what should I do next?

Stove pipe

Stove pipe

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Hi, I got a nice ammo deal from one of my friend. The bullets are Sellier & Bellot 180 gr FMJ in 308 WIN. I shot those bullets from my little Merkel Helix with good results, I'm honestly not an insane shooter but I can get 1 MOA from a shooting stick (in optimal conditions).

Since I have lots off those bullets (somewhere near 450), I decided to buy Lapua Naturalis 170 gr tips to develop a hunting load.

I got myself a single stage press and Hornady dies. I started removing the FMJ tips from the S&B bullets, weighed the powder and crimped the Lapua Naturalis. The powder weigh is 38 grain.

MY QUESTION: to develop my new hunting load, what should I do:

- shoot the original load (38 gr) and prepare 37 and 39 gr bullets to see what group best or:
- go down since the original bullets where 180 gr, so 37 gr and 36 gr than see what I do from there....

Need your help, those Lapua Naturalis tips are expensive....
 
So if I understand you, you're removing the S&B 180gr FMJ bullets from their cases and replacing them with Lapua 170gr bullets.

Guess you're not going to get load data or powder information from S&B, so you're going to be working in the dark. I've noticed that the charge weight for a given powder usually increases when a lighter bullet is used, so at first glance I don't see much of a problem with keeping the same charge with the lighter bullet as you're doing, but I AM NO EXPERT.

The problem is if you wish to increase the charge, how do you know what's the recommended max from S&B?
 
hummm, I'm not expert either. It is a really good question. I guess I should just try and see what 38 gr of powder with 170 gr tips are going to do on paper, maybe I'll still get a decent grouping. Thanks for the input, it raise a flag on increasing the powder or not.
 
Grawfr said:
So if I understand you, you're removing the S&B 180gr FMJ bullets from their cases and replacing them with Lapua 170gr bullets.

Guess you're not going to get load data or powder information from S&B, so you're going to be working in the dark. I've noticed that the charge weight for a given powder usually increases when a lighter bullet is used, so at first glance I don't see much of a problem with keeping the same charge with the lighter bullet as you're doing, but I AM NO EXPERT.

The problem is if you wish to increase the charge, how do you know what's the recommended max from S&B?
Click to expand...

Yes, I am removing the S&B 180gr FMJ bullets from their cases and replacing them with Lapua 170gr bullets.
 
Maybe I am missing something here. What can you DEVELOP from this excercise without knowing what powder is used in these ammo?


Stove pipe said:
Yes, I am removing the S&B 180gr FMJ bullets from their cases and replacing them with Lapua 170gr bullets.
Click to expand...
 
I would not recomend that as a way to develop a hunting load. Like the guys already said changing weight of bullets changes things and not to mention you have no idea what kind of powder s&b uses and therefore no idea on what to expect for pressure.
I highly recomend just shooting the s&b for practice and load the brass normaly with a known safe load.
 
Ok, thanks you guys. I'll do my homework and see what is possible. "Developing" I meant just fine tuning so I could get the same grouping with this Lapua 170 gr. I will shoot the bullets I made and let you guys know what it does. I am not really worry about over pressure since I will not increase powder, I will cut back 1 or 2 grain by .5 increments. Mabe I'm out for lunch but if it does work I will post some pics. Thanks.
 
Dump the powder from the factory rounds. Measure a powder you have bought that has data for the weight of bullet you want to use. Then work up a load Example 35gr, 35,5gr, 36gr of powder. Go from min to whenever you see pressure signs or get good accuracy and speed.

Get a loading manual and read the front.
 
Stovepipe While what your doing will work it is not a very desireable practice. First seating a 170 gr bullet over the powder charge designed for a 180 gr bullet may be safe pressure wise it is not likely to give you the best accuracy. I would suggest you shoot the S&B 180 loads and save the brass cases. For the 308 cartridge Varget powder is a very good choice. From Hodgdon data about 46 grs is listed as max for a 168 gr bullet. I would suggest you start with 42 grs of Varget with your 170 gr bullet and work up 1 gr at a time watching for signs of excessive pressure (cratered primers, hard extraction etc). Once you have determined what is a max load in your rifle,I would drop back 2 grs and load 3 rds then load 3 rds of 1 gr less than max and finally 3 rds of max. Go to the range and from a steady rest shoot those loads to see if one group shoots a tighter group than the others. 3 shots will not determine your best group but it will point you in the right direction. Hope that helps.
 
I would go about it this way.

Measure 20 rounds powder charge and take that to be the average charge weight (assuming they are consistent with their charging) and set it aside. If it is in fact 38gr average I would make up some loads with 36gr, 36.5gr, 37gr, 37.5gr and so on up to 39gr. Do a ladder test and see what groups best.

Make sure all the rounds are from the same lot, mix all the powder together and shake it up.

Ideally have a chronograph to ensure safe pressures but in a pinch check the usually pressure signs.


Whats wrong with that?
 
How about this. Shoot the ammo as-is and enjoy the time training, keep the brass, buy primers and powder and reload the brass with the Lapua projectiles?
 
OP, what you are describing is a very old and common practice known as making "Mexican Match". This usually involves pulling a military bullet and seating a quality match bullet. The powder charge might get re-weighed, and it might get changed.

Your instincts are 100% correct. A straight substitution is a go. Trying 1 more or less grain of powder is a good idea because with mex match I have seen a 1 grain difference make a huge change in accuracy.

If you Google Mexican Match you will find lots of information, such as this:

http://m14forum.com/ammunition/83679-m118-match-vs-mexican-match.html

You might also find websites for making dates with Mexican girls.
 
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Great! Mexican Match!!!! I just interchanged the bullets and I am having tighter groups with the Lapua. I will post some pics next time I shoot and try to register the velocity with a chrono. I reweighed the powder and adjusted it to 38 grn. The factory ones measured between 37.5 and 38grn. Thanks for the comments.
 
Stove pipe said:
Ok, thanks you guys. I'll do my homework and see what is possible. "Developing" I meant just fine tuning so I could get the same grouping with this Lapua 170 gr. I will shoot the bullets I made and let you guys know what it does. I am not really worry about over pressure since I will not increase powder, I will cut back 1 or 2 grain by .5 increments. Mabe I'm out for lunch but if it does work I will post some pics. Thanks.
Click to expand...

Pulling 180 grain bullets from military ammunition and replacing them with 170 grain bullets of the same diameter, should be a completely safe operation. For many years after WW2, replacing military bullets was done extensively.
S & B did not fine tune the ammunition you have and it shoots great for you!
So why would you try to "fine tune," it, whatever that means.
Seat the bullets out so they will just nicely work through the magazine and your bolt will close on the new cartridge.
 
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