Pressure issue and not looking good

[338winmag]

A little history:
Reloading a friends fairly new 7mm Rem Mag. In the beginning, the Winchester 175 gr over the counter ammo he gave me was hitting 3100s. I was getting a few sticky bolts so I stopped even shooting it for comparisons.

I started with some minimum Sierra manual loads using the 160 gr SGK, H4831 powder, winchester brass and Fed215 magnum primers. The minimum loads were giving me average 2880 FPS. I then went to some higher loads with increments of .5 grain and the rifle started producing very high FPS (3180s) with just a very minor increment. I was getting bolt locks

So I decided to try different powders (H1000, IMR 4831 and RL22). The rifle started shooting extreme FPS with very minimum powder charges and started getting consistent bolt locks for every component testing. (yes I started even a grain or two lower than the minimum. Everytime out to the range, the first or second round gave bolt lockup or super sticky bolt regardless of the minimum load.

I made super super super sure the barrel was clean, the chamber was 100% clean and dry, the cases clean and dry, case perfectly prepped, powder charges carefully measured, loads all perfectly made.

Guys, this rifle is now shooting high velocities with minimum or below minimum loads, bullet seating .020 off lands, and bolt lock. This can be fire-formed brass or virgin brass. The FPS keeps at 3000 or above regardless of the powder charge. The only thing I have not tried is non-magnum primers.

I brought the rifle to a gunsmith today after the ridiculous performance. I was shooting 4 grains less Sierra's minimum and I still hit 3000??? and yes bolt lock.

The gunsmith believes that the the chamber area touching the the web area of the case (where magnums get their bulge) is not perfectly concentric. He is going to polish this area to make it concentric without affecting the caliber.

I am at a loss. Does this sound right or does anyone have other thoughts of what is going on with this rifle?

Thanks ahead of time
338winmag

 

[CatskillCrawler]

What does the fired brass look like?

 

[big rifle man]

Just a suggestion and I'm sure you have allready done this. Are you reloading with an electronic scale or balance beam? whatever one check for accuracy.

 

[338winmag]

The electronic scale was my first concern so I measured with both RCBS 5-0-5 and Chargemaster. Both on the money and I started having issue before buying the new Electronic scales. Also I reloaded in my truck yesterday with the manual scales.

The brass looks fine and so does the fired primer but .... the last trip before yesterday, primer blewout. It was the first shot of the day and the last shot with a minimum load of 60 gr of RL22 (bolt lock). I do have magnum belt bulge on almost every case even on the first firing which is strange since I do not have this on my 338 win mag.

The bottom line is no matter what the charge, the rifle is showing over 3000 and locking the bolt.

The gunsmith believes the uneven magnum bulge expansion is what is causing the lock.

My confusion question is the uneven chamber roundness causing the pressue issue that is causing the bulge and if so, why did it just start this last month and a half two omonths?

 

[Guest]

How long has your friend had the rifle? Did it always show high velocities? For the record, 3100 with 175's is smoking - but I suspect you're well aware of that.

Have you tried backing away from the lands to about .100" off? It may be that your measurement of the throat length is incorrect and you're jamming the bullets into the lands and creating pressure spikes. Just guessing here, but I can't see an out of round chamber giving you the aberrant velocities. Is there maybe some sort of barrel obstruction (partial, obviously) that could be creating the pressure spikes?

Also, check case length. It could be that you're a little long in the neck and basically "crimping" the neck at the end of the chamber when you close the bolt. That would account for pressure spikes.

Or, you could have a situation I've seen once before. This is a total long shot, but it has happened. A buddy of mine had a rifle that, for whatever (unknown) reason, blew off a small portion of the neck of one, or perhaps more than one, case, leaving a brass ring embedded at the end of the chamber, effectively shortening the neck of the chamber. We still don't know why it happened, but I am guessing some factory ammo was over-crimped and left a brass ring there (small one) and it kept building over time the more the gun was fired, until it was finally a very prominent brass ring, visible to the naked eye after a thorough cleaning. Just right at the end of the neck area at the throat of the chamber. His gunsmith removed it with the gentle hand-use of a reamer, I believe. We tried prior to that using numerous solvents, and probably could have gotten it out over time with some of the more aggressive copper solvents, but he decided to expedite the process and took it to the smith. Bizarre, but it could be what you're experiencing.

In fact, the more I think about it, the more it sounds like neck length issues and "crimping" when closing the bolt.

Keep us posted on what you find out.

 

[338winmag]

Hi Dubyam and thanks for the reply.

Yeah I have tried all lengths. on the lands; .010, 020, even .075 and .085. Same result.

Now the 7mm Rem Mag max length is 2.500 and trim to length is 2.490.
I checked my primed cases and they are in spec between 2.490 and 2.492. A few are at 2.494-2.495.

...but here is something interesting... with the exception of 2 cases, 5 cases are between 2.500-2.502. I am surprised my brass expanded that much but maybe that is because of this pressure issue? I am pretty sure one or two of those cases was virgin but now can't tell.

All these cases have been fired 3-4 times. All cases were annealed recently.
I have culled any cases with primer pockets very loose. The primer pockets still hold a primer but not like "new", but again virgn brass appears to show same pressure issue.

Your long shot sounds like something I am experiencing. Boy do I wish this is what the issue is. Gunsmith stated he will have the work done today.

I will definitely keep everyone posted.

 

[DrMike]

All that you report makes it sound as if the neck of the chamber is impinging on the case neck. Dubyam could be correct that there is a build-up of brass in the neck area. It should be an easy check and fix for your smith.

 

[Ridge_Runner]

an out of round chamber may cause rough sticky bolt but it wouldn't give those high velocities, it has to be something interfearing with bullet release, primers aren't flat, casehead expansion? ejector wipes?, has to be in the neck area.
RR

 

[DrMike]

has to be in the neck area.

+1

 

[338winmag]

Just spoke with the gunsmith:
He polished the chamber area where case bulge was happening. He stated there was alot of scarring and tool marks which he also corrected. I did not hear him ever state "neck" in any of his review. Everything that you guys state sounds so correct that is makes me wonder if the gunsmithing has corrected the issue? Honestly I am so far from being a well versed person in this type of situation. That is the beautiful thing about this Nosler site and I really appreciate everyone's input.

Here is what I am going to do tomorrow at the range. I believe I will see results (or non-results) in the first round for each bullet.

Before the gunsmithing, even these minimum rounds would have resulted with super high velocities and bolt lock. Using virgin brass, I will load the near minimum powder charge for two type bullets according to the Manufacturer's manual.

For Sierra 160 gr Game King SBT
Case - Virgin Winchester
Primer - Fed 215 magnum
Powder - H 4831sc
Powder Charge - 55.2 gr
Suggested Velocity - 2700
Seating Depth - .020 off lands


For Hornady 162 gr Interlock BTSP
Case - Virgin Winchester
Primer - Fed 215 magnum
Powder - IMR 4831
Powder Charge - 54 gr
Suggested Velocity - 2700
Seating Depth - .020 off lands

If the above rounds fire within normal performance
I will also load one of each above using some of the same fire-formed brass I have been using. See if the brass somehow had something to do with it. (Of course I am reaching here becuase an over the counter ammo was shooting with same issues but just to remove all doubt)

Thanks All
I will update tomorrow evening Mountain time
I sure hope this is corrected

Steve

 

[Ridge_Runner]

has to be in the neck area.

+1

OR check the bore for a tight spot, even if the neck was interfearing with bullet release it should flatten the primers, high pressure makes high velocity, its the absence of normal pressure signs that is mind boggleing, however if there was a tight spot in the bore for whatever reason it could boost the velocity without ruining every case.
RR

 

[Antelope_Sniper]

Was this rifle new or used when he got it?

 

[338winmag]

My understanding is New

 

[Guy Miner]

New rifle - I'd have likely returned it to the store or sent it back to the manufacturer for repair. The factory 175's at 3100+ fps are a giveaway that something isn't right - and is causing excessive pressure, let alone the bolt lockup.

Minimal chamber dimensions? Short neck? Tight neck? Tight bore? Something is producing very high pressures. I wouldn't even shoot it anymore until that is addressed, preferably by the factory.

The factory might not be happy since you've had a local smith work on it, but... I'd still recommend contacting them, hoping for a repair or replacement.

FWIW, Guy

 

[338winmag]

Well, the question is was this a new rifle when he got it.
The rifle has been through at least 1 hunting season and coming up to its second.

Also when I received the rifle, it shot a few hot pressure rounds, but was not always. It now is always. I will test tomorrow and give an update.

 

[1Shot]

Once you had the gunsmith work on the rifle you can forget about sending it back to the factory. If you are getting high pressure with min book loads there is nothing written in stone that says you can't lower the powder charge below the min book loads. If the gunsmith did not fix things it sounds like a re-barreling is in order or you could have the barrel set back a little and a new chamber cut or you could have it re-chambered to a 7mm STW. :mrgreen:

 

[SJB358]

Good luck Steve. I hope the smith figures it out for you. I imagine something will get discovered soon enough. What make and model of rifle is it? Scotty

 

[338winmag]

Model: 111 FCXP3

Thanks Scotty. I can't get this day gone fast enough to test.

 

[SJB358]

I bet, I know you are chomping at the bit to get out and test it. What did the smith come up with for ideas while digging around in the rifle, other than the slightly out of round chamber. Scotty

 

[BeeTee]

If you remove the firing pin and cocking mechanism from the bolt, you should be able to easily close the bolt on a factory loaded cartridge - as in very little resistance. If there's resistance, paint the round with a black felt marker, which might help you see where the primary contact is in the chamber.

My son's shooting group own four 300 WSM rifles between them. Three of them are Sako and one is a Savage. I'm told the Savage shoots 100-fps faster with all loads - factory ammo or otherwise.

Jim