Ejector swipe a false pressure sign?

[Geno C]

I've finally gotten around to working up a load for my brx with formed brass. While forming I was shooting 29.4gr of Varget under a 105vld .010" jammed. It shot many sub 1/4 moa groups and didn't show any pressure signs up to 30.0 but shot great at 29.4 and 2770fps.

I figured with the former brass I'd start at 31.0gr and work up .3 at a time. The first cases showed ejector swipes. Primers looked good, not even a hint of stuff bolt. I thought that was odd so I backed off to .005" off the lands and shot 31.3; still got swipes. I strapped the magnetospeed on finally at 31.9 and got 2970 with an extreme spread of 17fps.

I guess I didn't expect to have the ejector swipe on my staring load and I'm wondering if anyone else is seeing the same at such a low charge?

 

[Judd]

Sounds like you have a really short freebore...mine is .104 and I can shoot 32.6 with no pressure signs. After about 10-12 loadings on brass the pockets will get a little loose though.

 

[Fast14riot]

In AR'S the ejector can sometimes have sharp edges and cause premature pressure signs, adding a small radius or chamfer will help alleviate that, might help on a manual shifter as well. Of course, check other signs like case head swelling, primer condition, etc for pressure to be certain and safe.

 

[Geno C]

My freebore is .105", in at 1.695" base to the .241" diameter point of the bullet. I modified my comparator to read closer to the bullets bearing surface

 

[Geno C]

I'll check the ejector hole and put a little chamfer on it for good measure.

 

[Fast14riot]

Chamfer on the ejector plunger itself, not the hole.

 

[billlarson]

different barrels..... require different loads...... due to bore size and finish...... that`s assuming your brass is sized rite and neck tension is not excessive.......
bill

 

[Geno C]

Bill, I'm very aware that different barrels require different loads and shoot different speeds.

I was just asking if anyone had seen ejector marks but no other sign of pressure. I tried to provide as much info as I could in order to possibly rule out being over pressure. I haven't run into anyone that is this low in pressure and velocity as their max yet. Most I talk to and have read on here are above 32 and many are above 33. I figured I would make it to 32 before seeing any classics pressure signs. That's why I'm surprised to see the ejector marks at 31

 

[LCazador]

Bill, I'm very aware that different barrels require different loads and shoot different speeds.

I was just asking if anyone had seen ejector marks but no other sign of pressure. I tried to provide as much info as I could in order to possibly rule out being over pressure. I haven't run into anyone that is this low in pressure and velocity as their max yet. Most I talk to and have read on here are above 32 and many are above 33. I figured I would make it to 32 before seeing any classics pressure signs. That's why I'm surprised to see the ejector marks at 31

The best way to keep track of pressure is to measure head diameter on your new brass and then monitor this as you progress on your load work up. Bright spots from ejectors, flattened primers, and hard bolt lift are not the most accurate way of monitoring pressure IMHO.

 

[boltfluter]

Gene,

Is this, by chance, a new lot of powder. I have seen Varget vary quite a bit from lot to lot. Just thinking out loud.

Paul

 

[Geno C]

Thanks Paul, that was my first thought but I'm still on the same lot. I'll back down to 30.5 and see what happens

 

[Geno C]

30.5 there are no ejector marks. Velocity is 2847 with sd 4.3 and es is 11 over 5 shots. I guess this will just be a slow barrel with this combo. Might have to try h4350 like a few other guys on here.

Thanks for the help guys.

 

[XTR]

possibly still lube on the cases? Will give ejector marks every time assuming there is one.

 

[Geno C]

No lube. Spotless, dry cases. .002" neck tension also.

 

[BoydAllen]

Bone dry chamber?

 

[Geno C]

Yes

 

[BoydAllen]

Sharp shouldered minimum taper cases do not tend to show pressure on primers to the same degree that typical factory designs do, if the "headspace" of the ammo in the chamber is kept to a minimum. I would believe your ejector marks, and chalk it up to differences in barrels.

 

[Geno C]

Boyd, I believe that just might be he case. I shoot a fair number of ackley cases and primers have always been the first sign of pressure for me. I will have to settle for 2850 if I'm gonna stick with this combo.

There is a thread on here about some guys getting good results with H4350. I might give that a try and see if I can get a bit more speed out of it

 

[carlsbad]

Are your cases the right length? If your chamber is very tight, you'll get the swipe closing the bolt. Do you have slight resistance to bolt close? I was neck sizing only my 6br and found that I had this problem when I didn't bump the shoulder every other reloading.

--Jerry

 

[Arkrunner]

How much case head expansion is too much?