Excessive OAL

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BobWalls

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Hi,

I was reloading for my 30-06 BLR 150gr hornady sst. I was getting somereally inconsitent chrono readings with superformance and really crappy groups at 200y (like 3 MOA or more). I was using 0.050" less than the max OAL for a 30-06 according to SAAMI specs.

Anyhow I just measured my chamber length and it turned out I must have been jamming the bullet more than 0.50" into the lands and possibly even then pushing the bullet back into the case since they were not crimped. Going to retry with a sensible OAL but I guess this is a lesson to measure the OAL and not guess.
 
Best way to check is to make a dummy round and chamber it.

Polish the bullet with some 000 fine steel wool prior to chambering and any land marks will stand out.

I would have done this even before dumping powder in my first case.
 
CyaN1de said:
Best way to check is to make a dummy round and chamber it.

Polish the bullet with some 000 fine steel wool prior to chambering and any land marks will stand out.

I would have done this even before dumping powder in my first case.
Click to expand...


x2 on this..

but i will admit that if your .050 UNDER the max OAL you must have a very short chamber in your rifle and that is surprising... has the rifle ever been rebarreled?
 
My model 700 BDL SS .280 Remingtom built around 1997 or '98 has a short throat and a factory round might even jam into the lands.

X2 on checking it first using a dummy round.
 
A bullet's ogive shape will determine the cartridges OAL where the bullet just touches the lands. If you measure this by using the empty cartridge approach mentioned above, you will find the exact OAL when the bullet's ogive contacts the lands for the particular bullet you are seating. Every bullet shape will produce a different safe/accurate OAL. I use some very blunt (almost cylindrical) bullets in my 30-06 and have to keep the OAL very short indeed to prevent the bullet's ogive from engaging the lands when a cartridge is chambered. Imagine a tapered bullet with the point cut off which is seated to the same OAL as the original pointy version and you will see what I mean. Using a case with a loosely fitted bullet (loose enough to be set back into the case when the bolt is gently closed on it, but firmly enough grasped by the case neck so it comes out with the ejected case) will give you the exact OAL for bullet contact with the lands for THAT particular bullet. Keeping the OAL the appropriate amount shorter than this length is a good thing and puts one in the best accuracy zone as well.
 
I`m surpised that your clip, oh crap sorry detachable box magazine would allow you to seat bullets that far into the lands. I haven`t worked with a 06 BLR only a 243 and 308. Mags for them wouldn`t allow long seating. I don`t pay a lot of attention to published oal figures, instead i check my bullet seating depth according to chamber and mag lenght. then record that figure in a log book with other load data.
 
dead meat said:
I`m surpised that your clip, oh crap sorry detachable box magazine would allow you to seat bullets that far into the lands. I haven`t worked with a 06 BLR only a 243 and 308. Mags for them wouldn`t allow long seating. I don`t pay a lot of attention to published oal figures, instead i check my bullet seating depth according to chamber and mag lenght. then record that figure in a log book with other load data.
Click to expand...

i had to open the magazine up on my 30-06 blr to get the bullets closer to the lands .
 
I find an easier way (easier on the old eyes) to check is to get a permanent marker and 'paint' the bullet - stands right out.
 
The way I see it. I can't imagine a 30-06 chamber where a normally loaded 150 grain bullet would hit the lands, or even come close to the lands.
Just look at a factory loaded 30-06 with a 220 grain soft point and see how much bullet is sticking out of the case. I never heard of a 30-06 that wouldn't chamber a factory loaded 220 grain bullet.
IF, your 150 grain bullets were hitting the lands, it should result in very little velocity change, shot to shot, plus it should be an accurate load.
 
Hmm I am pretty confident I measured it correctly and I had real trouble chambering them (had to use a lot of force). I was well out from the cannelure on the Hornagy SSTs to cause this jamming, I've moved it onto the canelure and am now still near the lands.
 
Tried Superformance in 30-06 Sako 85 Finnlight on Sunday and today and despite having dummy round with Hornady 150 GMX and backing -0.05 from lands as measured from ogive I was not getting groups at all.
5 to 6 inches at 100 y. !!! disaster.
On Sunday I've shot one of each 61.0, 62.0, 63.0 and 64.0

Chronographed velocity 3006 ft/sec for 63 and 3011 for 64 those two bullets were touching at 100y.
So today I've shot 3-63.5
3-63.7
3-64.0

5-6inch groups at 100 y. Forgot my chrony so no velocity.

I can't recall groups like this ever,

Back to Barnes TTSX 150 and IMR 4350 for me.

So after my experience with Superformance I am thinking that OP BLR likes this powder as much as my Sako.
 
I measured this using a dowel which I cut to the length of the barrel when the chamber is closed. I then jammed a cartridge with bullet in there to see the change in length. This method works much better than measuring the OAL of the caartdieg after placing a bullet in the end jamming it and then removing it since this tends to stick to the lands and give a flasely long reading. I am trying to be 0.020" sh0ort of the lands for sensible hunting performance. It could be that I mis-measured this, I'm going to try again since I agree this seems a really small chamber.
 
Andrzej said:
Tried Superformance in 30-06 Sako 85 Finnlight on Sunday and today and despite having dummy round with Hornady 150 GMX and backing -0.05 from lands as measured from ogive I was not getting groups at all.
5 to 6 inches at 100 y. !!! disaster.
On Sunday I've shot one of each 61.0, 62.0, 63.0 and 64.0

Chronographed velocity 3006 ft/sec for 63 and 3011 for 64 those two bullets were touching at 100y.
So today I've shot 3-63.5
3-63.7
3-64.0

5-6inch groups at 100 y. Forgot my chrony so no velocity.

I can't recall groups like this ever,

Back to Barnes TTSX 150 and IMR 4350 for me.

So after my experience with Superformance I am thinking that OP BLR likes this powder as much as my Sako.
Click to expand...

The thing is that this un groups 1MOA at 200y with superformance and a barnes tsx (and that's a great group at minus 10C with gloves on a BLR)
 
OK so I have remeasured the chamber. 3.275 max OAL to the lands with the 150gr. This is 0.065" less than the saami spec. I made the last batch of these to 3.330" oal way too long. The further issue is that at 3.330" oal with the 150gr sst the bullet is only seated 0.363' into the neck of the case and since it is a boat tail only 0.200" is actually touching any case. I'll make up a new batch and test them on the weekend at the range at a new sensible OAL.
 
ATOM said:
I find an easier way (easier on the old eyes) to check is to get a permanent marker and 'paint' the bullet - stands right out.
Click to expand...

I did this type of thing and I blackend the bullet with a match. I am a fair bit longer than the OAL in my 7mm mag and the cartridges feed without flaw in my Tikka. In fact I know I could go even longer.

That must have been a long 30-06 cartridge.
 
Still - With your methodology, how do you know you are hitting the lands? In particular, with the length set by the cannelure. Hard chambering may be due to other factors such as tight brass.
 
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