Tight closing bolt help needed on factory PPU ammo please

stratts

Well-Known Member
Hi chaps,
I have a ZKK601 .308 that I have always used PPU 165gr rounds in as they were the 1st ones I tried when I bought the rifle and they group great. Whilst at the H4H shoot, I ran out so had to buy some at Bisley, but they only had some GGG 168gr which I bought and used (very well I might add get 40/50 on the running deer!!)

What I noticed was how much easier the bolt closed using the GGG ammo as opposed to the PPU.

What causes the tightness when closing the bolt with certain factory ammo?
Is it safe to use ammo where the bolt is tight to close?
Will it affect acuracy? This may (hopefully) be the reason I shot like a muppet on the stalkers test!!
Is there anything I can do to check for problems, ie, colouring in a round with black pen and looking for marks, etc? I have a couple PPU left in the ammo safe at home so don't need to buy a full box to try.

I know the chamber is nice and clean but I've never had the bolt to bits to clean so maybe this could be an issue? If so anyone know how to dismantle a ZKK601 bolt for cleaning?

Cheers

Stratts
 
When I tried PPU in my Tikka 243 both the 90 and 100 grain were really tough to close the bolt. Shot ok but not great, the two weights of PPU in my 308 shoot terribly but the bolt closes fine. I've read on here before that quite a few people have the same tight bolt with PPU ammo.
 
I have a ZKK601 in .243 as well but have not used it for ages. I'll check how it compares later as I honestly can't remember if it is as tight or not!! :doh:
 
Now that I've started reloading I plan to FL size some of the PPU brass and see if it fits any better or not.
 
Stratts

Two small questions:

Do you clean the bolt lug recess? Could be full of gunk.
Do you lightly lube the rearwards face of the bolt lugs? No lube is not good, too much lube is not good either.

Regards

JCS
 
Hi mate

Yes to cleaning the lug recess of sorts! I have never applied any cleaning product (I use wipeout) but I do use a cleaning mop on a short rod to wipe around in there. Maybe it needs a good soak and scrub out?!

No to lubing the bolt lugs! I do think the bolt needs a good clean (hence one of the questions) but I'm not sure how best to do it and if it comes apart easily? It looks like the end unscrews by using a big screwdriver but I'm not sure,

Cheers

Stratts

Stratts

Two small questions:

Do you clean the bolt lug recess? Could be full of gunk.
Do you lightly lube the rearwards face of the bolt lugs? No lube is not good, too much lube is not good either.

Regards

JCS
 
As far a I know the brass is thick on the PPU and causes it to be tight to chamber.

It's not a brass thickness issue, instead most likely a spec / tolerances one. Rimless cartridges such as the 308 Win 'headspace on the shoulder' that is the chamber and case dimensions from the locked & cocked bolt-face to a line around half way up the chamber shoulder section called the 'datum line'. The cartridge / case is similarly specified from the case-head to a matching invisible [datum] line on the case shoulder.

The cartridge controlling and registration body, in this case the American SAAMI for the 308W, produce the toleranced drawings for both to be used by all manufacturers. As nearly all affordable mass manufacture has to allow some tolerances from the ideal, the max and min allowed tolerances are quoted. For all ammunition to fit into all rifles, the cartridge case max allowed value for this measurement has to be a fractionally shorter value than the same aspect of the rifle chamber at minimum tolerance level.

In practice, most factory cases trend towards minimum and most factory rifle chambers towards maximum giving easy chambering of a new case / round but at the expense of a larger gap (excess headspace) than may be ideal for case life / accuracy. (Most people who handload set their full-length sizer dies too far in the press frame and also produce this situation or worse.)

Occasionally, you get a minimum SAAMI chamber and slightly over-max headspace case giving a slightly tight case to chamber fit. Not ideal, but there is no safety risk as long as the bolt can be fully locked. Fired brass retains that form and if it is neck-sized in a reload will continue to be hard to chamber, more so in fact as shoulders migrate forward slightly under firing pressures even if a crush-fit before firing, so a FL or 'shoulder bump' body die has to be used to 'bump' the shoulder back a few thou'.

A tight fit situation as described should show 'witness marks' on the case-head from the bolt being held hard against the face and turned in bolt lock-up and (possibly) smaller less obvious marks on the case-shoulder from being forced against the matching chamber surface on lock-up.
 
Clean the shoulder area of the chamber. Quite often hard crud can get built up on there resulting in difficult round chambering. Make sure it is clean & bright steel. (Cleaning solvent on a fine grade Scotchbrite pad wrapped round the end of a rod or dowel makes this easy - little force is required - don't go at it with a power tool or heavy steel wire brush!)
Clean the action lug recesses - particularly the front facing thrust faces. A proper action cleaning rod which takes dental swabs is good for this job.
Clean the bolt lug rear facing thrust faces.
If you can borrow one, use a headspace "GO" gauge, to measure the headspace. - The bolt should close on this one without resistance. -- If the bolt won't close on it, the chamber is short & you can expect resistance when chambering cartridges.
The Hornady Head space gauge which clamps onto a vernir gauge can be used to measure new ammo without cycling it through the rifle.
CZ 243 rifles often seem to have been made with tight chambers & suffer the tight bolt on loading malaise. But if kept properly clean as above,, most factory ammo will fit.
Don't assume the ammo is wrong - Measure & compare to verefy as above.

Ian
 
I have noticed .243ppu are somewhat tight in my Howa
but they are shooting good groups, better than most
other factory ammo.
 
Hi feller seen it a few times on .308/.243 rifles new out of the box howa rifles with ppu ammo , skipped the other posts so you may have already done this lol , try another brand feel you will find out the fault is with the brand ! if so return them as lots of others have had to . try geco had some for sale .243 .308 no takes at £10 a box at the h4h lol could have had it foc as it was an open box :doh:boss .
 
I have had premium brands of ammunition make an action tight. We measured the rounds and the differences were quite large. The bullets on some were seated to far out
 
I have not found a rifle that PPU fctory ammunition will chamber easily in. I need to lean on the bolt of my FN 6.5x55 and my Savage 308, my daughter's M-70 243, her husbands 30-06 Howa all have varying degrees of pressure needed to close the bolt. ~Muir
 
Can you gently run a round through a siser, or find the tight spot in chamber and ease with a bit of grinding past on a case
 
CIP dimensions for 308 are such that maximum cartridge will not fit in minimum chamber. Namely L1 and L2 in this drawing:

http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/tabical-en-page125.pdf

I have experience only with PPU FMJ 308 and 2 rifles. The bolt is a bit tight in Tikka T3, and not tight at all in Sabatti Mercury. Brass is OK, needs trimming after first FL sizing (which I do anyway, but PPU is a bit longer than most brands).

Regardless of ammunition used it's very good idea to keep locking lug area clean and lightly lubed with suitable grease, both action and bolt side. You often see galling in locking lugs in used rifles.
 
The 180 ppu I used in my T3 30-06 was tight as well. If you look at the bullets you will see they touch the lands. I think it's more to do with the bullet shape. Ogive I think it's called. Every single one had marks from the lands. They all shot 1/2" groups thou.

Just my observations.


Jon
 
I doubt there's any problem with the rifle - my rem 700 chambers all other factory without problems but the ppu .308 150 gr are terribly tight on the bolt leaving brass witness marks on the bolt face. We tried them in my friends Howa and it would not close at all. After firing in my remmy the bolt would then lift smoothly. Incidentally, the ppu 165 gr PSP rounds were far better with minimal tension evident on bolt closure.
Just for reference my remmy has recently been rechambered/barrelled in .308 by Steve Kershaw so I would expect the chamber tolerances to be spot on.
 
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