SCAR 17 _ Determining Bullet Seating Depth

John Spence · Dec 28, 2014

Hi Everyone,
I am relatively new to Reloading but have had a good success so far. When researching ways to correctly measure seating depth for my specific rifle I have found items such as the Sinclair Bullet Depth Tool with a comparator, but it says it will only work with bolt action rifles, Thompson Contenders, and some AR15 type rifles. Hornady makes another type of tool called an OAL Lock and Load that works with semi-autos but seems to be less accurate. There are other methods I have read about like the smoked bullet, and another method involving inserting bullet against throat then measuring with a dowel then measuring again with closed bolt, determining difference, etc. My question is what would be the absolute best and most accurate way to accomplish this in my SCAR? and any rifle for that matter? Thanks in advance for any help you can provide.
Johnny

sneakboxer · Dec 28, 2014

I have never pulled the barrel on a scar but i think with the barrel out you could use the Sinclair tool with the assistance of the AR adaptor. But you might want to just seat a smoked bullet in a fired case first and get a rough guess. Depending on your free bore, bullet profile, and mag long seating may preclude mag feeding. If your looking to single feed by all means go for it. I have the Sinclair tool and found it very repeatable with bolt rifles and my AR but i have never used the other tools. Just follow the directions closely and be impressed by the differences in your groups with a few thou in CBTO. A repeatable way to measure cartridge base to ogive will also be required. I use the Hornady caliber attachments.

John Spence · Dec 29, 2014

Man pulling the barrel sounds daunting for what I'm trying to accomplish. The repeatable case to ogive can be accomplished with a comparator right?

Nwcid · Dec 29, 2014

I thought have a reasonably quick change barrel was one of the selling parts of the SCAR?????

Aslo not sure what you are trying to accomplish. With this type of firearm why not just load to standard spec? I don't think you will have an accuracy gain that is significant, for this application.

Seating to a specific rifle will only insure it is good for that gun. You also have to make sure the rounds will still fit in the magazine.

John Spence · Dec 29, 2014

Well what I am trying to accomplish is just having accurate loads for my unique rifle, I want to try and find the recipe at which the gun will perform the best which I am sure is the reason most of us reload. At least that's why I was intrigued by it. To address your standard spec question here is a problem I rand into this weekend: So I loaded up some new Nosler Brass with some Nosler 180 Grain Partition (PPT) with 38 grains of IMR 8208 XBR and went by the Lyman book specs and came out with an O.A.L. of 2.780" or thereabouts. Rounds would chanber but would not extract. Bullet would actually stick in the barrel and brass and powder came flying out on all three I tried. The bullets I loaded were actually seated a bit deeper than the Black Hills Ammo I have on hand for comparison but they cycle fine. The only thing I could think of is because of the shape of the PPT which are more full in diameter while tapering closer to the end of the bullet tip than the rest of the bullets I have for comparison would be the reason bullet would be getting stuck. Thanks for helping to walk me through this.

Nwcid · Dec 29, 2014

Fair enough. Just seemed like a unique project for that kind of rifle.

Otter · Dec 29, 2014

How accurate is this rifle to start with? Honestly I think you are wasting your time trying to improve accuracy by adjusting seating depth with a SCAR. I've found seating depth will help fine tune a load in extremely accurate rifles capable of 1/2 inch or smaller groups, but have not found that to be the case in less accurate rifles. Do you shoot using wind indicators? If you want to reduce group sizes, figure out how to read the wind, which means you need some sort of wind indicator other than watching the grass and leaves move.

For my accurate/target bolt action rifles that benefit from seating depth adjustment, I start at hard jam and work my way back. In all cases with the match bullets I've found a jammed load shoots better than off the lands. However jammed bullets build more pressure so you have to be very careful how you proceed. Use this technique only if you know what you are doing and what to look for.

I also use the Hornady lock and load tools for finding the lands in other bolt action rifles, such as my large caliber hunting rifles. I never jam hunting bullets for several reasons, including not wanting to pull a bullet when I eject a loaded round from the chamber. Powder in your trigger and a bullet stuck in the barrel is not something you want.

AMProducts · Dec 30, 2014

I think you're wasting your time... you are not going to get better accuracy seating into the throat on a semi-automatic rifle, and my money says all you're going to do is create ammo that won't feed in the magazine, or won't be reliable.

Generally speaking the seating into the throat of the gun is what you do when you're trying to squeeze the last little bit of accuracy out of an already very accurate load. This is benchrest kinda stuff, where you're sick of shots being more than 1/2 a caliber off. I've never found an occasion where it really made anything that much more accurate to the kind of shooting I do, as long as they all go in the 10 ring I'm happy.

My suggestion is to load ammo with better components and see if that gets you the kind of accuracy you've been looking for. Please realize, you're shooting a semi-automatic rifle, not a sniper rifle, as a consequence you're never going to get bolt action sniper rifle kind of accuracy without putting a heavy match grade barrel on the gun. As a consequence, I think you're sacrificing much in the realm of reliability and safety for minimal gains.

John Spence · Dec 30, 2014

Otter and AMProducts....Thanks...I think that's the answer(s) I was looking for. I got into reloading because I have a .300 R.U.M. that I have taken out to 1,000 yards and after reloading the groups just got tighter. I was heavily encouraged to reload for that rifle and man what a difference it made. To answer a few of Otters questions: The SCAR is shooting groups of 3-4" at 200 yards (supported position prone) with 168 grain Black Hills Match so it is not a 1 MOA rifle, at least with me shooting it. The rifle is stock other than the Geissele trigger I installed. I am using a NK Kestral 400 for my shooting data such as wind and Density Altitude. I think my train of thought behind reloading was the claim HK has always made about the SCAR platform and how accurate it is so based on my own shooting results I was going to try and play with loads till I could get the rifle 1 MOA or sub MOA. However it seems that in my limited reloading knowledge I need to learn which guns I am simply reloading for cost savings and which ones I am reloading for accuracy.