75 grain bullets in 223

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  • Last Post 01 March 2012
CB posted this 29 August 2010

I have a new rifle that shoots jacketed bullets very well ”€œ well under a MOA for five shot groups.

It also has shot cast very well at times. Two days ago I shot a string of nine five shot groups without cleaning that averaged .85 MOA using my 75-grain MOS bullet . At the end of that string there were flakes and slivers of lead on the first patch but the last group had been2.0 MOA (half an inch at 50 yards).

Since then I have been lucky to get five good shots before groups double and often the first group has one out that doubles the group. I get a lot of three and four shot clusters under .7 MOA and a few five shot groups in the .8 - .9 MOA range usually the first group after cleaning.

I was shooting 700X at about 1,300 ft/sec. and have since switched to 4759 at 1,400 --1,500 fps, which seemed to help. I have also switched to Remington small pistol primers which also seemed to help at first. The 3 alloys I have tried have been from 13 to 18 BHN. I plan to try linotype next but doubt I can seat them far enough to seal at the front band without using a hammer.

The bullet shape is similar to RCBS Silhouette bullets. When I extract a round without firing there are strong land marks and 100% seal on the front band. In fact I am now seating them a tenth of an inch longer than needed to get 100 % contact.

The last two groups I shot last night were with PVC wads. There may have been some improvement but there was a little lead on the first patch afterwards. I will try some more this morning but I have never gotten improvement with wads and they are a pain to fiddle with.

From the way a tight patch of lead out cloth is easier to push through the central part of the bore, I fear that there is a loose area in the middle of the bore, just like all the recent Savages I have had trouble with. I will slug it this morning to check but that is also where I clearly feel the resistance of the lead with the first patch - starting maybe six to nine inches ahead of the throat.

I am about at wits end with this problem. I would appreciate any suggestions about what could be causing this.

John

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tturner53 posted this 29 August 2010

I'm no expert, but I've read that the little .22s should be cast from a very hard alloy. Works for me in my Weatherby Vanguard .223. Maybe your next batch with lino will do the trick. I use heat treated ww/1% and in all my .22s use them as fat as will chamber without debulletting. If your barrel is tight on the ends would it be possible to lap just the ends? Or more importantly just the business end?

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CB posted this 29 August 2010

Thanks for the suggestion.

What I'm worried about is that the constricted bore towards the chamber is squeezing down the lead bullets and since lead isn't elastic they don't spring back.  So in the larger middle of the bore they are then undersized and let gas blowby and cause the leading.  Jacketed bullets are elastic and able to spring back and of course if they don't, gas going past them is no big deal -- so they shoot OK.

I devised a scheme to lap out the chamber end of the bore of one of the Savages with the fat place in the middle.  I upset an undersized lap with embedded grit inside that end of the bore and only worked on the constriction near the chamber.  I made it closer to the bore diameter of the middle but stopped too soon so I have to take off the barrel and try again.

John

 

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tturner53 posted this 29 August 2010

That's a shame you got a lemon. I've always heard good thing about Savage barrels. My M40 Hornet looks like a mirror inside, shoots great. Maybe it's a warranty item.

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CB posted this 30 August 2010

I have had several Savages and they all shot jacketed bullets exceptionally well but the last four also had a bore that was loose in the middle which apparently affect jacketed bullets but perhaps is part of the problem with cast. I don't know what they do to consistently do that to at least their 22 barrels.

John

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Paul Pollard posted this 02 September 2010

Hey John,

You usually shoot the long, heavier bullets in your .223 Rem with the fast twist (1:9 or so)?

How do the shorter bullets shoot in that twist? RCBS or Lyman moulds in the 55 gr weight range. Better, worse or the same?

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CB posted this 02 September 2010

Hi Paul,

I haven't shot short cast bullets in the fast twist rifles enough to have an opinion but then I have never gotten short bullets to shoot better than 1.5 MOA in my 222s and 22-250 with slower twists.

Short jacketed bullets shoot fine in the recent Savages I have had with a one in nine twists they shoot good quality 40, 50 or 55 grain bullets to under .7 MOA for five shot groups. The danger of “overstabilization” (an oxymoran if there ever was one) seems to be non existent for jacketed bullets.

Hope to see you at the nationals?

John

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cityboy posted this 02 September 2010

John

If you do have a fat bore in the middle, perhaps you could open up the chamber end a bit with the fire polishing method proposed by Molly. Coat the rear end of the bore with bore paste and fire some reduced loads. I think Molly's method  can be found in the TESTING section.

Jim

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tturner53 posted this 03 September 2010

This is probably dumb, but what about cutting the barrel back?

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FilippoMo posted this 19 February 2012

Could you please provide a drawing of this bullets sincerely Filippo

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CB posted this 20 February 2012

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CB posted this 20 February 2012

Flllppo,

First time I have tried to post a picture and don't know the ropes.

The sketch in the post above is for an 85 grain 22 caliber bullet.

The 75 grain bullet I mentioned above is identical except that the overall length is .85” instead of .90". This means that the distance from the rear of the nose taper to the back of the bullet also needs to be changed from .60” to .55".

I have had good luck with both of these bullets and both have been stable and accurate in several 1 in 9 inch twist barrels although a 1 in 8” may be better for the 0.90” bullet.

Do not expect either of these to be stabilized in twists slower than 1 in 9".

Some manufacturers have seen the light and several 233 rifles (Savage, Ruger, Winchester, and others) now have 1 in 9” twists.

John

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FilippoMo posted this 20 February 2012

Thank you very much for your answer.We will try to make a mould similar to your drawing except for the spitzer ogive.We lathe bore our mould and it is rather difficult to make a pointed tool.As far as rifle twist are concerned my son has 1 in 9 and mine 1 in 8. The lighter bullet will work in both of them. Sincerely Filippo

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Ken Campbell Iowa posted this 20 February 2012

enjoying your trials with the 223 ...  have you thought about a 222 ?  has a longer neck ...  i got an extra ppg chamber reamer ..uses bore bushings ... minimun specs, but not small neck ... also throat reamers of different angles.  lemme know if interested....  of course this would not be ...production  ..  heh      

how did your lapping plan turn out ?

reminds me that i had a shilen match varmint in 22-250 that after 8 hours of tedious fitting was found to have a loose spot about 8 inches ahead of the throat ... it would shoot 1/4 moa  for about 6 shots, then build up a wad of black gooey deposit and groups got larger. then 20 strokes of rembore was necessary to get another 5 shots together.  since this was a customer barrel job , a lapping experiment was not authorized ....  i always wondered if it would have cured that problem ...   increasing the diameter up to the loose spot.

i need to mention that the shilens immediately replaced that barrel with another that shot beautifullly...  great people there ..

ken

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CB posted this 01 March 2012

Ken C. asked: "enjoying your trials with the 223 ... have you thought about a 222 ? has a longer neck ... i got an extra ppg chamber reamer ..uses bore bushings ... minimun specs, but not small neck ... also throat reamers of different angles. lemme know if interested.... of course this would not be ...production .. heh”

Ken,

Sorry for the delay and thanks for the offered reamer. I like to shoot production class and hunting rifle class so, as you point out, can't use the reamer. All the factory 222s have twists too slow for the long bullets.

I once built a BR rifle for the CBA Silhouette class with a fast twist Hart barrel. I choose to chamber it for the 222 run in .400” short ( which makes it a 221 fireball shortened 0.200"with a 222 length neck I guess.) It worked fine but CBA discontinued the Silhouette class about as soon as the rifle was done.

John

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CB posted this 01 March 2012

Ken wrote"

"how did your lapping plan turn out ?"

Ken, I tried fire lapping with soft cast bullets first. Such a trick is supposed to remove more metal near the throat and less further down the barrel and I thought that would make the constricted first few inches larger without removing the “choke” in the last couple of inches where the bore returned to normal diameter after the loose spot.

As with a lot of things, the theory sounds logical (more lateral pressure by the firelapping bullet against the bore where the pressure of combustion and less at near the end of the barrel where the pressure has dropped off) but it didn't turn out that way. The process removed a bit more material from the “choke” than it was removing near the throat.

I then tried lapping with a lead slug. The normal procedure involving casting the slug in the Muzzle obviously wouldn't work if I only wanted to remove metal at the other end. So I cast a slug less than the land diameter on the end of a rod, clamped the removed barrel in a jig, inserted the undersize slug with the grit rolled in, and upset the slug in the tight spot near the throat.

The method seemed to be working but metal removal was very slow. I need to take off the barrel again and give it another dose to remove the rest of the constricted spot.

John

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