Sticky bolt?

Greetings again,
I have done a fair bit of weighing .308 W cases over the years and together with data mostly from Handloader mag have found the following. Kiwijames my weighing of Lapua brass marked 7.62 x 51 and 308 Win is much the same as your results of around 173 grains. This is a little heavier than Remington and Winchester recent production but lighter than Federal which is about the same as LC 81. The Lapua brass also has a slightly larger head diameter so some of that extra weight is here. There is a strong correlation between weight and case capacity. Other than a larger diameter head or differences in the rim recess size can have an effect on these in new unfired brass. In fired brass all bets are of because the size of the chamber has an effect. Handloader data showed capacity of between 53.4 and 54 grains of water for Remington and Federal cases. Winchester cases held more but more recent production is heavier, close to Remington. Measuring case capacity with water is a little hit and miss as any air bubbles will give a false (low) reading. All in all I don't believe your bolt problems are due to case volume. Also I would be very surprised if any Lapua military cases are head stamped 308 Win. The presence of the stab crimps may be needed due to non toxic primers. It would be interesting to know what the original rounds were.
One thing that you may wish to check is if the projectiles are close to or touching the rifling. For hunting ammunition there should be at least .05 mm (.020 inches) of jump. Hunting projectiles vary slightly. If they are too close the odd one may touch giving a pressure spike.
Regards Grandpamac.

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Originally Posted by Gibo

Did you get that brass off me?

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That solves it! They've been in the microwave then haha

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Originally Posted by Dead is better

That solves it! They've been in the microwave then haha

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:D

Hard extraction/stiff bolt lift without any conventional pressure signs is often caused by brass not being sized enough by your dies, usually at the base.

Often the first couple of firings on new brass show no signs of stiff extraction, then as the brass expands after multiple firings and isn’t sized back down sufficiently by the dies, the brass doesn’t spring back enough after firing and grips the chamber walls causing hard extraction.

I suspect this may be what you are experiencing.

A small base sizing die, new brass or re-reaming the chamber with a slightly larger spec reamer are all solutions.

Greetings Again Kiwijames,
Another thought. The fact that the brass chambers easily each time suggests that the dies are doing their job. I am starting to think you may have a tight spot or ring in your chamber. These do happen, even in the best rifles, and can be hard to detect. There is seldom a problem with factory rounds and the ring can't be seen looking into the chamber. You may see a slightly shiny ring on the outside of the problem brass. The problem usually shows up as hard extraction after the brass has been fired a few times. Each time the brass is fired the body work hardens a little and springs back a little less. Eventually the body does not spring back enough and you get a sticky or hard bolt lift. In your or other posts above a lack of primary extraction is with the Forbes action is mentioned. This would aggravate the problem. As far as a fix goes setting the barrel back a thread and re cutting the chamber would probably be needed but you may be able to manage the problem to an extent depending on where the ring or tight spot is. Using once fired brass for hunting should stop the problem happening in the field.
Regards Grandpamac.

OK I think I may have cracked it. I have bought new brass, new powder and new pills. Measuring for OAL to the lands with the new bullet I figured I'd re-check my original measurement with the 150NBT. It appears I have 0.020" too less in my initial measurement so what was to be a 10 thou jump is now a 10 thou jam. I plan to run with CFE223 and 155A-Max bullets in my next brew. I can't see it being any better really but it's cost effective and available.
I hope this is the end of my issues. Cheers to everyone for your assistance.
James

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Originally Posted by kiwijames

OK I think I may have cracked it. I have bought new brass, new powder and new pills. Measuring for OAL to the lands with the new bullet I figured I'd re-check my original measurement with the 150NBT. It appears I have 0.020" too less in my initial measurement so what was to be a 10 thou jump is now a 10 thou jam. I plan to run with CFE223 and 155A-Max bullets in my next brew. I can't see it being any better really but it's cost effective and available.
I hope this is the end of my issues. Cheers to everyone for your assistance.
James

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If you are using Nosler Ballistic Tips be aware their ogive length varies WILDLY between batches......I have seen just over 45 thou...yep over 1 mm...FFS... :wtfsmilie:

That may explain the variability I’m seeing in my 06 with 180 gn NBTs on 57 gn of 2209. I’m jumping them 40 thousand but have had 2 in 30 blow the primers out!

Greetings All,
Not just Nosler. I have found significant differences between three different Hornady projectiles. The differences were between older and more recent batches and not within the batches. In short later projectiles needed to be seated deeper due to a sharper ogive with the .22 cal 55 grains and distance from the lands was reduced in the 140 grain 6.5 interlock and 174 grain .303 round nose. The differences showed up on the chronograph but only on the target with the .303. As the projectiles are not all made in the same dies even in the same box some variation should be expected although I have not detected any. My minimum distance from the lands is 1 mm to allow for some variation. With the .22 cal 55 grains this wasn't enough.
Regards Grandpamac.

Using a comparator length instead of a COL (cartridge overall length) solves varying projectile length issues for hunting type reloading

School up on what a just touch or 5 thou / 10 thou jamb looks like on your projectiles ogive/shank

Then load accordingly for either mag fit or max accuracy


Here you can see rem mag ammo (162 ELD-X) that’s loaded for a ZCL (zeroed comparator length) of 2.641 inches

My just touch length in the Sako 75 is 2.645

So I’m jumping these projectiles to the rifling lands by 4 thou

Measure EVERY bullet that you make.

Attachment 133368

I always sort of thought that the ring on oglive caused by seating die will be pretty darn close to same on any and all projectile shapes...eg projectiles in same batch may have different overal lengths but the oglive will be the same so the distance to rifling by the fat curvy bit will be the same no matter what overall length is.

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Originally Posted by 7mmsaum

Using a comparator length instead of a COL (cartridge overall length) solves varying projectile length issues for hunting type reloading

School up on what a just touch or 5 thou / 10 thou jamb looks like on your projectiles ogive/shank

Then load accordingly for either mag fit or max accuracy


Here you can see rem mag ammo (162 ELD-X) that’s loaded for a ZCL (zeroed comparator length) of 2.641 inches

My just touch length in the Sako 75 is 2.645

So I’m jumping these projectiles to the rifling lands by 4 thou

Measure EVERY bullet that you make.

Attachment 133368

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Yes. I'm measuring my ogive. I'll do the first handful then check every 5th or so after. I've not struck much problems and I don't load closer than 0.010" typically not have I needed to. https://uploads.tapatalk-cdn.com/202...aee8d724f7.jpg

Special Jimmy you big gut shooter. Whack those bullets in a bit deeper and off we go for a hunt.

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Originally Posted by Ginga

Special Jimmy you big gut shooter. Whack those bullets in a bit deeper and off we go for a hunt.

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Special Jimmy was great in Tropic Thunder[emoji16]

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Same sort of comedic movie like fuck ups occur when he’s on the end of his latest GPMG.

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Originally Posted by Ginga

Same sort of comedic movie like fuck ups occur when he’s on the end of his latest GPMG.

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Bwaaa Haa Haaa[emoji106]

I can only imagine.[emoji1787]

Sent from my SM-T510 using Tapatalk

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Originally Posted by Ginga

Same sort of comedic movie like fuck ups occur when he’s on the end of his latest GPMG.

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Oi, fawn slayer. You can shut the fuck up.

OK, this shooter is now in the sorted pile.
It shows pressure very early. I'm now running 3-4 grains under Hogdons minimum load for CFE223 and the 155 A-Max looks good.
https://uploads.tapatalk-cdn.com/202...a5db5db03b.jpg

Velocity? Speed. You must have speed.

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Originally Posted by Tahr

Velocity? Speed. You must have speed.

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Its going fast enough I'll bet. I do need to chrony it but I'm really only keen on accuracy at present.
Put it this way, 49g was giving 2871FPS but was a very tight bolt. 47g only just had the faintest of feel in the bolt. I'm going to play with the 45-46 load a little and see what works.
I don't have a chronograph and have typically validated at range to get speed.

feed it a big fat round nose and speed doesnt matter a shit....if you hit it,it is dead..lol pleased you have it sorted.