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I'm trying to work a load up for my 308 tikka barrel
If I seat them deep enough to feed they key hole, if I seat them out to engage lands they won't feed
I'm using lead cast flat nosed projectiles
What causes projectiles to key hole?
What things help to prevent it?
At what speed do lead projectiles grip and spin with modern rifle twists 1-10 to 1-11 ?
They should grip and spin as long as they exit the barrel, they may not be spinning fast enough to stabilse the lenght of bullet tho.
Is the trick to jam them into the lands or what?
I'd like a mag fed round if I could
How heavy are they? if you are trying to shoot 220gr subsonic out of a 11 twist you are always going to have problems.
@vietnamcam 200 gr flat nosed projectiles
Trademe cast ones 2 gas checks
And I'm using 8.5 gr of trailboss to push them
Accuracy is trash and they often go sideways thru targets
They are a bit 30 but for a 10 twist things should work in my brno but they don't seem toQuote:
Originally Posted by berg243
If it helps I'm happy to modify or change projectiles
if anyone's happy to share their tikka recipe I'm all ears
Might be better to try some of @shooternz s 150gr ones.
How soft is the lead? Are they stripping through the rifling?
get the accuracy sorted, but try to keep them hitting sideways. will probably be quite effective on pestilence....Quote:
Originally Posted by Bill999
Two gas checks? Measure the length of one and whack it in this formula 150 x the bullets diameter in inches squared divided by the bullets length. The answer is the twist rate
eg bullets diameter is .308, length is 1.5 inch
150x.095/1.5 = 9.5 the twist needed is 1:9.5
My 185 grainers measure 1 inch, I run them at 1450 fps with no gas checks but a good lube.
Maca has raised a good point even with a gas check if you try and push them too fast they will strip, tumble and give you a big cleaning job. A lack of lubricant will also do you in.
Geeze Marty lack of lube? Could be a age thing?beaver grease huh?
Dr Zogs sex wax, also good on surfboards
Hey Marty, does bearing surface length come into play with that formula?
Cheers
Quote:
Originally Posted by Bill999
I take it from what you say that they don't tumble when they are seated further out.
Seat one further out and use this until it feeds well:
Attachment 97594
You should still have some meplat left, the more the better of course.
Dont think so, its the Greenhill formula worked out by the royal artillery back in the 1850s. Works for solid lead and copper jacketed lead bullets only. Weight doesn't feature either Its still used today so they got it pretty much right first time.Quote:
Originally Posted by Fireflite
@Bill999 If they touch the lands do they still tumble? If poss show us a photo of the projectile and give us the dimensions.
Take weight out of the back.
It like a mortar. They don’t fly backwards
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The twist calculator on the Berger website is very good from memory
Try the 170g ones from shooter nz,i use 8.5g trail boss and they shoot an inch @ 50m thru my sako A7,I find they feed better than the 151g ones as they are a longer bullet and pointed profile not flat nose.
And pays not to jam them in the lands as you will sometimes end up pulling the projectile from the case and filling the action with powder if you try and eject the unfired round,,I know from experience..
My sub guns action is Stained with the lube that comes with the projectiles so I think there is plenty of lubeQuote:
Originally Posted by Marty Henry
The bullets measure 0.984inches
Am I right to think a gas check is a recessed ring at the base of the projectile filled with lube? As there's two of those and one more above that's not lubedAttachment 97609
If I replace 1.5 inches with .984 it gives me 144 which I imagine is 14.4 inch twist
One gun is 1/10 and the other is 1/11 both seem to keyhole around a third of shots
I'm not having this issue with 165gr ballistic tips at around 1050fps
The only lead bullet Iv recovered so far was too damaged to tell if it's taking the rifling or pushing past it
Attachment 97610
If I seat them out they won't mag feed into the barrel with the flat face at allQuote:
Originally Posted by Marty Henry
If they won't mag feed I'm going to change projectiles regardless of accuracy as it won't work for the follow up shots which I sometimes need due to such low expansion/terminal effect
So Iv limited myself to brain shots this far with ballistic tips which works great because the load is accurate
But they are too hard to expand at subsonic speed so it more like poking with a knitting needle
No a gas check goes on the bottom of the projectile to protect the lead base from the propellant gases, mainly used for supersonicQuote:
Originally Posted by Bill999
https://en.wikipedia.org/wiki/Gas_check
@Bill999 thanks for the photos the bullet looks to be a flat base and the two red rings are lube. The third groove is a crimp groove and shouldnt be lubed. A gas check is a little copper cup crimped onto the bullets base there should be a recess to allow this.
The recovered bullet shows one rifling groove that looks to extend up to the mushroom.
The bullet is what is called a bore rider where the nose of the bullet is just land diameter with the grease grooves being slightly over groove so for a 308, the nose is usually 300 to 303 with the lube grooves being 309-310.
At that length they should stableise in a 10 twist but I have found that some rifles are quite picky about what they eat with cast bullets. The expansion looks normal for a lead bullet made from hard alloy.
I suggest you have chat with shooter nz about other cast bullets. I run a 170 grain round nose ungas checked in my 3030 and 308 over 10 grains of blue dot if thats any help. Flat nosed bullets feed fine in the 3030 as thats what the design is for but you need an ogive to run the bullet up with most box mag rifles.
Hi Bill999, You got those 200 grain flat points off me, In theory they should be stabilised with a 1:13" twist at 1050fps, I have two .308s one shoots them the other won'tQuote:
Originally Posted by Bill999
it's just one of the mysteries of shooting, I have a new mould for .30 cal casts a 200 grain HP PM your address and I will send you 50 to try no cost.
Thats a good bugger right there.
not wrongQuote:
Originally Posted by Marty Henry
That sounds great mateQuote:
Originally Posted by shooternz
Is HP hollow point?
I'm getting the feeling that I'm not setting these ones up right.
Are there hard and fast rules to getting lead projectiles right?
I'm pushing them with 8.5 gr trailboss to get under the sound barrier
With cast projectiles the first lesson that needs to be learnt is that " Forget what you already know and work from there " .
For subs soft lead is all you need . You don't need gaschecks and soft lead will " fill " the bore better .
Generally projectiles should be bore size to .003 thou bigger . I get good results at .002 thou .
Projectiles should be up close and personal with the lands . And carry a break down cleaning rod ;) .
Yes they are Hollow point and the lead mix is soft with the lube is good to 2000fps before lead fouling happensQuote:
Originally Posted by Bill999
they should expand to around .400" at 1050fps, 8.5 of Trail Boss is ok for sub loads, if you want a bit more range
AR2206H is good to push up to 1900fps
Right from the start I intended to make an overgrown subsonic .22 so fast lead hollow points really are my ultimate projectile
At the moment I can stack ballistic tips at 25m but when I dig them out of the ground they look ready to load back up again
The standard jacketed bullets need an impact velocity of 1800 fps to expand the only jacketed bullets that will expand are the special subsonic ones
coming out now but they are very expensive, The cast bullet has been killing things since the 1850s no reason why they won't work now.
I have gear for expanding subsonic jacketed bullet manufacturing in 30 and 44 + a lot of other tooling and components.
If anyone is interested in purchasing it I’d take $7k ono for the lot as simply don’t have time to use with other commitments. $20k+ to buy new with a 2yr wait.
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Have you got a photo of the new 200g pills Robert?i might be keen on some.
Yea mate they just arrived
Attachment 97997
I only have 4 primers left so I need to wait till next week for them to arrive
They look like perfection for a subsonic projectile, the ballistic tips I'm using at the moment look like I can re use them when I dig them out
Attachment 97999
I haven’t read this entire thread so maybe above
If you are shooting cast bullets you need to make sure they are oversized for the bore
309 or 310 in this case
It could be twist rate related for sure also
Gaschecks on bullets although they shouldn’t affect functionality at subsonic speeds they are not required for slower load a flat base lead bullet should be just fine unless you’re going to load the same bullet supersonic and can’t be bothered with 2 bullets
Just looked at your recovered bullet photos, thats quite solid rifling engraving with a bit of metal scraped into in the boat tail. With a cast bullet which is larger you could be getting tails of metal off the bullet that upset the aerodynamics. Just anothet thing to consider.
At subsonic velocity the range the bullets are used at 150 metres or less I don't think aerodynamics will be a problem, From what I have seen the lead scraped
from the bullet ends up in the lube grooves and the gap in front of the gas-check
