22-250 CARTRIDGE CASE HEADSPACE

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joeb33050 posted this 16 December 2016

22-250 CARTRIDGE CASE HEADSPACE

 

12/15/16

 

I have had  RCBS Precision Mics for 308 and 223 for several years, and recently bought one for 22-250.

 

The Precision Mic measures cartridge headspace, with, in 22-250, the zero = 0 on the micrometer at DATUM = 1.5749”/1.5849”.

 

I set headspace on Savage rifle barrels with a few FL sized cases; the headspace dimension being “my dies, my cases, FL sized”.

 

I record ctg headspace thus: “2” is plus two thousandths” on the micrometer; -5 is minus five thousandths” on the micrometer.

 

I used to FL size 22-250 cases and left the lube on the cases-lanolin. Then learned how to size cases in a Lee Collet die, no lanolin.

 

I noticed every now and then a primer backing out of a fired case, suggesting that the cartridge headspace was shorter than the proper dimension.

 

Yesterday I shot 50-60 grain bullets with 7/Titegroup, in cases that were last shot with the same bullets and 8/Titegroup.

 

I measured the cartridge headspace before firing, oiled the cases on a paper towel pad with synthetic oil, fired them, and measured the cartridge headspace again.

 

The measurements before firing ranged from 2 to –17; after firing from 2 to -2. The oiled cases expanded.

 

I measured the unfired cartridges, they ranged from 5 to –10. I’ll oil and shoot them.

 

I don’t know if excessive cartridge headspace affects accuracy, but will oil all low velocity cartridge cases from now on.

 

joe b.

 

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onondaga posted this 16 December 2016

joe b.

I'd bet a silicone impregnated gun wiping cloth would be perfect for lubing cartridge cases.  I do that but sometimes instead I lightly Johnson Paste wax them for hunting ammo and don't buff them.

 

Gary

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Ken Campbell Iowa posted this 16 December 2016

here are joeb's numbers ..table-wise.

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SierraHunter posted this 16 December 2016

The main problem with excessive head space is case head separation. You can get quite a few more firings from neck sized only cases.

I don't like oil in the chamber of my gun. The oil seems to make the cases stretch a bit more, and this also leads to case head separations, as well as having to trim more often, and I hate trimming.

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Premod70 posted this 16 December 2016

Anytime you shoot reduced loads in a rimless case the primer forces are pushing/crushing the case forward and the burn of the powder does not make enough force to drive the crushed brass back to the bolt face/breach head resulting in increased headspace. The fix is to drill the flash holes to a larger size thus allowing the primer flash to escape to the burn chamber without crushing the brass. If and when you do drill out the flash holes be sure to segregate the brass and never ever use high pressure loads in the modified brass. Good luck.

Forrest Gump is my smarter brother.

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joeb33050 posted this 18 December 2016

I started shooting, reloading and casting bullets in 1960; have shot mostly cast bullets since, and as far as I can recall have NEVER had a case head separation-NEVER-not one.

 

I lube/oil the outside of loaded cases and do not see any/much case lengthening, and never have to trim cases after the first time. I use a Lee case trimmer at the range, sometimes, with 22-250 cases between shots, just to check, and see little or no lengthening. Case lengthening seems to be caused by yanking the maybe dirty case neck over the expanding button during FL sizing. I brush the inside of each case after firing, at the range, and on the rare occasions when I FL size cases, I lube the inside of each case neck with a Q-Tip and Marvel Mystery Oil. Remember, case neck tension/friction does not affect accuracy, so lubing inside case necks doesn’t either.

 

When SOME reduced loads are fired in rimless cases, the case does not expand and grip the chamber wall and the primer acts as a piston, pushing the case forward into the chamber and shortening the case headspace. The fix is to lubricate the case, which allows the reduced charge to push the case back over the primer such that case headspace remains proper. Drilling out flash holes works, but is, in my opinion, the wrong fix taking too much work and leaving the shooter with potentially, maybe, dangerous casers. Lube them cases!

 

Lubricated cases are alleged to increase force on the bolt face and cause the dreaded case head separation. So, don’t take a chance, lube only cases used with low velocity (cast?) bullets.

 

To read about extensive actual experiments regarding this matter, see “Cast Bullets For Beginner And Expert”, Appendix, 6.2 CASE SHOULDER SETBACK WITH REDUCED LOADS, readable online at

 

https://groups.yahoo.com/neo/groups/CB-BOOK/info

 

 

joe b.

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John Alexander posted this 31 December 2016

With light CB load in the 222-223 family of cases I have never noticed (protruding spent primers or loose chambering). Joe recently sent me his 223 headspace mic and the mic couldn't find a case with shoulder setback either. I have never enlarged a flash hole and since the Lee Collet die came on the market I have never lubed a case.

I understand that other case sizes set back and maybe the 222 sizes do as well,l but I have never seen it

What is other shooters experienced with light loads in the 223? 

Also, like Joe, after 60 years  of hand loading I have never had a head separation. I think I know why.

John

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David Reiss posted this 31 December 2016

Recently reading Fouling Shots & Cast Bullet back issues, I came across this letter to the editor, which deals with a similar issue with light loads in the .30-06. I will reprint it for those that don't have access to the article, but edited for content.

David Reiss

Preventing Case Shoulder Set-Back (The Cast Bullet issue no. 98 July - August 1992)

Dear Glenn,

Back in October of 1990 I wrote you about a problem I was having with light loads pushing the shoulder back on my .30-06 cases................................... Your advice was to make up some loads using jacketed bullets jammed against the lands. This solution did not appeal to me for three reasons: 1) I did not have any suitable bullets, 2) my supply of 4895 was about gone, 3) and did not want the job of getting the copper out of the bore so I could shoot cast bullets again..............................

As you pointed out in your letter, the case expands as the powder pressure builds up and grabs the chamber wall. If the pressure is too low, friction will hold the case against the wall and the case will not blow out properly. It seemed that one possible solution to this problem would be to reduce the friction between the case and chamber wall. Case lube or oil would probable work but are too messy and would pick up dirt. The best solution would be some kind of dry non-sticky lube. It happened that I had a can of silicone spray lube handy and tried it on a few cases. The stuff dried quickly and gave the cases a very slick non-sticky coating. 

I had 40 rounds on hand using 20 grs. of SR4759, a 205 gr. bullet and cases with the shoulder pushed back. So I decided to give the silicone lube a try. It worked like a charm. The cases were nicely blown out. This trick has been tried several times now and has never failed to work. This is how I spray the cases. A number of them are spread out on a paper towel and sprayed. They are then turned 180 degrees and sprayed again. I don't know how many firing the lube job is good for, bt it is not necessary to lube after every firing. My guess at this point is to lube after 3 or 4 firings. It may not be a good idea to shoot to shoot lubed cases with full loads. The thrust against the bolt face might be excessive. (Glenn Latham's Note: Definitely do not use lubed cases with full loads!)

The accuracy of my loads still leaves a lot to be desired and I don't know what the problem is. A sinclair case concentricity gauge has been ordered and may shed some light on the subject. If I come up with anything interesting I will pass it on.

Sincerely,

James F. Saltsman

P.S. I have used the silicone trick since I wrote this letter and it is still working fine.

 

David Reiss - NRA Life Member & PSC Range Member Retired Police Firearms Instructor/Armorer
-Services: Wars Fought, Uprisings Quelled, Bars Emptied, Revolutions Started, Tigers Tamed, Assassinations Plotted, Women Seduced, Governments Run, Gun Appraisals, Lost Treasure Found.
- Also deal in: Land, Banjos, Nails, Firearms, Manure, Fly Swatters, Used Cars, Whisky, Racing Forms, Rare Antiquities, Lead, Used Keyboard Keys, Good Dogs, Pith Helmets & Zulu Headdresses. .

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Larry Gibson posted this 31 December 2016

You will be hard pressed to find or develop case headspace setback using cases with SR primers.  As Premod70 states it is the force of the primer explosion driving the case forward.  The SR primer just does not generated the force needed.  However, LR primers do have sufficient force as Joe is experiencing with his 22-250 cases.  The situation is exasperated if the rifle is a push feed with a strong plunger ejector.  Many times these PFs don't allow the extractor to close over the rim when the headspace gets pushed back to far.  Of course with CFs and some single shots the extractor holding the case back allows setback only to that limited amount.  The problem is especially pronounced in PFs with reduced or squib loads that do not generated sufficient psi for the case to expand and hold onto the chamber walls.

 

The solution, again as Premod70 suggests is to use dedicated case using LR primers and drill the flash holes out.  I use a #30 most often and find the largest drill to use is a #28. I have thoroughly pressure tested such cases in both .308W and 30-06 with 311291 cast bullets loading them upwards of 50+ thousand psi as actually measured in the test rifles with an Oehler M43 PBL.  With the same cases (well fire formed to start with) I have fire 3 cases in the .308W 50 times with 3.2 gr Bullseye under a 90 gr cast bullet.  I had intended firing them 100 times but since after 50 firings the shoulders did not set back any measurable amount I quit testing.

 

Subsequently I have used drilled out flash hole cases in .308W, 30-06, 7x57, 6.5x55, 8x57 and 7.65 Argie without any further case headspace setback.

 

LMG 

Concealment is not cover.........

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Paul Pollard posted this 01 January 2017

Found it

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joeb33050 posted this 02 January 2017

Today with a 223 and cases with varying headspace, CCISR primers, one lot had 4 out of 30 not fire, another lot had 3 out of 56 not fire. Never had primer failures like this before, the firing pin protrusion is ~ .055", all primers nicely dented. I'm thinking it's the excess headspace cases that don't fire, don't know. Primers? ?? I threw the cases away. Bought 1000 Federal SR primers.

 

Such a puzzlement.

joe b.

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Ken Campbell Iowa posted this 02 January 2017

i hate it when the primers don't go off..

classic reasons are:

1) not seated deep enough ... should be a slight crush seating ... primers will be a tad below case level when seated

2) actually bad primers ...very rare but if same carton as good ones not probable.

3) too much head clearance .. can check with magic tape layers stuck on case heads ..1 is ok, 2 is barely ok, 3 is too much ( this is a crutch method but gives an idea )

4) gunked up firing pin channel in bolt .... spring bound up.... bolt handle rubbing stock . bolt shroud rubbing safety pieces.

let us know if you find the problem .  can be depressing when that happens .

ken

 

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joeb33050 posted this 03 January 2017

i hate it when the primers don't go off..

classic reasons are:

1) not seated deep enough ... should be a slight crush seating ... primers will be a tad below case level when seated

2) actually bad primers ...very rare but if same carton as good ones not probable.

3) too much head clearance .. can check with magic tape layers stuck on case heads ..1 is ok, 2 is barely ok, 3 is too much ( this is a crutch method but gives an idea )

4) gunked up firing pin channel in bolt .... spring bound up.... bolt handle rubbing stock . bolt shroud rubbing safety pieces.

Well Ken, this ain't it. I take Savage bolts apart all the time, and they're oiled lavishly with synthetic. Everything is free and clear, nothing I can find is binding and the firing pin protrusion is ~.055” I ordered an inirtia bullet puller yesterday, will pull the bullets and see if the primers that didn't fire are dead.

BTW, just averaged <1” 50 yds, 10 five shot groups with the Charger, CCI SV did it. Best 22rf ammo mid price so far. The trigger is still; horrible.

 

let us know if you find the problem .  can be depressing when that happens .

ken

 

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OU812 posted this 03 January 2017

I have had experience with misfires using CCIBR primers and excessive head space (-.006)...Winchester primers never misfired because of excessive head space.

Since using the Lee collet die my excessive head space problem went away. It may take up to 3 firings for cases to fully form to chamber and loaded cases are more concentric. Full length resizing is just plain wrong for low pressure loads.

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joeb33050 posted this 04 January 2017

Today with a 223 and cases with varying headspace, CCISR primers, one lot had 4 out of 30 not fire, another lot had 3 out of 56 not fire. Never had primer failures like this before, the firing pin protrusion is ~ .055", all primers nicely dented. I'm thinking it's the excess headspace cases that don't fire, don't know. Primers? ?? I threw the cases away. Bought 1000 Federal SR primers.

 

Such a puzzlement.

Above should read 4 out of 52 didn't fire.

1/4/17 same brass FED SR primers, 75 shots without a misfire. Don't know why, but it's the CCISR primers.

 

joe b.

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