reading pressure signs

[Banshee]

Sticky bolt, cratered primers, difficult to extract casing, shiny spot on base of brass.

All winchester brass, freshly trimmed and full length resized with Rem Magnum primers.

My 270WSM seems to have a few quirks. After two fouling shots today, I started with a ladder of Re17 and 130 gr Etips. The bottom of the ladder, 58 grains, had two of three rounds with sticky bolt and difficult extraction. Having experienced this before, I fired the 59 grain loads - no issues, Then the 60's and the 60.5's and 61's. No issues, minor cratering at 61 grains at 3259 fps.

What is up with the difficult extraction and sticky bolt at 58 grains? The chamber hasn't reached full temperature yet?

FWIW

I switched to 130 gr Ballistic tips again with RE17.
61 grains = 3308 fps
62 grains = 3347
63 grains = 3432

No craters, no sticky bolt, no difficult extraction, no shiny spots.

These seem way to fast. It was drizzling and I didn't use the sun shades. is this a known problem with chronies?

 

[DrMike]

My load with 130 grain E-Tips uses a max of 59.5 grains of RL17. I consider this to be a maximum, yielding about 3250 fps. I'd consider anything over 61.6 grains of RL17 to be excessive with a 130 grain BT.

 

[FOTIS]

They are way too fast. ! :shock:

 

[Banshee]

I agree, too fast.

Where are my pressure signs? That is the reason I thought the chrony might be lying.

 

[DrMike]

As long as your Chrony was fully opened, the distance between the eyes is a constant and the velocities generated will be accurate. The velocities appear excessive. Where did you get your data for developing this load?

 

[Banshee]

The basic load is from the Alliant site for a Speer BTSP bullet with Reloder 17. I subbed in a Nosler BT. That load maximum is 62 grains.

this was my second session for this load. I started at 58 grains last week and have seen nothing that would indicate it is over pressure.

As stated in the first post, this rifle has a quirk of giving the usual pressure signs early in the session. I've had more sticky bolts and hard to remove casings on minimum loads than maximums. I always fire a couple of fouling loads first, and then work upward.

Since this is development, I start by calibrating both scales and each charge is weighed twice. I label each case as it is loaded.

Without the chrony indicating too high of velocity, these would appear to be just fine.

 

[1Shot]

A lot of things could cause your situation. First off it could be a little oil film in the chamber left over from your cleaning. It could be barrel temp. When you first start off the barrel is a little cooler and thus the chamber is a little tighter. Fire a couple rounds and you change the barrel temp ever so slightly but the metal has expanded ever so slightly and that could be the difference. Some rifles will show higher pressure on the first couple shots when the bore has been cleaned really well of all fouling. The fouling in a bore acts as a lubricant and when none is present for the first shot or two the bullet has a harder time pushing down the bore and thus the pressure rises.