have access to a good range, I thought it made sense to get back into reloading to get better equipped for those longer shots (both in accuracy and terminal performance).

I settled on the 162 ELD-M, using 2208 in Win brass, and RWS primers. A mate suggested a load he had found to work, and I also spent a lot of time consulting forums to get a sense of where I might need to be powder charge wise. Also got into GRT, which proved helpful. Most folks seemed to be running a little over book max, which I was reasonably confident would be fine, but I thought I better do a pressure ladder to be safe. Pressure ladder looked fine up to a grain over max, with velocities in the expected range.

I picked a couple of charge weights to test below the value I had tested to and started shooting groups. Accuracy was ok, however what started showing up was some notable pressure signs - flattened primers, stiff bolt, case head marks, elevated velocities, and often fairly signficant flyers. What was strange is it didn't show up on every shot, maybe 50%.

Thinking that I must be over pressure, I dropped charge weight 0.5gn. This showed some improvement, but was still getting occassional pressure signs, which left me feeling uneasy. I dropped charge weight again, to well under book max, yet the problem continued. I spent a lot of time measuring every possible variable that I could on the overpressure cases - case base to shoulder, trim length etc. I then did the logical thing and gave the barrel (what I thought was) a thorough clean - no improvement - if anything, things were getting worse. By this point I was over 100 rounds deep into my "load development", and felt like I had nothing to show for it.

Further research led me to the possibility that it was a carbon ring causing the issue. I did another clean that I thought would help, even using a bit of autosol, but still no improvement. I decided I couldn't really sort this properly without seeing what I was actually doing in the barrel. Being a frugal character, I bought a $9 Ali endoscope, and managed to reduce focus distance with a lens from a Kmart microscope I 'borrowed' from one of the kids ("it was never very good anyway..."). Sure enough there was a distinct carbon ring, tracking quite a way back into the case neck area. Doing some targeted cleaning with a bronze brush (rotating it), and some patches with autosol, I eventually got the large majority of it cleaned out. I learned a lot about what it actually takes to clean hard carbon through this process.

Back to the range - and success. Much lower velocities, no pressure signs, and accuracy seemed to be on point. It proved an expensive learning in terms of components spent, but was happy with the end result.

Pic below was first three shots on a clean barrel last night. Velocities 2520, 2534, 2515. I've shot a couple of similar sized groups, but most average around 0.8moa. Plenty of accuracy for my purposes - impressed with the Howa.

Thanks for sharing, good outcome and valuable lessons. Did you try any of the dedicated Carbon fouling solvents eg Boretech C4 ?

Interesting. Can you say approximately how many shots fired to get such a carbon build up? Was any particular ammo/powder mostly shot? Wanting to understand what goes into carbon building up. I have several older rifles from 30 to 80 yrs ago. Some of them with a fair mileage. Carbon ring has not ever been something of concern to me. Is it a particular issue for current "tight " spec chambers perhaps?

Suppressors I think accelerate carbon build up

re. bore solvent - I'd been using KG1, with a nylon brush. Discovered that the nylon brush hadn't really been touching the hard stuff, after I ran a bronze brush down a few times and patches came out black. Part of me wonders if less aggressive cleaning proceedures that are possibly more common now, make carbon build-up more likely. I've since changed my cleaning routine to include an oversize brush rotation in the neck area of chamber.

re. shot count etc - I'm guessing around the 300 mark. I was confused by this as well, as many folk don't seem to have carbon ring issues despite high round counts. As chainsaw suggested, suppressors are said to accelerate carbon build-up. A number of people have said Varget/2208 is a particularly bad fouling powder. The other factor that gets suggested is case trim length - shorter lengths sometimes allowing more room for buildup (this doesn't make complete sense to me as there is always some 'headroom' past the neck where carbon can accumulate, even on longer cases). Carbon 'rings' can also apparently develop in the throat area, and start engraving the sides of the projectile, however I'm fairly sure my issue was limited to the case neck terminus.

My cleaning regime currently relies on plenty of bronze brush (10+ and rotating in throat area) then Hoppes soak for a couple of hours, dry patches x2-3, then another reaming with bronze brush, then dry patches. Then overnight soak in Hoppes & repeat. I find the soaking time with Hoppes helps loosen up the Carbon as well as Cu. After 100 or 200 rounds I’ll put thru a little bit of Autosol

I feel that cleaning the throat area after every use keeps a bit more control over the carbon buildup, no real scientific data to back this up though...

Knew a old guy that didn't use his rifles for over a couple of years, he just uesd Hoppes no9 them & left them and he reckon no harm done, patched them out & shot as before. My pratice is to hoppies until clear then wet patch hoppes to finish, leave ethier muzzle down or jam a piece of handy towel, into the chamber, stop it running into the workings. Leave it like that and patchout when ready to use, can be amazing how much copper comes out first patch. Too dirty I repatch it out with fresh hoppes. Seems to work 3000 rounds down with a supressor the lands have moved 50th but still shoots fine.

The load development might have proved frustrating, but some field testing proved much more rewarding. Decided to take the opportunity for a quick mission in the Ruahines while the weather looked decent. ELD-M seems to do the business. 305m and 135m. Also took the opportunity to validate drop on a rock out to 650m.

Howa barrels are pretty crap now, foul quickly and hard to clean.

Iv had a similar issue and man it took me ages to find the problem fair to say I clean differently now as well

A well written and considered item by the OP, the bonus being excellent grammar and spelling.

Being an F Open shooter, barrels are big in our thinking and we spend considerable time and effort keeping on top of them. Personally, I have come to the conclusion after shooting out quite a few barrels that solvents alone are useless with dealing with hard carbon and have shifted to a more abrasive approach. "Abrasive" is a somewhat emotive term for what is needed but you definitely need some mechanical action to shift hard carbon. Owning a borescope is essential in my opinion if you are serious and luckily they are now very affordable.

Here is what Litz has recently recommended and it is very close to my cleaning regimen:

https://www.youtube.com/watch?v=meXn3GiMhns&t=11s

I also do that, Kroil & JBs when accurracy seems a little off. Not as offen as he does

Originally Posted by 6x47

A well written and considered item by the OP, the bonus being excellent grammar and spelling.

Being an F Open shooter, barrels are big in our thinking and we spend considerable time and effort keeping on top of them. Personally, I have come to the conclusion after shooting out quite a few barrels that solvents alone are useless with dealing with hard carbon and have shifted to a more abrasive approach. "Abrasive" is a somewhat emotive term for what is needed but you definitely need some mechanical action to shift hard carbon. Owning a borescope is essential in my opinion if you are serious and luckily they are now very affordable.

Here is what Litz has recently recommended and it is very close to my cleaning regimen:

https://www.youtube.com/watch?v=meXn3GiMhns&t=11s

Thanks for the link - I'd recently discovered that video while doing a deep-dive on rifle cleaning. I enjoy the way Litz thinks about his process. In my limited experience, what seems to muddy the water, is the broad range of both cleaning procedures and end results. Some folk seem to do next to no cleaning, and report no ill-effect, while others feel it is neccesary to clean frequently with abrasives. I think moving forwards, I'll probably settle on a basic clean with solvent after each use (including targeting the throat area), and a more thorough clean using an abrasive at certain round-count intervals.

Yeh, that's entirely reasonable. Hunting is very different to target shooting in the round counts. We would generally have fired at least 40 shots in a day, was hunting last weekend and both rifles had about 4 shots each through them.