COL problem - 30-06 - what's wrong??

[bison]

I'm a newbie and thx in advance for help - I'm loading 30-06 with 180g Hornady Interlock BTSP's to work up a hunting load. My manuals show a COL for this of 3.30", but when I loaded to this length I first noticed that this seemed long as the cannelure was well outside the case. When I chambered a round in my rifle (new Win M70) and closed the action I felt some resistance, and sure enough when I unloaded the round the bullet had been pushed back in the case somewhat after hitting the lands. COL after this was down to about 3.26", which looks right as the top of the brass is right about at the bottom of the cannelure. 0.040" seems like an awful lot of difference - what do I do? Clearly I can't load longer than 3.26" and I don't think I want the round gooshed against the lands.

BTW I'm using H414 and had loaded 5 rounds at 51, 52, 53, 54, and 55 gns. Manuals show 50-55.5gns.

Thx!

 

[dmazur]

1. The Hornady data I have for bullet #3072 BTSP shows a COL of 3.245".

My understanding is that higher pressures can result if you have the bullet forced into the lands. From your description, it sounds like 3.245" should be about right.

Speer data shows a 180gr BT Spitz SP (#2052) at COL 3.250", and a 180gr Spitz SP (#2052) at COL 3.160".

Sierra has a 180gr SBT with a recommended COL 3.300".

The ogive on the bullet determines where it hits the lands, not the overall length. Note the considerable difference in COL for the 180gr bullets listed above. They have different profiles.

So, the question is, was it really Hornady data for the recommended COL of 3.300", or data for a different bullet of the same weight?

2. I believe it is customary to shoot a few rounds to establish a group, then work up gradually toward max, comparing group sizes for each charge weight and checking for signs of overpressure. I'm not sure that measuring distance from POA to POI for 5 rounds with 5 differing charge weights would prove anything. (There is some error introduced by the shooter, as far as I know... )

 

[ranger335v]

"I'm a newbie and thx in advance for help - I'm loading 30-06 with 180g Hornady Interlock BTSP's ... My manuals show a COL for this of 3.30","

A LOT if newbies get confused by book OALs. What's in the book is the length the book makers used to develop their data, it's no more a "rule" for the rest of us to slavishly follow than their powder charges are.

First thing to find about any OAL is will it feed through a magazine. Second is, is it off the lands (that does raise start pressure). And that does come from the ogive, no rifle cares where the point of any bullet hangs in the air.

Most sporting rifles shoot most bullets most accurately when there is a jump from .025" to as much as four times that much to the lands.

 

[USSR]

What's in the book is the length the book makers used to develop their data, it's no more a "rule" for the rest of us to slavishly follow than their powder charges are.

Yep. You load for your individual rifle, not for the reloading manual writers.

Don

 

[sourdough44]

I've loaded that bullet for 2 Savage 110's. I measured the chamber 1st, even though the same model gun there was a slight difference. I do remember I was down in the 3.24 range or so. With rifle loads you have more leeway to adjust COL without the pressure worries of some handgun loads. You do not want a bullet stuck in the lands while out hunting. Also don't worry where the crimp groove ends up. Under most circumstances you don't need any extra crimp, 'neck tension' on the bullet will be fine.

 

[243winxb]

COL after this was down to about 3.26",

Seat the bullet deeper by .010" to .015" off the rifling, this will be ok for hunting.

 

[bison]

Thanks to all - I guess I did have the wrong bullet - I was using the Lee info for "180 Grain Jacketed Bullet" and the Hogdon data for (what I now see is wrong) "180 gr SIE SPBT". Man, this terminology is confusing! Thx

So if the correct COL is 3.245, what's the recommended powder load for H414?

Fyi I should have said I was loading 5 rounds EACH at the different powder loads.

 

[NCsmitty]

So if the correct COL is 3.245, what's the recommended powder load for H414?

Your intention is to work up the range of powder anyway. The maximum recommended charge should not be an issue with the small difference in COAL dimension. However, you can set your own tentative limit to perhaps 54gr and see how accurate the loads are up to that self imposed limit. It's a good bet that your accuracy load will be midway between upper and lower charges. Not always, but more often as not. H414/Win 760 are good powders in the '06 but IMO, they work better using magnum primers.



NCsmitty