To establish the Over All Length for my Swiss rifles I have always take a case fired in a particular rifle and placed a bullet in the case and run the bullet into the lands then backed it off 30 thousandths to establish the O.A.L. for this particular round in this gun. I was reading on here the other day that another way to establish the proper O.A.L. was to put a bullet in a case and then run the bullet up to the lands then take a cleaning rod and draw a line around it at the end of the barrel where it stops. You then remove the bullet and reinsert the cleaning rod into the barrel until it rests on the closed bolt face. Okay, here's what I don't understand. I did this both ways and I am coming out with a difference of about 3.8th of an inch. By the method I had been using, the O.A.L. came to 3.040 and by measuring with the cleaning rod it came to 2.851. Any idea what I am doing wrong? The bullets I am using are Privi 168gr. HPBT. Thanks in advance for your help!
Establishing Correct O.A. L. - I'm Confused!
- Thread starter PCCUSNRET
- Start date
- Status
rcmodel
Member in memoriam
Did you remove the empty case too?
If not you are measuring the thickness of the case web with the cleaning rod method.
Other then that? I don't have a clue.
There is another way to find the correct OAL though.
Just load to the same OAL as military spec loads and forget about it..
Some of the most accurate ammo made in the world, for use in any rifle, is factory loaded GI National Match, Black Hills Match, or Federal Gold Medal Match.
They load it all to SAAMI standard length, with no regard to where the leade in every rifle ever made is.
Seating just shy of the leade sounds good in theory, but is not always going to make any differance at all in accuracy.
rc
The only problem with loading to match a known good round is that the K-31 std ammo is GP11. That round uses an extremely long taper bullet - just can't find bullets here to match that ogive.
The Hornady manual and actual GP11 would suggest 3.059 IIRC and loading SMKs or Nosler Custom Comps to that length will really wedge them into the lands. Most end up loading for K31s right around an OAL of 2.88 - 2.92.
/Bryan
The Hornady manual and actual GP11 would suggest 3.059 IIRC and loading SMKs or Nosler Custom Comps to that length will really wedge them into the lands. Most end up loading for K31s right around an OAL of 2.88 - 2.92.
/Bryan
I did remove the case.
Any idea where I can find the SAAMI standard length for a 7.5 x 55 Swiss round using a 168gr Privi or 165gr PSP-BT bullet? The GP11 rounds made by the Swiss for these guns use 174gr. bullet that has a slightly different profile than either of these Privi bullets. I also load 150gr Nosler Ballistic tips for this gun. Your help is appreciated.
Chuck
Thanks Bryan,
You posted this while I was typing my response to RCModel. The problem is I have several of these guns and I am trying to establish an O.A.L. for a 168gr bullet that will work in all of these guns. I have been loading to 2.88 in the past, but now it appears there may be a 3/8" jump to the lands in the first rifle I tested. This sounds a little excessive to me. I think I will continue measuring these rounds without the rod and see if I can come up with an average O.A.L lentgh for each of the 3 main bullets I use in these guns (168 gr hpbt, 165 gr. PSPBT and 150gr. Spitzer BT).
Chuck
Thanks Walkalong! The neck on brass I used may have been too tight as there were marks from where the bullet hit the lands. I will losen the tension and try measuring it again to see if this helps.
I thought maybe the cleaning rod may have stoped on the ejector and not the face of the bolt but I checked this and this definitely wasn't the case (no pun intended).
Chuck
jfdavis58
Member
SAAMI probably isn't the 'standards' basis for this cartridge. There is a CIP drawing in the Wiki:7.5X55.
Standards diagrams don't specify by bullet, rather (SAAMI) they list minimum chamber plus allowance/maximum cartridge minus allowance specifications.
There seems to be some final comments in the WIKI that the Swiss don't actually follow CIP either.
Standards diagrams don't specify by bullet, rather (SAAMI) they list minimum chamber plus allowance/maximum cartridge minus allowance specifications.
There seems to be some final comments in the WIKI that the Swiss don't actually follow CIP either.
Too loose and the bullet can pull back out a bit as well. A little trial and error, and you will get it right.
Those are your clues.
As rcmodel posted though, you may find any old reasonable O.A.L. will shoot very well. It is fun to tweak and play with things to try to tighten groups up though.
twice barrel
Member
- Joined
- Oct 21, 2009
- Messages
- 226
You could use a wooden dowel as well. If the cleaning rod is a hollow tube the bullet nose can protrude into the rod but when you remove the case and measure to the breech it stops on the shoulder of the rod.
I prefer to take a fired case and lightly touch enough in the sizer to just establish a small amount of neck tension and place the bullet I want to load in the case, chamber in the gun and gently close the bolt. As you close and cam the bolt it will seat the bullet to the lands. Then very gently open the bolt and ease the round out and catch it before it flips out. Measure the COL and do it a few times to be certain its consistent. This will let you know what COL engages the rifling. You can seat the bullet to a little shorter COL if it will feed thru the magazine. If it won't you'll have to seat deep enough to accomplish that.
For other action types you'll have to modify the process as needed.
Hope this helps,
TB
I prefer to take a fired case and lightly touch enough in the sizer to just establish a small amount of neck tension and place the bullet I want to load in the case, chamber in the gun and gently close the bolt. As you close and cam the bolt it will seat the bullet to the lands. Then very gently open the bolt and ease the round out and catch it before it flips out. Measure the COL and do it a few times to be certain its consistent. This will let you know what COL engages the rifling. You can seat the bullet to a little shorter COL if it will feed thru the magazine. If it won't you'll have to seat deep enough to accomplish that.
For other action types you'll have to modify the process as needed.
Hope this helps,
TB
TB, Thank you! That is exactly what I was doing wrong. The tip of the bullet was going approximately 3/8" into the cleaning rod which made the round appear shorter using the rod method. Sure glad I didn't load all this brass without asking this question.
Chuck
Wow!? 3/8ths into the rod nose? That must be a big rod or a really pointy bullet.
The Surplus Rifle site has has a description of measuring with the two stops and a rod method - they suggest tipping the rod with one of those plastic pointed jags after filing the point flush.
/B
The Surplus Rifle site has has a description of measuring with the two stops and a rod method - they suggest tipping the rod with one of those plastic pointed jags after filing the point flush.
/B
- Status
Similar threads
- Locked
