.338 lm in AI rifle C.O.A.L. questions

FORESTBARBER

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I am a new reloader. After lots of questions and lurking here I put together the basic equipment to load for my new AI AW SM .338lm.

I bought all lapua components, excepting primers. Lapua brass. VV n165 powder. Lapua 250 gr lock base. Lapua 250 & 300 gr Scenar.

The data showed the Lock Bass round at 3.602 COAL and the scenar rounds at 3.681 COAL

Followed all instructions and Ta Da! beautiful ammo that I loaded all by myself.

Yup, problem is that when loaded to COAL specs in both Sierra and Lapua specs the Scenar rounds at 3.682" are too long to fit in an AI magazine that measures a max length of about 3.012".

The 250 scenars will not chamber with the bullet contacting the end of the chamber before the bolt closes. The 300 scenars are too long for the mag of course but will chamber and run velocities indicated in the reloading data for the combination loaded.

I measured the chamber length with a Sinclair gauge and the length is 2.750" fwiw.

I pulled apart a Lapua factory 250 gr Scenar round that does indeed have a 3.600 COAL. It held 92 gr of a a powder that is shorter grain than the N165. I am assuming that it is vv powder but it does not match up with any powder weight for this bullet in the Lapua specs.

I went ahead and reseated all the scenars at 3.602 with no apparent issue.

Am I ok using the stated specs for reloading, but just seating the bullet to a length that will fit in the mag?

Thanks,

Forest
 

mdmp5

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  • May 7, 2009
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    Re: .338 lm in AI rifle C.O.A.L. questions

    One question. Are you sure that an AI magazine for .338 can only accommodate a 3" round? That seems awfully small. AI mags for short action can hold about 2.90". Something doesn't sound right there.

    Also, don't bang your head against the wall trying to replicate factory ammo. Most of the time they are using powder blends that you cannot obtain. Your loaded ammo will outperform that stuff if made correctly anyway.
     

    desertHK

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    Re: .338 lm in AI rifle C.O.A.L. questions

    Depending on the year of your AIAWSM, the older ones (like mine, 08) have a mag length of about 3.640". I load both the 250 scenars and the 300 SMK at 3.600". Both shoot subMOA and fit mag length.
     

    Lt. Arclight

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    Re: .338 lm in AI rifle C.O.A.L. questions

    Don't try to match the Factory Lapua ammo. The powder is NOT VV-it is generally Norma MRP2.

    I too have an '08 AIAWSM. You should have no issue loading ANY of the projectiles at magazine length. 3.640" is MAX-I won't load longer than 3.625" with mine.

    I doesn't make sense when you say the scenar won't chamber-its the Lapua LOCKBASE that is shaped so that the OGIVE is farther forward than the scenar.

    Using the sinclair bullet comparator(looks like a hex nut) The scenar loaded at a coal of 3.602 measures 3.941" with the comparator. The Lockbase loaded to a much shorter 3.566" measures 3.950" with the comparator.Using a dummy round and then measuring it with the comparator is the most accurate way of determining WHERE the rifling starts.

    You should be concerned about reliability and feeding without issue from the magazine. Loading at 3.600" will provide sub mao accuracy like DesertHK mentioned.

    DON'T use the coal listed in the manuals-load to 3.600" and tune your loads accordingly.
     

    FORESTBARBER

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    Mar 21, 2010
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    Re: .338 lm in AI rifle C.O.A.L. questions

    Thanks all!

    You are correct re mag length. That was a typo my end.

    I'll double check today re the bolt closing on the 250 Scenars. The Lapua site's loading data spec's the Lock Base at 3.602 vs the 250 Scenar at 3.681, as it does the 300 Scenar, which might make the ogive difference immaterial in this case?

    That said, it did strike me as odd the 250 Scenar contacted the lands and the 300 Scenar did not. However, those two bullets are strikingly different as to their shape. I'll get the Sinclair bullet comparator.

    I'll load to the mag length. Just wanted to make sure that was not dangerous with the powder type and quantity they spec for a round that will not fit in the mag.

    I did single load the 300's and the velocity was as per the loading data with no signs of over-pressure.

    It does seem less than optimal that there would be more (I think) than wanted jump from round to rifling given the short overall length. I see other rounds being loaded with little or no jump and this being desirable?

    Finally I have measured, and will double check the chamber length, with the Sinclair button in a case gauge at 2.750".

    With the above chamber length in mind my once fired Lapua brass measures 2.716" case length. Is it a necessity to trim the case back to the original 2.714" length after resizing? I understand it is proper to do so, but just seems unnecessary to this ignorant new reloader.

    Thanks to all!