Chamber? Bolt face? or Dies?

Buffalobob · #1 05-02-2005, 08:34 PM

Bulged cases

All of the fired cases come out of my Rem 700 in 17 Rem with a bulge above the case head on one side. This is noticeable if you run a finger nail down the case it will suddenly drop over the end of the bulge right above the web. It is only one side and seems to taper away as you go up toward the shoulder and taper away as you go around the circumference. Every fired case is the same.

I just full length sized a lot of cases and when they are rolled on a flat surface they are curved. When you stand four or five of the full length sized cases next to each other on their bases it is clear that they are not square with their base. They lean every which way or you can rotate them and get them to all lean in the same direction.

What is the likely cause of this? Is it that the gun does not have a square bolt face or is the chamber out of alignment or something with my dies. The dies are off the shelf RCBS and were bought with the gun.

This gun is totally factory stock with absolutely no modifications and I purchased it new in about 1973. It has always and forever for 30 + years shot 0.5 MOA with five round groups with hand loads and 25 gr. Hornady HPs and did so yesterday even though every case has this bulge in it after firing. I assume that this bulge has always been there and I just never noticed it. The bulge is not present in cases that have been full length sized. These are the original 100 cases that were bought with the gun and have been fired maybe ten times and usually only partial neck sized.
The cases probably need to be thrown away and start with some new ones which are really cheap at $23.00 per hundred.

I really do not mind the bulge being as the gun shoots as well as I can keep it still on the sandbags and in the field hunting, half MOA is good as I can do on a good day. But if it is just the dies I can certainly afford new dies.

chris matthews · #2 05-02-2005, 09:46 PM

It's your chamber- Remington crams a reamer in there at mach 3 and calls it good. I am suprised the gun shoots that well, because if the chamber is that crooked the throat normally is too.
If you ever decide to rebarrel it, look me up I am a HUGE 17 fan and have built several of them- minus the bulge of course...LOL!!!!

Fiftydriver · #3 05-02-2005, 09:51 PM

Buffalobob,

This is simply a case of the chamber dimensions being on the loose side. When you chamber a round in a loose chamber(factory), the loaded round will sit in the bottom of the chamber if you will. Gravity will pull it down.

When it is fired, the bottom of the case is already laying on the chamber so the only place for the case to expand is up. The expands the case to fill the chamber and results in the buldge on the one side of the case.

With repeated firings, this generally will even out all around the case to some degree but is it simply from the chamber being much larger then needed.

The only way to cure this problem is with a rebarrel job and a properly designed reamer that will limit this expansion and reduce this buldge.

Once the case is fireformed, and if you neck size or partial full length size, you will generally get good grouping if the rest of the rifle is put together well which it sounds like it is.

Repeated full length sizing will work harden the brass and could result in some case body splits.

This is typical in factory rifles, some to a higher degree then others but very common.

Nothing to worry about and don't try to get rid of the buldge with your case sizing. The case is just expanded to fit your loose chamber and let it stay that way for best results on target!!

Don;t give it another though and have fun with your little hot rod!!

Kirby Allen(50)

gonehuntingagain · #4 05-02-2005, 09:51 PM

This seems to be a common problem with the Rem 700's. My gun and 4ked Horn's 308's do exactly the same thing that you are describing to the case after firing.
Eventually there will be a line that you can feel on the inside of the case around the base (where you see the bulge). If you stick a unfolded paper slip down the inner wall of the case, you will feel a line that feels like a "thin spot" in the brass and may be indicative that a case-head separation will happen soon.

I have no clue as to why this happens - it may not be just one thing, but a combination of variations that would occur in the mass-production process.

Buffalobob · #5 05-03-2005, 06:56 PM

Thanks everyone, it looks like at least I am in good company with Gonehuntingagain and 4kd horn.

Chris

If I should be so lucky to get enough time and shooting to shoot this barrel out I will certainly let you fit me another and work the action over.

Kirby

Keep working on those magnums - speed is good and more speed is better.

#6 05-03-2005, 07:06 PM

Wow

This is a great thread. I also have the same issue in a Win 70 yote. 300 WSM It's amazing the stuff you learn on this site.

Joe

brian b · #7 05-03-2005, 10:37 PM

[ QUOTE ]
This seems to be a common problem with the Rem 700's. My gun and 4ked Horn's 308's do exactly the same thing that you are describing to the case after firing.
Eventually there will be a line that you can feel on the inside of the case around the base (where you see the bulge). If you stick a unfolded paper slip down the inner wall of the case, you will feel a line that feels like a "thin spot" in the brass and may be indicative that a case-head separation will happen soon.

I have no clue as to why this happens - it may not be just one thing, but a combination of variations that would occur in the mass-production process.

[/ QUOTE ]Gonehuntingagain,
You are absolutely correct IT IS a combination of variations that causes this. #1 saami spec. reamers (that are oversize in comparison to most brass if not all). #2 HEAD SPACE ( if you are getting thin spots in the web area most likely head space is long in the chamber or you are oversizing your brass) Remington is famous for this but absolutely the worst I have seen is Thompsons in some of there contender chamberings where the web of the chamber is .010 larger the head space is .015 longer and the throat is unreachable. this can ruin even the best of brass after only a few firings. that is why most of the people on this forum try an AFTERMARKET experience (custom barrels,snug if not tight neck chambers ,good if not great reloading equiptment and patience with mediocre things that we wished we had control over but DONT.) B.