Very short col/throat length problem?? advice needed

[F. Guffey]

I don't use that method as the newer bullets tend to stick in the lands even with very slow gentle bolt closing.

I do not have any of those problems because I am the fan of 'all the bullet hold I can get'. I do not use neck tension because I can not measure neck tension. I do have tension gages ; none of my tension gages measure tension in tensions. All of my tension gages measure in pounds and or deviation.

I do find it is helpful to know the two diameters of the barrel/rifling.

F. Guffey

 

[Metal god]

I assumed the reference COL he mentioned applied to a specific bullet. Sierra shows their 69-grain bullet seated to 2.260", the SAAMI maximum (as does Nosler, with theirs). Vihtavuori shows the Sierra bullet seated to 2.244" but Hodgdon shows the Sierra's seated to 2.235", which I assume they found necessary for some reason. But nothing as short as the OP arrived at. Most curious.

Once again you point out something I failed to notice . I use SMK's all the time and is why I use there manual . I also use the Lyman 49th/50th as well as Hodgdon online data . I however have never actually looked at Hodgdon's COAL recommendation for the 69gr smk . Most curious is right , because I have and refference the Sierra manual so often which has 6 Hodgdon powders in there 69gr bullet data . I never considered Hodgdon would have a different COAL for the Sierra bullets then Sierra them selves does .

I looked at both Sierra's 223 (AR-15) data as well as there 223 Rem only data thinking they might have different COAL for the same bullet but they don't . At first I thought "maybe" since the AR tends to have the longer leade/throat . The AR data would use the 2.260 while the 223 data might use a shorter COAL do to the 223 generally having a shorter leade/throat but both data's use the same 2.260 as the recommended COAL .

I'm assuming since you said " Most curious " when referencing these differences . You don't have a reason why you think these powder companies ( Hodgdon and Vihta Vuori ) are using different COAL's then what the bullet manufacture recommends when using there powders ???

Most curious indeed

 

[44 AMP]

You don't have a reason why you think these powder companies ( Hodgdon and Vihta Vuori ) are using different COAL's then what the bullet manufacture recommends when using there powders ???

I have a reason, though I have no idea if it's the actual reason, or not. Apologies for not also mentioning this in my earlier post.

Think of what COAL s are. They are a number for the overall loaded length of the round. They don't have to be the maximum allowable length, they can be just the length the round ended up being, when a specific bullet is seated to the desired depth. I think this may be where some of the confusion is coming from.

Break it down to basics, and look at the standards, vs different length numbers from this or that maker with certain specific bullets.

SAAMI COAL is the US standard, and is intended to provide a maximum allowable length that will work through the actions and barrels of all arms chambered in for that cartridge. It is based on the common bullet styles in use when the standards were created. It's meant to keep you off the lands, even if you load a full wadcutter to its stated length.

It is quite possible that bullets of unusual or uncommon profiles and lengths cannot be loaded to meet the listed max standard. It is also possible that certain bullets can be loaded to exceed the max listed length, and still be off the lands. The very long (for caliber) low drag bullets, and all copper bullets (which must be longer than lead for the same weight) are fairly recent developments. Most of the SAAMI standards pre-date the invention of these bullets.

Here's what is not being addressed when looking at the COAL alone, bullet seating depth. And, to a significant degree this matter MORE than COAL.

Take two bullets of the same weight, and the same base style (say flatbase), but different nose profiles, seat them to the exact same depth, and you can have two different COALs. Lets take .30 cal 150gr for example. Spitzer, and flat point/round nose. Same weight, different LENGTHs. Seat both to the base of the case neck, and you have the same seating depth, but different COALs. Change the spitzer flat base to a boattail, and you have yet another COAL when the base of the bullet is seated to the same depth as the others.

How far into the barrel the point of a bullet goes (the portion too small in diameter to contact the rifling) doesn't matter. How far into the case the base of the bullet goes can matter.

Maybe the different lengths listed from the different sources (other than SAAMI) are simply the length the round ended up being when the desired bullet was seated to their desired depth.

Maybe, that number ISN'T a requirement, its just reported because that's what they used.

 

[hounddawg]

no need to overthink this stuff

If you have a stock from the factory rifle your barrel is SAAMI spec so any load you find in a load manual is supposed to work

For 69 SMK's here is the factory load data

N140 Vihtavuori load data for .223 starting load is 23.6 gns

https://www.vihtavuori.com/reloading-data/rifle-reloading/?cartridge=7

Sierra manual 21.4 to 26.4 N140

http://accurateshooter.net/Downloads/sierra223rembolt.pdf

use the Sierra recommended COL, and the recommended starting load from the powder manufacturer then go shoot

 

[Metal god]

SAAMI COAL is the US standard, and is intended to provide a maximum allowable length that will work through the actions and barrels of all arms chambered in for that cartridge.

Agreed

It is quite possible that bullets of unusual or uncommon profiles and lengths cannot be loaded to meet the listed max standard. It is also possible that certain bullets can be loaded to exceed the max listed length, and still be off the lands.

Agreed again and understood with both quotes . The thing that seems odd is that Sierra the maker of the bullets in question and who has data using those other manufacturers powders uses the 2.260 number . If the maker of the bullet suggest a length while at the same time uses your powder . Why wouldn't you ( the powder company ) use the same max COAL . That is in fact what that number usually suggest in order to fit in any SAAMI spec chamber .

I load that cartridge with that bullet and use IMR 4064 and 4895 . The amount of compression I'd get would be so great if I seated my bullets to 2.235 . The bullets would push back out . I need to use a drop tube when seating the 77gr smk to reduce the compression at 2.260

Maybe, that number ISN'T a requirement, its just reported because that's what they used.

Agreed again but I'll take it a step farther . It's not only NOT a requirement , it may not even be there recommendation unless they are using the same data for multiple bullet profiles . It could be that 2.235 will allow any bullet profile to chamber at that bullet weight ???

 

[Jim Watson]

Then you have the problem of adherence to specs, any specs.
Somebody once did chamber casts of various .223, 5.56, Wylde, etc. barrels and found wide variations. Tight 5.56, large .223 seemed about as likely as spot on military or commercial.

 

[cw308]

Ii can't remember the last time I measured or cared about OAL . Last year I tried 100 Amax Hornady 168 grain match bullets , was a big difference in shape compared the the Sierra 168 gr. MK . The case base to ogive measurement will be the same at the time of loading , no matter what bullet your using . I load one at a time . Like we all have mentioned in other posts , dummy rounds being tested in your chamber until it chambers without resistance. First with the case then using that perfect sized case , seating the bullet long and seating lower until it chambers with no resistance will get you a good starting point. Start with a safe starting powder load and work from there . As long as you follow all the steps in case prep reloading is pretty simple .

 

[HiBC]

Forgive me for not reading most of the previous posts.

First,you have a 1 in 9 twist.Beautiful for 69 gr bullets! Sweet spot.Varget is made in Australia.It probably has another designation.In my experience,its my "sweet spot" powder for 69 gr bullets.Your N-140 is in the proper burn rate zone.Its a subtle shade of grey difference.The N-140 should be fine.

Some folks say a 75 gr bullet will stabilize from a 1 in 9. But maybe not.I would not buy or load many without testing first.

I can't confirm it,please do not bet your face on it,but I have heard N-140 is the same powder as REloader-15. That might be wrong.

The Hornady handbook has an AR-15 match load section.From there,in my experience,REloader 15 is my #1 choice with a 75 gr Hornady BTHP Match.

Powder capacity? I load to about 2.250 to fit magazines. Powder to the base of the neck is not an issue for that LOA.If you are getting too much compression,just back off a grain or so.Your long range shot MIGHT need one more click elevation.So what?You will twist the knob anyway. A 10 or 12 inch drop tube may gain you a little compaction.

You might check to see what range you go subsonic.The transition can make a difference in stability.Accuracy may "hit the wall".