caution!!!! need some opinions

[alaskabushmaster]

This was 31 grn lil gun under the 300grn deepcurl. Any input on why besides the obvious that its pressure? Anybody ever had this at somewhat low velocities and pressures? Now only 4 out of 20 did this.


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[Hoot]

This was 31 grn lil gun under the 300grn deepcurl. Any input on why besides the obvious that its pressure? Anybody ever had this at somewhat low velocities and pressures? Now only 4 out of 20 did this.
http://i60.photobucket.com/albums/h27/tzeek777/Brass.jpg

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It can happen when the bullet is traveling slow enough that as it passes the gas port, the gas blows back to the BCA and starts the unlocking rotation (hence the swipe) before the bullet clears the barrel allowing the pressure to bleed down enough to un-seize the case from the chamber wall. It is referred to as a timing issue. Normally rotation of the bolt is timed to start unlocking shortly after that pressure has fallen enough for the case to release from the chamber wall and the case actually rotates with the bolt as opposed to sitting still while the bolt rotates against the head, hence no swiping. At least that's how I understand it. Solution, more velocity. Lil Gun is a little on the fast side for 300gr bullets. If you chronied your shots, were those a little slower than the ones that didn't swipe? Oh yeah, some times, there is no obvious explanation, expecially if it's only occurs a couple of times, mixed in with shots that didn't do that. Seen it go both ways.

Hoot

[Siringo]

What weight buffer are you using? I have shot a lot of resized 300's using 30.5 grains of LG and only had that problem when I had a carbine butt stock with a 2.8 OZ Buffer. All I use now is an H3 (5.0 oz).

Maybe someone else (Hoot) has a better feeling for this --- but I sometimes wondered if the heavy bullets/cartridge slammed into the bolt face more violently than the 250's --- before the chamber sealed off. Look at the case and see the extrusion of base into the ejector hole. When I shot 400's, it was much more prevalent than with the 300's.

[alaskabushmaster]

Hoot I feel you are right about the timing issues. I looked at all the cases and sure as hell they all have the marks. The others are much lighter than these but still there. I was scared i was running too much pressure for a second but its a swipe and unlocking issues it seems. I bumped it up to 35grns loaded three and sacrificed a flower pot in the yard. Guess what! no ejector marks or swipe marks....up to this point this load has been accurate with no issues. I did change primers to remingtons from the federal match...maybe that changed the velocity enough to mess with my mojo!

[kottke_35]

Just fyi,

I've loaded the 300 up to 37gr lilgun with no I'll effects. Best accuracy was at 36.5.
Rem 7 1/2 primers with a T/C at .475.

B.

[Hoot]

Just fyi,

I've loaded the 300 up to 37gr lilgun with no I'll effects. Best accuracy was at 36.5.
Rem 7 1/2 primers with a T/C at .475.

B.

These are all good inputs about swiping issues. Another factor alluded to by Siringo's observation is to make darn sure that your chamber is clean and free of lubricant. If you run your rig really wet, which they love, lubricant can some times get thrown around and get into your chamber along with the round. It can also happen if you attempt to improve feeding by lubing your magazine which can rub off onto the rounds. I make sure I degrease my rounds after loading them up. While the pressure generated during ignition is significant enough to displace that lubricant and still stick the case in place, it may take a few microseconds longer. That can allow it to shove back a little before seizing up. That's where you get embossing of the ejector and extractor into the head, though too much pressure more often causes that. At such a modest charge as you were using, I doubt that was the problem.

Federal 205M primers are almost identical in performance to the Remington 7-1/2, though the Remingtons run a tad hotter and IMHO, are the better choice for this caliber. We're talking only a few FPS difference, out of thousands of FPS total, between them with the edge going to the Remmys.

Side note: I hope with some of our recent concerns over Remington cutting corners on their QC, that it doesn't ripple into their primers as well.

Hoot

[wildcatter]

Hoot is Spot-On, also HEED his advice about Lubes in the chamber, and Siringo provides, a cure. Of course, upping the charge provided another cure and also has a Ballistic Advantage.

I know you're about to go out on a Hunt, so go with what you've got, but in the future, you'll find better results, with these 300's, with 296/H110, 4227, or prolly 1680 being the best choice (with heavy bullets only).

MAKE SURE, you Thunk-Test your reloads, at the bench and then cycle every-single-round (in a safe area), BEFORE YOU GO OUT ON THAT HUNT!!

..t

P.S.. That Advice, is payed with a quart of Highly-Seasoned & Canned, Bear Cubes/Chunks..wink..t

[Texas Sheepdawg]

P.S.. That Advice, is payed with a quart of Highly-Seasoned & Canned, Bear Cubes/Chunks..wink..t

There he goes again thinking about food.

[LlindeX]

Alaskabushmaster,

For what it's worth to you; My Opinion is: I'm Jealous of you!
Living in alaska and having the ability to test out my 450B the way you can would make my retirement heaven. Good luck on your bear hunt! Post some pics when you get back. You'll really turn me green with envy.

[alaskabushmaster]

I didn't set up the chrono this time around but I bumped the charge to 35 grns and loaded ten rounds. All ten rounds fired fine no cycle issues, 2 inch groups at 75yds. Not the kind of accuracy I get from the barnes but I can hit a bear over the baiter in the heart at 50! The swipe marks are gone from the cases. I went back to the remington 7 1/2s as well. Tonight I will load 20 rounds with the 300 deepcurls and 20 with the barnes XPBs. I don't believe I will be taking the deepcurls as my primary ammo. The barnes will stay in the pack with the deepcurls as a back up. I also cleaned my chamber as good as I could before shooting. I do not run my guns very "wet" just a little hoppes gun oil. Thank you all for the solution to my problem. I have a purple mark on my cheek from the bushy and the 300 today time to find a frozen chunk of meat.