Ok then chummy, but at least give me the opportunity to point out what needs to be done with the rifle. As I say, the test being proposed will establush beyond doubt that there was no sound moderator fitted to the barrell of the anshuzt rifle that fired the fatal shot under the chin which sent the fatal bullet up through the voud of her mouth into her brain. After which you can have your say based on the information which I have not yet provided. What is now known, is that the rifle in question only fired one of tge two bullets shot into her neck region. The one that was fired sideways across her throat was fired by a different gun...
Sorry but you have a poor track record with respect to understanding the mechanics of firearms and markings left on bullets/shell casings.
The way to determine whether bullets were fired from a gun or not is to match the lands and grooves. Some bullets expand or are damaged too great for there to be enough lands and grooves to try to match up.
There is no marking left on a bullet by a suppressor such as the one in question. Thus there is no way to determine whether a suppressor was used in the firing of any particular bullet by inspecting it.
If a bullet has sufficient numbers of lands and grooves it can be matched to a particular gun model. If not then it can neither be matched nor ruled out as having been fired from a particular gun. These are called the class characteristics. In addition there are imperfections unique to a singular weapon that can leave marks unique only to that weapon. These are called accidental or individual characteristics.
A bullet where the class characteristics of the weapon that fired it are unable to be discerned can neither matched nor ruled out as having been fired by a particular model of weapon that uses such caliber of ammunition. A bullet that fails to exhibit individual characterists can neither be matched to a specific gun nor rulled out as having been fired by that specific gun. If matched to a specific gun through individual characteristics then it is ruled out as having been fired by any other gun.
The spent shell casings can also be tied to having been fired by a specific gun. The firing pin impression, extraction marks, and breech marks will be peculiar to a specific weapon. Thus they can often be matched as having been fired by a particular weapon.
Unless the bullets and casings are still in existence or blowups made by examining them under a microscope still exist there is little hope of even attempting to prove a different gun was used.
The only way to prove a different gun was used would be to look at the bullet, find striae (lands and grooves), measure the striae and determine that such doesn't match the class characteristics of the murder weapon.
This would not reveal whether a suppressor were attached or not to the weapon that fired it, it merely would speak to whether the gun itself (with or without the sound suppressor) could have fired the bullet in question.
PV/19 and PV/20 were the bullets removed from Sheila. They were .22 rounds. They were intact enough to determine this for certain. The 25 shell casings were all .22 Eley.
The police had no .22 rimfire weapons so they had no means to fire any of these rounds. That alone means your suggestions are likely to go no where fast let alone more analysis of the lands and grooves to try to determine they were fired by a different make of .22 rifle than the murder weapon.