A buddy of mine's situation

[GardDog]

I was talking shooting with a buddy of mine at work when he said that he was having drastic vertical stringing with some handloads. He said that he loads his own .270 for deer season. When sighting in, he loaded the magazine (Browning BAR - stock everything) with rounds made with two different batches of the same powder and zeroed at 200 yards. He said that when he got to the rounds from the other batch of powder, he saw 4-6 inches in drop from zero. I was expecting a little difference, but when he said that the drop was that drastic, I figured that something more is seriously wrong. Returning to the loads from powder batch A hold zero, but batch B are consistently low. He throws the powder, then trickles in the last few 1/10th of a grain.

I thought maybe it was scope issues or ring issues, but he said that he verified everything was snug.

It could be breathing inconsistencies, but he's grouping well with the other batch's loads.

Is 4-6 inches of drop able to be blamed on different powder batches? I would doubt that, but looking for others' input.

 

[Graham]

Re: A buddy of mine's situation

...and this happened to a buddy, not to you, right?

 

[GardDog]

Re: A buddy of mine's situation

Yep. I don't own a .270 or a BAR.

Thanks for the sarcasm.

 

[1911fan]

Re: A buddy of mine's situation

I'm thinking I'd call the maker of batch B, AFTER I had verified the following:
Action screws, scope base & ring screws all tight.
Verify correct/same powder used. Make sure your friend knows there is a difference between two powders with the same number by different manufacturers. Same case, bullet, primer too.

HTH,


1911fan

 

[427Cobra]

Re: A buddy of mine's situation

He did something different, maybe the scale wasn't zeroed, or a different lot of powder brass primers or even bullets, could be new brass on one batch and fired in the other, he did something different.

 

[GardDog]

Re: A buddy of mine's situation

He used a balance style scale. I'm partial to digital, so I suggested moving to digital. Less chance of a fauxpas.

 

[Graham]

Re: A buddy of mine's situation

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GardDog223</div><div class="ubbcode-body">Thanks for the sarcasm.</div></div>You're welcome.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GardDog223</div><div class="ubbcode-body">He used a balance style scale. I'm partial to digital, so I suggested moving to digital. Less chance of a fauxpas. </div></div> The dispensing units are, frankly, not as accurate as a good beam scale. I use an electronic scale, but I'm not a fan of them. In my experience they're not bad for getting averages of many things, like cases or bullets. But I make sure to keep mine plugged-in and warmed up. Otherwise, it's hit and miss, and needs to be re-zeroed and calibrated frequently. I've seen many of them with this same problem. Start it up cold, don't calibrate it, and there's a good chance that it will read incorrectly.

 

[Hummer]

Re: A buddy of mine's situation

It is very common when changing lot numbers of propellant, brands of primers or even lot numbers of primers to get variations in velocity.
For canister lots the procedure used to be to test it for pressures and if too hot blend it with a cold lot, and if cold blend it with a hot lot so that the "loads" will correspond with a commercial loading manual.
The big changes come in bulk lot. Propellant is purchased for say 1/2 million round lots and the excess gov't surplus is often sold off to propellant vendors to break down the 150 lb drums and repacked in 8s or 5s. Gov't ammo is loaded to pressure or velocity whichever is attained first. If velocity is reached and pressure is low it will be restricted, excessed etc. For instance WC 852 is known to be Hot Lot or Cold Lot. The cold lots developed peak pressure way down bore and were restricted to 30.06 loaded for Browning 30 cal MGs as they don't use gas to drive them. If pressure is met and the ammo chronographs within the "window" all is fine.
Using a cold lot of WC852 would wreck the gas systems on M1 Garands but would be fine for bolt guns and MGS.

 

[Rovieairto]

Re: A buddy of mine's situation

This is normal, especially with an autoloader.
The projectile exits at a different vibratory node.
The autoloader's vibratory node is usually more exaggerated because of the extra gas forces flexing the barrel prior to bullet exit.

This is why many folks do ladder testing during their load development.
This is much less pronounced on a bolt gun but it will still be present.

Heavy barrels resist these vibrations and are generally more consistent with varying load recipes.

 

[AUJohn]

Re: A buddy of mine's situation

Normal to have some change, can be small or big but some.